Fused deposition modeling: process, materials, parameters, properties, and applications

Abstract

In recent years, 3D printing technology has played an essential role in fabricating customized products at a low cost and faster in numerous industrial sectors. Fused deposition modeling (FDM) is one of the most efficient and economical 3D printing techniques. Various materials have been developed and studied, and their properties, such as mechanical, thermal, and electrical, have been reported. Numerous attempts to improve FDM products’ properties for applications in various sectors have also been reported. Still, their applications are limited due to the materials’ availability and properties compared to traditional fabrication methods. In 3D printing, the process parameters are crucial factors for improving the product's properties and reducing the machining time and cost. Researchers have recently investigated many approaches for expanding the range of materials and optimizing the FDM process parameters to extend the FDM process’s possibility into various industrial sectors. This paper reviews and explains various techniques used in 3D printing and the various polymers and polymer composites used in the FDM process. The list of mechanical investigations carried out for different materials, process parameters, properties, and the FDM process's potential application was discussed. This review is expected to indicate the materials and their optimized parameters to achieve enhanced properties and applications. Also, the article is highly anticipated to provide the research gaps to sustenance future research in the area of FDM technologies.

Graphical abstract

1 Introduction

The need for greater versatility and the evolution of customized products has directed the precipitous technological advancement of additive manufacturing technology. 3D printing is an additive manufacturing technology, also called rapid prototyping by the ASTM F42 technical committee, to differentiate between conventional production (subtracting manufacturing method) processes [1]. Originally, AM methods were used only for concept visualizations and validation. However, the advancement of the technique has led to the development of end-use components and tools [2]. The component manufactured by the AM technique is shaped layer by layer using the digital data designed using CAD and CAM [3]. In recent years, the use of AM technology has snowballed due to its ability to bring the product to market quicker than conventional methods [4]. As reported by Forbes in 2017, 57% of the global manufacturers have invested in 3D printing research and development, and 95% of manufacturing companies perceive 3D printing technology provides a significant market advantage. Finding also reveals that 47% of 3D printing businesses have been more successful than in previous years [5]. In the next 5 years, analysts predict that the 3D printing industry’s average growth will be 24% or 35 billion dollars [6]. In 2020, the AM industry grew by 7.5%, or nearly $ 12.8 billion. Figure 1 indicates the global annual report of AM parts’ production from independent service providers (in millions of dollars) by Wohler.

Fig. 1

Global annual report of AM parts production from independent service providers (in millions of dollars) by Wohler [7]

Fused deposition modeling is a popular AM technology because of its fast production, cost-efficiency, ease of access, broad material adaptation, and capability to produce complex components [8, 9]. In 1988, Crump-patented fused deposition modeling (FDM) and formed Stratasys in 1989. The initial system has essential fundamental aspects of AM except for the possibility of generating complex geometry [10]. Later, several optimized series were introduced, such as FDM Titan, FDM Dimension, FDM Vantage, FDM Maxum, FDM 3000, and FDM Prodigy Plus [11, 12] that can produce complex geometry designs. The structure is created three-dimensionally over the build plate per CAD design using thermoplastic filament in the FDM process. Once the initial layer is printed, the bed goes down, and the second layer is printed over the previous layer, and the process continues. Materials such as acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) are the most widely used materials in the FDM because their thermal and rheological properties make it easier to manufacture parts [13]. Other possible materials for FDM are nylon, ULTEM, polyetheretherketone (PEEK), polypropylene (PP), polyphenylsulphone (PPSF), thermoplastic polyurethanes (TPU), polyvinyl alcohol (PVA), high-impact polystyrene (HIPS), and composite filaments [14]. These materials have developed components for various industries such as automotive, electronics, biomedical, construction, aerospace, and domestic appliance industries [15]. The processing parameters have been reported to be the crucial factor determining the output product's quality and behavior. The different processing parameters used in the FDM process are layer thickness, infill pattern, infill density, raster angle, raster width, printing speed, build orientation, printing, and bed temperature. FDM manufactured parts are heavily affected by deprived mechanical and anisotropic properties. Several researchers have investigated the FDM process parameter's effect on mechanical behavior [16]. Lanzotti et al. [17] investigated the effect of layer height, raster angle, and shells on the tensile strength of a PLA. The author observed the tensile strength reduces with raster angle increment and increases with lower layer thickness. Ziemian et al. [18] analyzed the anisotropic properties of the FDM printed ABS and reported that the direction of the fracture depends on the raster direction and strength of the individual layer. Chacón et al. [19], in their work, reported that lower layer thickness specimen resulted in higher tensile strength and ductility; these higher mechanical properties were achieved at flat edge orientation. The FDM technology has also been shown to form porous internal structures in the manufactured component, which leads to inadequate mechanical strength and the “stair-stepping” effect to other problems such as poor surface finish [20, 21].

Literature studies attest that FDM technology has been used in various applications. This technology potential to produce functional products by using innumerable polymers and polymer composites. At present, most of the reported works seem to focus on developing polymers and polymer composites to be used with the FDM process. The components produced with this method are reported to have lower strength compared with the other conventional methods. Research in the field of additive manufacturing or 3DP has been increasing every year. The number of publications in this area from 2000 to 2020 is shown in Fig. 2. After 2012, the rate of research contribution in this area has been augmented significantly. The present review paper summarizes the crucial advancements in the FDM process, material characterization, and process parameters to develop the optimum print quality and enhance the FDM process's product quality. Also, the present paper attempts to present the property matrix for all the materials investigated. Since most researchers focus their review papers on particular areas, the current work concentrates on the overall FDM review. This current review paper includes the following sections: materials, properties, parameters, applications, technical challenges in the FDM process, and the conclusion.

Fig. 2

source from google scholars)

Number of journal publications on FDM for the period of 2000–2020 (

2 3D printing technologies

The International Standard Organization (ISO) and the American Society for Testing and Material standards (ASTM) have categorized the techniques of 3DP/AM [1]. They have classified AM technology into seven categories and discussed them in the preceding sub-sections.

2.1 AM categories

Sheet lamination, material extrusion, powder bed fusion, direct energy deposition, binder jetting, material jetting, and vat photopolymerization are the main categories of AM technology. Each technique has different abilities depending on its applications. The various processes and the methods of AM are shown in Fig. 3.

Fig. 3

Techniques and process of AM

2.1.1 Sheet lamination

In the sheet lamination process, the raw material is added together to form the final product in the form of sheets. The raw materials (worksheets) are cut by laser or cutter as per the geometry before the lamination process. The sheets are stacked layer by layer, and the stacked sheets were bonded by diffusion instead of melting [22,23,24]. Laminated object manufacturing (LOM) and ultrasonic additive manufacturing (UAM) are the main techniques in this process. The processing speed is relatively high, with low operation cost and ease of handling material [23, 25]. Various materials such as polymer, ceramic, paper, and metals can be used in this sheet lamination process. This process's main advantages are integrating as a hybrid manufacturing system, working with ceramic and composite fiber material, and without the necessity for support structures. The limitation of this process is the availability of limited materials and removing the excess materials after the lamination. Compared with other methods, the wastage is high in the sheet lamination process. In addition, the strength of the bonding relies on the lamination technique, and in certain instances, adhesive bonds will not suffice the strength and integrity required for the long term.

2.1.2 Material extrusion

In this material extrusion process, a continuous filament of thermoplastic or composite material is used to construct 3D parts. The polymer filament is forced over the nozzle and fed over the build plate or previously solidified substance, and the product is built layer by layer technique at a constant speed and pressure [22, 23, 26]. This process is primarily used to build complex geometry that is impossible to produce by the traditional manufacturing process. Also, multi-material can be used in this extrusion process [27, 28]. Operation time and cost are minimal compared to other methods, and the main techniques in these processes are fused deposition modeling (FDM) and fused filament fabrication (FFF) [23, 25]. Low initial and running cost, easily understandable printing technique, small equipment size, simple and easy changing of print material, and comparably low-temperature process are the main pros of this process. The main cons of this process are visible layer thickness and the support structure may be required. In addition, part strength in the Z-axis is lacking, the structure of the parts is delaminated due to warping and temperature fluctuation.

2.1.3 Powder bed fusion

In this powder bed fusion process, the raw materials are in powder form. Initially, the powders are fed over the base plate, and the materials are sintered using heat, laser, or electron beam. Next, the Z-axis moves downwards to spread the powder over the layer uniformly by a brush or wiper, and again the process repeats [22, 24]. Selective laser melting (SLM), selective laser sintering (SLS), electron beam melting (EBM), and direct metal laser sintering (DMLS) are the main techniques of this process. In this PBF process, the previous layers are reheated to reduce anisotropy, and this process is used to fabricate intricate structures without additional supports [29, 30]. The process advantages are as follows: (1) comparatively low cost as it does not require any supporting structure, (2) a wide range of materials can be used, and (3) the remaining powders in the process can be recycled. However, the limitations of the process are relatively low speed, very long print time, post-processing requirement, high power usages, weak structural properties, and surface texture.

2.1.4 Direct energy deposition

This process creates three-dimensional objects by melting material as it is deposited using concentrated thermal energy such as a laser, electron beam, or plasma arc. A gantry system or robotic arm manipulates both the energy source and the material feed nozzle. In here, a movable chamber is fixed along with a laser. The metal powder is routed into the nozzle to the specific area simultaneously; the laser operates and melts the powder and solidifies the layer. The movable chamber is not fixed at a particular axis, and it moves in various directions. Depending on the material feedstock, the DED process is classified into two types: (1)metal powder and (2) metal wire [24]. Comparative from PBF, different types of substrates can be used in DED. This process produces high accuracy products with the minimized void formation and improved density [31, 32]. The primary techniques used in this process are laser engineered net shaping (LENS), direct light fabrication (DLF), and direct metal deposition (DMD). High build rate and faster build time, used for built larger parts, fewer material wastages, multi-material range are the advantages of this method. The limitations of this method are low build resolution, high capital cost, and without support structures.

2.1.5 Binder jetting

In this process, the binder liquid bonds the powder and forms the final part. Initially, the powder is spread over the bed evenly, and the bonding agent is dropped over the powder using the print head. Next, the electrical heater is used to solidify, forming the desired shape. After the formation of the first layer, the powder bed moves down, and the powder is spread over the previously printed layer, and the method continues [24, 33, 34]. The energy utilized is low compared to other AM processes, and the operation cost is also relatively low [35]. Various parts can be made using this process, and this process is faster than other processes. The double material approach gives several different variations and mechanical characteristics of binder powder. This process's limitations are that it is not suitable for structural parts, post-processing is required, and high cost.

2.1.6 Material jetting

In this MJ process, liquid polymers are used as the raw material. Using the piezo print head, the droplets of polymer liquids are deposited over the build plate, and the solidification is carried out using ultraviolet lamps [22, 36]. This process is categorized into three types: (1) Polyjet technology, (2) nanoparticle jetting, and (3) drop-on demand. The process is capable of printing large components compared to VP [37]. The material jetting process is similar to ordinary inkjet printers, where the droplets are controlled layer by layer to produce a 3D object. After the layer finishes, it is cured in the photo-sensitive material with ultraviolet light or heat for metal and ceramic pieces. The advantage of this process is that it can be used to develop complex geometry components, high precision, and efficient techniques. The main techniques are inkjet printing (IP) and material jetting (MJ). This process is capable of building high-accuracy parts at less than 14 μm. The injection molding process has a better surface finish, print multi-material, and low wastage of materials due to high accuracy printing. The main limitation of this process is non-suitable for function prototypes. Compared with other AM techniques, the machine is expensive, the parts are relatively brittle, and the high accuracy can be achieved on limited materials such as polymers and waxes.

2.1.7 Vat photopolymerization

In this VP process, the materials are mixed with the high reactivity acrylate resins. The mixed photopolymers are placed in the platform, and the laser is used for sintering. Here, the stereolithography (SLA) uses a laser, and direct light printing (DLP) uses a projector for the sintering process. The laser is exposed over the mixed metal resins, and it undergoes a chemical reaction to become a solid. It is a photochemical process where small monomers are linked together like a chain to form a solid object [38, 39]. This process has high accuracy and surface quality. This process is also relatively quick and typically used to build large components at a size of 1000 × 800 × 500 mm and a maximum weight of 200 kg. The limitations of this process are that the machines are relatively expensive, post-processing time and the removal of resins time takes a significant amount of time, and the material selection is limited.

2.2 Major techniques of AM

All the AM methods have various printing techniques with unique characteristics. Some of the techniques are cost-effective, high accurate, user friendly, but few techniques have low printing quality, are not an end-user product, and require post-processing. The most common methods used in the various industrial sectors are as follows.

2.2.1 Stereolithography (SLA)

This stereolithography (SLA) technology is a polymerization-based process that was commercially introduced in 1986 [40]. Two techniques are used in this SLA process, one is top–bottom, and another one is bottom-top. The top–bottom technique is the most popular than another one [41]. Photopolymerizable monomers of epoxy or acrylates resins are used for laser irradiation. The resins cover the building platform, and the laser head is computer-controlled. At first, the boundary layer of the product and the supporting structures are printed before the primary structures [42]. Then, a thin amount of resins is placed over the building platform, and the laser is exposed over the resin; the photo-sensitive layer undergoes polymerization, known as the first layer of the prints. After the first layer print, the platform lowers at the y-axis, and the resins are spread over the specific area. The process repeats until the whole component is printed. The excess material in the platforms is removed after each layer formation. This process prints the product layer by layer at the range of 50–200 µm [43]. This process is categorized into two types based on the ultraviolet light used for curing: (1) projection-based stereolithography and (2) scanning-based stereolithography [44]. In PSL, the lamp is exposed over the entire area in a single pass, but each layer is scanned individually in the SSL. This SLA technique is relatively quick and has the highest resolution compared to other AM techniques. This drawback of this SLA technique is the slow printing process and high cost.

2.2.2 Selective laser sintering (SLS)

Selective laser sintering (SLS) is one of the best powder-based AM techniques developed in 1987 by Carl Deckard [45]. In this technique, the powder particles are sintered using a laser source to produce the solid structure [46]. Two chambers are used in this SLS technique, the feed chamber with a roller is to load the powder to the bed, and the building chamber is for printing. Initially, the feed chamber feeds the powder evenly to the built chamber base plate with the help of a roller. Before the laser is exposed, the building chamber is heated (below melting temperature) then the Co₂ laser is exposed over the powder to cure the material. The building chamber then slightly moves down, and the feed chamber applies the powder over the printed layers. The excess powders in the building chamber act as a supporting structure and are removed after completion, and the excess material is reused. This is a cost-efficient and flexible procedure to make high-density prototype products [47, 48]. However, due to the high power of laser input, the operation cost is high and the product quality compared to the SLS process is low [49].

2.2.3 Inkjet printing (IP)

The modern inkjet printers were invented by Canon and Hewlett-Packard in 1987. The inkjet printers are mainly classified into two types based on the operation: continuous inkjet printer and drop-on-demand inkjet printer. In the continuous inkjet printer, the ink droplet creation is constant. Meanwhile, in the drop-on-demand inkjet printer, the ink is emitted when necessary. The resolution of continuous inkjet (CIJ) printing is lesser than the DOD printing [50,51,52]. This CIJ printing ink is extended through a small nozzle by a high-pressure pump controlled by a piezoelectric crystal. The charger electrodes selectively charge the inks from the print head, and the droplets form the image on the matrix. The excess materials are deflected to the gutter and its reuse. In the DOD process, the ink droplets are generated by the piezoelectric actuation or pulses of the thermal resistor or thermal buckling. In the thermal process of DOD, the ink chamber is heated to a high temperature for vaporization, and the bubbles are formed on the heater surface, which will create the pressure pulse, push the ink from the nozzle, and form the objects. The advantage of this technology is to minimize wastage, environmentally friendly, and post-processing is minimized [53].

2.2.4 Laminated object manufacturing (LOM)

Laminated object manufacturing (LOM) is a vastly handy technique to produce small to big-sized objects, and Feygin and Pak developed it at Helisys Corp in 1991 [54, 55]. Initially, the raw material is stored as a roller and supplied to the Platform, and the sheet material is cut by using a cutter or laser. The same process endures on the second layer and is placed over the first layer. Then, using a heated roller, pressure is applied over the two sheets containing adhesive coating in-between the sheets. The laser is then used to remove the excess materials [56, 57]. Plastic, metals, fabrics, paper, and synthetic materials are commonly used materials in this technique. This technique’s main advantage is mainly used to produce high-strength objects compared to the conventional process, lower tooling cost, post-processing not required, support structures not needed, and less time to manufacture larger products [58, 59].

2.2.5 Fused deposition modeling (FDM)

Fused deposition modeling (FDM) is the most popular material extrusion-based additive manufacturing method invented by Scott Crump, co-founder of Stratasys, in 1989 [60]. FDM is a material extrusion process using thermoplastic polymers. Acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), and polycarbonate (PC) are the base material of this FDM process [61, 62]. The layout of the FDM is shown in Fig. 4. Here, the filaments are stored in the roller and directly connected to the extrusion head. This head moves in X and Y directions, and the build platform moves in the Z direction. An electric motor controls the movable head, and the filament is directly connected to the extrusion head. Generally, two types of material filaments are used for this process. One is built material, and another one is the supporting material. The filament diameter is typically 1.75 to 3.0 mm. This FDM technique is consists of three stages for the production: (1) pre-processing, (2) production, and (3) post-processing.

Fig. 4

Basic layout of the FDM process [291]

The product’s design is drawn using CAD software and saved in STL format in the pre-processing stage. Then, before slicing the file, essential parameters for the process are considered, like slicing parameters, building orientation, and temperature condition of the machine. These are the vital parameters of the printing that will affect the final product’s mechanical properties [63, 64]. The essential parameters of the process are shown in Fig. 5. Once this procedure is completed, the slicing is done using the software (e.g., idea maker, quick slice, etc.), and the tool path is labeled as G-code. The G-code is a computer numerical controller code to control the extrusion process. Figure 6 shows the step-by-step process of the FDM process.

Fig. 5

Important process parameters of the FDM process

Fig. 6

Process flow of FDM

After the pre-processing, the feedstock material connected with the head is regulated by temperature and heated to the semi-liquid stage. It forms the 2D layer over the build platform [65]. The layer forms one over another until the 3D objects are created [62, 66]. The filament is heated at a temperature between 150 and 300℃ and printed over the plate at the dimensional accuracy of 100 µm [67]. The support base is initially printed before the required object is printed. The building platform moves downwards after every layer is printed, then the extrusion process is sustained, and the object is printed.

The post-processing technique is carried out for the final product. Post-processing is a vital process in FDM since the printed parts are not entirely ready for instant usage. After the printing process, the product is taken out from the bed platform, and the supporting structures are removed and undergo post-processing. This process is mainly used to improve the surface quality of the product [68, 69]. Kumbhar and Mulay [70] reported that the post-processing techniques are usually used to improve the surface finish. The post-processing process is categorized into two that are mechanical and chemical methods [71]. The chemical method uses painting, coating, heating, and vapor deposition process [72, 73]. In contrast, the mechanical method includes machining, sanding, abrasive, vibratory, and barrel finishing to improve the parts' surface quality and mechanical properties [74, 75].

Daminabo et al. [27] and Bryll et al. [76] are reported the different mechanisms in FDM methods classified by the heads and feed mechanism. Figure 7 shows the different types of FDM processes.

• Single-head method

• Dual-head method

• In-nozzle impregnation method

Fig. 7

Single, multi, and in-nozzle impregnation FDM methods

Only one filament is used for production in the single head FDM method, and it is a traditional method. Composite materials of polymers with fiber, wood, and metals are used in this method. The drawback of this process is, it is not possible to fabricate products with more than one material type. In the dual-head method, two material filaments are used for this process. This method feasible the development of components with two different materials. It is relatively quick compared to the single head method. This method is used to make skeletal structures like honeycomb and square cells. Compared to the previous processes, this in-nozzle impregnation method is unique. Here, the filaments are directly fed into the nozzle head. The polymer filament and the add-on materials (e.g., carbon fiber, glass fiber) are directly fed into the nozzle, and the filaments are mixed, and printing is performed.

The significant advantages of this FDM process are ease of access, less cost of the machine, and multicolor product printing; compared to other RP techniques, this technique is cheaper and cost-effective. On the other hand, the main limitations of this technique are poor surface quality and it needs support structures. The various materials used, the product quality of the technique, merits and demerits, and the applications of these techniques are shown in Table 1.

Table 1 Materials used and characteristics of different AM printing processes

3 Materials for the FDM process

The materials used for FDM are usually polymer-based, having different physical, mechanical, and thermal behaviors. The selection of the polymer materials depends on the different applications and as per the requirements. However, at present, limited types of polymers are available and have restrained FDM technology. Also, high melting point materials could not be used in this process since the commercially available FDM machines melting capability are around 300 ℃ [77]. Due to these constraints, thermoplastic polymers and several low melting temperature materials are ideal for this process. Thus, various attempts have been made to improve the quality and properties of the polymers by adding fillers such as ceramics, nanoparticles, metals, and wood fiber.

3.1 Polymers

In the 3D printing process, polymers are the most common materials used to form the prototype or products. The common materials are used in the FDM process are acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polyethylene (PE), polypropylene (PP), nylon/polyamide (PA), and polycarbonates (PC) [25, 78, 79]. Pure polymers such as ABS, PLA, and PA are mainly used for prototypes as they have low physical properties. In contrast, polyethyleneimine (PEI), polyetherketoneketone (PEKK), polystyrene (PS), and polyetheretherketone (PEEK) are used for components that require improved properties. These materials have high mechanical, thermal properties and chemical resistance [77]. Some special materials of ABS such as ABSi, ABS-M30, ABS-M30i, ABS-ESD7, and ABS plus are also used as the printing material in the FDM process [80, 81].

PLA is a biodegradable, easily compostable, and non-toxic material obtained from sugar beets and corns. PLA is the low-temperature thermoplastic, and it is the reinstate of petroleum-based thermoplastics. They are mainly used for biomedical and tissue engineering and scaffolding [82, 83]. Due to their low operating temperature, the cost of operation is reduced with desirable mechanical properties. However, low melting strength and slow crystallization rate are the main limitations of this PLA. Due to this drawback, the application of PLA in different sectors is constrained [84].

ABS is the most used petroleum-based material having high mechanical strength, easy processability, corrosion resistance, and high melt strength. In the FDM process, the strength of printed ABS can achieve 80% of the raw material [85,86,87]. Compared to PLA, the ABS has better mechanical strength. In addition, the ABS material can be easily extruded because of less friction coefficient, and they are mainly used to print household products [88]. However, ABS is not suitable for medical applications as they are not biofriendly, and the layers do not merge completely to create a watertight device [72].

Polyamide (PA)/nylon has been one of the most popular engineered thermoplastics with excellent mechanical and thermal properties [89]. PA/nylon has higher mechanical properties compared to the PLA and ABS [90]. The most promising biocompatible polymer with exceptional mechanical qualities and outstanding processability is polyamide/ nylon. However, this material exhibits the most challenging material characteristics compared with some other polymers [91]. Pure PA-based FDM products are seriously warped, lack shape infirmity and are distorted. Due to these limitations, their applications are restricted [92].

PEEK is a high-performance, non-toxic, semi-crystalline thermoplastic polymer with good mechanical strength, high-temperature resistance, and excellent dimensional stability [93]. PEEK has a high melting point and mechanical strength compared with PLA and ABS [94, 95]. PEEK is a biocompatible material used in biomedical applications and automotive, aerospace, electronics, and medical industries [96]. It also has good chemical resistance and mechanical properties up to 240 ℃ and is usually used as an alternative material for the metal in high-temperature applications [97].

3.2 Composites

Pure polymers were the primary filaments used in the FDM process because of the low melting point and low cost, process flexibility, and availability. 3D-printed polymer products have a high degree of geometric sophistication, and their wide application presents a significant challenge with the lack of mechanical strength and functionality. Pure polymers as a filament have many obstacles to increasing the product’s strength some other materials added with the polymers. Combining different materials to obtain the required mechanical and functional properties is a promising way of solving this problem. The production of composite materials compliant with current printers has also gained significant interest in recent years. Many promising findings were demonstrated in producing new printable composites strengthened by ceramics, metals, fibers, and nanomaterials. The composites are mainly classified into four types, and that is shown in Fig. 8.

Fig. 8

Basic composites of FDM

The polymers, ceramic, fiber, and nanomaterials were added with the base polymers to create the composite filaments. The materials used with the polymer materials are mainly classified into two types: (1) biodegradable materials and (2) non-biodegradable materials. Figure 9 indicates the various types of materials used in the FDM process.

Fig. 9

Biodegradable and non-biodegradable materials in FDM

3.2.1 Biodegradable materials

The increasing drawback of fossil supplies in blend with a society that needs environmentally friendly and ecological procedures has led to forming a market for biobased plastics. The biodegradable materials are non-toxic so that this type of material is mainly used in medical applications and recyclable products. The development of the filament as a biodegradable material was primarily motivated by this demand. Biodegradable materials are natural materials, and the properties of these materials are relatively low compared with non-biodegradable materials. Here, the bio-based polymers are added with other bio-based polymers, ceramics, natural fillers, and natural fibers. PLA and ABS are the standard materials used as a base material in the composites because of their low cost, ease of availability, and good mechanical properties [98].

3.2.1.1 Biodegradable polymer blends

In recent years, a number of research on polymer blends have been conducted aiming for biomedical applications. Researchers mainly focus on PLA/PCL blends due to their compatibility in biomedical. Haq et al. [99] investigated the mechanical properties of PCL/PLA composite blended with PEG at different molecular weights. In their investigation, the 5 phr of PEG containing the composite result showed the highest elastic modulus value (396.43 MPa). Meanwhile, the 15 phr PEG containing composites showed the highest impact strength of 0.14 J. Menčík et al. [100] analyzed the mechanical, thermal, and morphological properties of poly(3-hydroxybutyrate)/poly (lactic acid)/plasticizer biodegradable blends. Tributyl citrate C-4, acetyl tributyl citrate A-4, acetyl tributyl citrate A-6, n-butyryl tri-n-hexyl citrate B-6 was used as a plasticizer. The PHB/ PLA/plasticizer ratio is 60/25/15 wt%, and the filament size is 1.75mm. The result shows that the elongation of acetyl tributyl citrate (A-4) and tributyl citrate (C-4) improved by 308% and 155%, respectively, compared to the PHB/PLA composite blends. Poly(butylene succinate) (PBS)/polylactide (PLA) polymer blend was analyzed by Ou-yang et al. [101]. The PBS-PLA with the composition of 20, 40, 60, and 80 wt% and filament diameter of 1.75 mm were studied. The layer thickness used is 0.1mm, and the printing orientation angle of the first and second layers is 45° and 135°, respectively. The result shows that 40 wt% of PBS added into PLA showed a good tensile and low degree of crystallinity. Kim et al. [102] analyzed the PLGA/β-TCP/hydroxyapatite nanocomposite scaffolds for a rabbit. The scaffold enrooted into the femoral defect of the rabbit body and its osteoconductive and biodegraded in 12 weeks. Polycaprolactone(PCL)/tricalcium phosphate (TCP) composite scaffolds in vitro degradation analyzed by Lei et al. [103]. The scaffolds were immersed in simulated body fluids (SBF) at 37 ℃, and the degradation behavior was monitored for a different period. The findings revealed very good degradation behavior.

3.2.1.2 Polymer ceramic composites

Ceramic materials are naturally biodegradable and are mainly used as a human bone replacement. Ceramics are favorable biomaterials because of their similarity to natural bone structures. The standard ceramic biomaterials used for medical applications are alumina, silica, zirconia, calcium phosphate, and bioactive glass–ceramics [104]. Liu et al. [105] investigated the mechanical properties of PLA/ceramic and other composites. Their analysis reported that the maximum tensile modulus of PLA/ceramic was 1056.3 MPa, the tensile strength was 46.3 MPa at the angle of 45°/ − 45°. The tensile modulus of PLA/ceramic composites was found to be higher compared to all other composites. The composition of polyamide 12 with 15 wt% zirconia and 15, 20, and 25 wt% of β-TCP was analyzed by Abdullah et al. [106]. Their analysis concludes that the specimen’s physical and mechanical properties were affected upon the addition of the fillers more than 30 wt%. Chen et al. [107] investigated the microstructure, thermal behavior, printability, and mechanical properties of poly(vinyl alcohol)/β-tricalcium phosphate. β-TCP was mixed with the ratio of 5, 10, and 20 wt% respectively with PVA. The printing parameters of the specimen were infill percentage of 40%, raster angle 90°-layer thickness 0.3 mm, and the printing and the bed temperatures at 175 ℃ and 25 ℃, respectively. The experiment's outcome shows that the 20 wt% of β-TCP with PVA has the most optimum properties. The maximum stress improved from 8.3 to 10.7 kPa and was identified as a potential candidate for bone tissue engineering. Poly (e-caprolactone)/bioactive glass composite was studied by Korpela et al. [108]. Their experiment suggests that PCL with a 10 wt% BAG composition is stiffer than the standard PCL structure. The operating parameters of the specimen preparation were the layer thickness 0.4 mm, raster angle 0°/90°, and the temperature at 190 ℃. Wu et al. [109] investigated the morphological and mechanical properties of polylactic acid (PLA)/hydroxyapatite (HA) composite. Compositions are 5, 10, and 15 wt% for HA with PLA at the operating parameters of 0.6-mm layer thickness and the printing head and the bed temperature was 210 ℃ and 60 ℃, respectively. The mechanical properties of the composites were found closer to the human bones, but the addition of HA into PLA composition reduces the quality of the printing.

3.2.1.3 Natural fillers

Recently, the addition of natural fillers into biodegradable polymers has received seemingly interest due to the increased demand for biodegradable materials in the medical sector. Fillers such as wood, bamboo wood, sugarcanes, kenaf with PLA, and other base materials have been in progress for exploration. Ayrilmis et al. [110] investigated PLA with 30 wt% of wood by using FDM. The water absorption and mechanical property changes were investigated at various layer thicknesses of 0.05 mm, 0.1 mm, 0.2 mm, and 0.3 mm. The finding indicated that the increase in layer thickness would increase the porosity and reduce the specimen's mechanical properties. PLA/raw sugarcane bagasse and PLA/sugarcane bagasse fiber were analyzed at different compositions of 3, 6, 9, and 12 wt% by Liu et al. [111] and reported to have the best properties for industrial-scale applications. A study on bamboo/PLA composite preparation using FDM was carried out by Zhao [112]. The addition of bamboo powder into PLA polymer was found to reduce the nozzle clogging and has superior biodegradable behavior. Daver et al. [113] analyzed the morphological, mechanical, and thermal properties of cork-filled PLA at various infill percentages. The printed parts’ tensile and yield strength were low compared with the compression molded composites, but the elongation at break was higher. PLA/wood flour composite was examined by Tao et al. [114]. Their result exhibits that the melting temperature of the composite does not change with the addition of 5 wt% wood flour into PLA. Vaidya et al. [115] analyzed the composite’s warping behavior with respect to fillers addition polyhydroxy butyrate (PHB) and Pinus radiata wood chips). The 20 wt% added filler into PHB changes the melt viscosity and improves the warpage from 34 to 78% compared with pure PHB printed parts. Tran et al. [116] analyzed the thermal and mechanical properties of polycaprolactone (PCL)/cocoa shell composite. Different composition of cocoa shell added into PCL resulted into a low temperature composite that suitable for printing biomedical scaffolds and toys. Frone et al. [117] studied the morpho-structural and thermomechanical properties nano crystal cellulose added with Polylactic acid (PLA)/polyhydroxy butyrate (PHB) composite and Dicumyl peroxide (DCP) as a cross-linking agent. The reported good bonding and thermomechnical properties of the specimen.

3.2.1.4 Natural fibers

The use of natural fibers as a filler in the thermoplastic composite has been increasing. In many applications, natural fibers are used as an alternative to petroleum products. Natural fibers have a high specific strength, are relatively cheaper, light in weight, and are biodegradable [118]. Mechanical properties of the harakeke composite surpassed the plain PLA, as reported by Hu and Lim et al. [119]. The harakeke was added at a composition of 30, 40, and 50 wt% into PLA, and the findings exhibit that the 40wt% fille composite has the highest mechanical properties. Le Duigou et al. [120] experimented on PLA/continuous flax fiber (CFF) composite. The filament and printed sample microstructure were characterized, and mechanical properties were analyzed. PLA/jute fiber and PLA/flax fiber composites were examined by Hinchcliffe et al. [121]. The jute fiber composite filament size was 2 mm, and the flax fiber was 0.5 mm. The findings revealed the tensile strength increased by 116% and 26%, respectively. The stiffness of the product was increased by 12% and 10%. The effect of different l/d ratios of PLA/ Bamboo fiber and PLA/Flax fiber were studied by Depuydt et al. [122] and reported an increase in the stiffness. Le Duigou et al. [123] investigated and showed that it is possible to print hygromph biocomposite of PLA/wood fiber composite with dedicated bilayer microstructure. Mechanical properties and potential of the hemp and harakeke reinforced with Polypropylene were studied by Milosevic et al. [124]. The ultimate tensile strength and Young’s modulus were reported to improve by 50% and 143%, respectively, compared with pure polypropylene. The mechanical properties of thermomechanical pulp (TMP) fiber reinforced with BioPE composite were analyzed by Tarrés et al. [125] and reported that the printing quality improved. Thibaut et al. [126] examined the mechanical properties and anisotropic shrinkage of Carboxymethyl cellulose (CMC) with natural cellulose fiber during drying. The result showed that the 30 wt% composite has better mechanical properties and reduced shrinkage.

3.2.2 Non-biodegradable materials

Non-biodegradable bioplastics are fascinating because they balance the advantages of decreased carbon footprint during processing and better resource quality with microbial degradation persistence [127]. However, most materials are toxic, not easily decomposable by natural factors, and have relatively poor mechanical properties. Therefore, metals, fibers, nanomaterials have been used as filler materials to improve the mechanical strength and biodegradability of the materials.

3.2.2.1 Non-biodegradable polymer blends

Peng [128] prepared and investigated the mechanical properties and shape memory effect of polypropylene(PP)/nylon 6 (PA6). The composition of 10, 20, and 30 wt% of PA6 was added into the PP. The specimen was printed with the parameters of 0.1-mm layer thickness, 45°/ − 45° orientation, and with nozzle and bed temperatures of 250 ℃ and 110 ℃. The findings revealed that 30 wt% of PA6 blends with PP have high dimensional stability and mechanical properties and a suitable SME deformation temperature of 175 ℃. S. Chen et al. [129] developed a polymer blend of 10, 20, and 30 wt% of polymethyl methacrylate (PMMA) with ABS as a primary blend. They added a small amount of methacrylate − butadiene − styrene (MBS) with the blends. The specimen was produced with layer thickness 0.2 mm, the orientation of the first layer is 45° and the second layer is 135°, and the infill density of 100%. The impact strength of the ABS/PMMA blend found to be 14.9 kJ/m² is lower than the ABS. Singh and Singh [130] prepared PolyFlex™/ABS blend at the composition 70/30 vol%. In this research, the polymer blends’ mechanical properties were compared with the other materials. Their analysis shows that the PolyFlex™/ABS blend has attained exceptional standards of both strength and elasticity. Ahmed et al. [131] investigated the time-dependent mechanical properties of FDM process conditions using a definitive screen design of polycarbonate (PC)/ABS blends. Their result exhibits that parameters of layer thickness 0.2540 mm, an air gap of 0 mm, raster angle 0° and the print direction at 20° are the optimum conditions for good properties.

3.2.2.2 Polymer metal composites

In these polymer-metal composites, metals in powder form are reinforced with the base materials and extruded in filament form. However, the major drawback of using metal is the viscosity effect. Still, it can be improved by using additives such as plasticizers and surfactants [132]. Aluminum and iron powders are the most commonly used filler material in the PMC. Magnetic iron and bronze fill powder reinforced with the PLA’s mechanical properties were compared by Fafenrot et al. [133]. The specimen is printed at various compositions and temperatures. The results exhibit the mechanical strength of the composites is lesser than the original material. Sa’ude et al. [134] investigated the dynamic mechanical properties of the ABS/Copper composite. The filament composition was 57 to 63% ABS and 22 to 24% of copper powder, and 15 to 19% surfactant. The outcome of the differential scanning calorimetry (DSC) analysis glass transition temperature (T_g) was obtained at 74% of ABS and 26% of the copper composition. The finding revealed improved T_g, tan delta, storage modulus, and loss modulus. ABS-iron polymer-metal composite metal flow analysis was performed by Nikzad et al. [135]. The thermal conductivity of the 10wt% iron infilled composite was found to have increased to 0.258 (W/m.K). Masood and Song [8] investigated the iron with nylon P301 PMC. Tensile properties of the PMC at different compositions 70% nylon, 30% iron and 60% nylon and 40% iron, and 60% nylon and 40% iron were investigated. The 70% nylon and 30% iron reported giving better tensile modulus (E) of 54.52 MPa than the other two compositions.

3.2.2.3 Fiber-reinforced composites

The fibers were added with the polymers to overwhelm the inadequate mechanical properties of the 3D printed products. Fibers are mainly classified into two types: (a) short fiber and (b) continuous fiber. These fibers are naturally corrosion resistive, rigid, have high dimensional stability, stiffness, high strength, and are lightweight compared with natural polymers [136]. These FRCs are mainly used in the aerospace and automobile sectors to reduce weight and increase the product’s strength. However, the main limitation of the fibers is non-biodegradable and non-eco-friendly. Therefore, Kevlar, carbon, glass fibers are widely used to improve the performance of the polymers.

3.2.2.3.1 Short fiber reinforced composites

Due to the insufficient strength of the pure polymers, the short fibers are reinforced with the polymers to enhance the resilience of the FDM printed part. The fiber-reinforced composite is generally made by adding the fiber particles into the molten thermoplastic polymers [137]. When manufacturing a fiber-reinforced filament, it is essential to monitor the orientation of the fiber, the percentage of the fiber mixture, and the ideal size of the fiber to avoid unwanted problems such as obstruction of the extruder during printing that will affect the mechanical properties of the final product [138]. Carbon fiber has good thermal conductivity, electrical properties, corrosion, wear, and moisture resistance; thus, many analyses were performed using CF [139]. Li et al. [140] analyzed the flexural properties of CF/PEEK fiber-reinforced composite. The geometrical models of the specimen were designed by using CATIA V5. The nozzle and bed temperatures are 400 ℃ and 160 ℃, the layer thickness of 0.1 mm raster angle of 45°/ − 45°, printing speed is 15 mm/s, and the air gap is 0.18 mm are the parameters used to print the specimens, and the specimen printed different orientations (horizontal and vertical). The CF/PEEK flexural properties of the vertically printed specimens were higher than the horizontally printed specimens; the porosity and uniform nucleation of the CF added PEEK was improved compared with pure PEEK. The microstructure, processability, and mechanical properties of the ABS/CF reinforced composite were examined by Tekinalp et al. [141] using the FDM printing and compression molding techniques. The CF was reinforced with the ABS at 10, 20, 30, and 40 wt%, and the filament was extruded at 1.75 mm diameter. The specimen is printed at 0.2 mm layer thickness using a 0.5 mm diameter nozzle at the temperature range between 220 and 235 ℃ and the bed temperature of 85 ℃. The author mentioned that the filament containing 40 wt% of CF with ABS could not be printed due to the nozzle clogging during the FDM printing. Apart from these difficulties, both FDM and CM processes are reported to have comparable tensile strength and modulus. Spoerk et al. [142] investigated the anisotropic properties of the short carbon fiber (SCF) filled polypropylene (PP). SCF was mixed with 10, 15, and 20 wt% into the PP also stabilizer and compatibilizer were added with the composition. Specimen printed 0.25-mm layer thickness using single screw extruder the 1.75 mm diameter filament feed to the printer at 230 ℃ temperature and different orientation angles. This study concludes that 10 wt% of CF with PLA has excellent characteristics compared with the 15 and 20 wt% of CF with PP.

3.2.2.3.2 Continuous fiber reinforced composites

In 3D printing technology, continuous fiber reinforcement (CFR) is a major challenge for researchers. The CFR composites offer significant mechanical properties compared to the short fibers. Since the fiber is continuous, the printing adapts the co-extrusion method or uses dual-head printers [143]. The thermoplastic and CFR filaments are supplied to the nozzle separately, and they will be fused inside the nozzle and deposited over the build platform. Another method is a dual head method [144]; the thermoplastic and the CFR filament are fed separately to the printer and printed through two different nozzles. Fabrication of nylon thermoplastic with continuous carbon, glass, Kevlar fibers, and their mechanical performance was analyzed by Dickson et al. [145]. The standard filament diameter of the nylon was 1.75 mm, and the Kevlar, glass, and carbon were 0.3, 0.3, and 0.35 mm, respectively. The specimen was printed at different sizes from 4 to 32 layers at 0.1 mm layer thickness and fiber laydown at concentric and isotropic. The author exhibits that the carbon fiber reinforced composite has better tensile, flexural strength, and flexural modulus. Li et al. [146] examined the continuous carbon fiber reinforced PLA composite’s thermodynamic and mechanical properties. The PLA particles partially dissolved in a magnetic stirring process for 30 min with the methylene dichloride solution to increase the filament’s interfacial strength. The analysis result shows that modified CFR/PLA composites’ tensile strength improved by 13.8% and flexural strength by 164% better than the other composite. The storage modulus was 3.25 GPa, and the glass transition temperature (Tg) was 66.8 ℃. Mechanical properties of the continuous Kevlar fiber with nylon thermoplastic composite was analyzed by Dong et al. [147]. The specimen was made of 0.1 mm layer thickness and infill density of 100% with different fiber orientations. It was reported that continuous Kevlar/nylon composites have an elastic modulus of 27GPa and ultimate tensile strength of 333 MPa. The strength of the Kevlar composite found to be close with some metal-polymer composites. However, the author reported the bonding between Kevlar and nylon was relatively weak.

3.2.2.4 Nanocomposites

Thermoplastic polymers used in FDM products have poor mechanical and thermal properties. Thus, to enhance the product’s strength, the nanomaterials are used in conjunction with thermoplastic polymers. The lack of adhesion contact between nanofillers and polymer material consequences the brittleness of the composite material [21]. Many hydrogels and polymer matrices, thermoplastics, and thermosetting resins have been introduced with nanofillers such as carbonaceous nanofillers, nano clay, and metallic nanofiller to develop functional and property-enhanced structures. In the fabrication of electrically conductive nanocomposites, metallic nanowires and nanoparticles, carbon nanotubes, carbon nanofibers, and graphene have been used owing to their excellent conductivity. These improved composite structures have been used in various applications, ranging from sensing instruments (e.g., liquid sensors, strain sensors) to protect electromagnetic shielding in aerospace to household industries [148]. Ivanov et al. [149] analyzed the electrical and thermal properties of PLA/Graphene/MWCNT composites. The composition of PLA/Graphene and PLA/MWCNT were also studied. The mono-fillers PLA/Graphene and PLA/MWCNT composition were 1.5, 3, and 6 wt%. Meanwhile, PLA/Graphene/MWCNT's bi-filler composition varied between 3 and 6 wt%. The mono-fillers had 6wt% GNP and MWCNT were reported to have conductivity compared to the pure PLA successfully. The 6wt% of PLA/graphene/MWCNT composites reported having measured thermal conductivity of 0.4692 (W/m.K) than the other bi-filler and mono-filler composites. Sezer and Eren [150] analyzed the MWCNT reinforced into ABS thermoplastic. The specimen is printed by FDM using the parameters of 100% infill rate, 0.2 mm layer thickness, and the nozzle and the bed temperature of 245 ℃ and 110 ℃, respectively. Their study result shows that 7wt% of MWCNT with the ABS has a tensile strength of 58 MPa at a raster angle of 0°/90°. Raster angle 45°/ − 45° resulted in a lower tensile strength. The 10 wt% of MWCNT achieved the highest electrical conductivity of 232 e⁻² S/cm with the metal flow index (MFI) value decreased to 0.03 g/10 mm due to the nozzle clogging issues. The mechanical and thermal properties of ABS/montmorillonite nanocomposites were researched by Weng et al. [151]. The results showed that the overall mechanical strength of the FDM printed parts is lower than the injection molding process. However, the thermal stability of the OMMT nanocomposite was reported to increase. Coppola et al. [152] analyzed the FDM printed PLA/clay nanocomposite. Different types of PLA were used, PLA 4032D and PLA 2003D, with a layered silicate of 4 wt%. The study mainly focuses on the specimen printed using three different temperatures for PLA 4032D (185–200–215 °C) and PLA 2003D (165–180–195 °C), and the properties were analyzed. The experiment demonstrates thermal stability, and the elastic modulus of PLA/clay nanocomposite was higher than the ordinary PLA. Kim et al. [153] analyzed the piezoelectric properties of polyvinylidene fluoride (PVDF) and Barium titanate (BaTiO₃) composite. N-Dimethylformamide was used as a dissolving agent in the fabrication of the PVDF/BaTiO₃ composite. The finding revealed that, compared with solvent-casted nanocomposites, this nanocomposite has three times the higher piezoelectric response.

Table 2 establish the detail of various analysis carried out in the FDM process and the data obtained from various literatures [21, 89, 103, 112, 118, 131, 138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,224,225,226,227,228]. It specifically identifies the materials used in the FDM process and the various test such as mechanical, electrical, and thermal investigations.

Table 2 List of mechanical tests conducted in polymers, blends, and composite materials

In this section, the various materials used in the FDM process and their findings were clearly discussed. ABS and the PLA are the most commonly used materials for the entry-level. Materials such as nylon, polycarbonate, PEAK, PEEK are mainly utilized for high-strength properties. Moreover, various composite materials were added with the polymers to increase the product's strength and other properties. In many applications, fibers and nanocomposites are used to increase the product’s strength. Biocompatible polymer blends and polymer composites are mainly used in the medical sectors for human tissue and organs.

4 Parameters of FDM process

The noteworthy performance of the FDM products depends on the proper selection of printing parameters during fabrication. Due to the availability of several competing parameters, the influence on the accuracy of the variable and the material properties varies. Appropriate process parameters are attributed to the fabricated part’s efficiency and mechanical characteristics [217]. The optimized process variables for the FDM process are shown in Fig. 10.

Fig. 10

Cause-and-effect diagram of FDM process parameters [218]

The process parameters affect the efficiency of the production and the properties of the product. The essential parameters used in the FDM printing are infill pattern, infill density, raster angle, raster width, layer thickness, build orientation, printing speed, air gap, and operating temperature.

4.1 Infill pattern

The infill pattern is the structure, shape, and technique of the material inside of the part. Grid, honeycomb, cubic, rectilinear, rectangular, triangular, octet, and wiggle are the commonly used infill patterns shown in Fig. 11. In terms of the properties, i.e., the tensile and compressive properties of the product, they reported changes with different infill patterns.

4.2 Infill density

Infill density implies the total amount of material used for printing the specimen. The mechanical properties of the specimen are primarily affected by the infill density. Groza and Shackelford [217] denotes three types of filling styles in the study. A “solid normal” infill has a tough interior and good mechanical properties. In “spares,” the printing time and the material volume are also minimized by leaving gaps, and it utilizes a uni-directional raster. Finally, in “sparse double dense,” the printing time and material volume are reduced in “sparse double dense,” using a crosshatch raster pattern.

4.3 Raster angle

The raster angle is the most common printing vector for FDM printing optimization. The raster angle is how each layer is oriented while printing the desired shape. Figure 12b exhibits the raster angle used for printing. The generally used raster angle differs from 0° to 90°, and regularly used raster angles are (0°/90°) and (45°/ − 45°). However, it is possible to control this variable for each layer either at one angle or at a different angle. The raster angle proved to affect the properties, and various experiments have been carried out to study the impact of the raster angle. Rajpurohit et al. [138] and Es-Said et al. [139] analyzed the effects of raster angle on mechanical properties in both experiments. The raster angle of 0° was reported to have better tensile and impact resistance. Meanwhile, the raster angle of 30° presents maximum impact and tensile strength [220, 221]. Nancharaiah et al. [222] reported the 0° angle having the best surface finish and the worst at 60°. The differences in the CAD models and other parameters have led to differences in the interpretation of various authors.

4.4 Raster width

Raster width is the size of the deposition of the material droplet of the product. This raster or road width is usually 1.2 to 1.5 times the nozzle diameter. Figure 12b shows the raster width, which varies on the diameter of the nozzle. Thus, the reduced width value leads to improved strength and reduced build time. Sood et al. [223] and Arumaikkannu and Uma Maheshwaraa [224] reported the top surface finish and dimensional accuracy could be obtained using minimum raster width.

4.5 Layer thickness

The layer thickness is the breadth of material deposited by the nozzle on the vertical axis, as shown in Fig. 12c. The size of the nozzle tip usually determines or controls the layer thickness. The effect of layer thickness and other parameters of a specimen has been analyzed by Mohamed et al. [226], and the result displays 0.1-mm layer thickness has the best flexural force. Therefore, this experiment directing less amount of layer thickness will increase the flexural properties of the product. On the other hand, Wu et al. [96] also mentioned that the increase in the size of the layer thickness would reduce the product's strength.

Fig. 11

a–i Various infill patterns used for the FDM process [225]

4.6 Build orientation

The build orientation is the most versatile and impressive pre-processing parameter to obtain the best surface properties. The machine coordination system can be modified in the CAD model to achieve desired objectives by the angle of orientation or deposition angle. It indicates the orientation of printing of the specimen inside the build platform in respect of X, Y, and Z directions. Figure 12a shows the orientation and style (flat, on-edge) and orientation angles. The X, Y direction printed parts do not need supporting structure, but the Z-direction requires support structure. Afrose [188] investigated and observed the fatigue life and best capacity to store strain energy specimens printed at 45° orientation.

4.7 Printing speed

Printing speed is the pass-through speediness of the nozzle on the build platform during the printing. The printing speed regulates the build time of the product. Also, the printing speed has a maximum effect on the deformation of the product because, during the production, this fast printing could induce substantial residual stresses. Vinitha et al. [227] examined the printing speed effect of burning parts built by FDM. They reported that reducing the speed of the printing would increase the surface finish of the product. When thinner layers are printed, the impact of the print speed is considered negligible [228].

4.8 Air gap

In the same layer, the gap between two contiguous raster's is denoted as the air gap. The default value of the air gap is usually zero, which results in the two closest beads being touched. The positive air gap will reduce the density of the part and reduce the product's build time. Hence, the denser structure (negative air gap) would have a longer build time, and the raster has good bonding strength. Also, the negative air gap was testified to significantly improve the tensile strength [229]. Meanwhile, with negative and positive air differences, the surface finish generally increases [223]. The air gap between the rasters is shown in Fig. 12b.

4.9 Operating temperature

The operating temperature is categorized into nozzle temperature (extrusion temperature) and bed temperature (build platform). Before the printing process, the nozzle is required to reach a specific temperature to melt the filament to print the product, called nozzle temperature. Similarly, during the printing process, the building platform bed needs to be at a suitable temperature, termed bed temperature. Due to the delay in the solidification, the higher temperature produces smooth surfaces. Vasudevarao et al. [230] distinguished after the layer thickness, raster angle, the operating temperature is the third most significant factor affecting the product surface finish.

Fig. 12

a Printing orientation of specimen [130], b operating parameters of raster angle, air gap, raster width, contours, and c layer thickness of the product [231]

Quite a number of research have been carried out on FDM parameters to improve process parameters aiming to enhance surface finishing, dimensional precision, and the mechanical features of printed components. Since the process parameters are essential for enhancing mechanical properties, build time, dimensional accuracy, and surface roughness. Several investigators proposed that the effects of process parameters on FDM processed parts be analyzed with sufficient computational designs and optimization techniques to reduce the experimental effort and feasibility. The optimal process parameter combination was established experimentally in most cases, and the best experimental result was deemed the optimum solution. The optimal process parameter combinations may vary from the experimental combinations but must be within the process parameter range. Researchers used several optimization techniques to address this flaw. It is a mathematical model of the connection between process parameters and a single part attribute. Multi-objective optimization represents the connection between process parameters and various component attributes using mathematical models. This shows the FDM machine’s maximum and lowest levels of process parameters, or a range of process parameters proven to provide excellent component qualities.

Many studies have utilized the full factorial, fractional factorial, and face-cantered central composite designs to get more information from fewer trials. Alternatively, the experimental design established optimal values for analyzing component properties. In some of the researches validating the relationship between the part quality and process parameter by creating various mathematical models such as quantum-behaved particle swarm optimization (QPSO), differential evolution (DE), genetic algorithm (GA), non-dominated sorting genetic algorithm II (NSGA-II) were used. Peng et al. [232] produced ABS components based on a standardized experimental design. Controllable factors in their case study were line width compensation, extrusion velocity, filling velocity, and layer thickness. Additionally, they inferred from the experimental findings that a thin layer thickness was preferred for dimensional accuracy improvement. Additionally, they found the optimal combinations of these four process parameters for three response variables, including dimensional accuracy, using the response surface method (RSM), fuzzy inference system (FIS), artificial neural network (ANN), and genetic algorithm (GA). Several studies improved the features of more than two components concurrently to find the optimal combination(s) for multiple conflicting qualities. Sood et al. [233] identified the optimal combination of five process parameters (layer thickness, build orientation, raster orientation, raster width, and air gap) for dimensional accuracy in three dimensions (length, width, and height). The authors optimized all dimensional accuracies using the Taguchi technique and found an optimum solution that reduced three-dimensional dimensional accuracy. The author also used an ANN to make predictions. Montero et al. [234] examined five process factors (raster width, air gap, filament color, extrusion temperature, and raster orientation) and used a fractional factorial design to conduct their experiment. The experimental findings indicated that the air gap and raster orientation were two important tensile strength factors and that a negative air gap and 0° raster orientation were preferred for maximal tensile strength. The effect of build orientation and raster orientation on tensile characteristics was investigated by Durgun and Ertan [235]. Their testing findings indicated that the 0° raster and 0° build orientations were appropriate for optimizing tensile strength. The orientation of the build was shown to be more important than the orientation of the raster. The optimal combination of five process parameters (raster width, layer thickness, build orientation, raster orientation, and airgap) that optimize the tensile strength of ABS printed components was determined by Rayegani and Onwubolu [229]. A mathematical model that linked process characteristics to tensile strength was developed using the group method of data handling (GMDH). To enhance tensile strength, a DE optimization technique was used to optimize each parameter. The optimization findings indicated that the minimum layer thickness, build orientation, raster width, and negative air gap increased tensile strength. Raster orientation was shown to be less important.

Dimensional accuracy and surface quality of the FDM component were investigated by Nancharaiah et al. [222]. The properties of the component affected due to raster angle, raster width, air gap, and layer thickness were analyzed, and the analysis was conducted adapting Taguchi's DOE method. The findings were evaluated statistically to assess the relevant variables and their relationships. The ANOVA analysis reports that the part accuracy and the surface quality of the product were affected significantly by the raster width and layer thickness. Meanwhile, the air gap has more impact on dimensional accuracy and little influence on surface quality. Pavan Kumar and Regalla et al. [236] analyzed the support material and build time optimization on FDM adapting the DOE method. Based on the ANOVA result, the specimen’s orientation was found crucial to minimize the build time, and the build time is decreased as the layer thickness, raster width, contour width, and raster angle increased. Using Taguchi's DOE method, the effect of the process parameters on the PLA filament using FDM was analyzed by Alafaghani and Qattawi [237]. Adapting the L9 DOE method, infill pattern, infill percentage, layer thickness, and extrusion temperature were investigated for the specimen's dimensional accuracy and mechanical properties. Their result showed that the lower infill pattern and infill percentage of hexagonal infill pattern at 190 ℃ have fewer dimensional errors and better dimensional accuracy. The processing parameters of 0.3 mm layer thickness, 100% infill percentage at 210 ℃, and triangular infill pattern reported having good strength and young's modulus. Also, the author exhibits the product's mechanical properties while printing in high extrusion temperature, and the rectilinear infill pattern has better strength and stiffness than the triangular pattern. The best relationship consequence and process variables are said could be established using the Taguchi method [238]. In contrast, compared with the RSM method, the number of experiments could also be reduced using the Taguchi method [239]. Table 3 exposes the different mathematical optimization methods that have been commonly used to analyze the process conditions of the FDM prototyping process.

Table 3 Previous analysis of mathematical optimization methods for analyzing the process condition of the FDM process

This section demonstrates the importance of the process parameters in the FDM process. The most studied FDM parameters were layer thickness, build orientation, raster orientation, raster width, air gap, and infill density. According to the previous research, the layer thickness and the build orientation are the most important factors on dimensional accuracy and surface roughness of the product. Reducing the layer thickness will increase the dimensional accuracy and surface roughness. Also, the shrinkage happens along the X- and Y-axes of construction platforms, whereas growth occurs along the Z-axis. Low print speed and extrusion temperature are also important factors to increase the surface finish. The build orientation determined the tensile properties of the product, also the tensile and flexural strength was greatest at 0°. To increase the infill density and the extrusion temperature is recommended to increase the strength. Reducing the air gap of the layer would form voids in the products, which reduce the properties.

5 Mechanical properties of FDM parts

The mechanical properties of the FDM printed specimen are mainly dependent on the material and the input process parameters. Layer thickness, build orientation, raster angle, raster width, and air gap are the primary factors affecting the mechanical properties of the 3D printing parts [205, 247, 248]. The build orientation significantly affects the mechanical properties and the surface roughness compared with the raster angle [235]. Research groups used ASTM standard criteria in preparing the sample and performing mechanical experiments; e.g., ASTM D638 was adopted by nearly all research groups tested for tensile tests [176, 205]. Most of the research findings reported that the process parameters mainly affect the ultimate tensile strength, yield strength, elasticity, and elongation of the component. Also, in most published literature, the mechanical behavior was revealed to be contingent on printing parameters [249]. The tensile strength of the product is mainly affected by the build orientation and the poor interlayer bonding. Likewise, high tensile can be obtained in the printing direction on parallel and longitudinal [250, 251]. Anisotropic mechanical properties of the FDM printed ABS were analyzed by Ahn et al. [205]. Their study shows that the negative air gap increases the tensile and compressive strength of the FDM product compared to injection molding. Reese [252] investigated the mechanical behavior on various raster angles of PEEK material prepared by FDM. Their result showed that maximum strength was observed at a 0° raster angle. Fatimatuzahraa et al. [253] studied the mechanical properties and the microstructure of the FDM printed ABS parts at different raster angle orientations. Their result showed that the angle at 45°/ − 45° at crisscross cross-section structures has a higher strength for flexural, deflection, and impact tests. Hossain et al. [254] examined how to improve the ultimate tensile strength, young’s modulus, and tensile strain by modifying the raster angle, contour width, air gap, and build orientation. Three approaches have been used for this assessment: default, insight, and visual response. The finding revealed that a higher UTS could be obtained by optimizing process parameters using the insight revision method. Ognjan et al. [255] investigated the effect of raster angle variations in tensile, flexural strength, and surface finish. The researcher recommends 0° raster angle delivers higher mechanical strength with lower surface finish. Caminero et al. [256] assessed the effects of orientation, layer thickness, and fiber volume content on impact properties of Kevlar, glass, and continuous carbon-reinforced nylon composites. Their results exhibit that the layer thickness has a higher impact on strength. Table 4 shows the properties of different polymer materials and composites by various process parameters.

Table 4 Mechanical properties of the FDM products by using various materials and process parameters

The materials used in the FDM process have various ranges of strength and modulus. The wide range of materials has the ultimate tensile strength between 40 and 70 Mpa, and Young’s modulus range is between 0.5 and 2.5. Figure 13 indicates the Ultimate Tensile Strength and Young’s modulus of polymers, polymer blends, and various composite materials used in the FDM process.

Fig. 13

Ultimate tensile strength and Young’s modulus of polymers, polymer blends, and various composites

The mechanical properties of the FDM printed polymers and polymer composites are demonstrated clearly in this section. Printing parameters played an important role in the mechanical properties. Reducing the layer thickness and infill density seen could increase the strength of the product. Besides, the materials like PP, PA, PE, PLA, and ABS are reported to have lower properties compared with other materials. Hence, composite materials were added with the base polymers to enhance their properties. Compared with the other composites (Polymer blends, ceramic, metal), the fiber and nanocomposites are shown to have high strength, stiffness, surface finish, and toughness. Also, the research is mainly focused on the fiber (GF, CF) and nanocomposites (CNT, MWCNT, CNC) for the medical and aerospace sector.

6 Applications of FDM process

FDM can generate virtually any geometry that can be designed. This technology can print hollow interiors and irregular shapes with elegant geometrical forms. The essential benefits of using FDM technology in various industries are printing lightweight products, multi-material printing, short production time, reduced tool investment cost, and optimum materials usage. This technique is used primarily for prototyping and rapid manufacturing since it is inexpensive compared to conventional fabrication, which requires expensive machines. Many potential applications for FDM parts include aerospace, automobile, electronics, biomedical, and construction sectors. Figure 14 shows the global use of additive manufacturing in various sectors.

Fig. 14

Global additive manufacturing application of various sectors [267]

6.1 Aerospace

Most of the components in the aerospace industry have complicated geometry, and manufacturing these components has high costs and is time-consuming. Compared with metal, the polymers have lower strength and flame retardant, but these thermoplastic parts are used to reduce the weight of aircraft parts and improve fuel efficiency. In addition, the aeronautical industries have always been expensive as many iterations on the design occur for large products and limited production. For these reasons, FDM could be the alternative to produce parts without any tool modifications and low production volume [268]. Using FDM and other AM technologies, metallic and non-metallic components such as engine parts, heat exchangers, and turbine blades can be manufactured for aerospace applications [269, 270]. FDM is primarily used to produce plastics, ceramics, and fiber composites [271]. For rapid part production and tooling, Stratasys has adopted FDM processes along with several other aerospace industries like NASA Bell Helicopter and Piper Aircrafts [272]. Figure 15a shows Evektor aircraft components fabricated using FDM. In NASA’s Mars rover, nearly 70 FDM-printed thermoplastic components have been used and reported to be fairly robust to survive space rigors. Stratasys and Aurora Flight Sciences also reported significant production time reduction in producing polycarbonate cabling pipes of V-22 Osprey of Bell Helicopter using FDM technology [273].

6.2 Electronics

3D printing technologies testified to shorten production times for geometrically fitting electronic prototypes [274]. The 3D-printed polymer composites shown could act as electronic instruments and can be used in various forms in combination with leading electrical materials. Using FDM, the carbon-black/PCL composites were added to electronic sensors to convert the piezoresistive to capacitive. Capacitive sensors may be printed as part of the custom interface system or embedded in smart vessels [275]. FDM printed PLA/graphene electrodes for electrochemical sensing were analyzed by Manzanares Palenzuela et al. [276]. A basic activation process consisting of the DMF supported the partial dissolution of the polylactic acid insulating polymer shown to contribute to the rise in electroactivity. Similarly, PLA/graphene printed electrodes were established for electroanalysis of picric and ascorbic acids with successful efficiency of sensing [277]. Figure 15b shows FDM printed electric circuit with an LED. Electrodes fabricated by carbon nanotube (CNT) /zinc oxide (ZnO) and CNT/copper (Cu) were blended with PLA and used for the electronic tongue research as cyclic voltammetric sensors [278]. Dawoud et al. [279] developed the carbon black–filled acrylonitrile butadiene styrene (ABS) composite strain sensor using FDM capable of analyzing the internal stresses.

6.3 Biomedical

At present, the biomedical sector accounts for 11% of the overall AM market share and is anticipated to be the driver for AM production and growth. Unique requirements of biomedical applications such as high complexity, ease of access, small production quantities, patient-specific needs, and customization have been the driving factor for the FDM technology. In medical applications, using magnetic resonance imaging (MRI) and computed tomography (CT) technology, 3D images of organs and tissues developed with high resolution [280]. The obtained image data allows 3D printing technology to generate patient-specific tissues and organs with sophisticated 3D micro-architectures. Currently, several biocompatible natural and synthetic polymers are used for biomedical applications [281]. Printability, biocompatibility, strong mechanical properties, and structural properties are consideration factors for biomedical applications [282]. Teixeira et al. [283] described that the FDM printed PCL/TCP composite scaffold degradation rates were faster than the PLA in PCL scaffold. Polydopamine coating (PDA) with PLA scaffolds assists in smoothing over the scaffold of the type-1 collagen. The study has contributed to increased cell response and extracellular matrix deposition and enhanced PLA postinduction. Rasoulianboroujeni et al. [284] reported that the polylactic-co-glycolic acid (PLGA)/TiO2 scaffolds have higher compression modules, wettability, and glass transition temperature compared with pure PLGA. Medicines produced from polyethylene glycol filaments filled with indomethacin (IND) and Hypromellose succinate (HPMCAS) are less bitter and dissolve quicker [285]. Chai et al. [286] prepared hollow intragastric floating sustained-release (FSR) tablets to reduce the frequency of the administrating tablets. FDM printed human ribcage as replacement are shown in Fig. 15c.

6.4 Construction

The application in the building sector started in 2014. Casting, molding, and extrusion are the traditional methods of the building industry. 3D printing can be used in the construction industry in areas where limitations such as geometric complexities and hollow structures are required. The contour craft technology for automated constructions of buildings and structures and space applications was developed by Khoshnevis 287]. The technology can be readily used to construct low-income homes and build a shelter on the moon because of its capacity to operate in situ materials. Using special bioplastic on XXL 3D printers and FDM technology, the European Union constructed the ‘Europe Building’. Also, using the 3D printer, a Chinese company ZhuoDa Group built a two-story villa in 3 h at which cost of $400 to $480 [288]. Figure 15d shows the FDM concrete printing process and the first FDM printed house by WinSun company in 2014. The house parts were initially printed in pieces; after that, the pieces were assembled. The cost of 200 m² homes is stated to be less than $5000 [289]. Mainly, the FDM-constructed buildings are classified as green buildings; more than 30% of energy costs are saved.

Fig. 15

a Evektor aircraft components and FDM printed duct adapter [290]. b FDM-printed electric circuit with LED [291]. c FDM-printed Ribcage [292]. d FDM concrete printing process and the first FDM printed house by WinSun company in 2014 [293]

6.5 Automobile and other sectors

The FDM process is also frequently used in automotive and other sectors for prototype development and functional prototypes, architecture models, jewelry, toys, household products, and end-user products. High strength polymers such as polycarbonate, nylon, ULTEM have been used in numerous applications essential for automobile production. The main applications in the automotive sectors are for printing jigs, fixtures, check gauges, interior accessories, air ducts, lights, bezels, and full-scale panels [294]. This technology is also used in the jewelry industry to minimize wastage and to produce complex geometries. The FDM process was found to be a time saver and cost-effective in this sector [295]. This technique is also used for children’s toy fabrication and is also used in household product creation.

7 Technical challenges of FDM process

This review discussed the techniques used in additive manufacturing, the materials, properties, process parameters, and FDM applications. The properties of the FDM products shown could be improved by anticipating proper processing parameters and materials. Also, different materials like polymer composites, metal polymers composites, ceramic composites, polymer blends, fiber composites, and nanocomposites used in FDM are discussed in detail. Several significant studies are required in terms of technical advancement, considering the advantages of FDM printing, such as design freedom, customization, and the ability to print complex structures, seem required. On the other hand, the limited materials availability, accuracy and quality, anisotropic mechanical properties, limited application in large production, mass production, printing time, clogging, and void formation also need extensive research.

Materials and process parameters play an essential role in this process. Currently, low gradient thermoplastic polymers and some composites are used in the FDM process. These delimited materials do not satisfy the range of industry application criteria, so the range of materials should be expanded. Most of the products prepared by suing FDM are stated to have low mechanical strength; the main reason for this delinquent is the void formation between the subsequent layers of the part. Thus, it results in inferior and anisotropic mechanical properties of the product. A proper selection of the parameters would minimize the problem. I.e., increasing the layer thickness will reduce the porosity but degrade the cohesion in the composite, reducing the tensile strength. Alternatively, reinforcing fibers with polymers helps to improve the product’s properties. However, the addition of fiber during feedstock preparation and part fabrication results in void formation, which affects mechanical behavior. Several investigators have overcome this problem by adding a thermally expandable microsphere to reduce the void formation and increase the strength. Another vital challenge is the nozzle clogging due to the fiber or particle reinforcement. The clogging significantly affects the quality and quantity of the production. Also, the filament will be brittle with the addition of a high amount of fillers.

Another limitation of the FDM technology is the mass production and larger product fabrication capability. Compared with the traditional manufacturing process, the 3D printing process is not suitable for mass production. Still, currently, researchers are attempting to fabricate large product manufacturing using FDM and other 3D printing technology. At present, 3D printing technology has advanced to another phase of manufacturing technique known as 4D printing technology. 4D printing uses shape memory polymers as the printing materials. Also, 5D printing technology is taking up the feasibility and possibility of additive manufacturing technology and is anticipated to capture the market very soon. Compared to the 3D printing process, the 5D printing process is highly accurate and efficiently minimizes material wastages.

8 Conclusion

This paper presents a detailed review of AM process and materials, properties, process parameters, and the applications of the FDM technique. The present review paper also discusses the advanced materials used in the FDM process and the various parameter optimization to achieve maximum mechanical properties and dimensional accuracy. Compared with the conventional machining process, FDM is cost-effective and user-friendly. The fiber-reinforced polymers and nanocomposites are shown to have excellent characteristics than other pure materials. But in the filler reinforcement composites, increasing the composition percentage by more than 30 wt% produces clogging in the nozzle. Numerous analyses show that the layer thickness, raster angle, infill pattern affects the printing quality. Various studies also show that the product’s tensile strength increases in 0° raster and concentric patterns. Furthermore, the product’s surface finish increases by reducing the layer thickness, decreasing the air gap, minimizing the porosity, and increasing the product's strength. Currently, the research in FDM focuses on developing new polymer composite and optimizing the parameters to achieve better quality products for applications in various manufacturing applications. Nanopolymer composites have gained significant attention in many applications, especially in medical fields for scaffolds and tissue engineering. However, very few researches have been carried out using nanopolymer composites. The nanocomposites testified could reduce the issues related to bonding and clogging, which will feature a significant advantage. Finally, the present review is anticipated helpful for researchers in the field to understand the FDM in general and identify the gasp for future research in this area for betterment.