Lean Management in a Medium-Scale Foundry to Improve Productivity

Abstract

In the present, highly competitive market, foundries need to implement lean principles to cope up with demands and to supply superior-quality casting products. Foundries need to produce quality castings with minimum production cost and lead time. Lean manufacturing is generally inspired by the Toyota Production System which has been expended on the subtraction of seven types of waste and refining the client’s delight. This chapter addresses the identification of critical product by Pareto analysis of previous year sales data of the medium-scale foundry. The current state Value Stream Map of Critical Product was drawn to understand material flow and information flow. After that, the Kaizen event was conducted with the assistance of the Kaizen team for five days to identify bottleneck activities and the Kaizen report was generated for the possible elimination of it. The Special Purpose Venting Machine was designed and developed to make venting operations faster and more accurate. The drying mold system is recommended to improve mold drying process regarding the elimination of casting defects like blow holes and substantially less time in drying operation. With the help of future state Value Stream Map, the possible improvements are exposed.

15.1 Introduction

A foundry is a manufacturing facility that produces metal castings. Metal casting is one among the oldest metal shaping approach acknowledged. Sand Casting interprets as the pouring of molten metal into a sand mold and letting it solidify inside the mold [1]. Molds are generally provided with a cavity of the shape to be made. The pattern is used to build a mold cavity. Geometry and dimension of the pattern are the same as the final part to be cast with some allowances like shrinkage allowance, draft allowance, machining allowance [1]. Relying on production volume, different pattern materials especially wooden, aluminum, ferrous metal are utilized in practice. Sand casting contributes approximately 60% of total metal casting worldwide. Lean is outlined as a technique for achieving vital continuous improvement in performance through the elimination of all wastes of resources. Lean manufacturing is a methodology that specializes in minimizing seven types of waste inside the production system at the same time as concurrently maximizing productivity. The seven types of waste are Overproduction, Inventory, Waiting, Motion, Transportation, Rework and Over processing [2]. Lean manufacturing is based on some the unique concepts, together with Kaizen. Kaizen is a Japanese word that means continuous improvement, the word ‘Kai’ means continuous and ‘Zen’ means improvement. Kaizen thinking may be pragmatic to any workplace situation due to its simple nature [3].

The Indian foundry industry manufacturers metal cast components for applications in Auto, Tractor, Railways, Machine tools, Sanitary, Pipe Fittings, Defense, Aerospace, Earth Moving, Textile, Cement, Electrical, Power Machinery, Pumps/Valves, Wind turbine generators, etc. Foundry Industry has a turnover of approx. USD 19 billion with export approx. USD 2.7 billion in FY 2018–2019. There are approx. 5000 units out of which 90% can be classified as MSMEs (source: Foundry Informatics Centre). Hence foundry is the backbone of other industries. The growth of other industries depends on the foundry. The foundries are the mother of other industries and the development of industrialization and industrial success will be measured by the progress of this foundry industry of a nation. India has emanated as the third-largest casting manufacturer in the world followed by China and the United State of America, respectively. India has installed capacity of 15 million tonnes per year but actual annual casting production bent on between 6 and 9.5 million tonnes which mean 9,000,000 tonnes (60%) to 550,000 tonnes (37%) per year lagging behind of total capacity (refer Figs. 15.1 and 15.2) [1]. This statistics illustration itself that improper utilization of available recourses in India. Thousands of MSME foundry units have tackled the threat of a shutdown. When the government of India is concentrating on employment generation with persuasive attention on skill development, the foundry is a sector that faces thousands of skilled workers leaving this industry to choose alternative means of survival. Also, due to ensure government policy, the next generation of existing foundry unitholders has initiated migrating into high yielding sectors including information technology and others. Thus, a homogeneous approach is needed to long-term development of this foundry sector.

Fig. 15.1

Methodology of project

Fig. 15.2

The Pareto analysis of sales data of the financial year 2017–18

The foundries are underneath lots of pressure because of the increasing sophistication of markets and frequent changes in decisions of customers and international competition. It is evident that there is a priority to the boost performance of the product development process, as the time taken to introduce a new product in the market is critically necessary for competitiveness and long-term survival of the product. So, in this post-capitalist society organizations must perform continuous process improvement in their production processes and be innovative to achieve success. From the past few years, industrial organizations view Continuous Improvement (CI) as a tool to attain a competitive edge through better control of the production process and product quality. The foundries are underneath lots of pressure because of the increasing sophistication of markets and frequent changes in decisions of customers and international competition. It is evident that there is a priority to the boost performance of the product development process, as the time taken to introduce a new product in the market is critically necessary for competitiveness and long-term survival of the product. So, in this post-capitalist society organizations must perform continuous process improvement in their production processes and be innovative to achieve success. From the past few years, industrial organizations view Continuous Improvement (CI) as a tool to attain a competitive edge through better control of the production process and product quality.

Lean Manufacturing (LM) is seen as a major advance method and is widely employed by major industries all over the globe. The goal of LM is to retrenchment the production cost and lowering Cycle Time (CT) by eradicating the Non-value-added Activities (NVA). The concept of LM is to make a production system pull production system. In the pull production system flow of material is driven by downstream as opposed to traditional batch-based production in which production is pushed from upstream to downstream based on a production schedule. The LM suggests that the finished product is the sum of all value-added-activities in the company. But in reality, there are three types of activities arise in the company.

These three types of activities are the following:

• 1. Value-added Activities (VA) (for these activities customer pays).

• 2. Necessary Non-value-added Activities (NVA) which support the value-adding activities.

• 3. Unnecessary Non-value-added Activities (NVA).

15.2 Methodology

A case study is conducted at Shree Steel Casting Pvt. Ltd. Higna, Nagpur, Maharashtra which is a medium-scale foundry. The methodology used is shown in Fig. 15.1.

15.3 Identification of Critical Products Using the Pareto Analysis

The Pareto principles state that in any situation, 20% of inputs or activities, are responsible for 80% of outputs or results. The principal named after an Italian economist, Vilfredo Pareto and it’s also known as 80/20 rule. But the inverse is also true, which means the other 80% of inputs are only generating 20% of results.

It is better to concentrate on products that earn a major percent share of the total revenue of the Shree Steel Castings Pvt. Ltd. These products can be discovered from Pareto analysis as shown in Fig. 15.2. The Pareto analysis identifies that 20% of the input creates 80% of the result. The author has congregated the data by himself and received from the employees of Shree Steel Castings Pvt. Ltd. in terms of two genera, qualitative and quantitative [4].

The qualitative method is used when interviews are conducted and the quantitative method is used when the data is collected and analyzed. In the financial year, 2017–2018 the Shree Steel Castings Pvt. Ltd. has sold 201 different castings with different quantities and earned revenue of ₹273,875,140/-, in which 40 castings has earned revenue of ₹202,288,790/- that is 74% of total revenue. Pareto analysis has been done on sales data of the financial year 2017–2018 and found that 20% of product generated 74% share of total revenue.

15.4 Current State Value Stream Mapping

A value stream is a set of all actions (value-added as well Non-value-added) which might be required to convey a product (or a group of products that use the same resources) through the main flows, beginning with raw material and ending the customer [5]. The Value-added ratio (VAR) defines as value-added activity time to the lead time. The Value Stream Map of ‘Rear-end frame’ shown in Fig. 15.3 is drawn because it is a critical product that shares 10% revenue of total revenue. It is found that lead time (LT) and Value-added ratio (VAR) for ‘Rear-end frame’ is 15,589 min and 24.50%, respectively.

Fig. 15.3

Current state VSM of rear-end frame

15.4.1 Takt Time

Takt time is the maximum amount of time wherein a product needs to be produced so that it will fulfill customer demand. Mathematically takt time is the ratio of available time for production to the production demand [6]. The takt time calculation of ‘Rear-end frame’ is the following:

• $$\begin{aligned}\text{Available production time} &= 7.5\,\text{h}/\text{shift}\times 2\,\text{shift}/\text{day}\times 26\,\text{days}/\text{month} \\ &\quad \times 12\,\text{months}/\text{year}\\ & = 280{,}800\, \hbox{min} \end{aligned}$$

• Customer demand in the past 10 years is shown in Table 15.1

  Table 15.1 Customer demand in the past 10 years

  $$\begin{aligned} \text{Takt time} & = \frac{280{,}800\,(\text{min available time per year})}{33.3\,( \text{average demand per year} )} \\ & = 8432.43\, \hbox{min} /\text{Rear-end frame}. \end{aligned}$$

If lead time and takt time of the product are equal that means on-time delivery of the product to the customer. In this case, a lead time is approximately 15,589 min and takt time is around 8432 min that means takt time very less than lead time. The Shree Steel Castings Pvt. Ltd. recently facing a problem of delivery date mismatching which leads to penalties and customer dissatisfaction.

15.4.2 Kaizen Event

Kaizen, or continuous incremental improvement, refers to a philosophy that is a manner of thinking and behaving. It is about empowering and unleashing the innovative power of individuals who actually do the work, with a purpose to design greater effective and efficient processes [7]. The Kaizen event was conducted at the Shree Steel Castings Pvt. Ltd. for 5 days and Kaizen charter is prepared which is shown in Fig. 15.4. The targeted department was pattern inventory, sand molding and machining shop. In this Kaizen event, four waste (Muda) is identified which is inventory of casting pattern, under processing of vent hole-making operation at molding section, under processing of mold drying process at molding section and waiting at the machine shop. The Kaizen event charter contains every detail of the Kaizen event and some of the details are the following:

• The scope of the Kaizen event is to find out bottleneck activities or activities that are not adding any value to the material.

• In the Kaizen event charter, the areas or particular station is mentioned which contains waste (Muda). In this Kaizen charter targeted areas are pattern inventory, molding shop, marking for machining and machining shop.

• The team member and their belonging department are also mentioned in the Kaizen event charter.

• The metrics are selected to optimize them, in this Kaizen charter mold cycle time, pattern withdrawal time from pattern inventory and machining time is selected to optimize.

• In the end, short term and long-term objectives are mentioned.

Fig. 15.4

Kaizen event charter

15.4.3 Kaizen Event Brainstorming Sheet

The brainstorming sessions have been done with top to bottom level employees and finally brainstorming sheet is prepared which describes corrective action, the feasibility of an idea, complexity to make it possible and possible potential returns illustrated in Table 15.2.

Table 15.2 Brainstorming sheet for Kaizen event

The brainstorming sessions can give birth to new ideas to improve current foundry practices. The brainstorming session has done with the Kaizen team at Shree Steel Casting Pvt. Ltd. As the Kaizen team having members from each department, all kinds of ideas for improvement can be possible.

The best ideas are noted in a sheet that includes the feasibility of the idea, complexity of the idea and potential return out of the idea. Based on the scale of 1–3 these parameters are evaluated. The best possible solutions are mentioned in this table.

15.5 Kaizen Reports

A Kaizen report is a document that illustrates a summary of continuous improvement activities. It is used to share improvements and best practices across an organization, division or group. The Kaizen event report documents that characterize the results after the completion of the Kaizen event. A Kaizen Report is a form that leaflets and recapitulates continuous improvement activities. It is used to share improvements and best practices across the foundry. There are many ways to share Kaizen reports including public display boards, dedicated Kaizen bulletin boards, emails and the intranet. In all cases, Kaizen activities should be written clear and simple so that every team member can easily understand them. Additionally, Kaizen reports with photos and drawings tend to capture more attention.

15.5.1 5S in Pattern Inventory

In Shree Steel Castings Pvt. Ltd., the withdrawal time of casting patterns is significantly high and fluctuating. As shown in figure casting patterns are set haphazardly in pattern inventory. Implementing 5S will solve this problem and preserves the casting pattern. The guideline for 5S implementation is shown in Fig. 15.5. Guidelines for 5S in a pattern inventory is shown in Table 15.3. In the Kaizen event, it is observed that patterns are set haphazardly and unorganized in the inventory which is shown in Fig. 15.6.

Fig. 15.5

Kaizen sheet 1

Table 15.3 5S guidelines for pattern inventory

Fig. 15.6

Pattern inventory at SSCPL

The withdrawal time of pattern for making a mold is uncertain and considerably large because of this messy inventory of patterns.

The Kaizen report 1 is shown in Fig. 15.5 which illustrates the before vs after situation and advantages. The benefits of 5S in pattern inventory is the following:

• The withdrawal time of the pattern will be less as the location of each pattern is documented.

• The material of the pattern is wood and characteristics of wood are to absorb moisture which leads to change in geometry and dimension. Careful preservation and protection can abolish this scenario.

• A well-organized pattern inventory tends to declines the damage of wooden patterns, hence improvement in useful life and lessens pattern repair cost.

• A clean and pleasant work environment enhances the morale of workers towards their job.

15.5.2 Special Purpose Venting Machine

The vent holes are made to escape hot gasses when molten metal is poured in a mold cavity. Making venting is tedious, repetitive and laborious work. As shown in figure Special Venting Machine is designed in SolidWorks2013 which can reduce the time of venting operation and centre distance vent hole will be accurate (refer Fig. 15.7).

Fig. 15.7

Kaizen sheet 2

The venting operation in mold making is time-consuming and laborious. Also, vent holes of cope and drag mismatch their alignment because it made randomly by workers. An unaligned vent hole does not permit to pass hot gasses easily when pouring molten metal into the mold. These unescaped gasses stay in the mold and generate blow holes in casting part. Hence there is a need to design a machine that reduces the cycle time of operation and reduces human intervention. The special purpose venting machine is designed after rigorous brainstorming with the Kaizen team to semi-automate the venting operation.

The special purpose machine can reduce the cycle time of operation and align the vent holes of cope and drag which facilities the hot gases to pass. Here the word ‘special’ is used because this machine is not universal for every mold box (flask), but it covering the domain of 2500 mm × 1800 mm size of the mold box.

In Fig. 15.8 the CAD model of the special purpose venting machine is shown with each component of the machine. This machine contains the structure frame made by 2″ × 2″ of angle which having sliding rod. The array of venting rods is assembled with a piece of wood which reciprocates in sliding rod. The manual handle is provided having rack and pinion arrangement with a wooden piece of an array of venting rods. In Fig. 15.10 the exploded view of the special purpose venting machine is shown.

Fig. 15.8

The CAD model of the special purpose venting machine

The alignment of the vent hole of cope and drag can be achieved by the special purpose machine is shown in Fig. 15.9.

Fig. 15.9

The CAD model of venting rod

The optimum distance between two vent holes is one foot, total 48 vent hole is required for the mold of the rear-end frame. The spring is provided with venting rod to deflect vent rod when it touches the pattern inside the sand mold, the CAD model of venting rod is shown in Fig. 15.10.

Fig. 15.10

The exploded view of the special purpose machine

The alignment of the vent hole of cope and drag can be achieved by the special purpose machine is shown in Fig. 15.11. The optimum distance between two vent holes is one foot, total 48 vent hole is required for the mold of the rear-end frame. The spring is provided with venting rod to deflect vent rod when it touches the pattern inside the sand mold.

Fig. 15.11

A vent hole alignment of cope and drag

The first step is to place the machine on the mold box with the help of Electric Overhead Traveling (EOT) crane and then handwheel is rotated by the worker. The torque applied on handwheel by the worker is transfer via a shaft to pinion and pinion to rack. The rotary motion of pinion is converted in a reciprocal motion of rack. This rack is fabricated with trolley or assembly structure which contains an array of venting rods. The required force to make vent hole is calculated using thumb rule.

The weight of the wooden board, venting rod and structure exerts the force downwards so this force is also calculated and considered here. The force calculation is given below:

• $$\begin{aligned} \text{Weight of Wooden Board} &= \text{Required Volume}\times \text{Density of Teak Wood}\\ &= 0.12\,\text{m}^{3}\times 630\,\text{kg}/\text{m}^{3}\\ &= 72.33\,\text{kg}\end{aligned}$$
• $$\begin{aligned} \text{Weight of Assembly Structure} &= \text{Require Volume} \times \text{Density of Cast iron Angle} \\ & = 0.02\,\text{m}^{3}\times 7200 \,\text{kg}/\text{m}^{3} \\ &= 135.05\,\text{kg}\end{aligned}$$
• $$\begin{aligned} \text{Weight of one venting rod} &= \text{Require Volume}\times \text{Density of Steel} \\ & = 0.000066\,\text{m}^{3}\times 7870 \,\text{kg}/\text{m}^{3}\\ & = 0.52\,\text{kg}\end{aligned}$$
  • $$\begin{aligned} \text{Weight for}\, 48 \,\text{venting rod} &= 0.52\,\text{kg}\times 48\,\text{venting rods} \\ &= 24.96 \,\text{kg}\end{aligned}$$
• $$\begin{aligned} \text{Total Weight} &= \text{Weight of Wooden Board} + \text{Weight of Assembly Structure} \\ &\quad + \text{Weight of}\, 48 \,\text{venting rod}\\ & = 72.33 + 135.05 + 24.96\\ & = 233.89 \,\text{kg}\end{aligned}$$
• $$\begin{aligned} \text{The Gravitational Force} &= \text{Total Weight}\times \text{Gravitation Acceleration} \\ &= 233.89\,\text{kg}\times 9.81\,\text{m}/\text{s}^{2}\\ & = 2294.47\,\text{kg}\,\text{m}/\text{s}^{2} \\ & = 2.30\,\text{kN}\end{aligned}$$
• $$\begin{aligned} \text{Total Force} & = \text{Number of venting rods}\times \text{Cross-section area of venting rod}\,( \text{mm}^{2} )\\ &\quad \times \text{Resisting stress of Sodium Silicate}\,(\text{N}/\text{mm}^{2} ) \\ & = 48 \times\frac{\pi }{4}\,( 5)^{2} \times 10.20 \\ & = 9608.4\,\text{N} \\ & = 9.6\,\text{kN} \\ \end{aligned}$$
• $$\begin{aligned} \text{Required Force} &= \text{Total Force} -\text{The Gravitational Force}\\ & = 9.6\,\text{kN}- 2.3\,\text{kN}\\&= 7.3 \,\text{kN}. \end{aligned}$$

15.5.3 Mold Drying System

The mold drying system can uniformly remove moisture from the sand mold. Moisture-free sand mold can produce defect-free casting parts [8] (refer to Fig. 15.12). The moisture-free mold can produce defect-free castings. The biggest opponent of casting is moisture content in a sand mold. Especially in monsoon and winter season, the moisture content is very high in the atmosphere. In current practice, foundries are using a gas flame torch to heat up the mold to remove the moisture. But in this method moisture remains in the boundary portion of the mold and non-uniform heating of sand mold which leads to defect like blowholes. The mold drying system is designed to eliminate this problem completely. The Kaizen report 3 is shown in Fig. 15.13 which explains the benefits of the mold drying system.

Fig. 15.12

Kaizen sheet 3

Fig. 15.13

The exploded view of the mold drying system

The following are components of the drying mold system:

• Blower

• Heater

• Vacuum Chamber

• Exhaust Plate

In Fig. 15.13 the components of the mold drying system are clearly shown.

The heated air is passed through the entire mold to uniform eradication of moisture. The heater raises the temperature of air blown by a blower which enters to vacuum chamber fitted on the top portion of the sand mold via a pipe. This hot air passes uniformly through entire sand mold and exits from exhaust plate. At the exhaust plate, hot air will be moist air as it absorbs the moist from the sand mold. The working of this system is shown in Fig. 15.14.

Fig. 15.14

The working of the mold drying system

15.5.4 Spray Gun

The coating is done on the mold cavity surface to get a good surface finish of the casted part. Unevenly coated surface will produce a poor surface finish. This problem can be eliminated by using a compressed air spray gun. The benefits of using spray gin are displayed in the Kaizen report 4 (refer Fig. 15.15).

Fig. 15.15

Kaizen sheet 4

15.5.5 LEKIN Scheduling Software

LEKIN is interactive scheduling system for machine environments which is a freely available source. The LEKIN system is capable of scheduling various machine environments: (1) Single machine (2) Parallel machine (3) Flow shop (4) Flexible flow shop (5) Job shop. In this case, study Single machine scheduling is done. This software can compare different machine shop scheduling algorithms like SPT (shortest processing time), LPT (longest processing time), FCFS (First come first serve), General SB Routine, etc. [9] (refer Fig. 15.16).

Fig. 15.16

Kaizen sheet 5

15.5.6 The Big Surface Plate

The marking is done to identify unwanted material in casted parts. For rear-end frame 2 × 1 m surface plate is used for marking and requires time to mark is 60 min. If 3 × 2 m surface plate is used then two rear-end frames can be marked and cycle time will be reduced by 50%. Further details are mentioned in Fig. 15.17 Kaizen report 6.

Fig. 15.17

Kaizen sheet 5

15.6 Future State Value Stream Map

The future state VSM displays the improvements by Kaizen blitz. In the molding shop three improvements are done which are venting operation, mold drying operation and mold coating. Here, the value-adding activities are optimized. In a machine shop, one improvement is done, the waste as await is reduced. The summary of improvements is shown in Table 4.5. The future state VSM is shown in Fig. 15.18

Fig. 15.18

Future state VSM of rear-end frame

15.7 Conclusion

This chapter demonstrates the recommendation of Continuous Process Improvement on a medium-scale foundry. The objective here was to optimize Value-added activities, reduction in necessary Non-value-added Activities and eradication of unnecessary Non-value-added Activities. In current state VSM, Value-added ratio and the lead time was 24.5% and 15,589 min, respectively. After a conducting Kaizen event, Future state VSM was drawn and found that VAR and LT are now 25.44% and 15,374 min, respectively. In Table 15.4 Current state vs future state is summarized with improved productivity. Continuous improvement is a never-ending cycle, more Kaizen events should be conducted for further improvements.

Table 15.4 Current state versus future state