Applying Lean methodologies in a plastic crate manufacturing industry to optimize lead times, reduce wastes, ensuring faster delivery of plastic crates leading to customer satisfaction and as well as an increase in revenue.

1. LEAN IMPLEMENTATION IN A PLASTIC INJECTION MOLDING
INDUSTRY
ISE 251
Managing the Lean Enterprise Improvement Program
COURSE PROJECT
BY
PAVITHRA BALASUBRAMANIAN
PETER KAVITHA STANLEY MOTHA
AISWARYA SHANMUGAM
GAUTAM SINGH

2. Table of Contents
Abstract ................................................................................................................................3
1 INTRODUCTION ..................................................................................................................4
2 PROCESS.............................................................................................................................5
3 DMAIC PROCESS .................................................................................................................7
3.1 DEFINE PHASE..................................................................................................................7
3.1.1 CHARTER ...............................................................................................................................8
3.1.2 SIPOC ....................................................................................................................................8
3.1.3 CTQ TREE.............................................................................................................................10
3.2 MEASURE PHASE............................................................................................................ 11
3.2.1 DATA COLLECTION ...............................................................................................................12
3.2.2 VALUE STREAM MAPPING....................................................................................................13
3.2.3 CONTROL CHART..................................................................................................................15
3.2.4 PARETO CHART....................................................................................................................17
3.3 ANALYZE PHASE............................................................................................................. 18
3.3.1 ROOT CAUSE ANALYSIS ........................................................................................................19
3.3.2 HYPOTHESIS TESTING...........................................................................................................19
3.4 IMPROVE PHASE ............................................................................................................ 21
3.4.1 PDCA...................................................................................................................................22
3.4.2 5S........................................................................................................................................22
3.5 CONTROL PHASE............................................................................................................ 25
4 ECONOMIC ANALYSIS........................................................................................................ 25
5 IMPLEMENTATION OF LEAN AND SIX SIGMA..................................................................... 26
6 ENVIRONMENNTAL EFFECTS ............................................................................................. 27
7 CONCLUSION .................................................................................................................... 27
8 FUTURE RECOMMENDATIONS .......................................................................................... 28
9 REFERENCES ..................................................................................................................... 29
10 APPENDIX....................................................................................................................... 29

3. Abstract
Lean and six sigma methodologies aim at the continuous elimination of waste throughout the production cycle.
This project addresses the implementation of lean and six sigma principles and tools in a small scale plastic
injection molding industry. Our objective is to plan and test several strategies that improve the process efficiency.
A systematic approach was used for the implementation of lean and six sigma principles deploying value stream
analysis (present and future), 5S, SIPOC, Pareto chart, Ishikawa diagram, hypothesis testing on means before and
after improvement. The present and future states of value stream maps were constructed to improve the relevant
production process by looking for opportunities to improve production and to improve the overall process flow.
It was shown that following continuous improvement methodologies benefitted the operation by bringing about
a standardized procedure that was adopted by the plant for hassle free and green operation. It was also learnt that
the injection molding plant can attain 85% efficiency if the lean procedures are followed religiously but in the
course of the nine days where we implemented lean solution we obtained a process improvement of 26.5%.

4. 1) INTRODUCTION
Royal Autoplast is a small-scale plastic injection molding division of the Royal engineering private limited, an
ISO 9001:2008 certified organization established in the year 2005 for heavy fabrication and material handling
equipment’s manufacturing. Currently, Royal engineering private limited is unable to attain their maximum
efficiency owing to mold problems, improper machine setting (PLC settings / all the actuators are controlled via
a SISO PLC loop), labor problems, machine downtime, and raw material shortage. Machine downtime is a result
of operator errors, delayed setup time, maintenance work, mold or machine failure as put forth by the job floor
supervisor. It is well known that quality and customer satisfaction are the key ingredients to success in any
manufacturing industry. The main objective of our project is to develop appropriate strategies that improve
efficiency by means of decreasing cycle time, set-up time and reducing defects which would eventually lead to
better production and efficiency.
We started our project by analyzing the present situation and understanding the process as well as its
prevalent shortcomings from the plant supervisor. Our first step of action was to understand the drivers of the
process deploying the CTQ technique. Production data, as well as the issues faced during that period, was
recorded for a period of 30 days. Root cause analysis was performed to identify the causes and their corresponding
effects. This aided in breaking down the current scenario and analyzing each factor individually to come up with
solutions for the same.
Suggestions such as following standardized procedures, developing preventive maintenance schedules,
following proper process and machine settings, encouraging good quality input supply were imparted to the
organization. Data was collected for 9 days after the implementation of the recommended solutions.
In order to prove that the efficiency did improve after the implementation of our strategy, a two sample
one sided t test was conducted. It was evident that the production had increased by following these techniques
and an improvement in production by 26.5% was noticed. In addition, future improvement strategies were also
suggested.

5. 2) PROCESS
Royal Autoplast primarily produces plastic crates which are a type of plastic container that is usually characterized
by portability and an air-permeable design. They are generally light-weight in their construction to allow for ease
of transportation. However, their lightness does not indicate compromised strength or durability.
Plastic crates can be designed in open or closed configurations. Royal plast produces open crates which weigh
around 3.3lbs, that are lidless and feature a grid pattern through which the crate's contents are visible. Most of the
demand for plastic crates comes from the food service and delivery industries. Dairy products, beverages, meats,
seafood, and all manner of other food items are delivered in plastic food crates. Plastic crates are often found in
general storage and warehousing facilities to organize, store and transport goods. They are often made with
handles and can be stacked or nested for easy storage. The plastic used to make crates comes in a wide variety of
colors, shapes, and sizes and can withstand variable temperatures, impact, and the weight of other loaded and
stacked crates.
Fig 2.1 Plastic crate
Plastic crates are manufactured through a process called plastic injection molding. An injection mold is a machine
that takes the raw plastic product, or stock, and processes it into a usable product. Most plastic injection molders
begin with a collection of stock in a hopper which is directed into a conveyance channel. A screw will turn in the

6. conveyance channel which, combined with heating, helps to liquefy the plastic in preparation for the mold. A
mold is a specially shaped cavity that, when filled with liquefied plastic, gives the plastic its shape. Under strict
temperature control measures, the newly molded plastic can cool and harden. Once hardened, the product is
cleansed of imperfections if present and then shipped or sent to additional processing.
Royal Autoplast has a 600-ton plastic injection molding machine that operates on a 3-shift day, ideally running
for 120 hours a week. The raw materials are purchased every week in quantities of 10 to 15 tons depending on
the production. The production capacity of the machine is 1500 crates/ day. At Royal Autoplast production data
was collected for 30 days (3 shifts per day) along with the opening/closing stock and rejected crates to calculate
the current efficiency of the company. It was found that the company has an efficiency of 37.6% and needs
improvement.
Fig 2.2 PLC of Injection molding machine

7. Fig 2.3 Injection molding machine
The project is ordered as follows.
● Define: comprises project deliverables and measurables’ like SIPOC and CTQ.
● Measure: the current production quantity in the injection molding process through data collection and
visualization using Pareto charts, control charts, and value stream mapping.
● Analyze phase - Comprises root cause analysis and hypothesis testing to show our results.
● Improvement phase - Explains the application of PDCA and 5S with respect to this project.
● Control phase - Established a process review mechanism and suggested improvements that benefit the
business.
3) DMAIC PROCESS
3.1 DEFINE PHASE
During the Define phase of the Lean improvement project, our goal is to have a basic understanding of the process,
validating business opportunity and identifying critical to quality variables.

8. 3.1.1 CHARTER
A charter document sets the ground rules and expectations for the project, in a contract between the management
and team. The management provides the resources for project development and execution, and the project team
carries out the plan. In our charter, we developed an overview and purpose of the project, defined the objective
and scope, described the time frame and also mentioned the project deliverables, importance and also the project
measures that will be used to judge the project success and to identify future improvement opportunities
3.1.2 SIPOC
SIPOC stands for Suppliers, Inputs, Process, Outputs and Customers. Sometimes “Requirements” is also added
as an additional feature. It can be defined at every level of the organization and for almost every type of product,
service, or information transfer. By investigating the SIPOC chart we have a better understanding of the process,
the variables to be measured for performance assessment and spot out areas that require improvement. The chart
provides a simple, ‘at-a-glance’ view of the process flow starting from raw material inflow to package and
shipment to customers.
The main functions of SIPOC are:
● Defines project boundaries (i.e., starting and ending points)
● Describes where to collect data
● Identifies suppliers and customers (i.e., stakeholders who need to be considered as part of your
project)
● Helps to support process thinking within your organization.

9. A regular supply of raw materials is obtained on a weekly basis week from United Industries and M. K Polymers.
The inputs are the colored plastic pellets that are fed into the injection molding machine and the output is the
plastic crate. The critical process measures that affect the overall efficiency of the process is identified.
Fig 3.1 SIPOC Diagram

10. 3.1.3 CTQ TREE
CTQ trees (critical-to-quality trees) are the key measurable characteristics of a product or process
whose performance standards or specification limits must be met to satisfy the customer. They align
improvement or design efforts with customer requirements.

11. Fig 3.2 CTQ Tree
In the CTQ diagram, we have identified the critical to quality parameters that improve the efficiency
of the process. The drivers essential to back up the process efficiency as well as the critical to quality
parameters that facilitate efficient performance of the drivers are also listed. Proper machine settings,
quality of the raw materials, mold quality and efficient labor force are identified as the main drivers to
improving process efficiency. Proper injection molding machine setting is backed up with a
temperature setting of 120-200 degree Celsius and a pressure setting of 1000-5000 psi. The high quality
of the incoming raw material is maintained by enforcing incoming quality checks and maintaining
quality suppliers. Mold cavities are also cleaned periodically to produce good quality craters. Finally,
technically skilled laborers who are able to perform consistently at a standard pace throughout the
assigned shift are responsible for contributing to the efficient process.
3.2 MEASURE PHASE
In the measured phase, we focus on gathering information about the opening stock in finished goods,
production quantity per day, rejection quantity, approved quantity and closing stock in finished
goods. The Measure phase involves numerical studies and data analysis.

12. 3.2.1 DATA COLLECTION
Data Collection is a critical step for statistical analysis and is an essential part of the project. In this section, we
created a baseline of the performance by collecting data in the existing situation and then compared it to the
process performance after we implement the improvements.

13. Table 1.1 Production quantity data before Lean implementation
3.2.2 VALUE STREAM MAPPING
Value stream mapping is a lean manufacturing technique is used to analyze and design the material / information
flow. It is also known as the material and information flow mapping. This includes not only the production process
but involves procurement, quality check as well reports collection from management information systems.
Takt Time = Available Daily Production Time (Hrs.)/ Required Daily Output(Nos)
= 24*3600/1500 = 57.6 sec/unit
VSM Before Implementing Improvement Phase:

14. Fig 3.3 VSM before state
VSM After Implementing Improvement Phase:

15. Fig 3.4 VSM after state
Necessary information was obtained from the plant personnel to develop the Value stream map. The business
process starts with purchase order release. This is followed by raw material procurement, which is ordered on an
average of 10 tons / week based on the available inventory. The suppliers for raw materials are United industries
and MK Polymers. The incoming raw material undergoes a quality check by a quality engineer. From here
commences the manufacturing process. The pressure, temperature, cooling rate are set in the PLC. The labor loads
the raw material into the hopper/loader. The machine runs continuously unless interrupted by various reasons like
power failure, machine problem, labor fault etc. The machine takes around 60secs to convert from plastics pellets
to the final product (semi-finished which needs trimming). So the process time for a single crate is 65 secs. The
end product undergoes a quality check by the supervisor, who inspects the crates randomly for scratches or any
other defects. The make to stock finished goods is dispatched based on the orders received.
The Ishikawa diagram shows that raw material and production process had to be improved and hence Kaizen was
implemented to make sure that frequently occurring problems were reduced. The total time comprising the value
added time and the non-value added time was reduced by 23 seconds after introducing kaizen principles.
3.2.3 CONTROL CHART
The control charts or the process-behavior charts are used to determine if a business process is in a state of
statistical control. The objective of the control chart is to find any "special" causes of variation as well as to
reflect on the process improvements that have been made.
The production data was collected on a daily basis for 30 days and an I-MR chart was constructed to analyze the
current performance ie., the common and assignable causes.

16. Fig 3.5 X-bar Chart for before data
Fig 3.5 MR Chart for before data
From both the x chart and MR chart, the production seems to be in control. Once the process efficiency has been
improved, the process was monitored to ensure that the production continues to be in control.

17. Fig 3.6 X-bar Chart for after data
Fig 3.5 MR Chart for before data
3.2.4 PARETO CHART

18. The Pareto chart provides a graphic depiction of the Pareto principle, a theory which emphasizes that 80% of the
output in a given situation or system is produced by 20% of the input. The graph clearly reveals which factors
have the greatest impact and where attention is likely to yield the greatest benefits.
Fig 3.7 Pareto Chart
As it is shown above in the Pareto Chart, we can see that the problem due to old mold has a major effect
on product output followed by machine and PLC settings, labor problems, machine parts/maintenance
problems and raw material quality issues. Therefore, focusing on these factors and taking the necessary
measures to improve them eventually leads to the overall efficiency of the company.
3.3 ANALYZE PHASE
In the Analyze Phase, we analyzed the root causes leading to reduced efficiency. We sought out the help of the
supervisor in understanding the production process starting from raw material procurement to the inspection of
the finished product. Root cause analysis was followed by hypothesis testing, where we concluded that after
implementing the new improved process techniques, we were able to improve the efficiency from 37.6% to 60%.

19. 3.3.1 ROOT CAUSE ANALYSIS
Fig 3.8 Fishbone Diagram
To identify the cause of the effect the brainstorming session is conducted in the company by the team members
from different functional departments in the company that are knowledgeable and have experience in plastic
injection molding process to obtain the cause of the defects. The company uses the cause and effect matrix to
prioritize the main factors that result in the problem by scoring the cause and effect relationship of the problem
and prioritize the score in the Pareto chart that minimizes the factor to 5 main factors.
3.3.2 HYPOTHESIS TESTING
Hypothesis testing was conducted to compare the production data daily before and after implementing
the lean and six sigma techniques. The production data before implementing the lean techniques was

20. collected for a period of 4 weeks and the data after implementing the lean techniques was collected for
a period of 10 days. Since the number of weeks was unequal, we chose one-sided t-test with unequal
variances for conducting the test.
The one sample T test conducted before the process improvement techniques were deployed is shown
below. It was done in an attempt to understand if the process achieved at least 50% of its efficiency.
Maximum production per day was about 1500 craters and 50% of it summed up to 750 craters. The
hypothesis test conducted to study the efficiency of the system is:
Ho: Mu = 750
H1: Mu < 750
Since the p-value = 0.0001 < 0.05 and the t value = -4.70 < t critical = 1.699, we reject the null
hypothesis. Hence, we conclude that the plant achieved lesser than 50% of its efficiency at ⍺ = 0.05
level of significance.

21. A hypothesis test was conducted after the improvement phase to justify the improvement brought about
in the process deploying lean techniques. The results of the hypothesis testing are as follows.
Ho: Mu1 – Mu2 = 0
H1: Mu1 – Mu2 < 0
Since the p-value = 0.0001 < 0.05 and the t value = -6.86 < t critical = 1.714, we reject the null
hypothesis. Hence we conclude that the plant achieved better efficiency after deploying lean techniques
at ⍺ = 0.05 level of significance.
3.4 IMPROVE PHASE
The goal of the DMAIC Improve phase is to identify a solution to the problem that the project aims to
address. This involves brainstorming potential solutions, selecting solutions to test and evaluating the
results of the implemented solutions. Often a pilot implementation is conducted prior to a full-scale
rollout of improvements.

22. 3.4.1 PDCA
PDCA (plan–do–check–act or plan–do–check–adjust) is an iterative four-step management method
used for the control and continuous improvement of processes and products. We applied the PDCA for
improving process efficiency.
Fig 3.9 PDCA Cycle
3.4.2 5S
The 5S tool describes how to organize a work space for efficiency and effectiveness by identifying and
storing the raw materials and finished goods used, maintaining a clean and hygienic work space and
goods, and sustaining the new order.
Sort: Proper settings for pressure, the temperature was not maintained which resulted in a lot of
rejection pieces. The shift operators were requested to follow up with the supervisor before the start of

23. their shift on the proper temperature and pressure control targets to be maintained in the PLC. The raw
material was stored in a highly ventilated storeroom that led to dust accumulation. This contamination
of raw material with dust resulted in poor quality. Hence the storeroom personnel was requested to seal
the room properly with sufficient ventilation and exhaust. We suggested them to appoint an employee
to supervise all these activities on a daily basis.
Set in Order: A preventive maintenance schedule was created and displayed in the employee
cafeteria. This allowed the employees to view the maintenance schedules for various machines that
were to be done the following day. PLC’s were calibrated once a year at Royal Auto Plast. The
supervisors were requested to calibrate the settings of the PLC for offsets at a much frequent pace as
the control settings, as well as the control tuning, varies with each batch of raw material as well as their
moisture and quality content. The equipment maintenance log, as well as the daily maintenance log,
are shown below.

24. Fig 3.10 Equipment maintenance log
Fig 3.11 Daily Maintenance log
Shine: The store had no proper cleaning schedule for the storage facility as well as the job floor that
housed the injection molding equipment. A cleaning schedule once a week was implemented which
the company was requested to follow regularly in the future. This helped the company to maintain a
clean and hygienic environment and manufacture quality products.
Standardize: Raw material quality received every morning was not inspected before racking up in the
shelves. We suggested that the employee receiving the fresh raw material batch in the morning should
be trained to inspect the overall quality of the raw material before transporting it to the storage yard.
Good quality suppliers were narrowed down and long term procurement agreements were placed with
them. Injection molds were checked for wear and tear at periodic intervals. New mold replacement was
recommended once the old mold gets past its guaranteed lifetime. This ensured lesser rejection of

25. craters. It was recommended that training is imparted to all the operators to follow a standardized
procedure at-least once in 6 months. The supervisor of a particular shift was assigned the duty of
making sure that all the employees followed the regular standardized routine for a hassle free
production environment.
Sustain: Maintaining the standard pressure settings at 1951 psi, screw rotation at 130 rpm and
temperature settings at 164 degree Celsius ensured that the cycle time (value added time) reduced
significantly rather than following haphazard settings. The owner was asked to encourage more ideas
of improvement from employees as well as pay keen attention to customer feedbacks. This increases
the quality of service provided.
3.5) CONTROL PHASE
Since the project is still in its pilot phase, control, and continuous monitoring is out of scope.
4) ECONOMIC ANALYSIS
Economic analysis in our project is analyzing improvements in revenue before and after deploying lean
principles. The production quantity in numbers before and after deploying lean principles as well as
the selling price is shown. The improvements in revenue are tabulated below.

26. Table 1.2 Economic analysis
5) IMPLEMENTATION OF LEAN AND SIX SIGMA
Lean and six sigma principles were deployed to improve the efficiency of the process. The development process
for the lean solution is described below.
Application of lean and six sigmas in a plastic injection molding plant
Lean and Six Sigma are powerful tools, which aid in improving business efficiency and effectiveness. Steps
involved in the application of the principles of Lean and Six Sigma to a plastic injection molding plant are as
follows:
 Focus should be on customers.
 In-depth understanding of the processes in the injection molding plant can be done through value stream
mapping. Value stream mapping is a lean management tool, which is used to analyze the current state of
the process and design a future state.
 The process flow of the system should be managed and improved.
 Proper removal of waste and non-value added steps should be done within the system.

27.  The decision should be made on the basis of facts, which helps in reduction of variability.
 Operators should be involved in problem solving and equipped appropriately.
 Improvement activity should be performed in an organized way.
6) ENVIRONMENNTAL EFFECTS
In the injection molding process, plastic crates that were condemned due to poor quality was disposed of as waste.
This resulted in a severe penalty from the pollution control board as disposal of non-degradable plastic was
hazardous to the environment. By reducing the rejects quantity and improving the overall efficiency of the process
we contribute to a reduction in waste disposal which is a positive environmental effect of our solution. In addition,
we suggest the installation of a grinding machine that would convert the defective pieces to shards of plastic
which can then be used to produce second or third grade plastic crates (sold to customers who are not particular
or whose processes do not demand high quality plastic) reduce disposing of defective pieces.
7) CONCLUSION
The objective of this project was to study the plastic injection molding process, identify the loopholes in the
process from the supervisor of the job floor and deploy lean methods (DMAIC) - continuous improvement
technique to improve the process. Root causes for the problems analyzed were identified deploying the fishbone
diagram for which improvement solutions were developed using value stream mapping, 5s, and hypothesis
testing. Data was collected for a month from which control charts were developed to identify the common and
assignable causes. The PDCA cycle, as well as 5s, was done to suggest improvements that would help improve
the efficiency of the process. Economic analysis that ensured improvements in the process was shown. It was
shown that following continuous improvement methodologies benefitted the operation by bringing about a
standardized procedure that was adopted by the plant for hassle free and green operation. It was also learnt that

28. the injection molding plant can attain 85% efficiency if the lean procedures are followed religiously but in the
course of the nine days where we implemented lean solution we obtained a process improvement of 26.5%.
Data after deploying Lean
Table 1.3 Data after Lean implementation
8) FUTURE RECOMMENDATIONS
 We suggested Royal Autoplast to follow the standardized procedures given to them stringently like
imparting technical training to the operators every 6 months, make a visual display of the process and
the process settings like process flow chart to help labors avoid making process errors and keep a
maintenance checklist to log the daily maintenance activities.
 Replace the old mold with a new mold to further improve the efficiency of the process. Currently, mold
issue contributes to the maximum rejection of the finished products.
 We suggested Royal Autoplast to use Plastic Grinders to reduce the plastic crates disposal.
 Time studies can be conducted to suggest appropriate fatigue allowances to the employees.

29.  We suggested Royal Autoplast to also consider other suppliers who provide high quality raw materials.
9) REFERENCES
[1] Michael Brassard, Lynda Finn, Dana Ginn, Diane Ritter, “Six Sigma Memory Jogger II: A Pocket
Guide”
[2]Rosnah M.Y,Othman A,”Lean Manufacturing Implementation in a Plastic Molding Industry”
[3] http://en.wikipedia.org/wiki/PDCA
10) APPENDIX