代写 lean productionand Six Sigma

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代写 lean productionand Six Sigma 
Chapter Eight

Discussion Questions

1. Explain why lean productionand Six Sigma are so important to successful supply chain management.

Ans.: Use of the term lean has begun to replace use of the term JIT, and is associated with the Toyota Production system. Lean is broader, although closely related to JIT, and describes a philosophy incorporating tools that seek to economically optimize time, human resources, assets, and productivity, while improving product and service quality. In the early 1980s, these practices started making their way to the Western world, first as JIT and then today, as lean production or lean manufacturing. Lean production has evolved into a way of doing business for many organizations. Quality assessment and improvement is a necessary element of lean production. First, as the process of waste elimination begins to shrink inventories, problems with human resource requirements, queues, lead times, quality and timing are typically uncovered both in production and with inbound and outbound materials. Eventually, these problems are remedied, resulting in higher levels of quality and customer service. Second, as the drive to continuously reduce throughput times continues, the need for a continuingemphasis on improving quality throughout the productive system results in the need for an overall quality improvement or Six Sigma program. Six Sigmastresses a commitment by the firm’s top management to enable the firm to identify customer expectations and excel in meeting and exceeding those expectations. Since environmental changes and changes in technology and competition cause customer expectations to change, firms must then commit to a program of continual reassessment and improvement; this, too, is an integral part of Six Sigma quality. Thus, to achieve the primary objectives of low cost, high quality, and reduced lead times, supply chain management requires the use of lean and Six Sigma thinking throughout the supply chain.

2. Briefly explain the primary concerns and objectives of lean production.

Ans.: Lean production emphasizes reduction of waste, continuous improvement, and the synchronization of material flows from within the organization and eventually including the organization’s immediate suppliers and customers. In many respects, then, supply chain management seeks to incorporate lean elements across the entire supply chain.

3. How is lean production associated with JIT?

Ans.: The term Just-In-Timewas originally associated withToyota managers like Mr. TaiichiOhno along withhis kanban system, encompassing continuous problem solving to eliminate waste.Use of the term lean has begun to replace use of the term JIT, and is associated with the Toyota Production system. Lean is broader, although closely related to JIT, and describes a philosophy incorporating tools that seek to economically optimize time, human resources, assets, and productivity, while improving product and service quality. In the early 1980s, these practices started making their way to the Western world, first as JIT and then today, as lean production or lean manufacturing. Lean production has evolved into a way of doing business for many organizations.

4. What does the Toyota Production System have to do with JIT and lean production?

Ans.: The term lean productionessentiallyrefers to the Toyota Production System in its entirety, which was created by several of Toyota’s key executives over a number of decades. JIT is an integral part of the TPS, using kanbans to manage the flow of materials.

5. What person or people at Toyota is (are) most responsible for the development of the JIT concept?

Ans.: Kiichiro Toyoda spent a year in Detroit studying Ford’s manufacturing system and others, and then returned to Japan, where he adapted what he learned to the production of small quantities of automobiles, using smaller, more frequently delivered batches of materials. This later was referred to as the Just-in-Time system within Toyoda. Mr. EijiToyoda, nephew of Sakichi, began working at Toyoda in 1936 and was named managing director of the renamed and reorganized Toyoda Automotive Works in 1950. Eiji too, traveled to Detroit to study Ford’s automobile manufacturing system and was particularly impressed with their quality improvement activities, most notably their employee suggestion system. Back in Japan, he implemented the concepts he had seen in the United States and this became the foundation of what was later referred to as the Toyota Production System.

6. Why was Toyota’s first U.S. car such a failure? What did they learn from this experience?

Ans.: Their first U.S. car was the Toyopet Crown. While popular in Japan, the car’s quality, speed, and styling problems resulted in sales of only 288 units in 14 months in the U.S. Consequently, Toyota withdrew from the U.S. market, to better analyze U.S. consumers and their demands for reliability. “No detail was unimportant, and they paid very close attention to customers,” says Dave Cole, chairman of Michigan-based Centre for Automotive Research. In 1965, the Corona was introduced in the U.S. and by 1972 U.S. sales had reached 1 million units.

7. Who was responsible for first using the term “lean” as it related to the auto industry?

Ans.: Actually, the term lean production did not originate at Toyota. It was first used in a benchmarking study conducted by the International Motor Vehicle Program (IMVP) at the Massachusetts Institute of Technology. The IMVP conducted a global automobile quality and productivity benchmarking study which culminated in the book, The Machine that Changed the World wherein the elements of lean production and the benchmarking results were presented. The word “lean” was suggested because the Japanese facilities the benchmarking study when compared to their U.S. counterparts, used half the manufacturing labor, half the space, and half the engineering hours to produce a new automobile model in half the time.

8. How is lean thinking associated with supply chain management?

Ans.: Simply put, the objective of supply chain management is to balance the flow of materials with customer requirements throughout the supply chain, such that costs, quality, and customer service are at optimal levels. Lean production emphasizes reduction of waste, continuous improvement, and the synchronization of material flows

from within the organization and eventually including the organization’s first-tier suppliers and customers. In many respects, then, supply chain management seeks to incorporate leanthinking across the entire supply chain.

9. Use an example to show how you could use lean thinking with a supplier and a customer.

Ans.: Reduce purchase lot sizes with a supplier and give them more business so they can afford to make more frequent deliveries. Negotiate with a customer to deliver your firm’s product more frequently to their location.

10. What is yokoten, and what does it have to do with lean thinking?

Ans.: Yokoten is a Japanese term meaning “across everywhere”. In lean terminology, it is used to mean the sharing of best practices. Lean firms are using yokoten to reach out to closely-linked suppliers and customers to make the supply chain leaner.

11. Which do you think is the most important element of lean thinking?

Ans.: Varies, but waste reduction will probably be mentioned the most.

12. What are the seven wastes, and can you discuss these in terms of a business you are familiar with?

Ans.: See Table 8.3.

13. What are the five-Ss? Apply the five-Ss to improve on how you should be completing your daily homework or study assignments.

Ans.: See Table 8.4.

14. What are the advantages of close supplier and customer relationships, when practicing lean?

Ans.: Quite commonly, firms must hold safety stocks of purchased products because their suppliers’ delivery times are inconsistent or the quality of the purchased goods do not always meet specifications. Internally, extra work-in-process (WIP) inventories are stored as a way to deal with temperamental processing equipment or other variabilities causing processing problems. On the distribution side, firms hold stocks of finished goods in warehouses prior to shipment to customers, in some cases for months at a time, to avoid stockouts and maintain high customer service levels. Holding high levels of these inbound, internal and outbound inventories costs the firm money while not addingmuch, if any value to the products or the firm; thus, they are considered wastes.When the focal firm, its suppliers, and its customers begin to work together to identify customer requirements, remove wastesand reduce costs, while improving quality and customer service, it marks the beginning of lean supply chainrelationships.

15. What are the advantages and disadvantages of making small, frequent purchases from just a few suppliers? How do we overcome the disadvantages?

Ans.: Advantages--This serves to reduce average inventory levels. More frequent deliveries though, mean higher inbound transportation costs; to reduce these costs, suppliers are often required to distribute product from warehouses or production facilities located in close proximity to the buyer. By using just a few good suppliers though, they get lots of the firm’s business, which makes them willing to absorb dome of the higher transportation costs.

16. Why should lean layouts be visual?

Ans.: Lean layouts are very visual, meaning that lines of visibility are unobstructed, making it easy for operators at one processing center to monitor work occurring at other centers. In manufacturing facilities, all purchased and WIP inventories are located on the production floor at their point of use, and the good visibility makes it easy to spot inventory buildups as bottlenecks occur. When these and other production problems occur, they are spotted and rectified quickly. The relative closeness of the processing centers facilitates teamwork and joint problem solving and requires less floor space than conventional production layouts.

17. What are manufacturing cells, and why are they important in lean production?

Ans.: Manufacturing cellsare designed to process similar parts or components, saving duplication of equipment and labor, as well as centralizing the area where units of the same purchased part are delivered. In many cases these manufacturing cells are U-shaped to facilitate easier operator and material movements within the cell. In assembly line facilities, manufacturing cells are positioned close to the line, feeding finished components directly to the line instead of delivering them to a stock area where they would be brought back out when needed. Manufacturing cells are themselves small assembly lines and are designed to be flexible, allowing machine configurations to change as processing requirements dictate.

18. Reducing lot sizes and increasing setups are common practices in most lean production settings. Why?

Ans.: To reduce inventory levels and hence also improve quality.

19. What is the origin of the term kanbans and why are they used in lean systems?

Ans.: Kanban is a Japanese word for card, and in lean facilities it has come to mean a signal. When manufacturing cells need parts or materials, they use a kanban to signal their need for these things from the upstream manufacturing cell, processing unit, or external supplier providing the needed material. Ideally, parts are placed in standardized containers, and kanbans exist for each container.

20. Why are lean systems also known as pull systems?

Ans.: In lean systems, nothing is provided until a downstream demand occurs. That is why a lean system is known as a pull system.

21. What is kaizen, and why is it so important for successful lean production? What is a kaizen blitz?

Ans.: To make the lean system work better, employees continuously seek ways to reduce supplier delivery and quality problems, and in the production area they improve movement problems, visibility problems, machine breakdown problems, machine setup problems, and internal quality problems. In Japanese manufacturing facilities, this is known as kaizen. A kaizen blitzis a rapid improvement event or workshop, aimed at finding big improvements.

22. Discuss the linkage between lean systems and environmental sustainability.

代写 lean productionand Six Sigma Ans.: Many organizations have realized the positive impact lean production can have on their environmental performance—adopting lean practices reduces the cost of environmental management and then leads to improved environmental performance. Further, lean production increases the possibility that firms will adopt more advanced environmental management systems, leading to yet further improvements in environmental performance.

23. Describe Six Sigma’s origins and the main parties involved. Why is the concept called “Six Sigma”?

Ans.: Six Sigma quality,many times simply referred to as Six Sigma, was pioneered by global communications leader Motorola in 1987, and is a statistics-based decision-making framework designed to make significant quality improvements in value-adding processes. Six Sigma (with capital S’s) is a registered trademark of Motorola. At the time, a senior staff engineer at Motorola named Mikel Harry formed a team of engineers to experiment with problem solving using statistical analyses, and this became the foundation for Six Sigma. Richard Schroeder, vice president of customer service at Motorola, heard about Harry’s work, and applied the methodology to his work at Motorola. Soon, both groups were announcing large reductions in errors and various costs. It is called Six Sigma to refer to the very small portion of the standard normal distribution that is beyond six standard deviations from the mean.

24. How is Six Sigma different from TQM?

Ans.: The Six Sigma concept though, is not just concerned with statistics. It is a broad improvement strategy that includes the concepts and tools of total quality management (TQM), a focus on the customer, performance measurement, and formal training in quality control methods. Six Sigma embodies an organizational culture wherein everyone from CEO, to production worker, to frontline service employee is involved in quality assessment and improvement. Six Sigma is proactive in nature and seeks to permanently fix the root causes of problems, instead of repeatedly spending time and money tinkering with and patching-up processes as problems occur in the business. In Six Sigma, sources of process variation are sought out and remedied prior to the time these variations can cause production and customer satisfaction problems.

25. Describe the Lean Six Sigma approach.

Ans.: The melding of lean production and Six Sigma quality practices. After the dot-com bust of 2001, many companies began considering implementing some form of lean, Six Sigma, or combination approach.

PROBLEMS

1. HeaveyCompressors uses a lean production assembly line to make its compressors. In one assembly area, the demand is 100 parts per eight-hour day. It uses a container that holds eight parts. It typically takes about six hours to round-trip a container from one work center to the next and back again.Heavey also desires to hold 15 percent safety stock of this part in the system. How many containers should Heavey Compressors be using?

Ans.: # of containers = CSDT)1(+= [(100/8)(6)(1.15)]/8 ≈ 8 7/8 or 11 containers.

2. Using the information from problem 1, if Heavey desires to reduce their number of containers to eight, how does this impact the system? What has to change, if it assumed that demand, container size, and safety stock percentage don’t change, and what is that change?

Ans.: Time, T, has to change. Since # of containers = CSDT)1(+, if 8=[(100/8)(T)(1.15)]/8, then T = 64/(14.375) = 4.45 hrs or 4 hrs and 27 minutes.

3. EakinsEnterprises makes model boats, and it is switching to a lean manufacturing process. At one assembly area, Eakins is using one part container that holds 250 parts, and it wants the output to be approximately 100 finished parts per hour; they also desire a 10 percent safety stock for this part. How fast will the container have to make it through the system to accomplish this?

Ans.: # of containers = CSDT)1(+, or 1 = [(100)(T)(1.1)]/250, or T ≈ 3.

4. Jim Corner, owner of Corner Bike Rentals, wants to start analyzing his company’s quality. For each bike rental, there are four types of customer complaints: bike not working properly, bike wrong size, bike uncomfortable, and bike broken during operation. During the past week, his company rented 280 bikes. He received 26 total complaints.

a. What is his company’s DPMO for the past week?

Ans.: DPMO = ))((unitsofnumberunitperOFDdefectsofnumber (1,000,000) = [26/4(280)]1000000 = 23,214 per million rentals.

b. What is their Six Sigma operating level?

Ans.: slightly less than 3.5, from Table 8.5.

5. Julie works at Gentry Flower Shoppe, which operates at the 4 sigma level, with about 6,000 DPMO, which was determined recently. At that time, Gentry was found to have 1500 total defects. They want to improve to the 5 sigma level, or about 500 DPMO. Assuming nothing else changes, what would their new total defect level have to be?

Ans.: DPMO = ))((unitsofnumberunitperOFDdefectsofnumber (1,000,000); 6000 = (1500/X)(1MM), so X = 250,000; then 500 = (X/250,000)(1MM); X = 125 defects

6. The following sample information was obtained by taking four doughnuts per hour for 12 hours from the Fawcett Bakery’s doughnut process and weighing them:

Hour Weights (grams) Hour Weight (grams)

1 110, 105, 98, 100 7 89, 102, 101, 99

2 79, 102, 100, 104 8 100, 101, 98, 96

3 100, 102, 100, 96 9 98, 95, 101, 100

4 94, 98, 99, 101 10 99, 100, 97, 102

5 98, 104, 97, 100 11 102, 97, 100, 101

6 104, 97, 99, 100 12 98, 100, 100, 97

For the data shown above,

a. Find the x and Rfor each sample.

Ans.:

hour x R hour x R

1 103.3 12 7 97.8 13

2 96.3 25 8 98.8 5

3 99.5 6 9 98.5 6

4 98.0 7 10 99.5 5

5 99.8 7 11 100.0 5

6 100.0 7 12 98.8 3

b. Find the xand R for the 12 samples.

Ans.: x= 99.2 and R = 8.4

c. Find the 3-sigmaUCL and LCL for the mean and range charts.

Ans.: For n = 4, A2=.729, D4=2.282, D3=0, then UCLx=99.2+.729(8.4) = 105.3,

LCLx=99.2 - .729(8.4) = 93.1, UCLR=2.282(8.4) = 19.2, LCLR = 0

d. Does the process look to be in statistical control. Why?

Ans.: mean--OK; range--not OK

7. Through process measuring of a number of pizza delivery times, Mary Jane's Pizzeria finds the mean of all samples to be 27.4 minutes, with an average sample range of 5.2 minutes. They tracked four deliveries per hour for 18 hours to obtain their samples.

a. Is this an example of variable or attribute sampling data?

Ans.: Variable data

b. Find the UCL and LCL for both the x andR charts.

Ans.: UCLx = 27.4 + .729(5.2) = 31.2; LCLx = 27.4 - .729(5.2) = 23.6

UCLR = 2.282(5.2) = 11.9; LCLR = 0.

8. A company produces 8-pound bags of rice. As shown below, it gathered 5 sampleswith 6 bags in each sample for quality control purposes. The weights of each of the bags are listed below.

Bags in each sample

Sample12345617.988.348.027.948.447.6828.338.228.088.518.418.2837.897.777.918.0487.8948.248.187.838.057.98.1657.878.137.927.998.17.81

a. Find the x andR for each of the five samples.

Ans.:x1=8.07, R1=0.76; x2=8.31, R2=0.43; x3=7.92, R3=0.27; x4=8.06, R4=0.41; x5=7.97, R5=0.32

b. Find the xandR.

Ans.: x= (8.07+8.31+7.92+8.06+7.97)/5=8.07; R=(.76+.43+.27+.41+.32)/5=.44

c. Find the 3-sigma UCL and LCL for the mean and range charts.

Ans.: UCLx = x + A2R=8.07+0.483(0.44)=8.28 (get A2 from Table 8.10)

LCLx = x – A2R=8.07 – .483(.44)=7.86;

UCLR= D4R=2.004(.44)=0.882; LCLR = D3R= 0(.44) = 0.

d. Does the process look to be in statistical control. Why/why not?

Ans.: no points above UCLx, no points below LCLx, nothing above UCLR. 4 of 5 pts. below R. Most points very close to x. With only 5 samples, it is very hard to tell about statis. control.

9. Ten customers per hour were asked by the cashier at Stanley’s Deli if they liked their meal, and the fraction that said “no” are shown below, for a 12-hour period.

Hour Fraction Defective Hour Fraction Defective

1 0 7 .1

2 .2 8 0

3 .4 9 0

4 .1 10 .2

5 .1 11 0

6 .2 12 .1

For the data shown above, find

a. P.

Ans.: 1.4/12 = .1167

b. σP.

Ans.: SQRT[.1167(.8833)/10] = .1015

c. The 3-sigmaUCL and LCL.

Ans.: UCL = .1167 + 3(.1015) = 0.42; LCL = .1167 – 3(.1015) = 0.

d. Does customer satisfaction at Stanley’s appear to be in statistical control? How could we improve the analysis?

Ans.: Yes—4 samples above the mean, 6 below, none out of CLs. To improve, could go back to hour 3 records to see what happened; could go through statistical process control improvement efforts—check sheets, Pareto analysis, fishbone dia., improvement, back to checking again.

10. A company collects 20 samples with 100 eggs in each sample. They want to construct a Pchart to track the proportion of broken eggs in each sample. The table below shows the number of defective eggs per sample.

SampleEggsSampleEggsSampleEggs138615525941603310917244112186521261926413520172141TOTAL72

a. Determine P.

Ans.: 72/2000 = 0.036 or 3.6%

b. DetermineσP.

Ans.: σP = ()()

n

PP−1= = 0.019

c. Determine the 3-sigma UCL and LCL.

Ans.: UCL = .036 + 3(.019) = 0.093; LCL = .036 – 3(.019) = 0

d. Does the egg process appear to be in statistical control?

Ans.: 1 pt very close to UCL; half above and below P; probably in control.

11. Roberto’s Steakhouse tracks customer complaints every day and then follows up with their customers to resolve problems. For the past 30 days, they received a total of 22 complaints from unhappy customers. Using this information, calculate

a. c.

Ans.: 22/30 = 0.733

b.The 3-sigma control limits.

Ans.: UCL = .733 + 3(SQRT.733) = 3.3; LCL = .733 – 3(SQRT.733) = 0
代写 lean productionand Six Sigma