1. Case descriptionTom Pulling Toys
is a major global manufacturer of educational toys for children. The
company produces over two hundred different types of toys in its plant in China and sells
them through most of the major retailers in Europe and the USA. The company’s head office
is situated in London. In recent years the competition from Chinese manufacturers has
reduced the company’s revenue and profits. To reverse this trend the CEO of the company
has initiated a new company-wide quality and efficiency improvement plan. The aim is to
identify and satisfy customer needs more effectively and to reduce waste at every level of the
organisation. As part of this plan, the company has recently adopted a number of quality
management tools associated with the Total Quality Management (TMQ). One of these tools
is Statistical Process Control (SPC) that the company wants to use to measure the
performance of their manufacturing processes to ensure that the processes meet the required
standards.
Statistical Process Control (SPC) is currently being implemented at the company’s plastic
toy factory in China. Mr John Smith is the new Quality Manager of the plant and is
responsible for implementing the new quality strategy and overseeing the application of
SPC. After careful planning and preparation, Mr Smith has selected a doll manufacturing
line for the trial application of the SPC. The decision is based on the recent number of high
customer returns due to inconsistent colouring and/or the size of the dolls. He has trained
you, as the unit’s production manager, to supervise the implementation of SPC and to report
your findings to him. You have now successfully put in the place the processes for the data
collection. After collecting data over a 30 day period you have decided to analyse your data
and to write a report of your findings to the Quality Manager. The collected data is
summarised as follows:
a) Each day for 30 days, the number of dolls with colour defects in a random sample of
200 units has been recorded. The results are shown in table 1.
b) Each day for 30 days, three dolls were randomly selected from the process and their
height was measured and recorded in centimetres. The results are shown in table 2.
study the data given in tables 1 and 2. Then, for both sets of data, consider the following issues:
1. What type of SPC chart(s) should be used to monitor the process and why?
2. What are the 3-sigma control limits for the process? Assume that historical data is
unavailable. Show the formulas and your calculations. Plot the control chart(s) using
MS Excel.
3. Is the process in control according to the control limits? Why or why not?
4. Is there a problem in the hydraulics production process? If yes, how would you
describe the problem? What the company should do next?
5. How might you use the quality tools discussed in Chapter 6 of the core textbook
(Heizer and Render, 2010) to determine the source of the defects