An Operator's Dilemma

Everyone who has faced a production problem with a need to solve the problem by using production data can relate to the notion of a brain teaser. The brain teasers have three parts: (1) the situation, (2) available data or other supporting information and (3) questions that various workers want answered for continual improvement. Recommended solutions follow in the next issue and on the Web at Quality Online (

Derek has been a machine operator for 23 years and has developed a sense of when his machine is not operating optimally. At times Derek notices that the machine makes strange noises, appears to slow down for some parts, or pauses slightly during the machining operation. Derek machines castings that are supplied by three companies and he suspects that differences among the castings have impacted the part's critical dimensions. Derek has talked to his supervisor and other operators about his suspicions, but everyone says the suppliers must be OK because the parts meet specifications.

After a particularly frustrating day, Derek decides to keep a log that records the parts that he measured, the suppliers of the parts and the measured values of the critical dimensions. To simplify the log, he plans to record the measurements from one part each hour. The only problem he has is that he doesn't know how to analyze the data to find out if the supplier's parts are different.

Available data
The data that Derek collected for two 12-hour shifts is given in the table "Machined Parts." The two critical dimensions are the heights, Height A and Height B, which are measured from the base of the part. The data values and specifications are coded in thousandths above 0.5 inches. The specification for Height A is 20 + or - 10 and the specification for Height B is 70 + or - 10.

1. When Derek asked how to analyze the data, he was told to make a process behavior chart. What can Derek learn from a process behavior chart of Height A and Height B?

2. What other method can Derek use to analyze his data?

3. Do the castings from the three suppliers differ?

Answers to January Brain Teaser
Q: How should Stacey analyze these data?
A: The best way for Stacey to see the behavior of the press over a period of time is to put the data on a run chart. If he then analyzes the data using an XmR chart, Stacey will see that the press operates efficiently for two to three days after the preventative maintenance. By day three, the stickiness reappears and escalates over the next several days of production. By the ninth day, the press has reached a point where the average number of times a bun sticks to the machine is 42.5 in a 10 minute period; it appears to level off at this point. See the chart "Number of Stuck Buns at the Press." By this time, the press is scheduled for maintenance.

Q: What can Stacey learn about the overall behavior of the press by analyzing the "stuck" bun problem?
A: If Stacey studies the "stuck" bun problem several times and sees the same pattern of behavior, he can begin to predict the behavior of the press with respect to the sticking problem.

Q: How can Stacey use these data to determine a better maintenance schedule for the press and still meet production targets?
A: After Stacey has enough evidence of the pattern of behavior with respect to the stickiness of the press, he can evaluate the cost of paying an employee to separate the stuck buns versus the cost of additional lubricating maintenance for the machine. Any additional maintenance procedures need to be done quickly so as to minimize the impact on production. If it is advantageous to schedule lubrication maintenance every two to three days, he can modify the maintenance procedure.

Did you enjoy this article? Click here to subscribe to Quality Magazine. 

Recent Articles by Sophronia Ward

You must login or register in order to post a comment.




Karen Spencer, Clinkenbeard's quality manager, discusses what makes the plant stand out, advice for other plants, and looks to the future.
More Podcasts

Quality Magazine


2015 May

The May 2015 edition of Quality Magazine includes articles on cloud technologies, depth gages, ISO 9001, digital inspection and cool new products.

Table Of Contents Subscribe

Topics to Talk About

What topics would you like to see Quality cover more?
View Results Poll Archive

Clear Seas Research

qcast_ClearSeas_logo.gifWith access to over one million professionals and more than 60 industry-specific publications,Clear Seas Research offers relevant insights from those who know your industry best. Let us customize a market research solution that exceeds your marketing goals.


Facebook2015_40 twitter_40px.png  youtube_40px.pnglinkedin_40px.png  GooglePlus_40