Part Seven Case Studies EXHIBIT 2 Toledo custom manufacturing samples produced. Operator 1-machine 1 Sample 1 0.500 0.498 0.502 0.499 0.503 Sample 2 0.496 0.497 0.500 0.502 0.499 Sample 3 0.504 0.503 0.503 0.496 0.495 Sample 4 0.503 0.501 0.498 0.497 0.500 Sample 5 0.500 0.502 0.503 0.498 0.495 Sample 6 0.505 0.496 0.504 0.503 0.502 Operator 2-machine 2 Sample 1 0.495 0.497 0.495 0.502 0.500 Sample 2 0.505 0.510 0.503 0.511 0.504 Sample 3 0.504 0.503 0.502 0.502 0.501 Sample 4 0.500 0.501 0.497 0.496 0.504 Sample 5 0.501 0.512 0.510 0.508 0.504 Sample 6 0.503 0.500 0.497 0.496 0.504 processes are in control before proceeding with full pro- conclusions from the charts about each operator- duction of the 5000 unit order. machine combination. 2. What should be done based on the calculations Discussion Questions from question 1? 3. What is the process capability for each operator- 1. Calculate the control charts (UCL, CL, and LCL) for machine combination? each operator-machine combination separately. Do 4. Can you be sure that all the parts produced by this for both x-bar (average) and range charts. Draw in-control processes will meet the specification?Case Study Toledo Custom Manufacturing: Quality Control excel Toledo Custom Manufacturing (TCM], located in Toledo, EXHIBIT 1 Push rod and hydraulic cylinder illustration. Ohio, makes metal parts to customer specifications. They have a variety of machines Including lathes. numerically controlled (NC) machines, grinders and drill ing machines. They can make any metal parts that -Push rod require use of these machines. TCM employs 65 work- ers, supervisors, and managers in its facility. TCM is very customer-oriented and prides itself on quality control. They take a Total Quality Management systems approach including use of control charts, ISO 9000 certification, employee training. and teams for continuous improvement of quality. TCM also selects its suppliers based on their ability to provide quality metal blanks and parts that are purchased. THE PRECISE STEEL ROD ORDER TCM recently received an order to machine 5000 push rods to be used In the production of hydraulic cylinders. The push rod is a precise steel rod that runs inside of a hydraulic cylinder to build pressure when activated. The push rod has very tight specifications to insure that hydray- -Hydraulic lic leaks do not occur. The particular rod ordered is 6" long cylinder and must be .500 inches in diameter (see Exhibit 1 for an illustration). The specifications call for 1.005" (5 one. thousands of an inch] tolerance. Therefore all rods must be machined to a diameter between .495" and .505" to meet the specification and to be acceptable to the customer. In order to meet the customer's delivery schedule, TCM will utilize two machines. each with its own opera- tor. The machines are similar, but operator 1 has more experience than operator 2. TCM must also insure that the supplier of blank steel rods will provide consistently good material for machining. process will need to be fixed before proceeding. After QUALITY CONTROL CHARTS fixing the process another six samples of 5 parts each In order to prepare for the order. TCM has decided to will be taken to see if the process is now in control and make 30 parts on each operator-machine combination. this Is continued until a satisfactory test is completed. Each operator-machine will run samples of 5 parts and The customer has asked that the final control charts make a total of six samples for 30 parts. Separate control used to verify the operator-machine combinations be charts will then be constructed using the samples to calcu- forwarded to them along with the 60 parts produced by late the grand average and average range for each operator. the two machines. They also requested, that control These averages will be used to construct an upper control charts be maintained by taking hourly samples and sub- limit, center line and lower control limit for each of the mitted along with future batches of the parts. In addition operators. Then the six samples will be compared to these to statistical process control charts, the customer would limits to see if the process is in-control or if there are out- like to receive a calculation of the process capability of-control points. If the process is in control, the operator index (C, and C.) to insure that the process is capable and machine can proceed to make good parts. Every hour of meeting the specification. a sample of 5 will then be taken and plotted on the chart The data collected from the first six samples of of insure that the process is still In-control 5 each are shown in Exhibit 2 for operator 1-machine 1 If either machine-operator combination is out-of- and operator 2-machine 2. These are the samples of 30 control based on the first six samples of 5 parts each, the each required to Insure that both operator-machine The case was prepared by Roger G. Schroeder for use in class discussions. Copyright O by Roger G. Schroeder, 2016. All rights are reserved. Reprinted with permission. 439