Case Study Toledo Custom Manufacturing: Quality Control
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Toledo Custom Manufacturing (TCM), located in Toledo, Ohio, makes metal parts to customer specifications. They have Page 455 a variety of machines including lathes, numerically controlled (NC) machines, grinders and drilling machines. They can make any metal parts that require use of these machines. TCM employs 65 workers, 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 hydraulic leaks do not occur. The particular rod ordered is 6" long and must be .500 inches in diameter (see Exhibit 1 for an illustration). The specifications call for ±.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.
EXHIBIT 1
Push rod and hydraulic cylinder illustration. In order to meet the customer's delivery schedule, TCM will utilize two machines, each with its own operator. 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. 1. Calculate the control charts (UCL, CL, and LCL) for each operator-machine combination separately. Do this for both x-bar (average) and range charts. What conclusions can you draw from the charts about each operator-machine combination? 2. What should be done based on the calculations from question 1?
3. What is the process capability for each operator-machine combination?