Original Date: 07/01/1991
Revision Date: 01/18/2007

Kurt Manufacturing faced a common problem in the current manufacturing environment: non-value added time is required to perform in-process inspection while meeting a larger corporate objective of zero defects. As primary manufacturer of 25mm O Give Fuses for the military, Kurt performed most of the process on an eight-spindle, New Britain screw machine capable of producing one part every six seconds. Customer requirements dictated a quality control sample frequency of eight pieces per hour with a minimum of seven critical characteristics measured and charted, using X-bar and R charts. Certified documentation of the statistical process control (SPC) was to be maintained by Kurt and reports forwarded to the customer with each delivery.

Under the original in-process quality control method, the machine tool operator was removed from inspection responsibility and control, due to the aggressive output of this machine. The timely task of measuring, calculating, recording, and plotting the SPC data was required of the quality control inspectors. Because of the cumbersome standard gaging, the machine tool location did not support inspection performance; therefore, the sample lot of eight parts per hour were hand carried to an inspection laboratory.

Once in the inspection lab, an inspector required approximately 35 minutes taking measurements on all seven characteristics for each of the eight parts. He then plotted the information on standard X-bar and R charts and relayed this information back to the machine tool operator. Within this same 35-minute time frame, the machine tool operator would have completed another 350 parts without process control feedback on how the machine was functioning. In addition, the certified hard copy SPC charts were typically untidy and cumbersome to store.

Kurt Manufacturing established the following goals for the new in-process SPC system: provide the machine tool operator with the ability to collect, record, and plot real-time SPC data in a short period of time; and provide the machine tool operator with a simple gaging technique which would also endure the harsh shop environment.

Kurt’s Electronics Division addressed this problem and developed a factory hardened IBM compatible PC and proprietary SPC software package which could directly interface with a number of vendor specific analog/digital measuring instruments. To accomplish the seven required measurements, a modular gaging system using Linear Variable Differential Transformer sensors was employed to provide multi-feature gaging of all seven characteristics at one time.

The information gathered is now quickly plotted and displayed for the operator to evaluate the current condition of his process. Archiving of the data is accomplished electronically through magnetic media (hard-drive/floppy) or optionally uploaded to a larger factory host through network hardware and communication utility software.

Use of this system has resulted in significant time and manpower reduction. Sampling of the eight specimens is accomplished by the machine tool operator in less than four minutes, eliminating the time lapse and the need for additional quality control personnel. Statistical plots and individual data elements are readily available with an estimated 86% faster response time. Data integrity has significantly improved, providing consistency from operator to operator in the gaging method.

Based on the in-house success that Kurt Manufacturing has had with this system, a complete line of Factory Hardened SPC Gaging Systems has been added to the corporate product mix and is being marketed under the name of Kurt Check Gaging System.

For more information see the Point of Contact for this survey.