This is the final installment of Crimp Quality Process Validation and Monitoring. In part one, we discussed pre-process validation. In part two we outlined real time monitoring process during production. In this segment, we will discuss the calibration and machine capability of crimping presses as an integral part of an overall quality strategy.
Process Capability
Process Capability is the total variation in a production process and the ability for that process to be reproduce-able over time and within stated production specifications. Measurements during the production process are taken then grouped together to form a histogram (bell curve). The distribution of measurement results provide an indication of present conformance of the item being produced. Process Capability is a valuable tool for making changes to improve the production process. The capability of a production process is based on multiple factors which are common among almost all production processes The major factors are People, Machine, Methods and Materials. Each factor has its own process variation and contributes to the overall process capability.
In crimping a wire to a terminal, these factors above come into play and can be controlled at the plant level in different degrees. For example:
Considering “People” as a factor, the manual locating of a terminal in a bench top crimp press is one level of variation. Training operators improves the process and is eliminated when an automatic processing machine is deployed. Methods can range widely but could include maintenance schedules, operator and set up personnel training, set up and operating procedures. Effects the Machine has on the process can include the machine age (wear and tear), maintenance and overall accuracy and repeatability of the machine itself. Machines can include the crimp press, terminal applicator and in the case of an automated machine the robotic assembly to deliver a stripped wire to the crimp press. The factor which the producer has less control is materials which include wire, terminals and weather seals. In the case of materials, specifications are generally established by the material manufacturer within their own production process.
Crimp Press Capability
The machine component which can cause excessive variation in the process and which is the last area companies look to for process improvement is the crimp press itself. Even with stable materials, methods, people and crimp applicators additional process variation can occur with the crimp press. Presses have a long production life cycle and in that time bearing, crankshafts and ram assemblies can get worn. Which will show up as piece by piece variation.
The illustration at the left shows a chart of a crimp press which was calibrated and the press was cycled to determine peak crimp force per piece. The top chart shows the shut height measurement and the bottom chart shows reference force. Excessive variation can be found in the force chart on a piece by piece basis. The shut height measurement was in control where the force was not in control.
The illustration at left was the same press after maintenance was performed to tighten up the press ram assembly. The force measurements were brought into statistical control. The shut height measurement also improved statistically. The result of this improvement will be a process that is in better statistical control and a product which will perform consistently better piece by piece.
The tool used is the C&S PAL3001 which can calibrate a press to the industry standard shut height and take force measurement readings to determine machine capability.
Wire Process Specialties can supply your crimp validation equipment and in-process measurement and data collection for ongoing process improvement. Connect You Way to WPS find out more.
