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When terminating a wire there is a specific sequence of steps that must be taken in order to ensure the quality and long useful life of a wire harness. Most of these steps deal with complying with engineering standards and the requirements of individual customers, but also with the maintenance and inspection of the various assemblies used to create and install wire harnesses: crimping tools and dies, applicators, and wire presses. Even in the even the termination is created by an ultrasonic welder, steps still must be taken to calibrate and verify the integrity of the harness.
The crimp pressure and crimp height of a wire termination are often used as an indication of whether it requires further examination. However, the best measure of all to determine whether a connection will pass or fail is the wire termination’s tensile strength. Tensile strength refers to the ability of the wire to withstand stretching force while still conducting an electrical charge or signal.
The best connection starts with careful selection of cable, contacts, terminals and fittings. Equipment such as dies and presses must also be regularly checked to make checked for proper gaging. Here are several ways to quality check your wire harnesses, and why pull testing is the best option for ensuring the quality of your terminated cable assemblies.
Crimp height refers to the measured height of a crimped or welded connection. The height of the crimping helps quality assurance personnel verify that the correct die cavity was used to crimp the wire, and minimal pressure was used. While an important variable for determining the overall quality of a wire termination, crimp height alone is not enough to determine a harnesses pass/fail results. Crimp height fails to check or address issues such as broken strands within the wire, partially or incorrectly removed insulation, or cracked metal components. However, crimp height is a relatively easy and non-destructive test, and can often be included in a quality assurance process with little difficulty.
Crimp pressure is another solid indicator of wire performance, the work of the operator who made the harness, and the equipment used in its construction. However, the crimp pressure or crimp quality monitor that is used to measure this variable is infrequently found on most presses in North America and never on hand tools. When they are used, they can produce a valuable point of data. If you do not currently have crimp pressure monitors installed, it may not be cost effective to introduce them into your current quality assurance methods.
Pull testing a wire or cable harness refers to testing the minimum tensile value or breaking strength of a terminated wire. To put it more plainly, pull testing answers the question, ‘to what force can a given wire be stretched before it no longer carries an electrical signal?’ Ultimately, what you and your customers demand from your cabling solutions is that they conduct a signal under their most prototypical conditions. Pull testers come in both hand tool form and in mechanical options.
By instituting pull testing into your quality control processes, you are guaranteed to reduce costs and failure rates. For more information on designing, testing, or using wire harnesses and cables, contact the electronics professionals at LoDan electronics today!