Validating and monitoring the process of crimpimg a wire to a terminal is a very critical in today’s wire harness production environment. So critical that some industries have mandated the use of advanced validating and monitoring crimp technology to reduce exposure (and liability) to financial loss if a defective harness is introduced into a a product. in this three part series, we will explore some of the techniques and technology being used in wire harness facilities worldwide. In part one, we will cover pre-production crimp validation.
Crimp Height is an initial pre-production test to determine if the crimp compression meets the manufacturer’s specifications. Crimp Height micrometers are used as they have a point on the spindle which rests on the underside of the crimp. The anvil side has a flat surface which rests on the upper side of the crimp. Using standard micrometers or verniers can provide false reading as they may pick up the points of the bottom anvil mark and not the center bottom of the crimp. Using digital micrometers allow the crimp height reading to be downloaded to data collection/analysis software.
Pull Testing is a destructive test to determine if the wire is properly secured into the wire crimp of the terminal. Pull test procedures require the insulation support to be peeled back so the pull test reading is based on the wire to terminal crimp only. A motorized pull tester pulls the wire from the terminal at a steady rate which improves the accuracy and consistency of the crimp. And a digital output provides the ability to collect and analyze the pull test data.
The model PT100 shown is used as a standalone pull tester, interfaced with a computer for data collection/analysis/capability studies or fully integrated into a plant wide validation and real time crimp monitoring system.
Crimp Cross Section
Once you have established your crimp height and pull test, do you assume everything you see outside is the same inside the crimp? Manufacturers of terminals work hard to ensure the wire to crimp size match properly and there is a science to establishing the proper shape and size of the crimp to fit a specified wire range. But outside of the manufacturer’s work to determine the proper crimp size to wire, other factors come into play which can affect the crimp:
- wire OD which can vary within a specified wire range.
- tool wear.
- wrong tooling used or wire size used which does not meet the terminal specifications.
The effect of these changes can cause the wire to be unevenly distributed inside the crimp. Something which cannot be determined without doing a cross sectional analysis. Here is an example:
In this case, the wire crimp looks normal but the wire distribution is not even.
Did you know, this effect is one factor which can cause false readings on in-process monitoring of crimping using crimp force monitoring tools? False readings can be rejecting good parts or accepting bad parts. The right wire gauge for the terminal, consistent wire distribution within a crimp and the proper crimp forming tools can provide consistent crimp quality.
Crimp cross sections are created by cutting the wire from the terminal, grinding/polishing the terminal down to the approximate mid point of the wire crimp and using etching chemicals to prepare the end of the wire. The crimp is loaded to a microscope and a digial image is produced. Further analysis include a calculation of the crimp area. A cross section is a pre-production analysis tool used in some critical applications but can be costly on a regular basis. Having the documentation on a crimp cross section on the introduction of a new wire termination is a good practice (mandated in some industries) as it provides an understanding of what to expect from the crimp monitoring process. Wire Process Specialties can assist in the equipment required for processing cross sections in house or through our Cross Sectioning Service.
Data Collection is a critical part of pre-production and production to ensure your crimp process is meeting your specifications. Data is used for validation prior to production, capability analysis and to document crimping results for review by your quality and production personnel, customers and external quality auditors to verify compliance with national and international standards. Data collection can be as simple as using the tools above to manually or automatically recording results, within a local inspection station where all tools are combined to provide a bigger picture of the crimp quality. For larger operations, client/server systems provide crimp specifications to the inspector, measurements are made and validated before production can commence. Then in process measurements are taken and stored electronically across all processing machines plant wide. In part two, I will outline typical tools for in process quality monitoring of wire to terminal crimping.
Wire Process Specialties partners with C&S Technologies, a global leader in the supply of crimp process validation and monitoring systems. We can supply simple inspection tools or create a complete integrated system for plant wide control of the crimping process. Connect Your Way to Wire Process Specialties to get a personalized assessment of your requirements.