Understanding Crimp Tool Setup Variability

In the past, set up of an applicator to crimp a terminal was a time consuming process. Applicators were often bolted into the crimp presses and a manual adjustment to the press ram was made in order to provide the proper pull test between the wire and the terminal. Companies would acquire a large quantity of crimp presses and most high volume applications were permanently fixed to a press to reduce set up time. But at a cost of facility floor space. This was also a time when run volumes of one application were larger and spanned days and often weeks. That was then.

Today we have presses and applicators designed around a universal press shut height. Press bases and ram assemblies accommodate quick change of applicators. The applicator adjust-ability is quick and the press is only adjusted to account for tool wear.

Applicator and Crimped terminals.

Despite the commonality of applicator setup, each setup needs to be treated as unique. This is even more important when crimp monitors are deployed and configured to detect small crimp variations. That does not mean significant extra time for setup. But extra effort to ensure the setup is done right and initial samples are validated and meet the quality specifications.

So what can vary from setup to setup? Let’s break those down.

Presses which are routinely adjusted to match the proper crimp height and pull test mean each application can vary from it’s intended crimp spec. As a general practice, the press should be returned to it’s calibrated shut height position after each job. When the press adjustment uses a graduated scale with positive adjustment points makes the change back to the calibrated position more predictable. When no positive adjustment of the shut height is available,then exact position of the shut height is not possible without re-calibration.

Micro-Adjustment of Crimp Press.

Presses have their own variation from press to press. If the applicator is installed in a different press, this is a source of variation. The way the applicator is installed in the press can affect the setup. Dynamic Press Analysis is a way to determine piece to piece variation within a press and between presses.

Applicator service and crimp tool replacement is a source of variation even when the same wire and terminal are used.

Wire of the same gauge but with different strand quantity and diameters is a source of variation. Crimp compression can affect electrical resistance and compression of the strands can vary with the stand thickness and number of strands. A wire with 19 strands will compress differently than a 41 stand wire.

Different wire gauges crimped to the same terminal. Each terminal has a range of wire it will crimp. The crimp geometry is designed to match the wire range. Generally speaking a terminal supplier will attempt to fit as many wires into one crimp size. Mainly to reduce the amount of terminals to produce and stock. A wide range of wires in one crimp section can affect headroom when using crimp monitors. Headroom is the difference between the force to crimp the wire and terminal and the terminal only. More headroom equals the ability to detect small crimp defects.

Different lots of terminals and wire. Variation can exist from lot to lot of materials.  Over the years, that lot to lot variation is smaller due to tighter process control by the supplier. But variation can exist so validation when materials (wire barrels/reels or terminal reels) change, a re-validation is recommended.

So why is this important? Consistency in setup is critical for consistent crimp quality. Especially when crimp force monitors are being used for in process monitoring. Crimp monitors can be affected by piece to piece variation from equipment wear, material matching and in process material changes. The more consistent these elements are, the more sensitive the process is for the monitor to detect smaller defects.

Conversely the less sensitive the process is, the more difficult it is to detect small defects. And the greater the risk of accepting defect parts.

Improving your current crimp process is ongoing. Reducing sources of variation gives a higher level of confidence in your ability to deliver a high level of quality assemblies to your customers.

Don’t know where to start? Crimp Quality Solutions can help.

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