Crimp Curves

Well Designed Mechanical and Electrical Crimp Curves

Crimping is inherently a mechanical process that must meet electrical requirements.

Electrical Crimp Curves

X Axis: Core Crimp Height (CCH)

This crimp curve shows the typical Mechanical and Electrical parameter relationship for a well-designed crimp. The main variable, once tooling, terminal and cable size are determined, is the Core Crimp Height on the X axis with increasing crimp height to the right. Typically, about seven sets of experimental test samples are needed to determine the related variables such as Crimp Cross Section (Compaction or Area Cross Sectional Reduction), Crimp Pull Off, Environmental-Low Energy Milliohm Resistance and Power Cycling Milliohm resistance. See SAE/USCAR 21-1 for test parameters.

Y Axis: Cross Section

Note that more 'voids' occur as the crimp height increases to the right, resulting in a 'loose' crimp. This looseness allows movement between the terminal and each strand resulting in an intermittently high crimp resistance. A crimp that is too tight is difficult to determine visually, but can result in low pull off value and increase resistance as the cross-sectional area of the cable is excessively reduced.

Terminal Pull Off

Note that this is a double value curve with respect to Core Crimp Height. Usually the optimum electrical results occur in a narrow tolerance range on the "up slope" of the Pull Curve. The core crimp generally becomes too loose on the down slope of the Pull-Off Curve. Terminal Pull-Off is generally only an indirect indicator of crimp electrical performance.

Environmental Electrical "Low Energy" Performance

Typically this is also a "Double Valued Curve" and is the opposite of the Pull Curve. If the cross section is too tight, the crimp resistance increases, and if it's too loose, strand movement occurs resulting in increased resistance. A narrow window of CCH will yield either acceptable maximum crimp resistance or crimp/resistance change in milliohms. The milliohm resistance is measured with a special ohm meter which restricts voltage to prevent oxide film breakdown.

Power Current Cycling

This curve is similar to the Environmental Curve but tests the current carrying capability of the crimp. See SAE/USCAR 21-1 for test parameters.