The Optimum Crimp

When wire and terminal are compressed together a number of 'microcontacts' are formed which will allow the current to flow through the connector; as the pressure increases so do the number and size of the microcontacts; thus it might seem that the tighter the crimp the better.

However, there is a point at which the wire cross section begins to be reduced, so offsetting the gain in the contact area; this also leads to a reduction in mechanical strength. So it is possible for a crimp to be too tight as well as too loose.

Crimp faults such as too much airspace, or the wrong proportion of wire to terminal, may be caused by using inappropriate tooling or terminals. Either of these mistakes can lead to hotspots, or even eventual burnout of the terminal. Where the wire is to large for the barrel, it is possible that the terminal was not designed to carry such a high current, so it is important to check that they are compatible. If the barrel is too large for the wire, it is impossible to achieve the correct compaction and the current carrying performance of the crimp will suffer. Worn, mismatched or badly set tools may lead to cracking or damage to the insulation. See figures C, D E and F.

Crimp Chamfers

Terminal with chamfers provide for smoother and more effective crimping as the chamfers reduce the forces involved so reducing the risk of flash between the crimper and the anvil. Chamfers also allow the terminal to stay in contact with the crimp tooling throughout the cycle. In addition the crimp is less likely to have missed wire strands. See figure G.

Good Termination

To achieve good termination the bellmouth should be at the insulation end of the wire barrel and preferably at the other end as well. The terminal itself should be straight and flat, not twisted or bent upwards or downwards. See figure H. Should any of these faults occur, a tooling adjustment is generally required. However, Faults can sometimes be attributed to worn out tooling so maintaining a stock of items such as punches, anvils, shear blades and shear blocks is a sensible procedure.

Crimping Index