Continuity Tubes and False Insertion Errors
Proper continuity lead sense is dependent upon the relationship between:
· the continuity tube
· the cutter
· the angle of the lead being cut
· the lead length as the leads are cut.
It is important the lead is bent and touches the continuity tube before the cut takes place, making the position where the lead enters the cut and clinch assembly very important.
As the cutter moves across to the cut position, the lead begins to bend in the direction of the continuity tube. However, once the lead is pinched between the cutter and the cutter bushing, the scrap portion of the lead will no longer be pushed toward the continuity tube. At this point the scrap portion of the lead will actually be forced in the opposite direction of the continuity tube as the cutter shears through the lead.
The following scenario describes what happens if the lead length is set too short. In other words, the lead entrance to the cutter bushing set so the lead is very close the cutter bushing shear point.
By setting the lead length too short, (the lead too close to the cut point of the cutter bushing), the scrap portion of the lead will not be bent far enough to reach the continuity tube as the cutter bends the lead, resulting in a false insertion error. In other words, if the lead reaches the cut point before it has been bent far enough to touch the continuity tube, a false continuity error may occur.
On the other hand, having the lead length too long may cause accelerated wear and damage to the continuity tubes. Forcing the lead into the continuity tube with too much force will cause denting of the continuity tube and wear of the plastic insulation, resulting in premature failure and false continuity errors over time.