Ferrule Crimp Development

[BlaineW]

Good morning gentlemen,

We are trying to develop a manufacturing process to attach a round stainless ferrule onto a 7 strand braided cable in an assembly. The hex dies that worked previously in prototypes are now currently causing failures. We are sort of at a loss to explain why we are suddenly getting so much variation and I was hoping somebody with experience in this sort of thing could maybe give us some ideas on how to solve it.

When destructive testing samples, we either get parts slipping at 20 lbs or going all the way up until the cable breaks at ~60. There is no variation in between, simply on and off. What could cause this? There is no visual difference between the two.

Background

Using arbor toggle press to generate load, dies are pressed closed(so any additional force shouldn't affect crimp) We did some instron testing to find out load that dies will be closed at when compressing the parts.

Small parts, ferrule is .050 is OD, .024 ID. wire is 7 strand braided sst cable with wires about .008 diameter.

There is a lot of discussion about changing the die geometry to make it smaller but my heartburn about that is that it seems to me there is some type of uncommon cause of variation that is leading to these results.

Not being too familiar with these sorts of processes my hope is someone on here can point us in the right direction.

Thanks

 

[BillPSU]

In any process which is showing variability all factors must be addressed until the process is repeatable. Examples are:

Is the press completing the cycle in the same closed location?
Is the die closing to the same size/location?
Is the part being presented in the same position and orientation?
Is the cable size changing?
Is the ferule consistent?

You will have to review the process and eliminate the variablity if possible. If the problem is the cable size if variable you may need to go to a supplier with a more consistent cable.

Good Luck,