Inge,
I've been in the connector industry for over 25 years and have come
across this from time to time.  I believe that IPC has some guidelines
for wire crimping, but this deals more with the area within the crimp
than behind it.
Questions:
1. Is this multi-strand or single strand wire?
2. What size is the wire?
3. How are you preparing the wire before crimping? Some times automated
cut-and-strip machines stretch the insulation which later contracts, as
you described.
General "Best Practices" for space from the wire crimp to uncrimped
insulation is 1/2x to 1x the wire diameter for low power applications
and 1/2xDia Max in high power (>35 Vac).

Doug Erb
Senior FAE
Hirose USA
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Friday, June 05, 2009 3:01 PM
To: [log in to unmask]
Subject: [TN] Cable insulation crimping

Hi TN crickets (as to all the noise of underfill and coating)

Our production want send back 10 kilometers of single power cords.
Insulator 
is a single layer of Polyolefin. Now, when we crimp or solder these
wires, 
the following happens: when bending and gathering wires into bundles for

strapping and fixing them to chassis, the Polyolefn begins to withdraw
from 
the connectors or single contact pin. It creeps a few millimeters and I 
think that won't have any kind of negative impact on  electrical
performance 
or reliability or what so everm The amount of withdrawal in our company
std 
is set to be maximum one halv of the electrical wire diameterm. I found
this 
being a weird requirment, because IPC says 3 times the diameter.

1) So, what do you think, is a little withdrawal of the Polyolefin
insulator 
anything to bother about?

2) Do you know of a real good paper describing all about crimping .
Molex, 
T&B and some others had, but covers only what makes money.

Inge

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