RE: [CAD_CAM_EDM_DRO] Re: Gecko burned out

Makes sense, but what about the response I posted from Eby saying it wasn't
a problem?

Still waiting to hear from Phoenix Contact.

Andy Wander
Verrex Corporation


-----Original Message-----
From: Don Rogers [mailto:Don@...]
Sent: Monday, October 18, 2004 7:16 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Gecko burned out


At 05:44 PM 10/18/2004 +0000, you wrote:

>BTW, did you know that tinning stranded wires is NOT recommended for
>wire-clamp-type terminals? The manufacturers specifically warn against it.
>They say it will cause the connection to creep and loosen.
>
>I still don't believe it by my "gut feeling", but I would guess they know
>what they are talking about.

You should believe them. Back in the early 80's, I was working with
development engineering on a large main frame computer. The thing used
400A buses go supply the voltage to the boards. They attached to the board
with, initially, a 1/2" screw. What was happening was that with the
thermal expansion, the copper busy was actually deforming because of the
clamp action of the screw. When it cooled off, the contact was not tight
and would start arcing, Power engineering went to a 3/4" screw, but the
problem got worse. The fix was two 3/16" screws with bellville (SP?)
washers on both the head and nut. The smaller screws could stretch a bit,
but not loose their elasticity and didn't deform the copper. Problem
resolved.

On a much smaller scale, that is what happens when you tin the leads and
then screw them down. There is no elasticity to allow for thermal
expansion, the solder is very soft and easily deformed, so soon they are
loose.

Don




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