On 10/5/19 8:16 PM, Larry McDavid wrote:
I've used Power-Pole connectors for many years successfully and I've
always crimped them with appropriate Power-Pole crimp tools. I never,
never solder crimped connections! Heating a crimped connection to
soldering temperature will relax the crimp force in the crimp zone and,
if properly crimped, there is no gap among the wire strands for solder
to flow into. The result is always a loss of connection quality.
Stranded wire can be tinned or coated with solder by the wire
manufacturer and crimped successfully so long as the wire is
"non-fused-tin-coated." But, much stranded tinned wire *is* fused to
keep the strands together after removing the insulation; this type of
stranded wire should not be crimped. Much MIL Spec wire is silver
coated, inherently non-fused and crimps well.
Professionally (in both aerospace and high-rel automotive air bag
applications), I've had the "crimp zone" of very many crimped connector
contacts metallurgically mounted, cross-sectioned and examined
microscopically after polishing and etching to reveal the individual
strands even in the crimp zone. This is the ultimate method to "qualify"
a crimped connection. A "gas-tight" crimp shows under microscopic
examination no air gaps within the crimp zone--the crimped wire bundle
has gone solid and is "gas tight."
"Crimp pull force" is another, production level, crimp quality control
method but the proper method requires making numerous crimps at various
"crimp heights" (how reduced in dimension is the height of the crimp
zone) and pull force testing the resultant crimps. The requires crimping
by a machine or qualified hand crimp tool that is adjustable. The pull
force values are plotted against crimp height and the shape of the curve
examined. A crimp height resulting in a pull force just as the pull
force begins to *decrease* after reaching a peak value is selected. A
"looser" crimp is not "gas tight" and a "tighter" crimp reduces the
cross-section area of the wire bundle enough to weaken the crimped
connection. Crimped connections have to be crimped within a narrow zone
of compression and only the appropriate crimp tool, appropriately
calibrated, can provide this. Forget about all types of "crimp pliers;"
these are worthless tools.
interesting...
And I assume, then, that the degree of compression (set by the dies and
their position in the crimper) is wire gauge dependent - that is, the
crimper doesn't crimp to a specific force, it crimps to a particular
mechanical dimension, so if the number and size of strands is different,
then the degree of crush is different.
That sort of makes the "crimping a tiny wire by folding it back on
itself" or "crimping a tinywire by putting it with a big wire" a tricky
operation.
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