ATC 2281 Astro Tool Corp, ATC 2281 Datasheet - Page 5

• Manufacturer Part Number: ATC 2281
• Description: TOOL EXTRACTION #8 CONTACT METAL
• Manufacturer: Astro Tool Corp

Specifications of ATC 2281

• Tool Type: Extraction Tool
• For Use With/related Products: Circular Connector Contacts
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Other names: ATC2281

Crimping Pin and socket Contacts
CRIMPING
Crimping may be defined as the art of joining a conductor to a pin or
socket contact by controlled compression and displacement of metal.
It has been used for many years.
In a good crimp joint, there is a mutual metal flow causing symmetrical
distortion of wire strands and contact material. The mil cross-sectional
area is but slightly reduced and all voids are practically eliminated.
Such a joint is similar to a cold weld. Mechanical strength and good
electrical continuity are established. Because of the new environments
to which electrical connectors are subjected, there has been a drastic
change in thinking relative to the use of precision crimp joints in
preference to solder.
CRIMPING CONFIGURATIONS
There are many different types of crimps employed
today. These range from the terminal fold-over
tab type of crimp to the single indent crimp, the
dual indenter crimp, the three indenter crimp, hex
crimps, and, finally, the MIL standard four indenter
crimp. The four indenter crimp (Fig. 1) provides
the most uniform displacement of wire and
contact material. The wire strands and the contact
material are formed together in a solid mass with
little or no reduction of the mil area of the wire
strands. A minimum of voids exists and very little
extrusion of the wire strands takes place.
The four indenter crimp principle
has been used to produce a
variety of impressions, the most
common being the “bathtub”
and “octadent” (also called
double indent) (Fig. 2) The
octadent configuration has
been chosen by the Military for
use in the M22520/1 and /2 tools.
CRIMPING CHARACTERISTICS
Connectors utilizing crimping contacts usually permit the removal of
these contacts several times so that modification, circuit changes, or
replacement of contacts may be made with little difficulty and with the
same quality assurance as in production line assembly. Crimping may
be accomplished either with hand tools, power tools, or automated power
tools. Repeatability of the crimp operation is characteristic provided
precision crimping tools are employed. These tools must be capable
of being gaged to insure that proper crimp depths are maintained.
Inspection holes in each contact permit quality control personnel to view
the wire strand ends thereby assuring that the conductor is properly
positioned in the crimp barrel.
MIL-DTL-22520
This specification covers all the requirements for crimping tools used on
removable type contacts in electrical connectors.
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© Copyright 2008 Astro Tool Corp. , 21615 SW Tualatin Valley Highway, Beaverton, OR 97006
octadent Crimp –
Horizontal Cross-section
fIG 2
4-Indenter Crimp
Cross-section
across axis
fIG 1
CRIMP DEPTH DETERMINATION
Having resolved an indenter design, the determination of crimp depth
range must be established for each application. There are many factors
which contribute to the selection of the proper indenter setting. These are
primarily related to contact material and dimensions as well as wire type
and size.
The proper crimp depth for a given contact is the one that yields the best
mechanical and electrical joint. To determine this setting, many contacts
of the same type are crimped though a range of indenter settings from
too loose to too tight. The crimped contacts are then subjected to tensile
and voltage drop tests.
WIRE PREPARATION
Proper wire preparation also plays an important part in making a
good crimp joint. There are two popular methods of wire stripping —
mechanical and thermal. During the mechanical stripping process,
extreme care must be taken to avoid nicking or removing wire strands,
otherwise a loss of tensile strength will result. Conversely, if the
insulation is not completely removed, erratic values may be obtained.
Heat stripping eliminates the danger of nicking strands. However,
depending on the type of insulation being stripped, too much heat can
cause actual charring of the insulation or decompose the insulation with
the evolution of corrosive gases which react with the conductor platings.
There is also a possibility of local annealing of the conductor. Too little
heat can deposit an insulation film which can act as a lubricant. Any of
these conditions can affect tensile results. Wire preparation is, therefore,
another area that requires control if proper tensiles are to be achieved
with a wire-contact combination.
Before making a tensile test it is also important that the stripped length
of the wire be checked to ensure that the wire extends all the way into
the contact wire barrel. During the tensile test it is necessary for the
uncrimped end of the wire to be held in such a way that the pull force is
evenly distributed to all the strands.
TENSILE TESTING
Tensile testing is a controlled pull test on the crimp joint to determine
its mechanical strength. It is a destructive test which usually results in
wire breakage in the crimped barrel, the wire pulling out of the crimped
barrel, or wire breakage outside of the crimped area. The method and
device used to conduct this test have a direct bearing on the results
obtained. Per specification, the testing device pulls at the rate of one
inch per minute. During the tensile test, the wire is elongating. The
breakage or separation point, therefore, is associated with not only the
pull force but also the rate of increase of this force.
Tensile curves are plotted for each contact and wire combination. They
will usually differ, depending on the type of wire, plating, size of wire,
and variations in contact design and material. A desirable tensile range
must be determined for each of these combinations.
MILLIVOLT DROP
Millivolt drop tests are performed across the crimp joint to determine the
electrical characteristics. The test current is passed through the contacts
and voltage drop is measured from a point on the shoulder of the contact
to a point on the wire. Voltage drop values under the maximum allowable
indicate a good electrical joint.
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