WIRE PREPARATION
GENERAL REQUIREMENTS
graphical representation of a multi-conductor shielded cable, a co-axial cable, a stranded conductor and a solid conductor

WIRE PREPARATION
GENERAL REQUIREMENTS

Wire conductors are available in many forms, ranging from single, solid insulated conductors, to highly integrated, multiple conductor cables.

Wires and cables can function as simple discrete jumpers on circuit boards, or woven into intricate harnesses that snake through a vehicle, functioning as the nervous system for the routing of command, control and signal impulses.

The correct preparation of conductors will result in a termination of high quality and reliability.

solid conductor with part of insulation jacket removed by stripping flat cable with outer jacket, conductive shield and conductor insulation jacket trimmed and removed

PREFERRED

CHEMICAL STRIPPING PROCESS

The insulation jacket has been neatly removed, with no damage to the conductor or insulation. No wicking of stripper or cleaner agents evident.

Note: Chemical stripping is suitable for solid conductors only.

PREFERRED

FLAT CABLE

The outer jacket, conductive shield (if supplied), and conductor insulation jackets have been neatly trimmed and removed, with minimal edge falsh and no mechanical damage. The conductors are in planar orientation, and the drain conductor and/or shield are undamaged.

coaxial cable with insulation jacket and shield trimmed stranded conductor with Kapton insulated conductor trimmed

PREFERRED

FLEXIBLE COAXIAL CABLE

The insulation jacket and shield(s) have been neatly trimmed, with minimal edge flash and no mechanical damage to the conductors, shielding, dielectric or insulation jacket. The center conductor stranding exhibits a normal twist pattern (lay).

PREFERRED
KAPTON® INSULATED CONDUCTORS

Kapton®-insulated conductors must be trimmed neatly and squarely, with minimal edge flash and no mechanical damage to the conductor or insulation.

NASA WORKMANSHIP STANDARDS
NASA logo Released:

03.31.2000
Revision:

B
Revision Date:
07.03.2002
Book:
1
Section:
1.01
Page:
1




WIRE PREPARATION
GENERAL REQUIREMENTS (cont.)
stranded conductor with jacket trimmed multi-conductor cable with outer jacket, shield, strength members and conductor insulation trimmed and removed

PREFERRED

MECHANICAL STRIPPING PROCESS

The insulation jacket has been neatly trimmed, with minimal edge flash and no mechanical damage to the conductor or insulation. Conductor stranding lay (twist pattern) is undisturbed.

PREFERRED

MULTI-CONDUCTOR CABLE

The outer jacket, shield, strength members and conductor insulation have been neatly trimmed and removed, with minimal edge flash and no mechanical damage. Conductor stranding lay (twist pattern) is undisturbed.

ribbon cable with the outer jacket, conductive shield and conductor insulatioon trimmed and removed solid conductor with insulation jacket trimmed

PREFERRED

RIBBON CABLE

The outer jacket, conductive shield (if supplied), and conductor insulation have been neatly trimmed and removed, with minimal edge flash and no mechancial damage. The conductors are in normal planar orientation,and the drain conductor and/or shield are undamaged.

PREFERRED

SOLID CONDUCTOR

The insulation jacket has been neatly trimmed, with minimal edge flash and no mechanical damage to the conductor or insulation. Chemical/thermal/laser-trimmed conductors may exhibit slight discoloration of the insulation jacket(s) at the trimmed edge.

stranded conductor with the insulation jacket trimmed stranded conductor with insulation jacket trimmed

PREFERRED

STRANDED CONDUCTOR

The insulation jacket has been neatly trimmed, with minimal edge flash and no mechanical damage to the conductor or insulation. Conductor stranding lay (twist pattern) is undisturbed.

PREFERRED

THERMAL/ EXCIMER LASER STRIPPING

The insulation jacket has been neatly trimmed, with minimal edge flash and no damage to the conductor or insulation. Slight discoloration of the insulation jacket(s) at the trimmed edge.

NASA WORKMANSHIP STANDARDS
NASA logo Released:

03.31.2000
Revision:

B
Revision Date:
07.03.2002
Book:
1
Section:
1.01
Page:
2




WIRE PREPARATION
GENERAL REQUIREMENTS (cont.)
conductor with braided shield stripped and trimmed conductor with severed shield braid strands

ACCEPTABLE

BRAIDED SHIELD

The shield has been properly stripped, evenly trimmed, and exhibits a fairly uniform coverage pattern (braid weave). No severed strands.

NASA-STD-8739.4 [ 10.2 ] [19.6.1.a]

UNACCEPTABLE

SEVERED SHIELD STRANDS

Severed shield braid strands shall be cause for rejection.

NASA-STD-8739.4 [ 10.2 ] [ 19.6.2.a.4 ]

properly exposed dielectric coaxial cable with center conductor exhibiting damage to the dielectric

ACCEPTABLE

DIELECTRIC

The dielectric has been properly exposed, exhibiting a smooth, clean cut with minimal edge flash. Minor edge discoloration (due to thermal stripping) and/or surface scuffing is acceptable.

NASA-STD-8739.3 [ 7.2.2 ]
NASA-STD-8739.4 [ 10.1.2 ]

UNACCEPTABLE

DIELECTRIC DAMAGE

Coaxial cables with center conductors exhibiting damage to the dielectric (i.e.: burns, charring, cracks, crushing, cuts, deformation, necking, nicks, ringing, etc.) shall be rejected.

>NASA-STD-8739.3 [ 13.6.2.a.1 ]
NASA-STD-8739.4 [ 10.1.2 ], [19.6.2.a.1]

insulation jacket with slight discoloration at the trimmed edge burned insulation

ACCEPTABLE

DISCOLORED INSULATION

Slight discoloration of the insulation jacket(s) at the trimmed edge is acceptable. Evidence of burning or charring is not acceptable.

NASA-STD-8739.3 [ 7.2.2 ]
NASA-STD-8739.4 [ 10.1.2 ], [19.6.1.a.1]

UNACCEPTABLE

BURNED/CHARRED/MELTED INSULATION

Burned, charred, or melted insulation is an indicator of improper process controls and/or stripping procedures, resulting in embrittlement, reduced dielectric properties and reduced reliability.

NASA-STD-8739.3 [ 13.6.2.a.1 ]
NASA-STD-8739.4 [19.6.2.a.2]

NASA WORKMANSHIP STANDARDS
NASA logo Released:

03.31.2000
Revision:

B
Revision Date:
07.03.2002
Book:
1
Section:
1.01
Page:
3




WIRE PREPARATION
GENERAL REQUIREMENTS (cont.)
acceptable edge flash on conductor edge flash on conductor in excess of one-quarter insulated diameter and with the stripped section exhibiting smearing

ACCEPTABLE

EDGE FLASH

Edge flash shall not exceed one-quarter insulated wire diameter (1/4 d). Edge flash is considered a contaminant, which may interfere with crimped or soldered terminations.

NASA-STD-8739.4 [ 10.1.6 ]

UNACCEPTABLE

EDGE FLASH/SMEARING

The edge flash is in excess of one-quarter insulated wire diameter (1/4 d), and the stripped section exhibits smearing (melted insulation/film) which is considered a contaminant.

NASA-STD-8739.4 [ 10.1.6 ]

identification member and strength member trimmed back to the insulation identification member not trimmed properly

ACCEPTABLE

ID RIBBON/STRENGTH MEMBER

The identification ribbon and/or strength member should be trimmed back to the insulation to prevent its inclusion into a soldered or crimped termination.

Best Workmanship Practice

UNACCEPTABLE

UNTRIMMED ID RIBBON/STRENGTH MEMBER

The identification ribbon and/or strength member has not been trimmed properly, which can interfere with the proper assembly of the soldered or crimped termination.

Best Workmanship Practice

acceptable amount of nicked shield strands nicked strands in excess of 10% of total number of strands

ACCEPTABLE

NICKED SHIELD STRANDS

Nicked shield strands shall not exceed 10% of the total number of strands.

NASA-STD-8739.4 [ 10.2 ] [19.6.1.3]

UNACCEPTABLE

NICKED SHIELD STRANDS

The number of nicked shield strands is in excess of 10% of the total number of strands.

NASA-STD-8739.4 [10.2], [ 19.6.2.b.2 ]

NASA WORKMANSHIP STANDARDS
NASA logo Released:

03.31.2000
Revision:

B
Revision Date:
07.03.2002
Book:
1
Section:
1.01
Page:
4




WIRE PREPARATION
GENERAL REQUIREMENTS (cont.)
flat ribbon cable with the individual exposed conductors in parallel orientation to each other flat ribbon cable with the individual exposed conductors not in parallel orientation to each other

ACCEPTABLE

PLANAR ORIENTATION
FLAT/RIBBON CABLE

The individual exposed conductors should be in parallel (planar) orientation to each other, following stripping.

Best Workmanship Practice

UNACCEPTABLE

NON-PLANAR ORIENTATION
FLAT/RIBBON CABLE

Non-planar oriented conductors are typically the result of poor handling. The conductors may be returned to their original orientation, provided no other damage is present.

Best Workmanship Practice

wire strands retwisted strands twisted in excess of the normal twist pattern

ACCEPTABLE

RETWISTED LAY

If the twist pattern (lay) of wire strands is disturbed, it shall be restored as nearly as possible to the original pattern. Retwisted lay is acceptable, provided no other damage is evident.

NASA-STD-8739.3 [7.2.4]
NASA-STD-8739.4 [10.1.4], [19.6.1.a.2]

UNACCEPTABLE

OVERTWISTED STRANDS

Strands twisted in excess of the normal twist pattern (lay) exert increased stress on individual strands, and may result in conductor breakage.

NASA-STD-8739.3 [7.2.4]
NASA-STD-8739.4 [10.1.4]

slight scuffing on the insulation surface damaged insulation

ACCEPTABLE

SCUFFED INSULATION/JACKET

Slight scuffing (a dull or rubbed appearance) of the insulation surface finish is acceptable, provided no other damage is evident.

NASA-STD-8739.3 [7.2.2]
NASA-STD-8739.4 [10.1.2]

UNACCEPTABLE

DAMAGED INSULATION/JACKET

The conductor insulation and /or cable jacket shall not exhibit any damage, such as nicks, cuts, or charring. Conductors/Jackets exhibiting damage (other than minor scuffing) shall not be used.

NASA-STD-8739.3 [13.6.2.a.1]
NASA-STD-8739.4 [19.6.2.a.2]

NASA WORKMANSHIP STANDARDS
NASA logo Released:

03.31.2000
Revision:

B
Revision Date:
07.03.2002
Book:
1
Section:
1.01
Page:
5




WIRE PREPARATION
GENERAL REQUIREMENTS (cont.)
smooth tool impression mark on the conductor surface large scratches on the conductor surface

ACCEPTABLE

SMOOTH TOOL IMPRESSION MARKS

Smooth tool impression marks (slight cuts, nicks, scratches or scrapes) on the conductor surface, which do not expose base metal or reduce cross-sectional area, are acceptable.

NASA-STD-8739.3 [7.2.3]
NASA-STD-8739.4 [10.1.3]

UNACCEPTABLE

CONDUCTOR DAMAGE

Cuts, nicks, scratches or scrapes which reduce the conductor's overall cross-sectional area, reduce the current carrying capability and/or expose conductor base metal are rejectable.

NASA-STD-8739.3 [7.2.3], [13.6.2.a.8]
NASA-STD-8739.4 [10.1.3], [19.6.2.a.2]

conductor stranding exhibiting a normal twist pattern stranded conductors exhibiting a disturbed twist

ACCEPTABLE

STRANDING LAY/TWIST PATTERN

Conductor stranding exhibits a normal twist pattern (lay).

NASA-STD-8739.3 [7.2]
NASA-STD-8739.4 [10.1], [19.6.1.a]

UNACCEPTABLE

DISTURBED LAY

Standard conductors exhibiting a disturbed twist pattern (lay) shall be rejected. Stranding which has been returned to the original lay is acceptable, provided no other damage is present.

NASA-STD-8739.3 [7.2.4]
NASA-STD-8739.4 [10.1.4], [19.6.1.a.2]

birdcaged strands burned and corroded conductor

UNACCEPTABLE

BIRDCAGED STRANDS

Birdcaged strands are typically the result of poor handling. The strands may be returned to the original twist pattern (lay), provided no other damage is present.

NASA-STD-8739.3 [7.2.4], [13.6.2.a.4]

UNACCEPTABLE

BURNED/CORRODED CONDUCTOR
(CHEMICAL STRIPPING)

Burns and/or corrosion are typically caused by the use of an extremely aggressive or chemically incompatible stripping agent, or excessive exposure.

NASA-STD-8739.3 [6.6.2.c], [13.6.2.a.7]
NASA-STD-8739.4 [19.6.2.a.2]

NASA WORKMANSHIP STANDARDS
NASA logo Released:

03.31.2000
Revision:

B
Revision Date:
07.03.2002
Book:
1
Section:
1.01
Page:
6




WIRE PREPARATION
GENERAL REQUIREMENTS (cont.)
burned strands conductor with a red mark over it to denote that it is not acceptable to used chemical stripping for incorrect conductor types

UNACCEPTABLE

BURNED/ETCHED STRANDS
(THERMAL STRIPPING)

Burned or etched strands are typically caused by current flow between the thermal stripper blades, or as a result of stripping an energized conductor.

NASA-STD-8739.3 [6.6.2.b], [13.6.3.a.7]
NASA-STD-8739.4 [19.6.2.a.2]

UNACCEPTABLE

CHEMICAL STRIPPING PROCESS
INCORRECT CONDUCTOR TYPES

Chemical stripping of other than solid, single-conductor wire (i.e.: coaxial cable, flat cable, multi-conductor cable, ribbon cable, shielded, stranded, etc.) is prohibited.

crushed strands frayed strands

UNACCEPTABLE

CRUSHED STRANDS

Crushed strands are an indicator of improper tooling, resulting in reduced conductor cross-sectional area, reduced current carrying capability and reduced reliability.

NASA-STD-8739.3 [7.2.3]
NASA-STD-8739.4 [10.1.3], [19.6.2.a.2]

UNACCEPTABLE

CUT OR FRAYED STRANDS

Cut or frayed strands are an indicator of an improper process or tooling, resulting in reduced current carrying capability and reduced reliability.

NASA-STD-8739.3 [7.2.3], [13.6.2.a.8]
NASA-STD-8739.4 [10.1.3], [19.6.2.a.3]

flat cable with damaged shield strands overlapping each other

UNACCEPTABLE

DAMAGED SHIELD

Cut, crushed, gouged, damaged or nicked shielding may result in reduced electrical isolation and/or short circuits.

Best Workmanship Practice

UNACCEPTABLE

OVERLAPPING STRANDS

Strands, retwisted and overlapping each other, will result in increased stress and difficulty in insertion, or the forming of a mechanical wrap.

NASA-STD-8739.3 [7.2.4]
NASA-STD-8739.4 [10.1.4]

NASA WORKMANSHIP STANDARDS
NASA logo Released:

03.31.2000
Revision:

B
Revision Date:
07.03.2002
Book:
1
Section:
1.01
Page:
7




WIRE PREPARATION
GENERAL REQUIREMENTS (cont.)
ringed conductor flat cable with unevenly trimmed insulation

UNACCEPTABLE

RINGED CONDUCTORS/STRANDS

Ringing is a symptom of an improper process or tooling. Ringing which reduces the overall cross-sectional area and/or results in exposed base metal shall be cause for rejection.

NASA-STD-8739.3 [6.6.1], [7.2.3], [13.6.2.a.8]
NASA-STD-8739.4 [6.6.1], [10.1.3], [19.6.2.a.2]

UNACCEPTABLE

UNEVENLY TRIMMED INSULATION

Unevenly trimmed insulation may result in reduced electrical isolation and/or short circuits, and may interfere with terminations.

Best Workmanship Practice

flat cable with unevenly trimmed shield wicking under the insulation jacket

UNACCEPTABLE

UNEVENLY TRIMMED SHIELD

Unevenly trimmed shielding indicates poor technique and may result in improper electrical termination during connector assembly.

Best Workmanship Practice

UNACCEPTABLE

WICKING

Wicking of chemical stripping and/or cleaning agents under the insulation jacket is a long-term reliability concern.

NASA-STD-8739.3 [13.6.2.a.9]












NASA WORKMANSHIP STANDARDS
NASA logo Released:

03.31.2000
Revision:

B
Revision Date:
07.03.2002
Book:
1
Section:
1.01
Page:
8


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