Chapter 4 Electrical Connections and Wire Harness Assembly 8/8/2015 Dr. Mohammad Abuhaiba1.

Chapter 4

Electrical Connections and Wire Harness Assembly

04/19/23

Dr. Mohammad Abuhaiba1

4.1 INTRODUCTION A descrambler for satellite TV reception.

10 PCBs 51 connecting wires or cables 31 circuit board jumper wires total of 164 connections.

Table 4.1: Original Design Assembly time = 7236s 68% of total assembly time of 10,613 s

Table 4.2: Redesign 10 PCBs could be combined into one eliminate interconnections and jumper wires Reduce assembly costs by 61%

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4.1 INTRODUCTION

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4.1 INTRODUCTION

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4.2 WIRE OR CABLE HARNESS ASSEMBLY Figure 4.3: Harness assembly Figure 4.4: principal operations involved:

1. wire preparation2. harness assembly3. installation in product

Harnesses are usually constructed by manually laying out individual wires or cables on a board that has a full-size schematic drawing of harness mounted on its surface to guide the assembly worker.

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4.2 WIRE OR CABLE HARNESS ASSEMBLY

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4.2 WIRE OR CABLE HARNESS ASSEMBLY During construction, ends of wires must

be held in position. If wires are to be terminated in a

connector, then connector may previously have been inserted into a receptacle mounted on board in correct position.

Ends of terminated wires are then inserted into back of connector.

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4.2 WIRE OR CABLE HARNESS ASSEMBLY Wire ends that are to be connected during

installation in product are retained temporarily on board.

Use of a helical spring mounted on board with its axis horizontal & perpendicular to direction of wire.

Once all wires or cables have been laid, they are bundled together using: tie wraps Lacing split conduit tubing bound with electrical tape.

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4.2 WIRE OR CABLE HARNESS ASSEMBLY When complex harnesses are assembled,

connector receptacles are wired to a computer that continually tests whether wires have been inserted properly.

Figure 4.5: sequence of operations for low, normal, and high complexities

Degree of automation used in wire harness assembly depends on: complexity of harness quantity to be produced

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4.3 TYPES OF ELECTRICAL CONNECTIONS

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4.3 TYPES OF ELECTRICAL CONNECTIONS - Low-Pressure Connections

can be separated without aid of a tool

frequent disconnection and reconnection

tend to minimize errors during servicing because wires remain in correct sequence when disconnected.

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General expectations from low-pressure connections:1. Sufficient contact force for good

conduction2. Good cleaning action during assembly3. Low resistance to mating of parts4. Low wear on parts5. Long life6. Ease in connecting and disconnecting

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Points to consider when choosing a connector:

1. types of conductors to be terminated

2. assemblies to be connected3. No. of contacts required4. final product function5. cost

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4.3 TYPES OF ELECTRICAL CONNECTIONS - 4.3.3 High-Pressure

Connections

Most commonly used methods:1. wire-wrap2. Crimp3. screw connections4. ultrasonic welding5. riveting

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4.3 TYPES OF ELECTRICAL CONNECTIONS - High-Pressure Connections

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4.3 TYPES OF ELECTRICAL CONNECTIONS - High-Pressure Connections

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4.4 TYPES OF WIRES AND CABLES Wire conductors are selected for their:

1. current-carrying capacity

2. mechanical strength

3. type of insulation

4. Cost Cables consist of two or more conductors within a common

covering and are terminated by one or more connectors. Electrical conductors include:

1. single solid or stranded wire

2. twisted pair and trio

3. multi-conductor cables

4. coaxial cable

5. ribbon cable

6. flexible flat cable

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4.4 TYPES OF WIRES AND CABLES Solid and stranded wire is designated by:

1. American Wire Gauge (AWG) number,2. diameter of the wire in mils (thousandths of an

inch), or3. X-section in circular mils (square of diam

expressed in mils). A twisted pair consists of two stranded

conductor insulated wires twisted together. A twisted trio is the same as a twisted pair

except that it consists of three conductors.

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4.4 TYPES OF WIRES AND CABLES Multi-conductor cable consists of two or more color-

coded rubber- or PVC insulated conductors. Coaxial cable consists of an insulated length of

conductor enclosed in a conductive envelope of braided wire shield and an outer insulating jacket isolating the shield from ground.

Ribbon cable consists of numerous conductors of same gauge held side by side in flexible strips of insulation. During termination, the U-contact displaces the insulation

and each conductor is then forced and wedged within a U-contact.

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4.5 PREPARATION AND ASSEMBLY TIMES - Preparation

Manual operation: (Figure 4.11) Insert wire to correct length into

proper station of a stripping tool. close tool to severe the insulation,

which is removed by the tool. Average experimental time = 7.0sMachine stripping: Grasp wire and insert end into a

stripping machine. This triggers machine to strip off

insulation to correct length. Average Stripping time = 3s

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Soldering iron Tinning time = 9 s

Solder pot tinning time = 7.2s

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4.5 PREPARATION AND ASSEMBLY TIMES - Preparation Figure 4.13: times for crimping one

terminal to bare end of a wire. Manual crimping:

insert terminal into a color-coded notch of a crimping tool

place bare end of wire into barrel of terminal. close tool to compress barrel so that it

clamps tightly onto the wire. Experimental time = 13.9s

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Semiautomatic crimping: place bare end of wire into die set, triggering crimping machine. After crimping, a new terminal advances automatically into die set

for next crimping operation. time = 3 s

Some Semiautomatic machines can strip wire and crimp a terminal after insertion of unstripped wire into the machine. Insertion of wire is carried out manually total time = 3.6s

Machines capable of automatically cutting, stripping, and crimping terminals to wires in one operation. Time = 1.8 s per wire end for a length of 3 m.

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30 s is required for stripping a multi-conductor having two wires

For each additional wire, a time of 6 s should be added.

Manual stripping of outer insulation = 18s

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Figure 4.15: manual assembly times for soldering contacts of circular or rectangular connectors. place connector into a fixture and fill all

solder cups. A handful of wires is then grasped using

one hand, with other hand holding soldering iron.

A solder cup is reheated and simultaneously a bare wire is inserted.

Wire is held in position until solder solidifies.

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time for filling solder cups = (6.8 + 3.1 Nc)

Time for soldering wires = (0.2 + 8.3Nc)

Total time ts for assembling a rectangular or circular connector : ts = 7+11.4 Nc (4.1)

This eq does not include cutting & stripping wires or assembling connector


Figure 4.16: manual assembly times for crimping contacts of circular or rectangular connectors. Insert a contact into a crimping tool place bare end of wire into the contact squeeze tool so that barrel of contact grips bare end of wire as well as insulation

on wire Operation is repeated for each contact With connector clamped in a fixture, wire contacts are then inserted one by one,

using an insertion tool. Times for crimping contacts to wires = (1.5 + 12.4 Nc) inserting wire contacts =(1.1 +4.9 Nc)

Total time tp for assembling wires to a circular or rectangular connector: tp = 2.6+ 17.3Nc (4.2) Nc =number of contacts

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Time given by this eq does not include cutting & stripping of wires and assembly of connector

Semiautomatic crimping of contacts to wires: 3 s per contact manually inserting the crimped

contacts into the connector =(1.1 + 4.9 Nc)

total time of 9 s for one contact add 7.9 s to basic time per

contact for installing more than one contact

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Figure 4.17: manual assembly times for one coaxial connector termination.1. Coaxial cable is cut to length2. outer insulation is stripped3. polyethylene dielectric and shield braid are cut to

correct dimensions.4. shield braid is then folded back smoothly and a plastic

grommet assembled onto the cable.5. The contact is crimped to the conductor after it is

assembled, flush against the dielectric.6. connector body is then assembled, braid clamp

crimped, and grommet pushed flush against the body.

7. time for assembling coaxial connector =152 s.

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Figure 4.18: manual assembly time for mass termination of a flat cable.1. place body of connector into the locator plate of a press.2. position flat cable into body of connector and the mating

connector cover is placed over the assembly.3. The UFIG contacts of the connector are forced into the flat cable

conductors by operating the press.4. cable connector is removed from locator plate.

Time for flat cable connector termination = 30 s For flat cable connector termination using a press machine, a

time of 2 s is suggested.

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4.5 PREPARATION AND ASSEMBLY TIMES - Assembly and Installation

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After one end of wire is attached, it is dressed to equipment chassis before other end of wire is attached.

Dressing time does not include cutting & stripping ends of wire, adding terminations, or attaching terminated wire

Experimental time for dressing:td = 3.4 + 1.2 Lw (Lw in ft)

td = 3.4 + 3.94 Lw (Lw in m)


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Dressing wire into U-channelAfter wire is attached at one end, it is inserted into U-channel before other end of wire is attached.Dressing time does not include cutting and stripping ends of wire, adding terminations, or attaching terminated wire


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Dressing flat cable after flat cable connector is attached onto its mating part.

Time for laying a flat cable does not include time for bending and pressing of cable so that it stays bent during laying.

A time of 15.1s per bend should be added to time for laying a flat cable.


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A wire is grasped and one end is attached to a holding device.

Wire is then laid on board according to wiring layout and finished, with the other end of wire being attached to another holding device.


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Time tn to assemble Nw wires simultaneously is


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selection of wire(s) after cable connector is installed on harness jig

laying wire(s) according to wiring layout, and attaching ends to a holding device.

Times do not include attaching cable connector to its mating part on harness jig.


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time tm to assembly Nw wires simultaneously from a connector is:

4.5 PREPARATION AND ASSEMBLY TIMES - Securing

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Times for: acquiring a tie

cord spot tying a

bundle of wires cutting excess

cord with a pair of scissors.

Experimental time = 16.6 s is


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Times for tying a cable tie or strap onto a bundle of wires. acquiring a cable tie,

looping tapered end of strap around harness

inserting it through strap eyelet.

strap is pulled tightly and excess is cut off with a tool.

Experimental time = 14.4 s


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Times for lacing a wire harness.

Completion of lacing terminates when end of cord is secured and trimmed.

Experimental time tst:

Nst = No of stitches


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Times for taping a bundle of wires.

Time for taping 1 in. =13.8 s for first wrap.

a time of 7 s per additional inch


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Times for inserting a precut tube or sleeve over a bundle of insulated wires.Time = 7.4s for inserting first inch of tubean additional 2.4s per inch is added for a tube longer than 1 in.


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1. Shrinking tube using a heat gun.

Time = 5.3s /inch

2. An adhesive cable clamp

Time = 9.4 s


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Times for labeling a wire.

Time =11.4s.

4.5 PREPARATION AND ASSEMBLY TIMES - Attachment

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Figure 4.33: times for attachment of a bare wire to its mating part. Wire is grasped with two hands, moved, positioned, and

bent with a plier around its mating part. Mating part can be mounted in either a terminal block or a

separate. Wire is secured.

Assembly time:1. 7.1 s for attaching a bare wire to a terminal block

2. 23.3 s for a bare wire/screw attachment

3. 30.6s for a bare wire/screw and nut attachment


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Figure 4.34: times for soldering a bare wire to its mating part.1. bare wire is grasped, moved, & positioned to its mating

part2. wire is soldered with a soldering iron. Before soldering,

the wire may be bent using pliers, in which case the bending time must be included.

Attachment time:1. 21.1 s for soldering a bare wire without bending2. 26.6 s if the wire is first bent


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acquire a pre-stripped wire & insert it into tip of wire-wrapping tool

Position Tool over terminal

squeeze trigger Tip of tool spins wire

around terminal to form attachment

Average time =13s


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Figures 4.36 and 4.37: times for attaching a wire terminal to its mating part. A wire terminal is grasped, moved, and positioned to its

mating part. Terminal can be a push-on using a quick disconnect

terminal or it can be fastened on a terminal block using a ring or fork terminal.

The wire terminal (fork or ring) can also be fastened using a screw or a screw and nut combination.


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Attach quick disconnect terminal = 5.4 s

Attach a fork terminal block = 12.5 s

Attach ring terminals to a terminal block = 22.8s


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Attach a terminated wire and secure with a screw = 17.1 s

Attach a terminated wire and secure with a screw and a nut = 24.7 s


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Average experimental times for attaching various types of connectors:Circular connector

install only 5.2 s bayonet type 5.2 s friction type 6.7 s screw thread type 11.3s

Rectangular type install only 6.5 s latch/snap-on type 8.1s spring clip type 9.8 s screw (2 x) type 24.0s

4.6 ANALYSIS METHODFor a wire harness with normal complexity, 3 distinct steps:1.Preparation of wires and cables:

cutting wires or cables to length and terminating them.

marking, sealing, molding, sleeving, labeling.

2. Assembly of harness on a board or jig: laying-in wires

and cables inserting wire

ends into connectors

tying, taping, or lacing bundles or wires, sleeving bundles.

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3. Installation of interconnections or cable harness into chassis or product:3. routing wires or

cables4. insertion of

connectors into their mating parts

5. dressing & connection of any wire ends to appropriate terminals.

6. securing of wires and cables to chassis.

Case Study

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Case Study

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Case Study

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Date post:	23-Dec-2015
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Chapter 4 Electrical Connections and Wire Harness Assembly 8/8/2015 Dr. Mohammad Abuhaiba1.

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