Defect causes and preventive measures of wire harness stranded wire products

2022-01-11
The 9 defect reasons and preventive measures of  wire harness stranded wire products.
  Defective products and waste products of beam/stranded wire, the main problems are:  
 
1. The twisted;  
2. Inner or outer layer single line fracture, missing strand;  
3. Single wire or stranded wire surface abrasion;  
4. Single wire back strand;  
5. Single wire peeling, spot scar, brittle break, arch, inclusion;  
6. Wire diameter out of tolerance or wrong mixing;  
7. Twist loose strands;  
Wrong twisted direction, serpentine shape, large twisted pitch and unqualified length;  
9. Disorderly wiring, crushing, scratching, bumping, and unqualified DC resistance of conductive wire and cable.   
01 a twist  
Over-twist refers to the phenomenon of over-twist twist in the process of twisting.  
 
Causes:  
 
(1) The number of turns around the stranded wire on the traction wheel is not enough, generally less than 4 turns, the friction force is too small and slip, resulting in excessive twisting.  
(2) The tension of the line is loose or the reel does not turn, and the body is still rotating, resulting in excessive twisting.  
 
Elimination method:  
 
A. If the outer single wire has been severely deformed and seriously damaged, there is no possibility of repair but cutting.  
B. If the single wire is not seriously damaged, the rotating part of the equipment can be separated from the traction part, and it can be turned in the opposite direction to the twisted part, so that the local twisted part back.  
→ use the hand to fix the line core, and the extra single line is wound to the reel, the equipment and the body traction in one.  
→ After the loose overpressure wire die, press the line forcibly and repair it manually with the mold, so that the production can be restarted.  
 
02 Stranded break/missing strand break  
Causes:  
 
The core is broken due to excessive tension.  
(2) The single wire is loose and disorderly when it is drawn, the line is not well arranged and the line is pressed across the line, resulting in the core being broken.  
The material of the single line itself has cracks, and the mechanical properties are not good and brittle.  
④ Improper installation position of the cable tray, axial shaking, resulting in wire break.  
⑤ The single wire jumps out of the pulley groove, and the machine is stuck.  
 
Elimination method:  
 
A. Adjust the wiring tension to make it appropriate.  
B. Pay attention to the selection of incoming wire. It is found that the drawing wire is loose and disorderly, and the machine can be operated after rewinding.  
C. Pay attention to the operation method, carefully check the position of the reel, so that the released line does not swing or jump, check the place where the single line passes, there is no phenomenon of jumping out of the regulating wheel groove.  
D. Check the surface quality of the wire core to see whether there are cracks, slag, spots and scars and other defects.  
D1. If the broken wire occurs in the inner layer and the broken wire has gone too long, it cannot be repaired. The only solution is to cut the core of the missing strand;  
D2. If the disconnection occurs in the outer layer, repair the cable before starting the machine.  
 
03 The surface is bruised and the wire core is scratched  
Causes:  
1. The wire nozzle on the wire distributor is worn.  
2. Single line jump out of pulley;  
3. Threading with wood or plastic pipe grinding;  
4. The positioning pin on the pusher plate of traction equipment is damaged;  
5. There are foreign bodies in the mould.  
 
Elimination methods:  
Replace the threading nozzle and the wood pipe and plastic pipe used for threading, check whether the direction of the wire core is normal, protect the wire core from direct wear with the equipment, and check whether the press die is in good condition at any time, and pay attention to the operation method.  
At present, most manufacturers use double pitch bundle system, so the wire bundle system of more than 19 strands of wire core, back strand, loose strand phenomenon is more serious than stranded wire.  
Elimination method for bundle wire (bundle products above L strands) :  
 
A. Improve the winding device of the bundle wire, and adopt the advanced single-wire tension winding device, so that the tension of each single wire can be adjusted and controlled.  
B. Use guide die, the aperture of guide die is beam wire to calculate the outside diameter knife 97% .  In this way the guide die can adjust the tension appropriately.  
C. Switch to a single pitch bunching machine. The bunching products of this bunching machine can reach the level of stranding.  
D. For the back strand and the bundle core with serious loose strand, the method of mold rewinding can also meet the requirements of use.  
E. Adjust pitch ratio appropriately.  
 
For stranded product back, loose thread elimination method:  
A. Adjust the discharging tension to make it uniform.  
B. Change the press die, do not loosen the core in the die hole, pay attention to the bell mouth of the press die, if the bell mouth has been damaged, can not be used.  
C. Adjust the position of the die holder to ensure that the stranding Angle of the stranded cable is reasonable.  
D. If the stranding pitch is large, it should be appropriately reduced.  
 
05 Single wire grooving/surface defects  
Causes:  
 
1. The pitting, spot scar, triangular crack, slag and other defects on the single wire surface are mainly caused by the material. Of course, there is a phenomenon of breakage on the surface of the wire core, and the unreasonable hole type of the drawing die cannot be ruled out.  
 
2. The grooving on the surface of the wire core is continuous, which is generally caused when the wire is drawn. The lubrication conditions of the wire are deteriorated, and the surface is caused by sticking aluminum.  
 
Elimination methods:  
A. Check whether the lubrication effect of the cable can meet the requirements of the cable. Replace the lubricating oil and the cable die in time, or remove the sundries stuck to the die.  
B. Carefully check incoming lines and eliminate unqualified incoming wires in time.  
C. Check whether there is any damage and debris in the pressing die, and repair and replace it in time.  
 
06 Wire diameter out of tolerance/mixing error  
Causes:  
1. The main reason is that the process regulations are not carefully implemented.  
2. There are certain problems in management.  
 
Elimination method:  
A. If the length of the wrong wire core is not long, you can remove it, replace it again, and repair it according to the wiring repair method.  
A1. If the length is too long, it can not be repaired, only to dismount and be dealt with separately;  
A2. Before the machine, the operator should carefully check and measure.  
B. Of course, managers should also provide a guarantee.  
B1. For example, whether the line gauge is too much, whether the tolerance is reasonable, whether the production scheduling is properly arranged;  
B2. Carefully consider the existing problems in management according to THE PRINCIPLES of PDCA, and avoid the generation of artificial defective products and waste products.  
 
07 Twisted wire core is loose  
Causes:  
1. The pitch is too large, resulting in the unsolid core of the stranded wire.  
2. The pressure die hole is too large to play the role of compaction and regulation.  The bell mouth of the wire mould is too large or worn or damaged.  
3. Unevenness of tension, loose and tight.  
4. The pitch ratio of each layer is not well coordinated.  
5. The state of wire core does not meet the technical requirements, especially aluminum wire core.  
6. Improper position of wire splitter and die holder, etc.  
 
Elimination method:  
A. Strict process discipline, implementation of process operation procedures, appropriate reduction of excessive pitch, good adjustment of wire tension and die.  
B. The position between the wire splitter and the die holder is generally adjusted to 200~250mm according to different structures.  
C. For stranding some stranding wires with particularly high tensile strength, the method of combination mould can be adopted, which also has good effect.  
D. The operator shall operate according to the method specified in the process operation rules.  
 
Wrong direction of stranding and unqualified pitch  
Causes:  
The wrong direction is mainly a misjudgment.  
 
Exclusions:  
A. The operator should strengthen the sense of responsibility and strictly follow the process card when operating.  
B. Flow inspection should be strengthened to prevent the generation of artificial defective products and waste products.  
 
09 The line arrangement is chaotic and the line is pressed  
Causes:  
 
1. Stranded products are generally supplied in plates.  
 
2. Large section, to be lined up one by one, especially the bottom line to pay special attention to neatly arranged.  
 
3. When the line is turned around, special attention should be paid to not leaving too much clearance between the upper and lower layers because there is a pause. The row spacing should be appropriate.  
 
Exclusions:  
A. Adjust the tension of wire retracting. When manually arranging wire, it is advisable to move the wire.  
 
B. Replace the line pitch according to the diameter of the wire core. The first layer is the key and must be neatly arranged.  Row the second layer, in the layer adjustment, to carry out manual line arrangement, to ensure the quality of line arrangement.  
 
C. Strengthen the sense of responsibility of operation observe the quality of wiring at any time, timely adjust if any problems are found, and pay attention to fixing the two wire ends and the distance between the left edges.