Quality Control in Automobile Harness Production

The car wiring harness is also known as the "blood vessel" of the car. It is often referred to as the central nervous system of a car. The position of the car harness design in the whole vehicle is very important. Studying the quality control points of the automotive wiring harness manufacturing process is of great significance for improving the vehicle qualification rate and reliability. There are four main processes in the production of automotive wiring harnesses: stripping – crimping – pre-loading – assembly. The production process sets the corresponding standardized operation specifications for different production processes, so that the quality of the wire harness products produced can be effectively guaranteed.

(Image from Internet)

Stripping process

Stripping refers to stripping the insulation on the wire according to the requirements of the work instruction, and the length should meet the requirements. Good stripping requires wire type, wire diameter, thread color, wire length, strip length, appearance, etc. to meet the requirements.
Precautions when stripping: 1 peeling length meets requirements; 2 insulating skin cut surface is uniform; 3 core is not cut or injured, the core is not scattered or twisted; 4 core has no loose wire; 5 core has no oxidation and black, if the line When the core is oxidized and blackened, it is easy to cause a virtual connection.
After the stripping is completed, the wires should be bundled into a handle according to a certain amount, and a protective cover should be attached to each stripping head to prevent the core from being forked or scattered, and placed on the wire rack, and the handling process should be minimized. In the production process, some companies do not take the necessary protective measures after the stripping is completed, or the protective measures are improper, which may cause the core to be scattered, bifurcated, twisted or broken. It is difficult to operate the crimping terminal in the subsequent process, and the quality of the crimping is poor.
Terminal crimp
The crimping process is the most important part of the entire wire harness production process. The crimping must first carefully check the wire type, specification, color and terminal specifications and crimping end stripping dimensions on the process card. It is especially important to check the quality of this link. The quality of the terminal crimping is mainly ensured by the crimping equipment and the crimping die on the equipment. The stripping head needs to be positioned in the terminal crimping, instead of being visually guaranteed by the operator. After the crimping is completed, the mechanical properties of the terminals and the electrical properties must be ensured by the pull-off test to verify the quality of the crimping.

(Image from Internet)

Terminal crimp inspection:
1 Appearance inspection: The terminal is crimped, and the first piece inspection must be carried out. The first piece needs to take 3~5 to judge. Visual terminal crimping Appearance is good; whether there is leakage of wire; whether the wire is broken or the insulation is pierced or cut. Whether the insulation layer, the wire and the terminal are tightly combined, and whether it is in the specified area;
2 Pulling force test: The pull-out force test is mainly to test the tightness of the combination of the terminal and the wire harness. Through the pull-off force test, it is confirmed whether the maximum pull-off force meets the specified requirements. The normal pull production can only be carried out after the pull-out test meets the requirements. The first piece must be saved to ensure subsequent traceability.
In the terminal crimping process, many companies pursue speed, and think that the operator presses the terminal as fast as possible to measure the performance of the employee. This is not advisable. Korean companies have clearly stipulated that the crimp terminals should not exceed a certain speed, because only at such speeds and conditions, the quality and yield of the crimp terminals are optimal.
Pre-installation process
Insert the wires of the crimped terminals into the connector holes in the order and method specified in the procedure. Or insert the waterproof plug into the connector hole. Key points: Before packing, carefully check the type of sheath and the type of wire specified on the process card. Check the quality of the sheath and wire and terminal crimping. If the material or semi-finished product is unqualified, it cannot be packaged. The terminals must be inserted into the position and flat, that is, the top ends of the terminals are in the same plane, without skewing, and the terminals are not deformed.
The assembly is not in place and the wires will fall out of the insert in the subsequent process. Therefore, pull back during assembly to confirm that the terminal is fully inserted into the cassette.
Quality Standard:
The hole position of the 1 terminal must be in accordance with the hole position requirement of the packing diagram. The hole position arrangement is seen from the terminal insertion direction; 2 The plug terminal must be implemented in three steps of “push”, “listen” and “pull” to ensure the terminal. In place, will not quit. In particular, it must be pulled back after the terminal is inserted. After the pull-back, the terminal does not exit, indicating that the terminal is plugged into the position;
After the 3 terminals are inserted, the appearance must be neat and in place, without skewing;
4 The wire drawn after the sheath shall be smooth, and there shall be no obvious difference in length and length, resulting in a single force phenomenon.
Final assembly process

The final assembly process refers to the wires that are inserted into the sheath, and the clamps are assembled according to the process requirements, and bundled and wound on the assembly board to form a wire harness for a specific purpose.

(Image from Internet)

Precautions in the final assembly:
1 Hole assembly error (also known as incorrect wiring), this is the most serious error in assembly, affecting the safety of use (points and quality requirements of each process of wire harness production);
2 In the assembly process of the wire harness, pay attention to the phenomenon of mis-slip installation. If the wrong leakage device cannot be found in time, it will cause large-scale repair work and cause secondary damage to the wire harness. The wiring harness has fewer clips, which makes it impossible to assemble when loading. The wiring harness is in the wrong position, resulting in the inability to load the vehicle;
3 Wire bundles are not entangled or entangled, resulting in loose wires and missing wires. In the assembly process of the whole vehicle wiring harness, the wire harness is scratched, and the single wire is accepted too large, eventually causing the wire harness to be damaged;
The 4-wire bundle has a fork, so be sure to straighten the harness and then bundle or wrap it. Otherwise, during the loading process, the wire harness may be twisted, or the size may be insufficient, and the buckle or the fixed point may be subjected to excessive force, causing damage to the fixed point, eventually abnormal sound, or wearing the wire harness;
5 After cutting the strap, the part of the tail should be 5 ~ 15mm, and there should be no sharp corners;
After the assembly of the 6-wire bundle is completed, the wire frame is hung on the wire frame. The wire frame should be made reasonably, and the wire harness should not be dragged on the ground, causing the sheath or the terminal to be scratched or trampled, causing damage.
Final test 
After the harness assembly is completed, the power check and the appearance size check are performed.
First, power on check.
The power-on check is to connect the sheaths and connectors of the harness to the detection device. After the connection is in place, the device will automatically judge each line. The device has pre-input detection procedures for each type of harness, all After passing the device, the device will display 0 K. If a certain line of a branch is faulty, the display of the device will be displayed in different colors. The inspection personnel will perform the inspection according to the equipment prompts after the inspection and repair. Until all qualified. Do not savagely pull the harness when testing to avoid damage to the harness. Products that fail to pass the test shall be marked with red tape and placed on the special non-conforming product box or designated trailer, and delivered to the designated maintenance worker for repair. The power-on check must be 100% checked.
Second, the appearance size check.
The appearance size inspection is placed after the power-on inspection, mainly because the terminal connectors on the power-on inspection equipment of some enterprises are damaged, which may cause the pins on the harness to be damaged, skewed, dropped, and broken. The visual inspection should start from one end of the harness and be checked one by one in order to avoid omissions. Check whether the stitches in each sheath are skewed, uneven, whether the wire bundle is thick and tightly wrapped, whether the waterproof plug is detached, whether it is assembled in place, and whether the buckle is loose. Once it is found to be unqualified, it is necessary to affix the mark to the unqualified place, write the unqualified mode, and place it in the non-conforming product area, and return it for rework.
Finally, the size check.

The dimension inspection mainly places the wire harness on the inspection tool, locates the wire harness, checks whether the position of each clamp is within the specified range, whether the length of the wire harness meets the requirements, and whether the length of each branch meets the requirements. After passing the inspection, the qualified label is attached and packed into the warehouse.

In order to facilitate users to better understand automobile Harness, Konnra Electronics hereby organizes the knowledge of automobile Harness, and hopes to be helpful to the majority of users.