Key points of quality control in automotive wiring harness manufacturing process

1 the introduction
Auto industry as a typical industrial products since the second industrial revolution, after more than hundred years development, the production technology has been very mature, with the advancement of industrial equipment of electrification and informationization, in the new period as the nervous system of car wiring harness manufacturing process has received people's attention, to explore the automotive wiring harness manufacturing process quality control points, to enhance the level of the automotive industry electrification, percent of pass is of great significance for both car equipment.
Basic classification of automotive wiring harness assembly
Automotive wiring harness assembly consists of main beam, the top of the car body wiring harness, wiring harness, engine tail wiring harness and other categories, including body main beam is to constitute the most complex automotive wiring harness assembly, and the most branches, features the most comprehensive harness, is central to spread around with driver dashboard, by linking the car dashboard overall hierarchical electronic devices and power systems, wiring system including generators, fuse wire switch, relay, and close points.
The wiring harness on the top of the car is connected with the main wiring harness, and the electrical system is connected with the electrical appliances on the upper layer of the car. When in use, the electrical signal enters the main wiring harness, and power is supplied to the equipment such as the roof lights and skylights. The tail wire harness and the top wire harness work in the same principle. After docking with the top wire harness, the electrical signal enters the main wire harness during use and supplies electricity to the rear Windows, Windows, windshield wipers, trunk and other equipment. Generally, the engine wiring harness is connected with the main wiring harness, which is responsible for the electrical signal transmission of the electronic injection control device, engine sensor, ignition system and other equipment. These wiring harness together constitute the assembly of automobile wiring harness production today, and it is the carrier of electrical system transmission at all levels.
Automobile wiring harness production process
The main processes of automotive wiring harness production include :(1) off-line; (2) Terminal crimping; (3) Pull-off force detection; (4) Terminal plugging; (5) Equipment assembly; (6) Electrification detection; (7) Several main processes such as appearance inspection.
The production of automotive wiring harness is developed on the basis of the labor-intensive industries, traditional industries, based on the working procedure is much by manual operation, due to the technical differences between workers and the instability of manual operation, in the process of automotive wiring harness production, completes the production control, proposed in view of the different production process operation standard is very important, each worker only in the process of production strict operating standards, can ensure that the yield of wiring devices.
The off-line process is referred to as "stripping head" in the industry, that is, workers will conduct centralized cutting of the wire according to the process standard. During the wire stripping process, the cutting length and method of insulation skin shall reduce the wire diameter, length and fiber core error to below millimeter level. In the process of wire stripping, the length of peeling shall meet the quality requirements, the incisions of wire insulation skin shall be kept smooth, and there shall be no loose wires and no oxidation in the wire core, so as to avoid wrong connection and virtual connection during wiring. After wire stripping, the stripping head shall be equipped with a unified protective cover to avoid oxidation and bifurcation of the wire core due to preservation problems. Before waiting for the next process, the wire shall be placed on the wire rack during transportation to reserve space for terminal insertion.
Key points of quality control in automotive wiring harness manufacturing
4.1 Material Inspection
For the inspection of industrial raw materials of various types used for automobile wire harness manufacturing, the inspection should begin with the conductor. The conductor raw materials should be smooth and complete by visual inspection, the surface of the insulation layer should be without notch and shiny, the thickness should be moderate, and the production error should not be more than 5 mm. The number and color of the wire core meet the wire bundle manufacturing standards. The whole wire has no oxidation blackening phenomenon. The resistance detection is conducted according to JASOD611/1994 standard. Secondly, the detection of plug and rubber parts is as follows: the surface metal coating film of the wire harness plug is smooth and has no gap; the supporting terminal materials are well combined to ensure the connection parts are fastened without looseness; the heat resistance of rubber parts is in accordance with the inspection standard of 70 hours of continuous heating at 100 ° C; the hardness change is limited within 15 ° C. Finally, the relay and thermal shrinkable tube inspection standard shall be set. The relay shall be seamlessly connected with the connector, and the fastening degree shall be good without looseness. The relay shall conduct frequency sweep vibration experiment in the silent environment, and meet the quality standard. The heat damage tube is visually free of impurities and bubbles, the overall structure is smooth and level without notch, and there is no leakage in the ventilation experiment. Flame retardant test, ensure self-extinguishing within 20 seconds from fire.
4.2 Offline inspection
Off-line inspection is the first process of automotive wiring harness manufacturing. The strict execution of off-line inspection is the basis of ensuring production quality. In the first step of off-line inspection, the cutting length of stripping head is measured with professional vernier caliper. Then, according to different wire harness classification, the full stripping and half stripping wire head are separated, and the half stripping wire length is reserved. Full strip wire to use special protection for pipe, avoid the improper storage wire core, insulator outer phenomenon such as fracture, qualified line shall be smooth incision neatly, without damage, wear phenomenon, no gap length multiconductor body to ensure consistent, copper wire inside show no sign of oxidation, bale transport process, 50 root/bundle conductor cross-sectional area shall be less than 4 was.
4.3 Terminal crimping
Terminal pressure welding is the key link in the process of automotive wiring harness production, the main technological process is connect electrical system and terminals, terminal and circuit using the machine process together and keep the fastening state, to achieve automotive electrical system and flexible operation, prompted the electrical conduction and the effect of solid, good terminal pressure welding device can reduce the line resistance, avoid wire oxidation of inner core, to ensure smooth and airtight structure in power system tightness. Most terminal crimping is single-wire crimping, but occasionally there is a parallel crimping phenomenon. The crimping of two or more lines is called the closed line. In order to ensure the quality of crimping, it is necessary to adopt the pull-off force test and the crimping height to judge the line crimping effect.
Pulled off force detection principle, in order to pull tester for testing equipment, wiring harness production process, due to the production standard is different for different wire diameter, standard equipment to detect pulled off force is not the same, the first part of the terminal detection process card into the device, and the other end of the circuit connected to the terminal facilities dynamic parameters of 125 mm/min pulled off force test, terminal to maintain pressure on the upper insulating layer is qualified.
4.4 Pre-installed process testing
Pre-installed process testing process, in accordance with international quality standards, to respectively by pulled off force detection and terminal pressure welding wires in accordance with the process sequence access equipment, testing before according to the requirements of the process for standard classification with wiring and protection equipment types, protection equipment and terminal pressure welding quality, such as a preloaded materials do not conform to the quality standard or semi-finished products unqualified phenomenon, should immediately stop the pre-installed, terminal crimping excuse must be intuitive and level off, without extensive skew, to ensure that the terminal integrity. Assembly process error, if any, in the assembly process, equipment cables will overflow, excuses and wire connecting the bad situation, so in the pre-installed phase shall be repeated to confirm terminal access, wire access hole should follow the production index of instruction, check the order, after the terminal clamp, such as back together after the terminal is not reset, namely that terminal connected to the correct terminal access after the smoothness of range estimation exterior, guarantee the shape and insulating mouth tilt, strip head protection device in the exposed wires to straighten out the inner core, cannot appear tangled lines and different length of the phenomenon.
4.5 Assembly operation detection
Assembly procedure is automotive wiring harness manufacturing process second half assembly phase of the process, at the end of the offline test and terminal crimping steps, will be offline in production order inserting clamp, strapping, wire wound on the mounting plate, pressure into a wiring harness, used for the wire harness assembly parts, assembly process, close attention must be false wiring error, this link error will cause electrical system chaos, serious impact on production safety, the second is to avoid wiring harness mixed phenomenon, error, if cannot be correct in the test link, follow links to review will be difficult to determine system fault, wiring harness system of secondary damage, cause production schedule lag, Or unable to connect the power system in the loading stage, which will affect the enterprise benefits after returning to the factory; Can appear sometimes assembly link wire winding don't tighten, pressure does not reach the designated position, cause comprehensive harness electrical order confusion, part of the line pressure is too large, wire current exceeds the design index, cause the open circuit, the phenomenon such as burning, so in the region of the wiring harness bifurcate should always check line core status, such as a fork, should according to the colors and materials sequence reserved conductor, secondary cutting and strapping according to production specification, otherwise the assembly process in wire length is insufficient, excessive pressure contact density and so on.
End of the wire harness assembly, according to the function to distinguish the hang on the special line, line of frame structure should be according to the characteristics of vehicle design, such as no skylight design, part of automobile body at the top of the beacon, without the top wire does not need access to the main line, but line to set aside the top wire space as room for technical reform, avoid wire redundancy, make the protection line set and terminals in the process of assembly and transport damaged, affect the assembly quality.
4.6 Key points of wire harness conduction test and final inspection
Wire harness conduction can be divided into two types: manual conduction test and equipment power on test. Manual conduction testing originated from an early stage of electrification, wiring harness production process, due to technical limitations and product stability, conducting inspection cannot enter electronic experiment, in the process of modern car production, some moment because did not finalize the design product, stamping machine tool structure, electricity testing may not be able to achieve the effect, so the manual conduction testing still have certain market in modern times. The tools used in manual conduction detection include buzzer, sensing equipment, indicator light, etc. With the cooperation of two staff members, electric shock measurement method is adopted to conduct conduction detection. Due to low efficiency and unstable human factors, manual detection is prone to missing detection, which needs to be completed under the guidance of relevant technical personnel.
Manual detection has been gradually replaced by on-off equipment detection due to many limitations and single detectable items. The wire harness conduction detector is the main equipment for electrification detection. It carries out multi-level project detection of the circuit according to the pre-set program. It has strong universal logic, precise and accurate data, simple structure and easy operation. If NG and continuous detection alarms occur, it indicates that the main contact of the line is bad or there is a pressing problem, which requires repair and troubleshooting by the production department. Conduction testing passed, wiring harness quality control in the final stages, need to check appearance and size, including check the terminal for a breakout, damage phenomenon, have pressure welding parts without damage and insulation gap phenomenon, ensure the wire stripping head outside the wire core tightly and orderly, no overflow and bending wire integration parts, size comply with the design standards.
5 conclusion
In the production of automotive wiring harness, must complete the terminal pressure welding inspection, not blindly pursue progress, should be completed at the right speed operation pressure, then connect the terminals for wire in strict order of access hole, assembly process, to avoid false wiring and error, etc. Phenomenon, after the wiring harness assembly, should be completed electricity inspection equipment general assembly. The production technology level of automobile wiring harness directly affects the quality of automobile leaving the factory. It is hoped that relevant research departments and enterprises can pay attention to it and actively explore more quality control methods.