Performance Analysis of Ties, Snaps, Brackets and Protective Tubes in Automotive Wiring Harnesses

Wire harness fixing design is an important part of wire harness layout design, and its main forms include cable ties, buckles, and brackets.

1 Cable ties

Cable ties are the most commonly used protective materials for fixing wire harnesses, mainly made of PA66 material. Most of the fixing in wire harnesses is done with cable ties. The function of cable ties is to fasten the wire harness and firmly and reliably fix it in the body sheet metal holes, bolts, steel plates, and other parts, preventing the wire harness from being damaged by vibration, displacement, or interference with other components.

Although there are various types of cable ties, they can be divided into the following categories according to the type of sheet metal: card round hole cable ties, card waist round hole cable ties, card bolt cable ties, card steel plate cable ties, etc.

Card round hole cable ties are commonly used in areas where sheet metal is relatively flat and wiring space is large, such as in the driver's cab, where the diameter of the circular hole is generally 5-8 mm

Card waist round hole cable ties are often used on thicker main or branch cables. After installation, this type of cable tie cannot be rotated freely and has strong stability. It is mostly used in the front cabin, with a diameter of generally 12 × 6 mm and 12 × 7 mm

Card bolt cable ties are commonly used in areas with thick sheet metal or uneven wiring, such as firewalls, where the aperture is generally 5mm or 6mm

The card steel plate cable tie is mainly used at the edge of steel plate sheet metal to clamp the sheet metal, making the wire harness smoothly transition, and avoiding the wire harness from being scratched by the edge of the sheet metal. It is mostly used at the wire harness and rear bumper located in the cab, and the thickness of the sheet metal is generally 0.8~2.0mm.

2 Buckles

The function of a buckle is the same as that of a cable tie, both of which are used to secure and protect the wiring harness. There are various materials available, such as PP, PA6, PA66, POM, etc. The commonly used types of buckles include T-shaped buckles, L-shaped buckles, pipe clamp buckles, plug-in buckle buckles, etc.

T-shaped buckles and L-shaped buckles are mainly used in places where the wiring space of the wiring harness is narrow due to the installation of exterior decorations, or where the wiring harness itself is not suitable for drilling holes, such as the edge of the cab ceiling, which is generally a circular hole or waist circular hole;

Pipe clamp buckles are mainly used in places where drilling is not suitable or impossible, such as engine bodies, which are generally tongue shaped sheet metal;

The plug-in buckle is mainly used in conjunction with the plug-in connector to fix the plug-in connector on the vehicle body. It is generally a circular hole, waist circular hole or keyhole. This type of buckle is more targeted and can only be used for a corresponding series of plug-in connectors.

3 bracket guard plate

The universality of wire harness brackets and protector is poor, and the wire harness brackets and protectors designed for different car models are not the same. There are various materials such as PP, PA6, PA66, POM, ABS, etc., and the general development cost is relatively high.

Wire harness brackets are generally used to fix connectors and are often used at the junctions between different wire harnesses;

Wire harness protectors are generally used to secure and protect wire harnesses, and are often used on wire harnesses located in the engine body.

Automotive wiring harnesses should have high and low temperature resistance, temperature and humidity cycling resistance, vibration resistance, smoke resistance, and industrial solvent resistance. Therefore, the external protection of the wire harness plays a crucial role. Reasonable materials and wrapping methods for the external protection of the wire harness can not only ensure the quality of the wire harness, but also reduce costs and improve economic benefits.

The car wiring harness is fixed to the entire vehicle body, and damage to the wiring harness directly affects the performance of the car circuit. Here are the characteristics and usage scenarios of various types of automotive wiring harness wrapping materials.

1 Bellows

The corrugated tube occupies a relatively large amount in the bundle wrapping process. The main feature is good wear resistance, with excellent high temperature resistance, flame retardancy, and heat resistance in high temperature zones. The temperature resistance is generally between -40~150 ℃. According to the wrapping requirements, it is generally divided into two types: closed corrugated pipes and open corrugated pipes. The closed corrugated pipe combined with the wire harness clamp can achieve good waterproof effect, but it is difficult to assemble. Open corrugated tube is commonly used in ordinary wire harnesses and is relatively easy to assemble. According to different wrapping requirements, PVC tape is generally used for full wrapping and point wrapping on the outside of corrugated pipes. According to the material, commonly used corrugated pipes for automotive wiring harnesses are divided into four types: polypropylene (PP), nylon (PA6), polypropylene modified (PPmod), and triphenyl phosphate (TPE). The commonly used inner diameter specifications range from 4.5 to 40.

PP corrugated pipe has a temperature resistance of up to 100 ℃ and is the most commonly used type in wire harnesses

PA6 corrugated pipe has a temperature resistance of up to 120 ℃ and is outstanding in terms of flame retardancy and wear resistance, but its bending resistance is lower than that of PP material

PPmod is an improved type of polypropylene with a temperature resistance rating of 130 ℃

TPE has a high temperature resistance level, reaching 175 ℃.

The basic color of corrugated pipes is black, and some flame-retardant materials allow for a slight gray black color. For special requirements or warning purposes, yellow can be used (such as airbag wiring harness corrugated pipes).

2 PVC pipes

The material of PVC pipe is soft polyvinyl chloride, with inner diameter specifications ranging from 3.5 to 40. The inner and outer walls of the pipe are smooth and the color is uniform, which can achieve a good appearance effect. The commonly used color is black, and its function is similar to that of corrugated pipe. PVC pipes have good flexibility and resistance to bending deformation, and are generally closed. Therefore, PVC pipes are mainly used at the branching points of wire harness bends to ensure smooth transitions of wires. The heat resistance temperature of PVC pipes is not high, generally below 80 ℃, and special high temperature resistant pipes are 105 ℃.

3 Glass fiber sleeves

Using glass yarn as the base material, woven into tubes, impregnated with silicone resin, and then dried, it is suitable for wire protection between electrical appliances that are prone to high temperature and high voltage. It has a temperature resistance of over 200 ℃ and a voltage resistance of over kilovolts. The commonly used color is white, and other colors (such as red, black, etc.) can be dyed according to different customer requirements. The diameter specifications range from 2 to 20. The fusible link in the general wiring harness is used in this tube.

4 tapes

Adhesive tape plays a role in bundling, wear resistance, temperature resistance, insulation, flame retardancy, noise reduction, and marking in wire harnesses. It is the most commonly used type of wire harness wrapping material. The commonly used adhesive tape for wire harnesses is generally divided into four types: PVC tape, velvet tape, cloth based adhesive, and sponge tape.

PVC tape is a roll shaped adhesive tape made of insulating polyvinyl chloride film as the substrate, uniformly coated with pressure-sensitive adhesive on one side, and has good adhesion, durability, and electrical insulation properties. After unwinding the tape, the film surface is flat, the color is uniform, the two sides are flat, and the temperature resistance is around 80 ℃. The main function of the harness is to tie it up.

Commonly used velvet tape is made of polyester non-woven fabric as the substrate, coated with high peel strength solvent-free rubber pressure-sensitive adhesive. It has no solvent residue, is corrosion-resistant, has noise reduction performance, can be torn by hand, is easy to operate, and can withstand a temperature of 105 ℃. Due to its soft and corrosion-resistant material, it is very suitable for use in noise reducing parts of automotive wiring harnesses, such as instrument panel wiring harnesses. High quality acrylic velvet tape can provide excellent temperature resistance, oil resistance, and aging resistance. Made of high-quality polyamide velvet fabric, with high viscosity, no hazardous substances, corrosion resistance, balanced unwinding force, and stable appearance.

Fiber cloth tape is used for high-temperature resistant winding of automotive wiring harnesses. Smooth and durable flexible automotive wiring harnesses can be obtained through overlapping and spiral winding. Made of high-quality cotton fiber cloth and strong rubber type pressure-sensitive adhesive, it has high viscosity, no hazardous substances, can be torn by hand, good flexibility, and is suitable for machine and manual use.

Polyester cloth tape is specially designed for high-temperature winding of wiring harnesses in the engine area of automobiles. Due to its high strength, oil resistance, and temperature resistance, the substrate is an ideal product for use in the engine area. It is composed of high-quality polyester fabric with high oil resistance and strong acrylic pressure-sensitive adhesive. Sponge tape is made of low-density PE foam as the substrate, coated with high-performance pressure-sensitive adhesive on one or both sides, and compounded with silicone release material. There are various thicknesses, densities, and colors to choose from, which can be rolled or die cut into various shapes. Adhesive tape has excellent weather resistance, adhesion, cushioning, sealing, and superior bonding properties, and is widely used.

Velvet sponge tape is a high-performance wire harness protection material. Its base layer is a layer of velvet composite with a layer of sponge, coated with a specially formulated pressure-sensitive adhesive. It plays a role in noise reduction, shock absorption, and wear protection, and is widely used in instrument wiring harnesses, roof wiring harnesses, and door wiring harnesses of Japanese and Korean cars. Its performance is better than ordinary velvet tape and sponge tape, but the price is also relatively expensive.

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