As a critical connection component in electrical systems, the terminal crimping process of industrial control wiring harnesses directly impacts contact resistance, affecting signal transmission stability and equipment reliability. Contact resistance is the additional resistance generated when current flows through the interface between the terminal and the conductor. Its value is influenced by multiple factors, including material properties, crimping process parameters, and the condition of the contact surface. Terminal crimping in industrial control wiring harnesses uses mechanical force to create a permanent connection between the terminal and the conductor. Improper process control can lead to a significant increase in contact resistance, resulting in localized overheating, signal attenuation, and even equipment failure.
The core objective of the crimping process is to achieve a tight bond between the terminal and the conductor through plastic deformation. The formation mechanism of contact resistance is closely related to the contact area, contact pressure, and material surface condition. Ideally, the contact surface between the terminal and the conductor should form a large area of direct metal-to-metal contact, where the contact resistance primarily depends on the resistivity of the material itself. However, in actual crimping, the contact surface is typically composed of numerous tiny contact spots. Current must pass through these discrete conductive channels, resulting in a contact resistance significantly higher than the theoretical value. If the crimping pressure is insufficient or the mold matching is poor, the number and area of contact spots decrease, further increasing the contact resistance. Crimping height is one of the key process parameters affecting contact resistance. Excessive crimping height can lead to poor contact between the terminal and the wire, resulting in gaps or cavities on the contact surface, obstructing the current path. Insufficient crimping height can cause excessive deformation, leading to terminal cracking or damage to the wire insulation, also worsening the contact condition. For example, when the crimping height is improperly adjusted, the terminal may not completely wrap around the wire, resulting in localized poor contact. In this case, the contact resistance will fluctuate dynamically, exacerbating the risk of poor contact under vibration or temperature changes. Furthermore, the precision and matching of the crimping die are crucial. Die dimensional deviations or excessive surface roughness will directly lead to deterioration of the microstructure of the contact surface, increasing contact resistance.
The impact of material selection on contact resistance is equally significant. In industrial control wiring harnesses, terminal materials are typically copper alloys or phosphor bronze. These materials combine good conductivity and mechanical strength, maintaining stable contact performance during crimping. Wires are often multi-strand stranded copper wires, whose flexibility allows them to adapt to complex installation environments, but the stranded structure also increases the difficulty of controlling contact resistance. If the electrochemical potential difference between the terminal and the wire is large, long-term operation may lead to oxidation of the contact surface due to electrochemical corrosion, forming a high-resistivity film layer. For example, when copper terminals are directly crimped to aluminum wires, the copper-aluminum contact surface will oxidize more rapidly in a humid environment, causing the contact resistance to increase significantly over time, eventually leading to connection failure.
The cleanliness of the contact surface and the surface treatment process are implicit factors affecting contact resistance. Before crimping, if there is oil, dust, or an oxide layer on the surface of the wire and terminal, it will form an insulating barrier, hindering current flow. Therefore, in the production of industrial control wiring harnesses, ultrasonic cleaning or chemical etching processes are usually used to remove surface contaminants, and tin, silver, or nickel plating is applied to the terminal surface to enhance conductivity and corrosion resistance. For example, tin plating can form a low-resistance tin-copper alloy layer on the contact surface, effectively reducing contact resistance; while silver plating, with its excellent conductivity and oxidation resistance, has become the preferred surface treatment solution for high-reliability industrial control wiring harnesses.
Quality inspection after crimping is the last line of defense in controlling contact resistance. In the production of industrial control wiring harnesses, tensile testing and resistance testing are typically used to verify crimping quality. Tensile testing simulates mechanical stress under actual working conditions to ensure the connection strength between terminals and wires meets requirements. Resistance testing directly measures the contact resistance value to determine if the contact condition is up to standard. For example, a high-precision milliohm meter can detect minute changes in resistance, promptly identifying problems such as loose connections or oxidation, preventing substandard products from entering the market.
The terminal crimping process of industrial control wiring harnesses directly determines the magnitude and stability of contact resistance by influencing factors such as contact area, contact pressure, material properties, and surface condition. Optimizing crimping process parameters, selecting matching materials, and strictly controlling surface treatment and quality inspection are the core paths to reduce contact resistance and improve harness reliability.
