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【Popular Science】Cold-Pressed Terminals: Classification, Selection, Wire Matching & Standardized Quality Control Processes
- Categories:Industry News
- Author:Guangdong Deke Electric Co., Ltd.
- Origin:https://www.de-ke.cn/
- Time of issue:2026-06-30 16:05
- Views:
【Popular Science】Cold-Pressed Terminals: Classification, Selection, Wire Matching & Standardized Quality Control Processes
- Categories:Industry News
- Author:Guangdong Deke Electric Co., Ltd.
- Origin:https://www.de-ke.cn/
- Time of issue:2026-06-30 16:05
- Views:
When wiring harness engineers, equipment procurement specialists and field electricians perform wiring operations, they frequently encounter failures such as stranded soft wire fraying, poor contact under long-term vibration, terminal overheating and even circuit open circuits. Tracing the root causes, the vast majority of failures stem from three core factors: non-standard selection and application of cold-pressed terminals, mismatched specifications between wires and terminals, and substandard crimping construction processes.
Combining three authoritative domestic and international standards including DIN 46228, GB/T 3956 and UL486E, this paper conducts a comprehensive and systematic breakdown and analysis from six dimensions: basic definition of cold-pressed terminals, material manufacturing processes, color code identification specifications, cable matching requirements, crimping scheme selection, and finished product quality inspection.
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DEKEELEC—— —— —— —— —— —— —— —— —— —— —— —— —— —— —— ——
I. Basic Definition & Core Application Value of Cold-Pressed Terminals
Cold-pressed terminals are electrical connectors that tightly bond wires and copper sleeves through mechanical crimping, requiring no solder or high-temperature processing during the whole operation. Multiple types are available on the market, including tubular, ring and fork terminals, among which tubular cold-pressed terminals are the most widely used for flexible wire wiring.
Unprocessed stranded flexible wires are like unprotected shoelaces, prone to copper strand fraying, abrasion and breakage after long-term service. Cold-pressed terminals act as a metal protective structure for wires, delivering four key practical advantages:
- Protect Conductors from Abrasion The metal sleeve fully encapsulates copper strands, preventing thin wires from being cut by locking screws and eliminating risks of partial wire breakage and overheating.
- Consolidate Strands to Avoid Fraying All strands of flexible wires are bundled tightly, preventing exposed copper strands that may cause short circuits when plugged into terminal blocks or circuit breakers.
- High Long-Term Connection Reliability The crimp forms an integrated metal contact surface with excellent vibration and shock resistance, delivering stable contact resistance without long-term drift.
- Compatible with Automated Mass Production Work with ratchet crimping pliers and fully automatic crimping machines to eliminate soldering procedures and drastically cut manual labor costs.
Key Manufacturing Requirements for Terminals (Mandated by DIN 46228)
Cold-pressed terminals are stamped from electrolytic copper strips. Stamping induces work hardening and higher hardness on sleeves; without annealing treatment, sleeves tend to crack or fail full forming during crimp curling. All tubular terminal series from Dekor adopt an extra annealing process to soften copper material, ensuring crack-free and tight-fitting sleeves after crimping, which meets the mechanical strength requirements specified in the standard.
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II. Color Coding Specifications of Pre-insulated Sleeves
The color of the plastic sheath on the outer layer of terminals serves as a standardized identifier for wire gauge instead of decoration. It enables quick on-site matching of wire specifications and reduces selection errors.
There are three mainstream color coding systems in the industry: German DIN standard, North American UL standard and French NF standard. The corresponding colors for the same wire gauge are inconsistent across the three systems. A single unified standard must be adopted for project procurement and production, and mixed use or assembly is prohibited.
The DIN 46228 color system is widely applied in domestic industrial control equipment and PLC wiring industries. Specifications can be matched directly against color charts during procurement.
DEKEELEC—— —— —— —— —— —— —— —— —— —— —— —— —— —— —— ——
III. Wire Classification and Terminal Matching Rules (Based on GB/T 3956 / IEC 60228)
Cable conductors are divided into four categories. Cold-pressed terminals shall not be arbitrarily mixed since their applicable scenarios vary greatly by conductor type:
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Class 1 Solid Hard Conductor Single thick copper wire for fixed wiring. With high cable rigidity, it generally does not require cold-pressed terminals under normal working conditions.
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Class 2 Stranded Compact Conductor Twisted strands of thick copper wires, mostly used for fixed wiring of equipment, compatible with standard tubular cold-pressed terminals.
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Class 5 Standard Flexible Conductor Twisted medium-fine copper strands balancing flexibility and mechanical strength, widely used for wiring harnesses of lighting and general equipment.
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Class 6 Extra-Flexible Conductor High-density twisted ultra-fine copper strands with excellent bending resistance, specially applied to precision instruments and frequently moving wiring harnesses.
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DEKEELEC—— —— —— —— —— —— —— —— —— —— —— —— —— —— —— ——
Key Pitfalls to Avoid in Wire Selection
- Lay pitch affects compatibility: The smaller the helical spacing of stranded wires, the higher the overall hardness of the cable. The inner diameter of the terminal sleeve shall be appropriately enlarged during selection.
- Nominal cross-section differentiation: Cables are rated by nominal cross-sectional area based on conductivity, while the actual total area of copper strands has minor tolerances. Terminal selection shall follow the nominal wire gauge.
- Mixed dissimilar metals are prohibited: Pure copper cold-pressed terminals must never be used for aluminum wires. Contact between the two metals causes electrochemical corrosion; dedicated aluminum cold-pressed terminals are required instead.
Standardized Procedures for Wire Cutting and Stripping
- Cutting requirements: Cut wires vertically at 90° with professional cable cutters. The cut end shall be burr-free with intact strands without fraying to fully retain the original stranded structure.
- Standard stripping length: For regular wires of 10 mm² and below, stripping length = metal sleeve length + 3 mm. After crimping, it is optimal for copper strands to slightly extend 0.5 mm beyond the sleeve, which ensures conductive contact while preventing short circuits from exposed metal.
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DEKEELEC—— —— —— —— —— —— —— —— —— —— —— —— —— —— —— ——
IV. Scenario Comparison of Mainstream Crimp Profiles
Three industry-standard crimp structures — hexagonal, quadrilateral and trapezoidal — all comply with relevant specifications. None is universally superior; selection should be based on terminal hole shape and service conditions.
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Hexagonal Crimp It wraps the sleeve evenly on six sides with a large conductor contact area. Its pull-out force is 15%–30% higher than that of quadrilateral crimps for the same wire gauge. Featuring outstanding fatigue resistance and tolerance to vibration under high and low temperatures, it suits automotive and high-power industrial equipment, and matches round terminal holes best.
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Quadrilateral Crimp It comes with lower costs for dies and tools, yet stress concentrates on four edges. The sleeve tends to deform under long-term vibration, so it is only suitable for static household appliances and indoor low-voltage fixed wiring. It requires a larger round socket opening for wires of equal cross-section.
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Trapezoidal Crimp It offers moderate tolerance for wire gauge matching, but jaw sizes must be precisely matched. It is applied to low-frequency thin wiring harnesses of miniature instruments.
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DEKEELEC—— —— —— —— —— —— —— —— —— —— —— —— —— —— —— ——
V. Standardized Quality Inspection System for Cold-Pressed Terminals
1. Preliminary Visual Inspection (100% inspection for mass production)
After crimping, terminals shall be free of distortion, sleeve cracks, scratched or oxidized plating. Standard flared funnels shall be formed at both ends of the conductor crimp zone without stray or broken copper strands. No insulation sheath shall be pressed into the conductor contact area.
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2. Destructive Pull-Out Force Test (Mandatory Type Test per UL486E)
A professional tensile testing machine is used to apply axial tension at a constant speed of 25 mm/min. The load shall be held for 60 seconds once reaching the standard threshold. The sample passes if no slippage or detachment occurs at the crimped joint.
Standardized Test Procedure
- Strip the wire to a length matching the sleeve dimension and keep all wire strands intact;
- Remove the plastic insulation sheath of the terminal to prevent the insulation from bearing tension and skewing test results;
- Secure the test specimen on the fixture of the tensile machine, pull it at a constant speed and record the critical pull-off force value. Average readings from multiple specimens of the same specification for judgment.
DEKEELEC—— —— —— —— —— —— —— —— —— —— —— —— —— —— —— ——
Cold-pressed terminals are fundamental components for electrical connections. Failure to meet standards in any link — wire matching, crimp structure, terminal material or quality inspection procedure — will create potential safety hazards such as overheating and circuit breakage.
All series cold-pressed terminals manufactured by Guangdong Dekor Electric are produced in strict compliance with DIN, UL and national Chinese standards. We provide complete product selection guidelines, crimping process instructions and pull force test reports. Our full product range includes tubular, ring and fork terminals, catering to wiring harness demands of industrial automation, new energy equipment, precision instruments and household appliances.
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Should you have any questions regarding terminal selection, crimping parameter adjustment or wire matching, feel free to leave a message for consultation. We provide one-stop technical support.
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