Test benches for crimp testing, cable pull-testing and cable joints are specialised instruments for verifying the mechanical strength of crimped terminals, electrical joints, cable terminations and soldered connections. Pull-off force is a key quality parameter of electrical connections: an inadequate crimp carries a risk of detachment, with critical consequences for electrical safety and service continuity. They are used intensively in the automotive, railway, aerospace, domestic appliance, industrial wiring and telecommunications industries.
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Types of test
The most widespread crimp tests are: pull-off of the terminal crimped onto the wire (pulling the terminal and measuring the force up to detachment or wire breakage); peel-testing of terminations; tensile tests on electrical cables to measure the breaking load of the conductor and of the insulation; pull-out tests on inserted connectors; mechanical strength tests on soldered joints. Standard IEC 60352 (parts 1-7) provides the acceptance criteria for electrical terminations of various types: part 1 – wrapped connections, part 2 – crimped connections, part 3 – soldered connections, part 4 – press-fit connections, part 5 – thermocompression, part 7 – insulation displacement (IDC).
Features of the benches
Pull-test benches for crimps are compact and motorised, typically with load cells from 100 N to 5 kN. They incorporate: dedicated grips that hold the terminal and the wire in alignment (the axis of the wire coinciding with the test axis, so as to eliminate bending components), programmable test speed (typically 25-100 mm/min according to the standard), a digital display with peak functions (to record the maximum force at breakage), USB/Bluetooth data output for archiving, GO/NOGO acceptance thresholds with visual and audible signals, and compliance with sector-specific standards.
Industrial applications
Applications are widespread: in automotive wiring lines (go/no-go checking of terminal crimps, sampling plans for batch acceptance); in industrial harness production lines; in electrical product certification centers; in laboratories qualifying new terminals and new crimping equipment; in production line maintenance (periodic verification that crimping tools are working correctly after a tool change, after servicing, after a restart); and in research and development of new electrical connections.
Typical acceptance forces
The minimum acceptance forces for crimps depend on the cross-section of the wire: for example, for 0.5 mm² wires the minimum force is typically 60 N, for 1.5 mm² it is 150 N, and for 2.5 mm² it is 230 N (indicative values from IEC 60352-2). Meeting these thresholds ensures that detachment does not occur under normal service loads
Selection criteria
The choice of pull-test bench depends on the wire cross-section to be tested (which determines the force range and the type of grips), on the test speed required by the applicable standard, on the accuracy of the load cell (typically class 1% F.S.), on the availability of interchangeable grips for different types of terminal, on the output interfaces for automatic archiving of the measurements, and on portability (for checks directly on the line). For high-volume production, integrating the bench with SPC archiving software and with an acceptance label printer is advisable.
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