EuroWire September 2021

Focus On UK

Tensile testing of crimped wire terminals Crimped wire terminals are a universal component of an electrical system. Being a joint, these elements are potential loca- tions of weakness. Most connectors are de- signed to be vibration-proof, but generally are not made to sustain any weight – the conductor thickness being related not to strength but to electrical current capacity. For maintenance purposes, disconnection must remain easy even after extended use, without risk to the crimped joint. The FMT-W40 is a motorised wire-terminal pull tester, available in two models with a tensile strength capacity up to either 500N (110 lbf ) or 1,000N (220 lbf ). Its motor drive enables wire terminals to be tested at a constant, controlled pull speed for greater repeatability of testing. The FMT-W40 provides seven different test speeds, as required by the relevant testing standards.

To ensure the best repeatability and accuracy, it is essential when pull-testing wired connectors that there is no jerking or sudden application of force. This is the reason why certain test standards state that there should be a “constant rate of pull”, and most define a fixed speed at which tests should be performed. Testers able to implement this requirement are suitable for type-approval testing. The semi-automatic nature of the motorised version also enhances operator safety: the test sample is loaded, and a start button is pressed to initiate the test at a safe distance. The crimp receptacle fixture has 12 slots ranging in width from 0.5 to 6mm (covering AWG 8-30) for quick and easy loading of the terminal. The cable is clamped securely in a cam by a fast-action lever before starting the automatic test. The digital display captures peak load at 1,000 Hz and clearly indicates the pull strength result of the test in newtons, pounds-force or kilo-force. Data can be From the small, single-head Mikron, through the aXis and Huron range, and into the larger twin-head Variform and MicroMac, Pave has designed machines to improve productivity across industries such as automotive, construction, refrigeration and medical. Products include twist-free wire-straightening systems, chamfer, threading and cold heading accessories, and easy-to-program robots. Pave has built and sold more than 2,500 machines, which are in use around the world, and recently designed and launched the Pave MX-12, a twin-head CNC wire-bending machine from coil for wire up to 4mm. The company also offers a rebuild service, taking back customers’ old Pave machines and updating them with new wiring and electronics, stripping them back to

▲ Loading a sample on the FMT-W40 motorised pull tester

A number of international and industry standards specify test methods, with little variation in their parameters other than definitions of acceptable load bearing. ASTM, BS, ISO, SAE, NASA and military standards bodies are among those with published methods. Those in aerospace or military applications are expected to be exceptionally robust. When tested, the tensile pull-off loadmust not fall below a specified minimum value, determined by the size, wire configuration and materials used in the crimp. Since elongation is not a measured parameter in these “test to destruction” methods, they can be performed by easy-to-use benchtop pull testers. These instruments can be used for a wide range of crimped terminal connections as well as welded wire-to-wire connections. Alluris, a PPT (Physical Properties Testers) brand, offers two tester lines for point-of- production quality assurance testing by all manufacturing personnel, with minimal training requirements. CNC solutions Pave was established in 1974, with the founders having seen the shortcomings in the wire forming industry at the time. In direct response to the need to automate labour-intensive manufacturing methods, the company began designing and building its own machines, leading to the development of the first computer- controlled forming machine in 1985. The company’s current premises, in Peterborough, UK, feature a purpose-built exhibition hall complete with a floating restaurant/bar area and accommodation. Pave has developed an easy-to-use visual programming system that requires minimum operator training, and is uniform across its range of machines. The range allows customers to manufacture wire formed products from 1.4 to 25mm diameter wire in mild steel, stainless steel and spring steel.

stored and transmitted to optional soft- ware for generating a test report. Additional features enable further analysis of the performance of the joint. Three selectable test modes allow for non- destructive as well as destructive testing: pull and break; pull and hold; and pull, hold and then break. For implementations where budgets are limited or a constant pull rate is not required, Alluris offers a manual pull tester. The lever operation of the FMT-W30 version makes it easy to use as a portable device, or where mains power is not available to run a motorised pull tester. Both instruments feature a compact design in a rugged, nitride-hardened steel casing, with a scratch-resistant baseplate and non-slip feet. PPT www.pptgroup.com the frame to rebuild, and replacing all necessary parts. With some customers choosing to upgrade to a new machine and trade in their old one, the rebuilt machines are also available to new clients alongside the new and ex-demonstrator models, providing firms with more options, depending on requirements and budget. Pave CNCWire Forming Systems Ltd www.pave-wire.com

▼ Pave’s MX-12 twin-head CNC wire-bending machine

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September 2021