Clinching is a rapid fastening method that requires no components parts. Instead a tool punches into the materials to be fixed to form a strong and resilient fixing. Sometimes also known as press joining, clinching is a high-speed, mechanical fastening technique for point joining of sheet metal components. It is suitable for ductile metal sheets from around 0.5 to 3mm thick, up to a total joint thickness of about 6mm. Clinching requires no consumables or pre-drilled holes and is performed in a single step, making it an inexpensive and simple technique.
In the RIVCLINCH® joining process, the materials to be joined are firstly forced into the die with the punch.
As soon as the lowest material is resting on the die anvil, it starts flowing sideways under the pressure being exerted by the punch. The movable die sections are pushed outwards. The flow of material forms the button-like joint.
The punch is then returned to its starting position by the operator or by a pneumatic timer which removes the force. The joined part can now be removed and the side sections of the die are pulled back together by a spring.
Clinching entered Böllhoff's portfolio of fastening technologies with the company's acquisition of Attexor (now known as Böllhoff Attexor) that makes advanced high speed tools for the technique. Indeed, Böllhoff Attexor sets the industry benchmarks for both speed and small size with its tooling. In some cases the company's hand operated tools significantly outstrip the productivity of even fixed automation and robotic applications.
Böllhoff Attexor's RIVCLINCH® joining system can be used to simultaneously set one or several points and can be integrated within manual machines and robotic equipment and systems.
Four essentials parameters characterise the clinch joint:
- Material ductility: the required ductility values are 20% for a rectangular (partial cut) joint and 30% for a round joint.
- Access from both sides: needed for pressing the material between the punch and the anvil.
- Better joint feasibility and strength: with the punch on the tick side, when joining sheet metal with different thicknesses.
- Residual bottom thickness, "St": is directly related to the interlocking effect and consequently the joint strength once the joint is formClinching has an advantage over resistance spot welding in that disparate materials can be easily joined providing they have sufficient ductility.Clinching is simple and enables cost reductions over other methods. It has the following advantages:
- No fumes, no sparks, very little noise
- Low energy use
- Environmentally friendly workplace
- No pre/post treatment required, e.g. no pre-cleaning or subsequent removal of spray deposits around the joint
- No thermal load on joining zone
- No damage to surface finishes on the work piece
- Interim layers or film or adhesive can be incorporated in most case
- Low maintenance cost
- No consumable items
- Very good joint reproducibility
Böllhoff Attexor has also developed specialised equipment for the fixing of filters and ducting for the ventilation industry.
Micro clinching
However, it is in the micro engineering field that the clinching technique has found the fastest growing favour. Developed first for fixings in the watch industry, the clinching technique has been taken up by electronics manufacturers for a broad range of applications.The Böllhoff Attexor 'Microclinch', as the company has coined it, has set new levels for miniaturisation of the tooling and can now clinch an industry best of just 1mm in width! This has enormous benefits to the microelectronics industry and has enabled applications such as the high seed clinching of LED components, copper foils and others.In such applications, the micro clinching technology produces significantly less obtrusive fixings, with easy access tooling, fast assembly and inexpensive final components.
Summary
While not quite as strong as riveting or spot welding, there are countless applications where clinch fixing is less expensive than those alternatives and is a clean and environmentally friendly technology. For more information visit www.bollhoff-attexor.com.
