Where the joining of sheet metals is required any two of these variables can combine to present challenges to design teams. It is often the case that more than two variables need to be considered concurrently, and this is where things can begin to get complicated from a joining viewpoint.

For example, in some materials joining applications, structural strength might be a primary consideration, or perhaps resistance to a bending moment. In others, if the joined sections or parts are in full view then the visual ‘look’ of the joints themselves might lead the design team to seek a joining process or method that also provides a visually appealing solution. Occasionally however, there are applications where joint integrity needs to encompass rather more than simply keeping various metal parts together, resisting bending moments and/or looking good.

An example of this is illustrated in the H&V market, where a primary consideration for the design team might be the integrity of ducting joints in respect of their ability to prevent the leakage of gases, exhausts or contaminated air from inside the ducting. 

Given the scale of some ducting installations and the amount of material used in them, the potential cost implications of removing and reinstalling any joints which leak can be significant.

Health matters 

The threat to the health and wellbeing of any persons nearby is a completely different matter in the event of leakage occurring. Bollhoff Fastenings says that in many applications in the H&V market, it is becoming more common to see its RIVCLINCH process used for joining ducting sections. The company states that its process is the only one of its type to have secured TUV Type D air tightness Certification covering “Duct connections for sheet metal air ducts with rectangular sections”. The TUV Certification provides independent assurance that joints have passed stringent assessments and thus deliver an assurance against the leakage of gases.

Capable of joining up to three layers of sheet metal with a combined thickness of up to 3.5mm, the RIVCLINCH system is a joining method that doesn’t involve the drilling or punching of holes in the material, rendering it suitable for use with pre-coated or pre-painted sheet. Typical joining cycle times vary between 0.5 and 0.9sec dependent upon material thickness. The RIVCLINCH tooling has been configured for use by companies large and small and can be specified in a wide range of configurations – from hand-held tools weighing less than 6kg in gyroscopic suspension for low volume work – to fully automated PLC controlled bespoke systems with multiple joining heads for high-throughput, heavier duty projects.  

Capable of fastening mild steel, stainless steel, aluminium and non-ferrous metals using the same tooling, the RIVCLINCH cold joining technique allows manufacturers to embrace advantages that may be not be immediately obvious. For example, it allows OEMs to dispense with the need for loose fasteners and helps prevent the onset of corrosion in the joined parts because the material is deformed not pierced. Moreover, where required, the RIVCLINCH process permits use of other laminates or bonding/sealing agents to be introduced as layers between the joined sheets or panels.  

Users can specify either a round or rectangular version of the joint at the point of contact. Further advantages are said to include the reduction of energy used compared to welding and a fume-free environment for production staff engaged on the assembly and joining processes.                         

Bollhoff Fastenings offers, free-of-charge, an Engineers Guide which compares the advantages and disadvantages of a range of fastening methods and types.