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Process Guide
Clinching Riveting and Spot Welding Compared
Choosing a sheet metal joining method when the panel is already finished
Introduction
Three methods dominate permanent sheet metal joining, and the right one usually depends less on joint strength than on what the panel's surface has to look like afterwards and what the joint has to cost per unit.
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Clinching
Clinching joins sheet by localised cold forming: the material is pressed into a die so the layers interlock. There is no heat, no filler and no fastener.
Because the process is cold and local, coated and painted sheet can be joined without damage to the surface finish. That single property decides a lot of applications, because it removes the touch up operation that welding pre-finished sheet creates.
The joint is visible and can be checked dimensionally on the line, so verification does not require destructive sampling. The cost per joint after installation is electricity and tooling life.
Self piercing riveting
A rivet is driven through the top sheet and flared into the bottom sheet. It generally produces a stronger joint than clinching at the same thickness and can join combinations that clinching cannot.
The cost is a consumable per joint, a feed system that can jam, and a stores line to manage. For high volume that consumable cost adds up in a way clinching does not.
Resistance spot welding
Fast, well understood and strong in bare steel. It is also a thermal process, which is the problem on coated material: the coating burns off at the joint and that becomes a corrosion start point.
It brings fume extraction, electrode dressing and, usually, destructive sampling to verify the joint. None of those are deal breakers, but they are all ongoing cost that the other two methods avoid.
How to decide
If the sheet is pre-finished and the appearance or corrosion performance matters, clinching is usually the first thing to trial.
If the joint has to carry more load than clinching will give at your thickness, riveting is the next step, and you accept the consumable.
If the material is bare steel, the volume is very high and you already have the welding infrastructure, spot welding remains hard to beat on cost per joint.
Trial on your own material
Coating type and thickness change how any of these joints form. Whatever the comparison table says, the decision should be made on trial joints in your actual production material, not a similar grade.
Takeaways
The Short Version
- Clinching is cold and local, so coatings survive the joint
- Riveting buys strength at the price of a consumable and a feed system
- Spot welding is fast and cheap per joint but damages coatings and needs extraction
- The trial should always be run on your own production material
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Equipment Discussed
Questions
Questions About This Article
What is the short answer?
Clinching is cold and local, so coatings survive the joint.
Does this apply to equipment we already own?
Most of it does. The engineering described here is not specific to Delkotech machines, although where our equipment is relevant we link to it.
Who should read this?
Engineering, maintenance and production people who have to specify, buy or live with the equipment. It is written to be useful on the floor rather than in a brochure.
Can Delkotech advise on our specific case?
Yes. Email [email protected] with the part, the operation and what is going wrong, and you will get an engineer's answer rather than a sales response.
Talk to an engineer
Ask About Your Own Application
Send the part and the problem. You will get an engineer's answer, including when the answer is that automation is not the right call.