“Bend Me, Shape Me,” was a minor hit in the late 1960's, but ought to be the metal fabricator's theme song. Shearing, cutting, punching and notching produce the pieces for your job, but they usually need bending into shape. Look at practically any metal fabrication – tool boxes, light boxes or bumpers for example - and you'll see multiple bends. Here's how we create them.
Our main bending machine is the press brake. We have nearly a dozen, so you can tell we do a lot of bending. A press brake uses a long thin tool to push a piece of metal down into a vee-slot. Technically speaking, the upper tool that does the pushing is the punch, and the slot is the die. Once the bend is made the punch lifts up, at which point the metal springs back a little.
Springback happens because metal on the outer side of the bend has stretched and wants to pull back. How much depends on the bend radius plus the properties of the metal, it's thickness and it's grain. If we put in too much or too little bend the metal fabrication won't go together properly. Minor over or under-bends can sometimes be corrected, but many metals crack if we take a second go. It's always preferable to get it right first time, which is why consistently making quality bends takes skill.
Most of what we do is classed as “air bending,” meaning the punch doesn't push the metal to the bottom of the die. This leaves a radius on the sheet metal and lets us work with a range of general purpose tools. Sometimes though the fabrication needs a sharp edge, in which case we bring the punch down until the metal bottoms in the die. This usually takes specially made tooling to create the exact shape.
Folder & Roll Bender
As well as press brakes we have a folder and a roll bender, which raises the question, what's the difference between folding and bending? The answer is, the bend radius. Folding forms a fairly sharp or tight radius edge. Bending on the other hand, usually creates a larger radius.
Our folder is similar to the press brakes, with one big difference. With a press brake most of the metal sheet goes behind the punch and die. As the punch comes down the sheet lifts up. On a folder most of the sheet stays in front of the punch and die. That gives it a few advantages on complex metal fabrications and especially when bending perforated sheet.
The roll bender is used for bending metal sections, which the press brakes and folder can't handle. So if we need to put a bend in a stainless steel bumper or architectural steel tubing, it goes on the roll bender.
Almost every metal fabrication involves bending. Here at Wiley Metal we know a lot about doing that well. “Bend Me, Shape Me” indeed!