Just for a moment, think back to High School. Not the parts you’ve spent years trying to forget, but the English class. Were you ever set those “compare and contrast” assignments? Well, we’re going to attempt one here. But rather than comparing and contrasting Sal Paradise and Dean Moriarty, (remember those rogues from “On The Road”?) we’ll do roll forming and press braking.
Roll Forming vs. Press Brake: Two processes, same result
When you look at a sheet metal fabrication – say a step or a shelf from an RV or trailer – while you can see the bend it’s often not obvious which method was used. However, roll forming and press braking are very different ways of achieving the same result, and their economics are quite different too.
Here we’ll explain each method, (with more time given over to roll forming because we’ve discussed press brakes several times before.) Then we’ll provide a comparison. On reaching the end you won’t be any wiser about Jack Kerouac’s American Masterpiece, but you should know a little more about metal fabrication.
Press brake bending
Quick summary: a long thin blade pushes the flat sheet down into a vee-shaped channel to create a bend. “Bending Your Metal Fabrication into Shape” and “Automated Bending vs. Manual Press Brake Bending” provide more detail.
The key points to note for this comparison are:
- Works on individual sheets
- Sheet size and bend length are limited by the width of the press brake
- Maximum material thickness governed by the length of bend and the tonnage of the machine
Metal roll forming
Here the metal is shaped by pulling it through pairs of rollers. One roller supports the underside, the other acts on the top surface. Each pair is matched and shaped to provide a little more deformation. For example, the bottom roller might have an hourglass profile while the upper roller would be football-shaped to push the metal down into the “waist” of the hourglass. On each pair, the geometry is increased a little more, until the last pair produces the final shape required.
In a sense, metal roll forming is similar to extrusion. It produces a long length with a uniform cross-section. Using more complex roller shapes, it’s possible to put in multiple bends. An industrial metal roll former could have a dozen pairs of rollers and can work on material up to 72” wide and 0.75” thick. (A machine capable of these biggest, heaviest gauges will be pretty massive though!)
Key points to note about metal roll forming are:
- Works on the continuous coil, not sheet
- No limit to the length of bend
- Bends must all be in the same direction
- Profiled lengths are cut to size after forming
Roll forming is sometimes confused with roll bending. Don’t make this mistake! Roll bending is using three rollers to put bends into the tube. Our Eagle CP40H pyramid roll bender does this really well, but it could never do the work of a roll former.
Process comparison
The press brake is flexible and very versatile. Almost any bend can be put in, in practically any orientation. (The only real limitation is that there must be room for the metal “legs” to bend up the required distance.) However, there’s a limit to the sheet size and/or length of bend. Even our big Cincinnati CB230 press brake is limited to 10′.
In contrast, metal roll forming works on long lengths of coiled material. And like extrusion, the shaped pieces then need cutting to length. This makes it a process for higher volume production while press braking is more of a low-to-medium volume process.
Product implications
Roll-forming is the process for making metal gutters, shelving, and racking. Basically, uniform sections in long lengths. Press braking is what we use for sheet metal fabrications like machine guards, enclosures, and boxes. If you’d like to discuss the best process for producing your designs, please call or email. Unlike our English classes from long ago, we love this stuff!