You don’t want to get your finger stuck in one, but press brakes are awesome machine tools. A close cousin to inventor George Keene’s cornice brake (which he patented in 1887), today’s press brakes use a hydraulic or electric servo-powered ram together with a set of male and female dies to hem, form, punch, coin, or bend sheet metal into some pretty amazing shapes. As with laser cutters, punch presses, and shears, press brakes are a common sight in any sheet metal fabrication shop.
There’s just one problem. Like most capital equipment, press brakes are expensive, and unless you have one at their disposal (used equipment graveyards are full of them, many resembling the cornice brakes of yesteryear) you’ll need to pay one of these metal fabricators to make your parts. There’s nothing wrong with this, but considering the long lead-times and relatively high setup fees typically charged by these do-it-all shops, doing so might be cost-prohibitive. Now what?
Wave hello to the solution
There is an alternative to all this headache. With a little ingenuity and some clever CAD work, a laser can be used to cut bend lines in practically any sheet metal part, making it easier to fold than a paper airplane (well, almost). I know, I know, you don’t have a laser cutter either, but SendCutSend does—three of them, actually—and we’re happy to share a little known method of leaping over the press brake hurdle and getting your project back on track. What’s more, because we specialize in quick-turn laser cutting, your parts will cost less and be in your hands more quickly than you might otherwise have imagined.
Bending at home
So how does it work? Here are some step-by-step instructions to help you visualize this magical process:
Grab an old book off your bookshelf and tear off the back cover (make sure it’s not from the public library, or the one that your Mom gave you for your birthday last year).
Using a fine marker, carefully draw a series of shapes on your pretend piece of sheet metal to look like Figure 1 below.
Now, take an X-Acto knife and cut those shapes out. Be careful not to hurt yourself. Feel free to make humming noises while pretending to be a laser cutter.
When done, pick up your masterpiece and bend it along the line. See how easy it was, and how cleanly it folded? Problem solved, no press brake needed.
Bridging the gap
Granted, this little exercise wasn’t done with metal, although it could have been. SendCutSend routinely makes these “wave cuts” in aluminum, steel, titanium, brass, and more, allowing our customers to bend their parts by hand and avoid a visit to your local sheet metal house. That said, there are some guidelines you should know about before starting:
The Gap: in our book cover example, this is the width of the white line. It should be 0.6 times that of the material thickness and a bit more than that in heavier or harder metals. For example, 0.125″ aluminum would need a gap of 0.075″, while 0.187″ carbon or stainless steel should be 0.130″ or so.
The Tab: that little angled section between each slot? That’s called the tab. Measured as the crow flies, it should be at least one material thickness across. Make it too wide and you’ll need arms like Arnold Schwarzenegger to bend the part; too narrow, and the part will be wimpy.
The Length: Similarly, it’s up to you how long each slot should be and therefore how many of them are needed across the bend length. Again, it depends on the type of material, its thickness, and the width of the bend, but a half dozen or so would be a good starting place for a typical part.
The Tail: If you have a two-foot long part with a fold in the middle, each “tail” will measure one-foot in length. Thanks to the huge amount of mechanical leverage in this example, even your Aunt Martha could bend it. Make that part just 6-inches long, however, and you’d better call Uncle Bob for help (that, or add more tabs by shortening the slot length).
Confused? It’s actually easier than it sounds. If you’re a CAD guy or gal, we have some .dxf templates you can use, otherwise give us a call and we’ll walk you through it. You should also be aware of something that press brake operators know intimately: when you bend metal, you lose a little bit of material to the radiused section (something called OSSB, or outside setback), so you’ll need to add that amount to your part length to achieve the correct dimensions. Google it if you need the formula. And again, we’re here to help if you run into trouble. Happy bending!