When you think of precision metal working, sheet metal fabrication almost certainly isn’t what comes to mind, but it should be. Sheet metal is a lot more than just press brakes now. Precision sheet metal work has continued to advance along with every other metal fab technique.
Cutting Sheet Metal
Sheet metal fabrication always begins with cutting. Engineers draw up plans for the raw stock, specifying what needs to be cut away to allow for bending to form finished parts. Advancements in layout and cutting have revolutionized sheet metal work in recent years. Cutting is now usually accomplished by one of four methods.
Punching and Shearing
Metal punching and shearing are the workhorses of sheet metal production. Despite all of the advances of recent years, standard shear cutting is still responsible for most sheet metal forming, and most holes are still punched with metal dies. Let’s face it -a couple of centuries of development leads to a high level of precision. Punching and shearing also have the benefit of producing relatively little work hardening over a very small area compared to some other methods.
EDM, or Electric Discharge Machining, relies on a strong electrical current which runs through an extremely thin wire. The wire superheats and cuts through the metal much like a hot wire is used to cut Styrofoam. It never actually touches the metal. CNC EDM machining leaves a kerf about the size of a human hair, but it’s quite slow, at less than an inch per minute. Obviously, at that speed, it’s really best suited for small parts, but those parts can be cut with incredible precision.
Water jet cutting is a newer development. Tiny garnets are fired through a water jet at pressures up to 60,000psi. The incredibly hard garnets abrade the metal away, leaving a kerf of just over a millimetre. Water jets can actually cut thicker plates than plasma cutters, though they can drift through very thick metals. Water jets are not as fast, averaging about six inches per minute, but they also do not heat up the metal like Plasma or EDM cutting.
Another common CNC precision sheet metal solution is a laser. CO2 lasers are used with fibre optics and powers reaching as high as 12KW. Higher power lasers can be amazingly fast, often measuring progress as several meters per minute. Laser kerfs vary but are less than a millimetre.
Forming Sheet Metal
Following the cutting comes the folding or bending, where the parts actually take shape. This falls mainly into three categories:
Today’s press brakes feature CNC functions for precision sheet metal fabrication. Individual tooling for each job is coupled with machine-calculated air bending techniques which boost speed and accuracy and reduce press artifacts on the parts. Complex shapes that used to be impossible are now routine.
When cylinders or conical shapes are required, metal rolling is the go-to solution. From giant rocket body sections to little rod guides, rolling plays a critical part in precision sheet metal fabrication.
Not to be confused with rolling, roll forming is passing sheet metal between shaped rollers to bend it into a specific shape. You’ve seen this process with seamless gutter companies who turn a roll of flat aluminum into a gutter as long as you need. Roll forming takes a series of rollers that gradually shape the sheet metal into more extreme cross sections until the desired profile is reached. Roll forming is gentle on the sheet metal, though it does induce work hardening.
There will always be a place for traditional tooling in sheet metal work. You can use a laser to cut a screw hole, but you can’t get the laser to thread it. If the part requires decorative or functional surface etching, a laser is probably the way to go. If you want to make bevelled cuts, you should probably avoid plasma. The particulars of a given job will dictate which precision sheet metal fabrication will work best. Ben Machine’s half-century of experience gives us the ability to understand and choose the best processes, whether for cutting or forming material. We know how to move a customer’s project forward in the most efficient and cost-effective manner.