Sheet Metal Fabrication - Punching - Forming Variables

One of the oldest technologies in sheet metal fabrication is "Punching".  Up to date punching machines and tooling have incredible flexibility.  The punching equipment can create holes, cut perforations, form louvers and emboss .  With all the capabilities and the fact that punching is usually one of the first processes in sheet metal fabrication, it is important to make sure its done correctly.  Without the focus on some key details, the process can go sideways. 


Every sheet metal fabrication shop has one or a team of CAD technicians or programmers that transform the digital drawings into something real produced out of sheet metal.  The designers (who may have never been in a fabrication facility or out of their parents' basement) see one thing on their screen.  The programmer sees beyond the screen to a physical metal part that can be manufactured.   

If the designer has put in an embossed section with a 0.500 inch flat section on top, a 0.200 inch height and a 45 degree angle – it looks great on the screen.  But in reality it's impossible to manufacture this as there is the sheet metal material to consider.  Something has to give.  The sheet metal forms to a radius – not a clean crisp line.   

Designers will specify material and thicknesses, with many of them putting in the requirement of "top of sheet to top of form".  Material gauge can vary 0.005 inches or more in some cases.  If the fabricator needs to hold the overall dimension – from bottom of the sheet to the top of the form – a challenge can rear up and bite you because material thickness varies slightly from one lot to another.  This is another case of the differences between the digital world and reality.   

When specifying and designing electronic enclosures or cabinets, it's important to work with an experienced sheet metal fabricator.  Critical tolerances in the design that cannot be compromised can be achieved if the CAD technician/programmer understands and takes into account all the nuances of the workability of sheet metal.  As with life, sheet metal forming on punching equipment is all about communication, compromises and expectations.   

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