Rapid Prototyping of Metal Components - Sheet Metal Parts
21 Jan 10
This is the second in a series of articles on rapid prototyping techniques for metal components. The first article dealt with CNC machining for producing prototype parts. In this article we look at prototyping sheetmetal components that would normally be metal stamped in production.
Sheetmetal Part Prototyping
Designers developing components that are ultimately to be produced using production techniques such as metal stamping, progressive stamping or metal pressing often need prototypes produced to test for form, fit and function. So what techniques are available to produce prototypes of their sheet metal component designs?
Many sheetmetal fabrication shops have the latest in CNC controlled equipment. This includes laser cutters, plasma cutters, CNC turret punches, CNC folding machines, CNC pipe and tube benders and stud inserters. This type of machinery is often thought of as more applicable for volume production. But far from it, this type of CNC sheetmetal equipment is extremely flexible, versatile and capable of producing complex prototype parts at low cost.
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For simpler, prismatic parts, an experienced sheetmetal component designer will be able to produce a sheetmetal development design showing the flat pattern, folding centrelines, folding directions and angles. This can easily be exported in dxf format to the sheetmetal fabrication shop where is is quickly nested and a program produced for cutting on the laser or plasma cutter (nesting is arranging of multiple parts to fit the stock material sheet to get maximum useage of the material). The parts are cut complete with screw holes, slots and cut-outs. For prototype parts, the cut components are typically sent to the folding machine to be hand folded to complete the shapes.
More complex designs may require raised bosses to be pressed, louvres pressed, raised mounts or a large number of perforations. For these types of parts, setup and programming to manufacture prototypes on a CNC turrent punch after laser cutting is again a straightforward and fast process. CNC turret punches use an array of different punches and forming tools, and production speed is fast which off-sets the setup and programming time. The lasercut and turret punched components can then be folded using hand folding machines or CNC folding machines and have clinch studs or clinch nuts inserted to complete the parts.
On some occasions, the part is designed to be progressively stamped to produce a final shape which is not reproduceable using CNC cutting and folding equipment. In this case for a prototype part, the component can be split into 2 or more parts and simply welded together.
Where a part has more complex 3D contours to produce it can be trickier but a prototype part is still possible to produce. If the curves are not too tight, it may be possible to produce a hard wood tool that can press out a few components. For tighter curves and more complex shapes, the part will more than likely need to be produced in multiple sections and welded together. Sections can also be cut from pre-formed shapes like tubes or metal spun sections using laser tube cutters or robotic lasers. Once each section is produced, they are welded together and the welds dressed to complete the prototype.
As a general rule of thumb, metal stamping and metal pressing of smaller components is seen as the low-cost production of sheetmetal components that can be produced by sheet metal fabrication techniques as described above.
So before getting an expensive press tool made, consult your sheet metal fabricator about producing prototypes for testing. It can save you expensive tool modifications later in production.
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Other articles in this series (linked once published):
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