Never Under-Estimate the Power of The Force. Additive Versus Subtractive Manufacturing.

3d printingA lot has been said about additive manufacturing, and through my work with Carbodeon, who have now launched their uDiamond® Nanodiamond Modified 3D printing material, I have a commercial involvement in additive manufacturing for the first time.

Generally people make a lot of the difference between an additive and a subtractive process, suggesting that it is hard work/ time consuming and expensive, as well as wasteful, to use a subtractive process and that is why additive processes are so good.  Working with the process for a while, I have to say that this is not the important point.  A CNC milling machine can subtract material out of a workpiece faster than any of the 3D printing machines can build it, whilst on the waste material side, it’s not so clear cut either with every 1kg or so of 3D print filament arriving on a 250-300g plastic reel.

The thing that is important though, is that in subtractive manufacturing there are huge forces applied to remove that material, which requires a big, solid machine with big motors and a powerful control system to drive it all, this takes up a lot of space and is of course expensive.  And then the other problem, something has to counteract those forces to stop the workpiece flying off into the distance (been there, done that).  You need fixtures, very often custom made for the part, and often requiring several different fixtures to produce the part in a number of steps.  And multiple tools are also used.  All this brings the problem that usually when you present a component design, a human has to look at how it should be made, and be involved in calculating the cost, before any work can start.

Compare this to the 3D printer.  Yes, it is a relatively slow process.  But because there are almost no forces on the part, you can have a lightweight, low cost machine structure that isn’t much bigger than its own working envelope, and you don’t need any additional fixturing either.  So a single piece of software can determine whether the part is manufacturable and how much it should cost, and then prepare the machine to build the part.  This simplicity is what counteracts the low speed of the actual process and why 3D printing is finding an ever growing number of uses.  But it has more to do with the lack of forces involved than with whether the process is additive or subtractive.

This explains why laser cutting of sheet metal is such a cool process.  I use this quite a bit for my own projects – a conveniently local company (Warren Services in Thetford ) have an online tool which gives prices and takes orders directly from an uploaded CAD file.  I think this is only practical because the process exerts no force on the material and so nobody has to wonder about workholding and fixturing.

So my question is, wouldn’t it be cool to have machines which laser cut in more than 2 dimensions…..?

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