Someone just asked the question what is 3d printing? I was going to respond,

Someone just asked the question what is 3d printing? I was going to respond, explaining how it was an additive process not a subtractive process and give examples and I realised I had only given examples of subtractive processes in the past.

This got me thinking about additive processes what are the current ones in use other than 3d printing?

I could only think of one being injection molding.

That got me to thinking about the main problem with injection molding being the setup cost in creating the initial mould. I realised that creating the mould for an injection molding machine would be an ideal use of 3d printing.

Your comments, criticisms and observations would be most welcome.

There’s a third one: shaping which is neither additive nor subtractive. Most mass market metal fabrication is done by a combination of casting and subsequent shaping steps, and only a little subtraction. Look at the way an adjustable wrench is made: first you cast a blank, then you forge it in dies successively closer to the final shape, dropping a ton or two on top each time (drop forged… It’s on there for a reason), and then eventually you snip off the little bit of excess that has spilled out between the seams and you (subtractively) machine the head to be nicely flat and have the hole in it for the jaw part and the adjuster wheel etc.

Or screw drivers: you take long pieces of thick steel wire, straighten them, cut them into sections, make the head (for flathead, you crush it into a wedge first, them remove the excess on three sides, for Phillips you just cut out the four slots) and at the handle end you crush some divots in it to hold it in place in the handle (without losing any more material) — and then after heat treatment you add a handle.

As industries mature, I suspect that you’ll see additive, subtractive, and neither steps all being used depending on what’s best for any particular bit of the final product.

Welding, bonding, casting, coating, spinning fibers together, textiles, sewing, fiberglassing, …

is 3D printing as quick as injection moulding?
3D printing is ideal for short run production
how would it compete on large production?

@graham_mewburn given current laws of physics: no, it wouldn’t compete very well. It’s entirely possible that the crossover point where investing in real mass production becomes viable will inch upwards from, say, tens to hundreds, or even a thousand, but if you want tens of thousands let alone millions it is highly unlikely any form of 3d printing we know of today will ever get there. Where we might get, though, is having the same strength as injection molded plastic.

I’m pretty sure 3D printing is used for prototypes for injection molding, unless the detail is too small. Perhaps then, a model can be cast repeatedly and the X% shrinkage between each cast could make the 3d printed object small enough for a final injection mold. I read an article that said Ford is using a 3D printer to directly create sand casting molds, as in the printer deposits sand and then metal is poured in.

@Jasper_Janssen yes, there really seems to be 3 types: additive, subtractive, and … formative? What’s a good word for casting/shaping things? Another example would be springs, rods of spring steel are just curled into shape and snipped off from the stock.

And then heat treated, which is more materials science/transformation than any forming process.