Guerrilla guide to CNC machining, mold making, and resin casting (2015)

I sent this right away to my son that does FIRST robotics. It's amazing the tools that he has available to him.

Notes vs 3d printers.

1. This guide is about making the mold-of-the-mold, the mold, and finally the final product. Its at least 3 steps before you get the final piece of plastic, rather than a single step process like 3d printing.

2. I hear that expensive software can help automate this process ("Design Product" -> "Auto build mold" -> "Auto build mold-of-mold"), but software is surprisingly expensive for hobbyists. Expect to be manually designing these molds and mold-of-molds unless you're willing to pay for some rather expensive software. That being said: "Rectangle -> Difference (product-shape)" is a good start.

3. The chief advantage of resin casting is the huge variety of paints and resins available. If you want a flexible material, get ShoreA 40 Urethanes. If you want a silvery material, buy silver pigments. If you want Red, you can buy red pigment. Compared to 3d printing, you have far more material selection (ShoreA soft materials, from grades 20 to 80, ShoreD harder materials from grades 20 to 80, etc. etc.).

4. There's also a "mass production" advantage. You can build multiple molds and "parallelize" the resin casting relatively cheaply. Once you have the "mold-of-the-mold", building 5 molds, and then using those 5x molds 10x each will be faster than waiting 50x iterations of your 3D Printer. Assuming your object is small enough to fit multiple molds inside your pressure chamber, of course.

5. If you are aiming at extruded ABS (aka: professional legos plastic), the mold-of-the-mold methodology is very similar (though made out of Aluminum and/or Steel, rather than Silicone like in this guide). There's still subtle differences between Aluminum molds vs Silicone Molds, but the similarities mean that you have a better idea of the final-final product with a silicone mold prototype.

6. EDIT: 3D printing is also compatible. If you wanted to make the molds or mold-of-molds out of 3d printers, you probably can do that. Its all just "shapes" after all. However, CNC Mills have far better accuracy than 3d Printers, so CNC Mills are just a better tool for this methodology. But if you don't wanna buy a CNC Mill to go through this process, feel free to play with the techniques listed here with a 3D Printer instead.

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The biggest issue with #5 are the "shapes" that molds can make. Its much more restrictive than the "shapes" a 3d printer can make. If you design your shape to be 3d printed, it might be impossible to make a mold out of it that builds that shape.

In contrast, if you actually go through the mold-of-a-mold / mold process as listed here, you innately are thinking about the final Aluminum/Steel die that Injection Molders will do. You have much lower chance of erroneously building a product that's impossible to die cast.

IIRC, the main mistake is that silicone molds are flexible. If a corner gets stuck or something, you can just yank it harder and the plastic will come out. Aluminum/steel dies are very rigid. You can't just do that. So if you're "aiming to prototype an ABS Injection Mold / Steel die", you wanna design your mold to "cleanly lift" off a piece without anything getting stuck.

Semi-related: As an average consumer I'm disappointed that nearly a decade of the "makerspace" has seemingly failed to produce any sort of meaningful Renaissance in small-scale US manufacturing.

I've purchased the odd 3D printed or resin cast tchotchke from small operations a few times at this point. But it's still disappointing that if you need professional quality products, you still either need to pay out the nose to have it fabbed or ship it in from China.

It seems to me the industry is very good at serving hobbyists and prototypers. But I think there is a huge market being missed out on easy-to-use, introductory products for mold tooling, plastic injection, and general manufacturing automation.

As cool as 3d printers can be, I don't think owning one scales up into a professional endeavour very well. However, developing a pretty good mold for a phone case would.

I think CNC machining is primed for developments that make it much easier to use for the home hobbyist. The tech is very close to what's needed for 3D printing but it has a few added requirements like the need for a sturdier frame and accommodations for a fairly large and powerful motor. Both are solvable with the right materials and the motor can be anything from a DC spindle to a repurposed wood router. The biggest hurdle to overcome would be the software. Right now, Fusion360 is the defacto standard for hobbyists but it leaves a lot to be desired for ease of use and handling complex models that a lot of people would like to mill. Having software that is as easy to use as a slicer for 3D prints would be a huge win.

The ability to make metal parts and carvings is a game changer even if you are somewhat more limited in the features that you can carve with a CNC vs 3D printing.

The other small fab tool that I think would be great to streamline would be a small foundry for casting aluminum, brass, and bronze but that one is much more difficult to automate beyond having a furnace with good presets. An ideal machine would be something similar to an injection molding machine for plastic but capable of melting metal, perhaps using induction heating with a graphite crucible and spigot for depositing the metal into a mold.

I'm also somewhat convinced that there may be a way to do aluminum extrusion with a much smaller setup than is normally used but the pressures and temperatures involved may make that uneconomical for an individual.

I also hold this unpopular opinion : the maker movement has ultimately failed.

I am not fully certain why, but think social factors are partly to blame. What I saw (in the UK) was that the new generation of middle-class, hobbyist makers weren't interested in engaging with and learning from the historical, working-class manufacturing sector.