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Hobby CAD, CNC machining, and resin casting (2015)
utorial for getting top-notch results with benchtop CNC mills and modern polymers Copyright (C) 2013, 2014, 2015 by Michal Zalewski (lcamtuf@coredump.cx) I'm a computer geek by day, and an occasional hobbyist robot builder by night. For most, the craft of robotics requires either deep pockets, or a combination of outstanding manual skills and easy access to a top-notch machine shop.
As discussed in section 1.3 of this guide, resin casting is a pretty amazing, simple, and user-friendly process that comes equally handy in CNC prototyping, 3D printing, and in manual DIY work; all its sophisticated uses aside, you will end up using it to replace broken parts in appliances or toys, make unique gifts, or even encapsulate backyard flowers or bugs (don't deny it). Optional: pressure pot There are some complex, multi-part molds where it may be hard to consistently avoid air entrapment, even with the aid of vacuum; on top of that, there are some resins that tend to be difficult to fully degas, or that will develop bubbles of carbon dioxide when not mixed perfectly well, or when exposed to residual humidity. Here's another tidbit you won't find in any other hobbyist reference on resin casting: it is possible, and in fact fairly easy, to chemically slow down many polyurethane systems to significantly reduce shrinkage; and to accelerate slow-curing ones to get your parts sooner or have fewer artifacts in thin sections of your molds.
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