I have a keycap in mind, but what scares me is a mistake in the design. I give the model to the manufacturer, they create a mold, do a sample run and it turns out e.g. the stem is 0.1mm too wide, so it is too loose. Then make another mold, this time it is 0.05mm too narrow etc. They gave me advice to create a model and order a 3D print to ensure it fits right, but I am not sure if 3D print will have a good enough precision. When I was 3D printing at home I was never able to get exact dimensions - print was either 0.99999x scale or 1.005x scale etc. I fear that a simple thing could turn out into multiplies of £10k and months of back and forth.