I came up with this design for a low volume platic injection molder awhile back. I was going to do indiegogo on it but cant get my partners motivated enough to do it. So anyway here it is. Ill do a batch of parts kits for it if anyone is interested.
I've been looking for a cheap way of doing limited runs of PBT keycaps. Going to have to give this a think.
Almost similar to Make Your Own Injection Molding Machine | Make: (which looks just a little more complete and beefier too)
I've been doing a bit of reading over the weekend and it seems like this can be improved on with a couple of 6 ton bottle jacks and an automotive coilover spring. The deficiency(?) of the hand pump method is speed of injection. (i have read) That the plastic begins to harden almost immediately so the faster you inject it into the mold the better things will be in the fine details and edges. Still very inexpensive and using the same principles but capable of a wider range of plastics and molds.