For quite some time now I’ve fancied getting into injection moulding. A couple of years back I bought Vince Gingery’s books on DIY injection moulding and had a go but the build fell off and I used the parts for other things. (1,2) The addition of pantograph and CNC capability in the shop has caused the project to resurface of late.
I based my build off of Vince’s drill press attachment but changed almost all of the dimensions to suit my own requirements and shop limitations. My initial foray was smaller than in the book to accommodate a short throw bench drill press but the subsequent purchase of a larger machine meant that I could have a stroke common to the Gingery plans. The bore was also enlarged to suit stock I had to hand. Originally I intend to use a nice precision ground rod for the ram but during machining I ended up scoring the bottom of the bore where the taper meets the side wall and on cleaning this up I had to enlarge the ram diameter which meant turning the ram out of 1.125″ CRS. Before preparing the new bore I saved myself further heartache by adding a combined micrometer/hard stop and a George H Thomas designed flat bottom boring bar and eccentric holder. Both have immediately found a place amongst my most used tools. Without them it was very hard to know when the bore ended and the taper to the nozzle started. At any rate, it worked, and I am the happy new owner of an injection moulder.
How the machine will be employed is yet to be seen but I have drawn up some mould cavities and made some tooling to help with cutting them. Surface area is the big enemy on such a small machine and I’ll be doing my best to learn how temperature, and injecting pressure affect clamping requirements which at time of writing are distinctly minimalist. My long range plan is to learn the most basic parts of the process and then, if possible, use the moulder as the core of a purpose made machine with part ejection. We’ll see… In the mean time a special collar needs to be made for the drill press I intend to test the moulder on in order to ensure the bearings take none of the injecting strain. It is just a simple collar that fits in place of the depth micrometer attachment on the end of the quill. There will still be some strain on the rack but a little protection is better than none at all.
1. Gingery, Vincent R. The Secrets of Building a Plastic Injection Molding Machine. Rogersville: David J Gingery Publishing, 1997.
2. Gingery, Vincent R. How to build a Plastic injection Molding Attachment for a Drill Press. Rogersville: David J Gingery Publishing, 2007.