Here's what you'll need:
1. A 3D printer
. Now, if you don't have a printer, but have an extruder and heater from an old printer or from a printer you're making, you may be able to construct a "free standing" version of an injection molding machine that may actually work better than the method I'm describing here.
2. A mold
. Printing the supplied mold will allow you to produce a true injection molded part, but it will still have all the external characteristics of a 3D printed part. As I've said, you can make a mold from just about any standard mold-making material, but I don't yet know what materials work best for this process. I've been experimenting with polymer clay, a hard, inexpensive, heat resistant and easy to use material that can be picked up at WalMart
. Silicone RTV rubber
is a material I've had success with and recently, I've tried a product called "Sugru
" which works better than polymer clay, but not as well as RTV. I've added instructions on how to make a mold out of Sugru in the next step, along with the instructions for using the downloadable printed mold. If you just want to get on with it and print the mold I'm supplying, You can download it at the bottom of this page.
If you have mold making experience, you may want to use RTV, or do as I did, use an old mold to prove to yourself this process works.
The pressures involved aren't large, so metal dies aren't necessary. However, if you do experiment with metal dies, I'd be very interested in hearing how it works out. I have no way of making metal dies myself.
If you use my printed mold, you'll also need higher and lower melting temperature filaments. I used ABS for the mold and PLA for the part. If you use a more heat resistant mold material, theoretically, you may be able to print in ABS, PLA, Nylon or any other material that fits through your machine (chocolate bars, anyone?). One person even suggested hot glue. None of these other materials have been tried. I've only used ABS for the mold and PLA for the injection medium. So far, other than the lack of color, I'm quite happy with it.
3. A watch.
You'll need to time your injections. Too short and the mold won't fill completely. Too long and you'll have to trim too much flash from around the parting line. The time it takes to fill a small mold is measured in seconds. Once you work out the best time for each shape, your parts should be good every time.
: The "proof of concept" demonstration in this Instructable will take about an hour of your time. Most of this time will be taken up by printing the mold. For best results, the mold needs to be warm, so plan to be there when the print finishes and you can make the injection then.
READY? Let's begin: