Make Your Own Injection Molding Machine

 

Above is the finished injection molding machine with a partially disassembled moped in the background. When I first set out to make this, all the information readily available was a few pictures of some home made injection machines and a few forums of people discussing making their own (very few actually showed what they had done). A lot that was designed had to be designed from scratch with the final product in mind. Which is why the final product is displayed first.
A video outline of the injection molder can be found here.

 

Drawing what the final product will look like is the best way to decide on what materials will be needed for the project. This entire apparatus centers around the heater block, detailed in the lower right side of the page. This drawing calls for a 3/4" hole drilled through the entire heater block. A 1/2" hole would give a decent shot of plastic and would have been MUCH easier to drill out of aluminum. If you do go with a 1/2" hole, be sure to adjust the pipe fitting and tap for the different hole size. The rod that fits into the hole will also have to be a different size (I hope that is obvious).

Another difference is that this drawing calls for a steel heater block. Though that would work better, drilling through steel is more difficult than drilling through aluminum. And if the machine is not going to be used for production... aluminum will be fine. 

Also note that the aluminum guide that is in the drawing is missing from the picture. That is because the tap broke off while finishing the guide. And since it works fine without it... motivation to make another one is completely gone.

 

The above list shows the likely cost for just the raw materials and the heating system. Other materials are needed to finish the project, as are an array of tools. 

1. A large drill press
2. Screw drivers
3. Hand drill
4. Tap and die set
5. Files
6. Pliers
7. Welder. 

The picture shows all the angle and flat iron welded together, but you could bolt them together if you are adverse to welding. When you are all done, don't forget to paint it so that rust has a harder time taking up residence.

 

The temperature controller is simple, it is centered around a generic PID temperature controller. The harder part is finding a housing and power entry for it. An old computer power supply housing with the power entry still attached and the fans removed works great. The purpose of this circuit is to protect the temperature controller relay from having to support 120VAC, and to add some more obvious indication of when the unit is heating up.

Notes And What Could Have Been Done Differently:

• A common supply of plastic to use in the injection molder, is plastic coat hangers. Most are made of Polystyrene(MI), which melt between 350 and 400 degrees Fahrenheit.
• Use a 1/2" hole and rod. Drilling through the heater block will be much easier that way. The added shot size with a 3/4" hole was not worth the hassle.
• Weld a nut on the base of the steel beam that allows the threaded rod to push the mold into the hot end. Possibly look into a better method of pressing the mold into the hot end.
• The hot end is simply a pipe end cap with a hole drilled in the middle.

Print Your Own Circuit Board

To print your own Circuit, you will need the following software:
Eagle CAD 
PCB to G-CODE
A good guide for using the plugin has been made by Richard Albritton.


You will also need the following hardware:

• CNC machine that can take the PCB size.
• CNC bed bracket to hold the board down.
• Double sided copper clad board.
• A 30 degree angled bit with a tip of 0.01"  

The first step is to create the circuit diagram that will be turned into a PCB. This can be done with Visio, Pspice, Eagle CAD, paint, or pencil and paper. The following circuit was created using Multisim.

 

After a circuit is created, the next step is to use Eagle CAD to draw the traces. Eagle CAD's website has a few tutorials to try out if you do not have any experience with it. Be sure to set up Eagle with the PCB to G-code plugin! As once the traces are made, that plugin will be used to turn the file into G-code. Use Richard Albritton's tutorial when setting it up and converting to G-code. The Gcode can be read by the software your CNC machine is compatible with. MACH3 was used with this project.

You may notice that a few of the holes are off or the pad (the CNC was manually controlled to make the corrections). This is because a 3020T-D CNC machine was used. The control board it uses is less than perfect, and may cause a few skips in the movement count. After the above PCB was created, some 0.47micro capacitors were connected between the ground plane (The trace going under the surface mount resistors) and pin 6 of the axis controller. The negative side of the electrolytic cap was connected to the axis controller.

 After the fix, the output to each axis was MUCH cleaner and stopped skipping steps! The board that was not cut perfectly was still functional, so it was used for it's intended purpose of controlling two matrices of LEDs based upon a microphone input.

As a bonus, print the description of each component on a clear sticker sheet and put it on the front of the board. This will make populating the board that much simpler.