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Injection Printing - Injection Molding with your 3D printer

by LeftAngle, published

Injection Printing - Injection Molding with your 3D printer by LeftAngle May 1, 2013

Description

Using the differing melting properties of ABS and PLA, you can use the functions of your 3D printer to make rudimentary injection molded parts.

For more information:
thingiverse.com/thing:83805

For even more information with complete instructions:
instructables.com/id/Use-Your-3D-Printer-As-An-Injection-Molder/

Recent Comments

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Anytime I aim to give helpful advice.
Thanks Robert... I'll certainly check those out. Nylon would be so much better not only for this, but normal 3d printing as well. I make a lot of parts for my customized car and nylon is a better material for that.
For molds you may want to print them in taulman 618 or 645 as the non stick properties of nylon will prevent the material from sticking to the inside of the molds plus it will help make your mold last longer as nylon has a higher melting temp.

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Instructions

This is one of those "I wonder if it can be done" exercises you can do in about an hour. This is only a proof-of-concept experiment that opens up the possibility of further development if anyone is interested.

The part I made is a true molded piece having no deposited layers.

The vent sprue I drilled in the front of the upper mold half didn't work as PLA was too thick to move through (you can see the tiny nub in the photos). When the die was filled, the plastic simply began to pile up around the extruder head, outside the die,.

The other issue I had was the extruder head was hot enough to deform the upper ABS die half. This didn't effect the part, but it made removing it from the mold difficult. The heat allowed the ABS mold material and the PLA part material to be mixed, making extraction impossible without wrecking the upper half of the mold.

Here's how I made this:

Print the stl file in ABS. When the print is complete, break off the upper half (the one with the opening) and place it on top of the lower half, which should still be adhered to the build plate.

Disengage the driver motors and move the PLA print head (or the same print head you used to built the die on a single extruder machine) Load PLA material into the extruder and raise the plate until the extruder head couples with the hollow on the top of the die. Turn the load function on. The PLA will flow, filling the cavity. When its full, the PLA will begin to squeeze out from around the extruder nozzle. That's when you should shut the extruder off.

Let the plastic cool completely before cracking the die open with a screw driver. If all went well, the part will be sitting inside the die, looking like a pearl.

Have fun, experiment and let us know if you make something really cool.
For molds you may want to print them in taulman 618 or 645 as the non stick properties of nylon will prevent the material from sticking to the inside of the molds plus it will help make your mold last longer as nylon has a higher melting temp.
Thanks Robert... I'll certainly check those out. Nylon would be so much better not only for this, but normal 3d printing as well. I make a lot of parts for my customized car and nylon is a better material for that.
Anytime I aim to give helpful advice.
Great idea!
Looks like you got a little warping in the mold!
:)

Hey! It's my first "injection print" (like the term?).

Thanks for the compliment.
Interesting concept, thanks for sharing!
What a cool idea. I bet it would work well with Nylon for the mold - it prints at high temp and is flexible!
Sorry laird, I don't think my response to your comment went thru. I think I had said something about not having the ability to create nylon (or perhaps glass-filled nylon for rigidity). I guess any material that's normally used for casting could be used as long as heat or pressure doesn't affect the outcome. If you have the ability to tool nylon, you may be able to make parts that could easily convert a printer over to injection molding parts.
If you can print with PLA, you can probably print with Nylon. Taulman Nylon filament prints just a bit hotter than ABS or PLA, onto an unheated print bed. The main trick is that you need to print onto a different surface than ABS or PLA, since Nylon doesn't stick to painter's tape or kapton tape. But it sticks nicely to Garolite.

Perhaps this weekend I'll try it.
Thank you. I wan't aware of that filament. I'll have to try it. There are many more things I could print with an engineering plastic, especially in an unfriendly environment like an engine bay.
Or you could shoot the mold with a hot glue gun. The low temp variety might be best...
That would certainly be a good experiment. The issue I have with hot glue is, even though it's a polymer, it's wax based. And that makes it 1. unstable and 2. unpaintable... However... You've given me a great idea:

If anyone has an unused extruder lying around, it could be mechanically connected to a box or frame having specific interior dimensions. Molds could be made to fit the box and the extruder would pump the material of choice into the mold. The mold can be removed, emptied and re-inserted into the box or frame for the next part. If there was a pressure switch between the box and the bottom of the mold, it might be possible to shut the extruder off when the cavity is filled.

Food for thought.
The problem is, filament is much more expensive than pellets. A standard injection molder would be cheaper to operate, and they are simple to make.
Thanks for continuing this conversation. I completely understand your position. I've been looking at Instructables (the OTHER great idea site) and have seen the DIY molders there. It's an excellent option, but if I can get this to work, there probably aren't that many items I'll need with that level of detail. And a new tool that requires me to make stronger molds wouldn't get used that much.

I enjoy making things with my hands, but drawing them up on a computer and letting the printer do the work is much more efficient. If I could also use the printer to cast, instead of using a 2 part resin with a shelf life measured in weeks and a price well above that of filament, cost becomes a moot point.

I doubt there will be many people who actually experiment with this method (understanding, I've only tried it once and have no more knowledge about how it'll work in the long run), but for those like me, who cast "once in a while" this may be a good alternative.

You seem to have experience with injection molding. I imagine the pressures of a stand-alone machine would blast the kind of molds I'm thinking of using to smithereens. How difficult is it to make a true injection mold?
A true injection mold requires a milling machine. But you could make a steel shell to withstand the pressure and 3d print the mold to fit snugly in the shell.
Hey Ron: I've been busy experimenting with the printer. i've also made another Thing to describe what I've discovered. I'll add the link to this thing as well:

thingiverse.com/thing:83805

I used to design parts to be injection molded in a former life. The tooling for industrial molding does, as you say, require milling machine level engineering. I was hoping to hear that home machines would do with less.

That being said, please check out the link above as well as my Instructables page:

instructables.com/id/Use-Your-3D-Printer-As-An-Injection-Molder/

I think you might be surprised (pleasantly) with my initial experiments using silicone dies. The pressure of the 3D printer is far less than that of a full-fledged injection molder. My results aren't to that quality (yet), but I have time to spend, and possibly, with more heat, using ABS, the results will be better.

Please check it out... And thanks for your expertise. Maybe you can help make this better.
Very interesting. I make silicone molds sometimes. I could print an original part, make a silicone mold then use the printer as you have to make duplicates. The silicone I use is fine with high temperatures. The only issue might be that it's not very stiff silicone so it may deform when full if not careful.
With a proper mold, ABS may be the material of choice. My original idea was to make a cube with the bottom open to the build plate to keep heat inside the mold. PLA didn't seem to need any additional heat to work. Like tmorris9, I usually make molds from silicone, but have played around with polymer clays that may work better here. Later this year, I'll be making another model of a pre-federal fort for a museum. I usually research the various types and sizes of guns on the original manifests and hand make the various sizes of original cannon and their trucks, mold them in silicon and cast them in resin. A polymer mold with injected ABS or PLA would go much quicker... Now I'm excited. Nice going guys.
I agree, very interesting. I am thinking along the same lines as you except use a separable casting investment or plaster mold.
Great idea LeftAngle!
With a proper mold, ABS may be the material of choice. My original idea was to make a cube with the bottom open to the build plate to keep heat inside the mold. PLA didn't seem to need any additional heat to work. Like tmorris9, I usually make molds from silicone, but have played around with polymer clays that may work better here. Later this year, I'll be making another model of a pre-federal fort for a museum. I usually research the various types and sizes of guns on the original manifests and hand make the various sizes of original cannon and their trucks, mold them in silicon and cast them in resin. A polymer mold with injected ABS or PLA would go much quicker... Now I'm excited. Nice going guys. And thanks for the compliment Boogle.
I wonder if a higher extruder temperature might be useful?

For printing we want the plastic to just barely melt so it can hold it's string like shape but with a mold a higher temperature may make the plastic conform to the shape easier.

If you did use silicone, you could preheat the mold in an oven fist so it allows the ABS or PLA to flow more, giving it time to conform to the shape. Just a thought.
Experiment, experiment, experiment. :)
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