@Kinnik_Kinnick had an idea to build an plastic injection machine in the Mass Producing 3d Printed Item thread. Thought I’d follow his advice and branch off into a separate thread so those interested (pinging @rsim, @teamcoltra) could start brainstorming and planning out the build together.
Here are some initial thoughts to get the ball rolling:
Reference materials
The design featured in the makezine article is based on a book that I’ve found a Kindle version of for $10. The same author has also written a book to do the same thing as a drill press attachment which is available as a hard copy only from amazon.com. It doesn’t appear to be available from the library.
Alternatively, there’s also an instructable that uses sections of pipe for the heater block instead of a machined one, which sounds like it would work just as well.
Design considerations
total volume of heater block chamber, which would determine the max volume of parts we’d be able to make
injection pressure - the lever throw and piston diameter would determine the amount of pressure we can inject the plastic at. I haven’t looked into this but as far as I know higher pressures are desirable for better feature detail
I should be free this coming Monday evening if those interested wanted to get together and hash this out in person.
I thought about that but it seems like a filabot would require some sort of augur design that continually melts pellets and extrudes them at a constant rate at lower pressures, whereas the designs linked here rely on a one time lever action to produce more pressure but less volume.
I’m not sure if makes a difference to inject with multiple pumps of the lever and refilling plastic in between - my intuition is that that would give the plastic a lot of time to cool and temperature variations could be undesirable during the extrusion process. In any case, it seems like it’d be pretty impractical to stand there for an hour pumping the thing to make a roll of filament.
A filastruder at the space would be pretty handy - it’s another one of those things that I’ve looked into but the math doesn’t really work out for personal use.
The filabot has an auger built in. I’m thinking the kit would work and attach the moulds at the nozzle end. Should screw in. Then work on a mechanism to open and close the mold.
Oh I see what you mean now, though I’m not sure if the augur design will be able to exert enough pressure (and quickly enough) for injection molding. I believe industrial injection molding machines also use an augur to feed and melt the pellets, but rely on hydraulic (or pneumatic?) pressure to then ram the plastic into the mold.
I would be free Monday to discuss things, I have basically zero experience in this so I feel like I would be there more for emotional support than anything else though.
@teamcoltra That’s not a problem at all - part of the fun would be to learn new things and figure stuff out as we go along.
To me, the most challenging part is actually taking the time to plan and build, since everything else we can find solutions to one way or another (it might just take longer).
Would it be okay if we picked this up January-ish? Let’s see if there are others interested in getting involved, and we can take our time brainstorming here in the meanwhile.
I have some experience working with heaters/temperature control and I should be able to supply most of the heater related parts, and I also have some very basic machining experience and would love to use this as an opportunity to get more hands on experience with it.
I could jump in and lend a hand with some machining and CAD work. I do
have a CNC Machine shop, so it shouldn’t be an issue. Time is only issue I
have with 3 soccer teams, a full time job and the shop.
Interested parties could meet at my shop so brainstorm.
You can add me to the list of people who want to help. I’ve been bouncing this idea around in my head for quite awhile now and have done some research. I just don’t have the time yet to do my own prototype up.
Count me in too! I was talking about this on slack a little while ago wondering how cheap such a machine could be. I also stumbled upon the drill press attachment and thought that was viable project within the means of a hobbyist. Why spend $5k on a machine if you can build your own for ~$500 or less?
Glad to see there’s more interest, and appreciate your offer to help with the machining aspect, @Big_Mak! Unfortunately, I won’t be back in town until Jan 11th, so I won’t be able to make it out to Steveston on the 10th.
Perhaps we can start discussing in a bit more detail as to how we are going to approach this project? One of the biggest/first design decisions is the frame. The options are:
In my personal opinion, the easyplasticmolding.com design looks the most robust, and it seems like the Gingery design has issues with side-to-side play. Keeping in mind that we’re looking to maximize the pressure we can produce, I’d personally would prefer to overbuild rather than vice versa, which is why I have my reservations about a drill press attachment as well, as it doesn’t seem like a drill press (especially a cheap one) is designed to handle that much compressive force. At the same time, I realize that building from scratch will be more involved, in which case an arbor press on a stand may represent a good compromise between build difficulty and frame strength/stiffness.
Eager to hear your thoughts on this - especially if there are other options we haven’t considered.
e: as far as material costs go, I really don’t see it being more than a few hundred dollars, and that depends mostly on what frame design we go with.
