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Portable desktop injection machine


  • This topic has 144 replies, 13 voices, and was last updated 2 years ago by Stan.

Portable desktop injection machine

27/01/2019 at 19:48

Hey guys,
it was suppose to be an easy thing I thought but I spent then 3 full days on it at the end, lots of hours on the lathe, 1-2 hours welding and a little bit on the mill. I wanted the best result possible, tight tolerances, smooth plunge and an easy to extrude plastic with a flexible nozzle. (btw. I can’t recommend building this without lathe or mill, it really wants it accurate to get a smooth plunge).

In the next iteration I will try to have it spring loaded which is pretty difficult as I noticed.

here you go, full metal desktop injection (some part are hardened to maintain this nice blob sound in the barrel) :

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28/01/2019 at 02:53

I made similar to that.  Looked good but the shot size was way too small to do the kind of things I wanted to do.  It also too a long time between shots because it didn’t have much plastic in it/thermal mass etc

28/01/2019 at 11:39

yeah, shot size is always problem 🙂

it’s still a nice build, can you add more pictures or details (the parts) ? You used a drill press as base ? Or are the parts milled ?


28/01/2019 at 19:11

Looks awesome, a bench injection machine is the next thing on my projects list 🙂

28/01/2019 at 19:51

@xxxolivierxxx, yeah i will keep you posted here. after a bag full of sleep i figured a few minor improvements i should do.i also think that PP definitely should work on something for the small pocket 😉 I was always amazed that these guys on youtube managed to ‘recycle’ with a few simple house tools like a mixer and a toaster.

the inspiration I’ve got from this machine :

28/01/2019 at 21:11

cgoflyn, your machine is a work of art. Thank you for sharing.

I just finished a desktop version (though much less stylish) using an arbor press for actuation. There are similar builds out on youtube. I used a rectangular piston configuration and a simple cartridge heater. The stroke volume is about 45cc. Much of the design was driven by what I had on hand. The purchased parts were well under $100. I machined out the cavity but I think it could also be assembled from off the shelf metal stock without machining.

29/01/2019 at 02:13

@s2019 ah that’s neat, impressive that this works. makes me wonder one could create universal mold building blocks (3d printed goes well too) out of a few shopping bags. ideally this thing could be a small plastic milling machine too, just plug a hand drill and  mount a guide and here go, a small plastic carpentry 🙂

29/01/2019 at 03:49

I’m in the experiment phase. I was interested in whether it was easy to use simple available forms to mold stock shapes that could then be used for other projects (bushings, pistons, stand-offs, etc.). Right now I started with HDPE. Some parts do end up with voids, so right now I’m looking at temperatures, mold heating, and form plugs to see what works. I tried using a bolt to mold an internal thread (3/8″-16). That worked pretty well. Because of HDPE shrinkage I ran a tap through it afterwards but otherwise it worked. You can also see a small void in the bottom right corner, that I’m trying to get rid of.

30/01/2019 at 02:35

nice, i was running similar tests against my desktop machine, with pretty much the same desire as you: little level jacks, pistons, etc..

i pretty happy actually with the results:

– plastic bags didn’t turn out well, but i guess i have to wait longer, i really want this thing to work for house hold waste 🙂
– bottle caps : awesome, i know now i have to enlarge the entry just, with a bigger heat band around and so I just need to push that caps without any shredding, cutting or folding into the injection.
– lever could be more powerful but i guess i replace this against a rack and pinion as in the abor press sometime soon.

so yeah, a small machine turns out pretty fun and useful after all, i have to ask the neighbors to get plastic waste, wtf. :-O

30/01/2019 at 03:58

Yes, no shredding. I found I can fill most of it with fairly large 1-2 cm wide strips and then feed some small pieces to top off (needle-nose pliers keep the burning skin to a minimum) . The large pieces make cutting up a plastic bottle by hand pretty quick.

30/01/2019 at 13:29

well, about the no-shredder I gave it another thought, actually I’d happy to have a little shredder (hand driven) in place. Cutting this stuff with the scissor makes the idea of a ‘micro recycling center for everyone’ less attractive but that’s another story (will try a shredder box with 5 blades only, hand wheel operated).

haven’t tried PET yet, I figured even those quality heat bands (100 Euro for 4) have a difficult time to get on temperature. let me try with 35 mm instead 🙂

30/01/2019 at 13:47

btw. does anyone has an idea on how to make adjustable molds with basic tools. from what I see now with this little injection, I’d love to have just a few primitive forms: box, cylinder and triangle. I guess this could be done with wood, nuts & bolts and a screw driver and later on from plastic. no idea… i am just guessing but yeah, a kind of lego like system would be cool, made of house hold waste

30/01/2019 at 19:22

A small shredder would be nice, I only use scissors for the thinnest material (milk and juice containers in the US) for everything heavier (detergent, etc) I use a utility knife and cut it into strips. This is relatively quick (for experimenting). I’m tempted to try one of the credit card capable paper shredder hacks.

30/01/2019 at 19:30

For simple molds, I made some clamp plates that can hold different shapes. Since the top and bottom plates (aluminum) handle the heavier load and temperature, the form plate in the middle can be wood or aluminum.

For the narrower forms, I just place them directly under the nozzle with a top washer or plate and then hold them in a C-clamp during cooldown.

31/01/2019 at 00:01

oh that’s neat, thanks so much for the input.

let me summarize in short what a mini PP station  would involve:

– credit card shredder : 50e (somebody here makes it looking possible, https://www.instructables.com/id/50-Plastic-Shredder-Grinder-Recycler/), on amazon it’s about 35$, in europe maybe cheaper

– heating segment: about 30 euro, 1 PID, 1 SSR, 3 heatbands (china stuff). possibly 50-60 when going for a larger diameter and better heat bands
– abor press about 70 Euro, new
– metals & wood : 50 Euro
– misc. stuff: nuts, bolts: 20 Euro

clamping/molds: if lucky scrap metal, sold per kg

so that’s about 300 Euro, possibly cheaper with some little efforts.

(not included : hand and power tools, around 300 for the complete set: angle grinder, welder (2nd hand), drill press. relative cheap stuff after all)

ok, so at this point we can recycle small stuff at home, shampoo bottles, caps, plastic bags; not too bad 🙂

about the ‘universal’ clamps: let me try something -) I was playing with the idea of a 4mm metal sheet and a whole patterns on it, so you you arrange some bars in the way you like and bolt it down and close it with another sheet (holes covered by a thinner sheet). the mold entry could be almost always a plug just, no idea, will have to play more. see you in a bit and thanks again,

31/01/2019 at 01:26

found this one, shreds up to 18 sheets, dvd covers, 30 mins long, super reviews : https://www.amazon.com/Fellowes-Powershred-Proof-Cross-Cut-Shredder/dp/B000YGO7HW/ref=lp_172591_1_8?s=office-electronics&ie=UTF8&qid=1548890277&sr=1-8#customerReviews. It’s originally 600$, now at 214$. A better entry and this should be enough for doing fun stuff with little house hold waste.

31/01/2019 at 04:36

Earlier I said that the captured form plate can be wood. Well apparently not the soft pine I tried. The goal was to make a knob with an embedded bolt. There are youtube videos where they make a nice aluminum tool. I wanted to try a simple wood form. Since  it it was a trial, I didn’t sand or prep it, just drilled and hole-sawed the main features. The pine split but the knob came out pretty well and solid. Using plywood or some other material that won’t split and doing some prep work smooth the form, a nice usable knob can be made easily.

I also made a couple of shallow wedges to position the mold under the nozzle and eliminate the need for shims. This worked well. The end grain has enough friction that the wedge holds under load. I was originally looking for a low profile scissor jack but for now this works great.

The other discovery was that for me the solution to reducing or eliminating voids is ….. patience…who knew? Giving the plastic extra time in the chamber to fully melt gave me much better results.

31/01/2019 at 04:58

Right now, I’m rethinking the shredder for the hobby set up. In my injection configuration, it is much easier to stuff larger strips into it with needle-nose pliers that it is dealing with small chips.

I like the paper shredders, except that you still have to cut the bottles to be somewhat flat. I’m not sure that they can handle just a flattened (double thickness) detergent bottle.

31/01/2019 at 15:07

good thoughts and work! keep going 🙂

I just ordered 2 pieces of the paper shredder seen below (the strong one from Amazon). And about the bottle problem, well the PP v3 shredder isn’t doing well on this one either 😉 Even with plunging it’s a pita. Apart from that, no idea yet how PET can be of use, the HDPE however makes the best fit for what i want. as soon i have the paper shredder hacked (better entry), i will post it here…

the results of your wood mold look promising, i guess this has to polished anyways, no matter what 😉

02/02/2019 at 03:12

OK, I did a rev 2.0 on the wood mold approach for making a threaded bolt knob. I used some left over engineered wood floor cut-offs. Most of the cross section is homogeneous instead of grain. I drilled the 8 holes to to provide the texture and then hole-sawed out the main body. Sanded smooth and then used aluminum tape to provide the smooth surface. I used HDPE scraps (milk containers) so the color is not exciting but the surface is very smooth and usable. I did lightly sand the top to remove some light swirls. The bolt is 1/4″-20 (~6mm) for reference.

I actually need a 12mm version to replace a broken one on my miter saw. That one will get some fun colors.

In conclusion, the aluminum tape provides a smooth surface and the part releases very easily

02/02/2019 at 03:34

awesome! thanks for sharing, will try this myself 🙂

02/02/2019 at 04:12

Looks quite interesting.


I too had issue with wood splitting when I tried a CNC routered mold using soft Canadian pine.


Another mold material that works nicely is steel epoxy and marine epoxy.


I tried mixing black iron oxide (sludge leftover from the CNC Plasma table to extend the marine epoxy and got nice results also.


I understand that it will get several hundred shots, although I have not done more than around 30 some shots with a epoxy mold.



03/02/2019 at 17:27

thank you both!

, thanks to your overwhelming (you’re a book on legs 🙂 input I think I figured now a how a flexible mold for a potential mini PP starter kit could look like. I was toying around with all that scrap cylinder cut offs today and realized I need only a bigger cylinder with 90% inner diameter. then, i do a piston like object which enables adjustable height. then i just need to make different sleeves to enable diameter and whatever shapes.

i have boxes filled with those cut off cylinders, finally i can turn precious metal into some precious plastic thingy 😉

greets from the shop, Sunday is my favorite to be here 🙂

03/02/2019 at 17:53

Yes, I had a similar thought. As a follow up to the machinable wax suggestion, I wanted to see how the plaster mold would work. I wanted to make sure it was well reinforced so yesterday I cast it into a tube cut off as you describe. The plaster retained good detail. I will give it few more hours to dry and then try it. If it works well, it may make that cheap CNC engraver viable since I think it won’t have trouble carving (though slowly) the part in the machinable wax and then cast the mold in well contained plaster.

03/02/2019 at 22:41

The plaster mold worked well. It replicated the detail and survived a couple of injections (HDPE) without any apparent damage. The small round mark on the black shell is probably due to warm up. It was the first injection of the day and the nozzle may have still been a little cool. The metal tube frame protected the mold well.

03/02/2019 at 23:02

I also tried a couple of cavity fill trials. The one on the right used the steel bushing inside the aluminum tube to form an annular cavity in the bottom portion of the mold. This was to see what it takes to fill narrower channels. It worked OK but the flow stopped about a half centimeter from the bottom. So either the injection temperature needs to be hotter or the mold needs a little preheat. Even without a taper I was able to tap the HDPE part off of the bushing. For larger diameters the bushing may need a taper or maybe be aluminum.

The second part on the  left was to see how well a relatively large diameter cavity can be filled (the nozzle is about 5mm). Worked well but you can see that the outer surface cooled into the swirls (HDPE). May try some with a wood plug and/or preheat of the form. May also need a bit more material.

03/02/2019 at 23:03

dude, i am blown away! that’s pretty much the best thing i’ve seen here since long. congrats ! really, i copy & paste this here, even though finding a plastic shell at the beach may be quite an awkward moment 🙂

so from what i learned, people could do this with some basic tools (did you this with your abor press hack?). all what’s needed is some press (ACME & Cylinder), an oven and basic shapes which serve as mold enforced containment. congrats, you’ve made my day.
see you in a bit, let me try this as next after i managed to have piston like base mold, followed by an adjustable rectangle mold 🙂

03/02/2019 at 23:05

i just realized you’ve posted whilst i was typing. regarding your last test, yes you could try preheat all in a small oven and fill the barrel (much easier). the results with plastic bags and bottle caps are much better and faster 🙂

03/02/2019 at 23:17

Yes, these were done with the setup I showed at the beginning of the thread. I used a small arbor press (1/2 ton) just because I had it. The next size up (1 ton) is still very cheap and manageable in size and weight but has a longer stroke. I may upgrade at some point to get the extra volume. I still think, with a little bit of cleverness, one could (in the US) build this for around $100 using a saw and a drill press (hand drill with great care).

03/02/2019 at 23:55

Just for fun, This is what the small annular cavity fill part (right side) looks like with a little clean up.

04/02/2019 at 00:17

amazing! gives me another idea on how to have a height adjustable plate to place the mold under the nozzle. pilling up a some extruded cylinders connected via shoulders or ACME rods, should do the job.
about the abor press again, there are 50CM long hydraulic cylinders (5T, car jack section) on Amazon, for peanuts. Only problem with them is that it takes ages to expand them. i saw a guy who made hacks on a habor freight press (20T, 150$) via air-compressor. looked quick promising. alternative is a module rack & pinion based press but you need to build a special housing (i just did) and something to extend the rack for the plunger (updates about soon in another thread).

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