Portable desktop injection machine
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) :
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.
Looks awesome, a bench injection machine is the next thing on my projects list 🙂
yup, we’re started right now 2 small scale sets for 2 clients in the field as pilot projects. as often those guys don’t know actually what they want nor what to do with the machines. many come up with the idea to let the kids bring plastic and currently I have to push them back already from their idea to recycle PET bottles (fume, hard to recycle,…), makes me headaches because apart from shopping bags there isn’t much left the kids could bring from home. Shampoo or ‘fairy’ bottles are pretty hard and would exceed the machine limits (2Kw) and also may require dangerous pre-cutting. Ultrasonic cutters come to mind but a nightmare in the class room 🙂
more or less that are the 2 major tasks to solve with or for them : the missing PP manuals (there’s lots to do, localized) and the actual workshop plan. the machines are more less clear to me now : for people from 1.30 – 1.70 meter high with little muscles and complete enclosures, water prove, and a door for the shredder as well all the measures we’ve mentioned recently.
I could of course just ‘send it’ but I’d love to work this out. There are some similar activities I came along on instagram but i have the feeling all this is at the very beginning. i don’t see much educational value in 1. shred some plastic and 2. inject a pre-made mold and send the kids back home with a spinner ..
way to go.
These really look great. From some of the other threads, it looks like there is an educational institution demand that these would be ideal for. I hope that works out.
Not sure, the shrinkage takes place on cooldown when the heater is off (I don’t ramp down the temperature control). The tube is fairly thick wall aluminum which is why I tried just one heater. The holes for the mount block go through, so there is a chance for the part to preferentially stick to one or two places. I also maintain compression during the solidification, not sure how that plays out. It is HDPE so the shrinkage is pretty high.
All good reasons to do more experimentation
The uneven shrinkage might be due to having only one cartridge heater on the side. Using 2 or three spaced evenly should give more consistent results. Adding a layer of insulation over the top of everything will also help.
So I turned the round stock to get rid of a flat spot and make it round. Ended up with a 36 mm diameter 150 mm long HDPE rod. Smooth, no pits or visible voids. Density is .85 g/cc.
Overall a useful piece of stock material.
I wanted to see if the arbor press actuated desktop injection machine could be used to compress a heated mold to make some stock material that is larger than the small injection volume. I took an aluminum tube about 41 mm ID and 184 mm long. I made a block that could be used to clamp a cartridge heater (300w) to the side. Both the tube and the block have a groove to accommodate the round heater (some aluminum tape is also used as filler). A second small block mounts the control thermocouple. The arbor press has a rod attached with piston sized to the tube. The bottom of the tube has a plug with a thread to allow attachment to the wooden base for stability. You can see all the parts in the attached pictures.
The mold heated up quickly. I filled it with large flakes from milk jugs (HDPE). To mostly fill the tube, it took a number of top-off and compaction steps. Once full I let it sit under compression and temperature for about 15 min and then let it slowly air cool. The result is a pretty solid, usable piece of round stock (though shrinkage away from the wall is not quite even and it is not quite round) . I have not cut it apart but I don’t see any voids near the surface.
The point of the exercise was to see how well locally heated compression molds would work without an oven. Thermally, the aluminum mold heated up quickly and took a long time to air cool so it is reasonably efficient (compared to heating up an entire oven). I could have used a band heater for this cylinder but I wanted to test the clamp on block approach which would be usable with flat molds. The part extraction process took a little trial and error, but given how cheap the cartridge heaters are, you could easily have a handful of molds ready to go. The arbor press was useful for all the intermediate fill/compaction steps, otherwise clamps would work as well.
Overall, while there is some process tweaking to be done, I’m happy with the results.
yeah, I could easily need a whole set of these. I am so messy sometimes that I search the whole house for a particular mallet/hammer…
using the injection as regular press: fantastic, you’re right. we call this in germany as “can’t see the tree because of soo much forest” 🙂
and yep, larger volumes are getting quickly a problem. i am still in the trial phase but it turns out that my 2 Nema-34 steppers (1600 oz) need a very specific leadscrew and a transmission to max this out. doing this with custom made parts on the lathe & mill isn’t much a big deal, but reproducing this with common available parts yes 🙂 possibly i better open another thread, looks like a black hole to me these little injections. my idea about was there at least one full-automatic machine available to PP users, below 1K, printing $$ non-stop. there is enough market. btw. there is a larger cooperation here in europe and elsewhere i think who bought all major and small producers and now they do price fixing. I had recently a catalog of small plastic parts (bricolage stuff) and I was shocked how expensive this small stuff actually is. anyway, soon more about 🙂
I love that mallet. I made some larger stock in the past using the oven, tube, and C-clamp approach. They came out OK but took a long time and I got dirty looks for using the kitchen oven. I think there is an option of using the injection machine actuation to compress a mold heated with cartridge mold heaters. I’ll have to try that in the future.
Good luck with your new build. I wonder if a larger volume, lower pressure pre-melt stage could handle the V3 flakes. An arduino could synchronize the transfer to the injection stage.
calculator: i did, i am so lazy and just wanna mess around 🙂
did you know this video. it’s plastic color g*ng b*ang o*gie
@btmetz, great. I am afraid i just understood the first half only of what you said, btw. your keyboard’s enter key seems jamming often 🙂 Anyway, i am looking into it this weekend.
@s2019, awesome work again ! this looks really promising so i went ahead with the screw idea : M20 acme rod and thread and bad a** hand wheel, it pushed PLA effortless through 25 mm tubing – almost on it’s on own since the handwheel was more of a flywheel. unfortunately my rushed welds were too bad so the thing broke apart the last part but it was enough to fill a flat cylinder. i gonna build this bigger and better this weekend. To me it seems this is a serious candidate to replace the plunger and even the arbor press driven injection, for larger things at least 🙂 I just need to kick the handwheel gently only and this thing keeps spinning whilst extruding, lovely.I turned also trapezoidal a screw now my self on the lathe, 25 mm diameter with a optimistic pitch to speed things up. I guess I will make the nut in plastic as well (Delrin again).
no, i didn’t but thanks for the hint and link, looks really neat and tempting, but managing this spring over there seems a little overkill, no ? i also afraid that anything ‘sophisticated’ like this doesn’t justify the involved on part work anymore. i could easily get lost full 2 weeks on it 🙂
let’s see how well it does, i have the slight fear that the transmission needs an extra gear…
apart from that, it’s was 3 days full-time work in a row, lots of mistakes done but the next one is pretty stream lined and cheaper to build for sure 🙂 So there will be 4 heatbands (one inside the bar), a 300 Watts, on the nozzle, 6 cm ID, on a brass sleeve going on our standard 35 mm).
i think this can be all done with basic tools: drill press, welder and angle grinder, if you’re good with hands, i won’t be that accurate as the lathe, cnc but good enough.
anyways, 150 Euro in materials, consumables and electricity, not too bad, 33kg steal.
seeya around soon, just ordered plaster and a shit load of expoxy 🙂
i just finished our own arbor press’s housing (see left). as often I bought too big; the rack is module – 3 (3cm x 3cm x 50 cm long) and the gear was 40 Euro only, I hope i get a good and flexible connection to an extendable plunger. this all has to fit in a hydraulic press like frame, a little tricky. i will weld a disc on the shaft to place some solid bars to make large hand wheel, 60 cm diameter or so. no idea how much power this gives yet but should be still way stronger than anything else i had 🙂
about the molds again, i could finally finish the first shapes : cylinder & hexagon in one cylinder (see right). i gave up on the piston, it caused to much friction and the plastic got it all badly. i still don’t know about the cap and clamp but i think i will go for 2 quick clamps which hold the upper cap (mold entry = M20 nut) on the cylinder. there is a little M10 thread on the bottom of each mold. i hope it acts as an ejector without too much damage. i also went for thinner walls, in hope it’s cooling down faster 🙂
soon more, I have to catch up with all your recent thoughts (expoxy, plaster,…)
see you in a bit
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).
Just for fun, This is what the small annular cavity fill part (right side) looks like with a little clean up.
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).
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 🙂
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.
thank you both!
@s2019, 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 🙂
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.
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 😉
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.
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.
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.
You must be logged in to reply to this topic.