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) :
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).
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 🙂
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$. A better entry and this should be enough for doing fun stuff with little house hold waste.
oh that’s neat, thanks so much for the input.
let me summarize in short what a mini PP station would involve:
– credit card shredder : 50e (somebody here makes it looking possible, https://www.instructables.com/id/50-Plastic-Shredder-Grinder-Recycler/), on amazon it’s about 35$, 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,
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.
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
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 🙂
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.
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
@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 🙂
@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 :
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 ?
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
I started work on a fume hood for my benchtop unit. In the spirit of recycling, I used some scrap rain gutter to form the hood and a computer fan for the exhaust. Mine is set up in the garage so I’ll add some of the flexible clothes dryer vent ducting to get the fumes closer to the door. May need an extra fan to pull that distance. A match test showed that the fumes near the <span style=”letter-spacing: 0.3px;”>hot end</span> inlet are pulled through the fan.
Unfortunately there isn’t a lot of information here on the fume topic. You can see from the photo that at 190-200 C some scorching of the HDPE takes place. You can also smell a light hot plastic odor so some extraction and exhaust should be done. This is especially true for the smaller units that are likely to be used indoors.
It would be interesting to know how the V4 team handles fumes in February.
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.
I took another step in working with the desktop injection unit. I tried some parts that had internal features. The first one is a sort of cup bushing. The wall thickness is about 2.5 mm both radially and at the end. It shrank about .25 mm in diameter but even without a taper it was easy to tap off of the central mandrel.
The second has some internal features. A more significant step in diameter and a flat section to key onto a shaft. It took a couple of tries with small adjustments in the mandrel diameter to get the right press fit onto the shaft but otherwise all the features were well reproduced.
This was HDPE, I will try other materials as well. It is nice to be able to make usable mechanical parts besides seashells.
To better illustrate the outer skin issue i mentioned, The cylinder below was almost entirely the matte gray tone surface you can see on the bottom section and the bottom itself. The top section I turned down .1 to .2 mm and immediately some of the internal patterns are visible. Still trying to figure out what causes the skin like surface layer and how to get rid of it for complex shapes.
The second image shows the cylinder with the whole surface turned down. It shows the much more interesting coloring available under the thin outer surface.
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