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 think for a desktop/home unit the 1 ton arbor press (such as https://www.harborfreight.com/1-ton-arbor-press-3552.html )is a very convenient option. It has a decent stroke and if someone has the capability you can always fabricate a longer rack. It is very quick to actuate and has good leverage. It also provides you with feel for when the mold is full which a hydraulic cylinder may not.
Of course it all depends on the preferred configuration and capacity.
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
I think the power or leverage should be the ratio of your wheel to the pitch diameter of your gear. For the arbor press I linked it is 20:1 I think my smaller one is similar. You may need a larger diameter hand wheel. The lever on my smaller one is effectively about a 23-25 cm lever length. My piston area is about 5.4 cm^2 and at times I’m pulling on it pretty good to generate pressure. I do have a fairly small diameter nozzle though. Maybe you can weld on a 1/2 inch drive interface so you can use a breaker bar https://www.harborfreight.com/12-in-drive-25-in-professional-breaker-bar-62729.html if needed. Actually it would be interesting to attach one of these https://www.harborfreight.com/12-in-drive-digital-torque-adapter-63917.html to see what torque is actually used. I may be able to cross drill a large socket to attach one to my press.
I noticed my press has two screws and a gib plate in front to control the rack and a couple of screws on the side as well. Do you have something similar?
On the assembled molds I made, having easy access to push the sprue out of the injection hole in the cap plate is useful. I usually just beltsand off what is protruding and then hand push the rest out.
Found this leadscrew torque calculator https://www.amesweb.info/screws/LeadScrewCalculationsAcmeThreads.aspx . You could drive it with a cordless drill/driver
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 🙂
You do realize you are repeating the work of the Gingery injection mold machine from a few years ago?
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 🙂
Actually, I think @cgoflyn approach of using the rack and gear is a significant difference from the Make magazine link and the PP design as well. This approach separates the leverage and the stroke length. The injection volume can be increased without increasing the injection effort or needing an increasingly long lever arm.
In continuing to tinker with the desktop injector capability, I went back to seeing if a usable, internally threaded part can be injection molded. I used some 3/8″-16 rod, made some bushings to center it in the form tool, the top bushing had an off center injection hole. Using some milk bottle HDPE, first try came out well (I just cleaned up the ends to be flat). It shrinks onto the rod but is removable, Since the thread shrinks, I run a tap through it by hand to get it back to the right size but after that, it is a great threaded bushing. I actually have a use for that one.
I also injected into a square tube to make some square stock. The picture shows a 1.9×1.9×10 cm part, 32.1 gm. That is close to the limit that my 44 cc injection machine can produce. Again, for me, a usable part.
Just a follow up to the micro-lumber theme. I machined the raw stock into a more finished form. The HDPE cuts very nicely.
The threaded bushing was shaped into final form. In the process I did find a hidden cavity. It was interesting that it occurred away from the thread. For my use it is a cosmetic, not a structural flaw but I will remake it, if for no other reason than to use some more fun colors.
The square stock came out well, You can’t even see the endmill marks. The slight cavity is probably there because I used the full stroke of my machine and the pressure wasn’t sufficient at end of stroke to avoid a shrink cavity. I used some low quality thin architectural steel because that’s what I had in the junk pile in that size. You can see how the pressure deformed it. I’ll have to get an assortment of thicker wall tubing.
It was interesting, the density of the finished part is .932 g/cc, probably a reasonable number for HDPE. It would be interesting to see what other people are getting in their injected or pressed parts.
IMO the Gingery machine is inferior somewhat to the Precious Plastic v3. Having used both. Although that angled frame does have something going for it.
My current injection molder is the PP blueprint with a substitute of 1.5 inchx6mm angle bar stock for the 30x30mm tubing. Here in the Philippines we get a mix of metric and imperial stuff.
the thick wall tubing is not as common source as the angle bar that is used in making roof trusses.
@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).
That looks great, love that wheel.
I think if you plug the acme dimensions into the calculator I linked, the torque required will be able to be driven with a cordless drill/driver. That way you can have a push button or toggle lever operated system.
I find it is interesting to blend the recycled colors. I think because I tend to use chunks or strips rather than fine shred I get some swirl. The surface tends to be muted but a light cut with an endmill makes it pop
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
In the spirit of that video I remade my threaded bushing part. With a little bit more fun color mix (pill bottle, detergent, flower pot and a dash of milk jug). It is interesting that the part blank tends to have a color skin and as soon as you turn through that, all kinds of stuff pops out. In the section view, the black dot on the bottom is the sprue inlet. How the flow goes from there is probably in the video.
Now to raid the recycle bin for more colors
OK, maybe I have too much time on my hands. I was trying to figure out how the cavity is filled in an injection process. I realize, mostly it is luck but there may be trends or ways to orient the inlet to affect the results.
This is an axial injection 4.7mm nozzle into a 22x22x67mm, 1.5 mm thick unheated steel form. In this case a swirl appeared to have happened in filling the form. What I was trying to understand is, if you look closely each of the layers has its own what appears to be stress rings from shrinking away from the form. The shrinkage compared to the corners ranged from .1 to .3 mm.
If you take a .5mm cut off of the surface, much of the light grey color disappears and the swirls appear to be one piece with no visible voids at their boundaries. I wonder if there is a way (for more comlpex shapes) to avoid the muted glaze at the outer surface for injected multi-color parts, and get at the more vibrant colors inside.
Oh yeah, if you need to make HDPE caterpillars a low speed endmill cut is your answer.
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.
Just a follow up on the simple wooden mold. I wanted to change the outer profile of the knob I had made earlier to make it more comfortable. So I took the wooden mold (3 layers of flooring) and added 8 pins (about 5mm) to form the indents. I borrowed this from a youtube guy that carefully machined it out of aluminum. Thought I would try it with wood….worked well. I think for quick prototyping, wood and or plaster can make some cheap, usable molds without the CNC or other machining.
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.
amazing stuff again @s2019! , indeed plastic bushings would find some use in our shop. if you don’t mind i use and reference your pictures in our blog 🙂
I am currently maxed out with work, so I will occasionally pass by. We started working recently on a smaller automatic injection, release date is in May, for max. 1000e. I have all the parts, drawings, etc… I just have no idea yet to get this work with recycled plastic chips coming from the v3 shredder (extrusion->pellets isn’t an option).
see you in a while
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.
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 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 hot end 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.
Any chance of moving the posts starting on 07/03/19 someplace else so this thread is more linkable?
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