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Portable desktop injection machine

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This topic contains 141 replies, has 11 voices, and was last updated by  Stan 2 months ago.

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Anonymous

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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warrior
14/03/2019 at 03:28
3

An update to the fume hood. Last month I added the sheetmetal and fan to my desktop injection machine. Today I added the rest of the fume routing. I needed some sheetmetal to transition from the square fan to the round duct. Sheetmetal (first image) comes in many flavors, this one happens to be cocoa wafers and some other food container that fits inside the tubing. The tubing (second image) is actually RV (caravan) sewage hose. For obvious reasons I used a new one (surprisingly cheap, 6m length for less than $8). At the exit is another CPU fan to help pull the fumes out of my garage door (image 3). This fan is larger so an unused bathroom accessory got adapted to form the transition cone. I did some match smoke tests and the system seemed to pull them out nicely.

The point is, if you are working with hot plastics indoors, with a little creativity, adding a fume extraction system can be very low cost. For some machines it may take more of an enclosure and stronger fans, but is still cheap compared to the alternative. Since we have no data on the fume hazards, consider it insurance and be safe.

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starter
14/03/2019 at 20:40
2

nice one @s2019, you’re right, anything which isn’t proven healthy is not safe (er,…this sucks at many levels). i just start researching this, indeed, there isn’t much. that’s pretty much the best i’ve found to start with : https://envirocare.org/plastic-fume-monitoring-exposure/

warrior
22/03/2019 at 01:49
2

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.

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warrior
22/03/2019 at 04:04
2

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.

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warrior
22/03/2019 at 13:44
2

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.

warrior
22/03/2019 at 17:18
2

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

starter
23/03/2019 at 19:30
2

nice nice, focusing on raw stock plastic opens recycled plastic to traditional handcraft, any wood tools will have it easy. I guess going for hydraulic and a heat chamber may make things even more easy, on the volume side. I still didn’t find the time to test all your precious input but things got a little relaxed on our end, so I hope I can join your work with attention soon 🙂

here’s btw. the output of 2 months messing around with the machines, mostly based on v3, just re-configured in a way that it fits on a bench top and more importantly, one the back seat of a car as we figured this stuff serves better public audience on wheels instead of a fixed workshop.. the machine on the right can be switched to ‘injection’, updates soon about this, basically enclosure and your fume extractor is missing, more or less 1m x 1m x 35 cm deep, 60 Kg but still easy to ship, 4Kw

warrior
26/03/2019 at 19:15
1

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.

starter
26/03/2019 at 23:24
1

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.
g

warrior
18/04/2019 at 01:53
3

I made some upgrades to increase the capacity of my desktop unit. I took the aluminum tube that I used for the compression experiment and made that my injection cylinder. Since this is a significant increase in area, I upgraded the arbor press to the next size up (1 ton).  This had two advantages. The first is the obvious increase in strength, but it also has a longer stroke (150 mm). For the arbor press designs, ram stroke is a free way of increasing volume without increasing the effort needed to actuate. Of course, I could have just bought a long rack for the existing unit (like @pporg uses in his design), But I didn’t want the overall height to keep increasing and the 1 ton press was off the shelf and very low cost. The assembly is shown in the first image. Overall, the total parts cost is still around 100 USD.

Since I knew I was going to be applying a lot more force, I changed the support path to react against the arbor press instead of going through the wood frame. I just used 6mm threaded rod. The specs say that two of them should be able to handle the 1 ton load so, since I had them, I used them. The black steel tube allows me to adjust the height of the piston rod up so that I have room to load the cylinder (second image) during the fill and compact steps in the process.

The overall stroke volume is up near 200 cc, about 4x of my previous version. For me this is more usable. I definitely takes more effort to actuate the bigger piston. I have a breaker bar I’m going to sacrifice to get more leverage. I also increased the orifice size to  almost 8mm.

The third image shows some of the test results, forming basic stock shapes out of HDPE. As you can see the molds are just basic wood and metal, bolted or clamped assemblies created out of the scrap bin. For me they generate usable stock material that can then be machined for other uses. The two long cylindrical parts were an experiment in constraining the part during cooldown. For both, the aluminum tube next to them was the mold. The ends were blocked with wood endcaps, clamped closed, and injected through the hole. The first try (the part next to the tube) came out well but came out bent (though it still fits in the tube). For the second (left most) part, I took the clamp off of the endcaps right after injection and let it cool down without axial constraint. The second part did come out straighter but is somewhat lumpy and the cross section is much less round. Material also bulged out of the ends. Interestingly, the square bar was constrained during cooling but stayed straight with a nice uniform cross section.

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warrior
18/04/2019 at 02:56
2

I’m still trying to understand what happens during the injection process and how it affects the resulting part geometry, especially when trying to fill larger volumes. While HDPE shrinks after cooldown compared to the mold dimensions. It looks a little different when it first comes out of the injection orifice. The attached image is the result of a typical ejection of residual HDPE after a mold is filled, to empty the volume. The cross section shows the orifice size with the blue ink mark. Not sure how the HDPE transitions from the high pressure in the injection volume to the final ambient pressure and when the final shape gets locked in.

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warrior
21/04/2019 at 06:27
3

Went back to trying to see how useful wood molds could be. I have several small solar panels that run pumps for decorative fountains. The ebay pumps and panels work well but don’t have an easy mounting point. One way to grab them is with a clamping block on the small black block on the back and then drill a mounting hole in the clamping block. The first image shows the arrangement.

I need a handful of these. One option is to make wood blocks but then this is precious plastic not precious lumber. It is not worth making a proper aluminum mold so why not try a wood mold. The second image shows the mold and the resulting part before the flashing is trimmed off. Since for this part only the channel dimensions matter, I used scrap wood without machining the corners tight. Aluminum tape provides a releasable surface and wood screws hold it together. The results came out well for the application (third image). I undersized the channel because I wasn’t sure how much the HDPE would shrink so a light cut  made for a light press fit on the solar panel block.

For something more precise, machine the wood to be true and fill any gaps, Should provide a well shaped part. Not intended for production, but for a handful of parts, it is a viable low cost approach. Next few will try some black PP

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warrior
21/04/2019 at 13:16
3

in case you have not seen it, here it is again. The guerrilla guide to mold making

 

http://lcamtuf.coredump.cx/gcnc/

 

Steel epoxy sprayed with silicone lube or silicone mold release spray works wonders.  You can mix it with steel wool or chopped strand fiberglass to make it even stronger.  I think a commercial trade epoxy is called kitty hair that has the fiber in it.  Saw a youtube video of someone using it to make custom stereo speakers.

warrior
21/04/2019 at 21:00
2

Thank you, I’ve seen some of the epoxy mold approaches. Right now I’m trying to see how far one can push very low cost materials.

warrior
06/05/2019 at 04:04
2

I anyone is still interested, I made several more upgrades to the desktop unit. First I found a convenient longer actuation bar for the arbor press https://www.harborfreight.com/12-in-drive-25-in-breaker-bar-67933.html . This breaker bar doubles the lever arm length. I ground the eye at the end down so it fits through the hole in the gear shaft. This retains the cross hole to attach an end stop. After using it, it works well but is swinging right around forehead height….so I added the two green safety devices.

Second, I made a new nozzle block and added a heater control channel. I wanted more than just the passive heating of the nozzle so I included a clamp for a flat aluminum PTC type heater (100W). The temperature sensor is mounted on the back side of the block. I also drilled a hole crosswise in the block for the typical cartridge heater I’ve been using, just in case I need it. This upgrade makes it closer in functionality to the PP design where you have a separate control channel for the nozzle region.

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warrior
06/05/2019 at 12:09
1

pporg, are you the guy doing the sunglasses in Spain from the videos?   Andrei told me he met the sunglasses guy the other day.

 

I been looking at that arbor press design although at the moment no budget to experiment aside from CAD drawings on it.

 

I have also been looking at the automated molder someone posted a video of.

 

Seriously considering that as my next line of building after the polyester fiber factory is built.

 

I am thinking a great product to make for the local market with the automated injection molder is buttons.  The kind for shirts and pants.

 

Seeing as the injection molder can be made with Arduino/Ramps/Marlin firmware as the controller, a couple SSR to run the heater bands and I found some small compression screws for 100usd (with barrel)  that will be the next project I hope to kick off here.

 

 

starter
06/05/2019 at 14:58
1

@s2019, yes, keep going! This looks near perfect to me; apparently this could go into the library, if you don’t mind to open another topic ‘arbor mini injection’, we could start making drawings when there are enough detailed pictures, instructions as well component selection in a way others can reproduce this; as well making a commercial version, ready to be build by builders for the bazar.

starter
06/05/2019 at 17:23
1

@btmetz, no, but the sunglass guys are around the corner 🙂 And yes, anything automatic coming out of PP in the desktop format would be great. Marlin and the like are great but the difficulty is to enable people adding or changing parts to the system without much programming. I wrote an visual editor one day where you drag ‘commands’ (ssh, serial, udp, arduino direct, printers, …) on visual objects like buttons and so on and the export the thing as web-app, more likely a touchscreen running off an RaspberryPI. If you like, you join this efforts in another topic (‘automatic desktop injection’), this days ..

warrior
06/05/2019 at 21:20
3

@pporg , Thanks.
This evolving design was never meant to be a specific design worth documenting with drawings but rather an example of a DIY process that takes the necessary off-the-shelf components and links them together using materials and techniques available to the hobbyist. As you’ve noted in the past, this forum is somewhat awkward for documenting a design. If it would be useful, I can put together a PDF with a bill of materials, some detail pictures, and rationale for why I chose that option. I would not expect anyone to duplicate my exact machine.
This design is in the DIY spirit and depends on the builder liking to tinker and hack, and also recognizes that this is hobby labor which does not cost anything. I think for anyone where these don’t apply, your desktop design that you have in the Bazar is a much better and ultimately cheaper way to go.

warrior
09/05/2019 at 05:27
1

I took another try at a wooden mold for the injection machine. I have use for a large robust clip/clamp. I started with simple softwood pieces out of the bin. I took some care that the dimensions defining the part were accurate and that the edges were sharp (first image). I taped the interior surfaces with aluminum foil and used a bushing for the sprue (second image). When I injected it with HDPE (some of my wife’s plant pots) I clamped the sprue during cooldown, maintaining some internal pressure. The part shrank primarily in length and maintained some of the other dimensions (third image)

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warrior
09/05/2019 at 05:41
2

The clip itself has mostly a nice smooth finish with only a little of the typical HDPE texture (first image). I think the wood having low thermal conductivity and thermal mass slows the cooling of the surface.

The second image shows the clip during a fit check (I later cut off the sprue) for its intended use as a mount point on the roof beams of a pergola in our garden. It is nice and robust (98g).  This will allow lights, solar panels, weather vanes, etc. to be mounted without screwing into the beams themselves. Since the clip kept the interior dimension, it is a nice slide fit onto the beam.At the end I got a “that will be usefull” instead of the usual headshake. I’ll call that success.

The mold survived without damage so I have a few more to make.

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starter
10/05/2019 at 00:54
1

insane great stuff Stan, congrats, really ! Did you considered post this on https://www.instructables.com/ ? All it takes are just a some pictures and little text! This page is pretty much the safest place I know for this kinda stuff.

warrior
10/05/2019 at 01:42
2

I dont see a thread for a automatic injection machine in the forums.

 

Start a new one?

 

I am thinking that maybe the $200USD ali express oil press machines can be modded for the automatic injection molding machine.  They have the hopper, geared motor, heater, extrusion barrel, compression screw, all in one unit.

 

Modifying the barrel with a sleeve to close off the slots where the oil comes out, changing the motor mounts to use a stepper, or if the existing motor is reversible using that.

 

 

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starter
10/05/2019 at 01:47
1

@btmetz, yeah sorry! was stupid stuck with a v3 shredder, seeya tomorrow on this 🙂 that’s an awesome idea, looks possible to me, you have a link to ebay or something i can buy ?

warrior
10/05/2019 at 03:15
3

Thanks @pporg I wanted to post some of the results here so people thinking of what to make broaden the options to making parts that make other things possible. In this case these pergolas are sold through a nationwide chain (Lowes) and there isn’t a good way to mount things without drilling holes and starting a rust spot.

I made a second clip in the mold and it is hard to tell the difference (first image). The wood mold held up well. I use wood screws to hold it together and if I’m careful it re-indexes pretty well on assembly (if only Legos could take the temperature). The second image shows the final install supporting the weather vane. One unplanned feature is that the bottom of the clip is just a bit tighter so it holds very nicely with no fasteners.

I’ll be making more of these…more odd stuff needs to go on top….Though we’ll stop before we reach Gaudi levels

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warrior
10/05/2019 at 09:45
2

Just a thought on the “if only Legos could take the temperature”…

…make our own blocks that can!

Or a more ‘Meccano’ kind of approach.

Or both?

 

Something that can be lasercut or cnc-ed anytime your machines are idle…

 

If I would venture a guess, the 3D’s are already out there and @pporg already knows where to find them 0:-)

 

 

 

starter
10/05/2019 at 18:58
1

@s2019, my wife joined the workshop a few months ago and she seems to catch up slow but good on what we are actually doing 🙂 She told me recently to make something useful out of the v3 shredder: put a wheel or handle on it and shred kitchen waste to make compost for our garden.  Obviously stainless is pretty overkill but making one from PET or HDPE should be possible with the little arbor press you have done, no ? Larger pieces (side plates) could be done breaking them into puzzle pieces (interlocking) and glue or screw them together just. That aluminum folie mold technique you have there seems fully enough to make all parts of a plastic shredder, what you think, i dont see much trouble doing so .

warrior
10/05/2019 at 19:08
2

Yes!

And use the injection moulds to make Chocolate bars!

starter
10/05/2019 at 19:13
1

funny you, i think you mean half deadly ninja choco knifes to throw at others, shredder knifes as boomerang, why not 🙂

warrior
10/05/2019 at 19:41
1

@pporg , Funny, I’ve gone through the “apply your technical skills to making a better composter” directive. I used a large plastic barrel on rollers, it had internal blades to stir the compost as you turned it…blah..blah…blah…rubbish. Too much work and it made the worms dizzy. My technical ego was crushed when my wife had me cut the bottom off of a large plastic (~75l) bin and set it in the corner of the garden. Now we just throw kitchen waste in, no shredding, put the lid on, the worms come up happily from the soil and do all the work. A few months later we move it to a new spot. So much for clever engineering.

@donald …Some of the better uses for CNC https://hackaday.com/2015/01/14/choctopus-chocolate-printer-x8/https://hackaday.com/2016/11/24/open-source-pancakes/ I think you can buy these off the shelf now…..Failed prints are not a problem

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