DIY 3D Thermoplastic printer from recycled plastic
LoopyByteloose
Posts: 12,537
Is this a project that anyone has been considering?
There are tons of plastic available and people are building DIY 3D printers, but I'd love to start with plastic from my own trash can.
One could start with a pre-processor that extrudes the waste plastic into a length of 1/4 inch or so diameter cord. Then this cord could be fed into a thermal printhead as required.
There are tons of plastic available and people are building DIY 3D printers, but I'd love to start with plastic from my own trash can.
One could start with a pre-processor that extrudes the waste plastic into a length of 1/4 inch or so diameter cord. Then this cord could be fed into a thermal printhead as required.
Comments
Plastics isn't for playing, as I always say.
-- Gordon
The above is an intro page to DIY 3D printers.
The plastic is fed into the machine as 3mm filament and in the near future in 1.75mm filament. I think they are using mainly ABS aka A Butyl Styrene.
You make several good point about exceeding the melting point by large margins or the problems with not knowing your material. PVC certainly has Chlorine gas as well.
Nonetheless, I was thinking of using tightly regulated temperature control and a flameless hot plate. If one were to acquire a second hand pressure cooker kettle as the main vessel for melting and drilling an outlet hole near the both for feed into an extrusion mold (lets say 3/8 inch copper tubing); one could then feed air pressure into the kettle to start and continue an extrusion process.
In cases where the melting point is under 212 degrees F, a water bath could be between the kettle and the burner to assure that the process doesn't go above 212 degrees.
This statement is quite old... the standard filiment currently used is the 1.75 filiment because it is easier to extrude with the NEMA 17 stepper motors that are commonly used on these printers. Also the plastic that is mostly used is PLA, or Poly Lactic Acid, which is a plastic made from corn, starch and sugar and is easy to manufacture. It's also quite durable and is biodegradable. Recycling is not needed with it.
The temperatures for melting plastic are much higher that that. The temps we use are in C, not F. PLA melts at about 190C and ABS at about 220C. Our print bed is usually in the 105C area, which is above the boiling point of water.
Bill
In our plastics extrusion machines we use up to 10,000 psi ....a touch high for a pressure cooker.....
Cheers,
Peter (pjv)
10,000PSI is way beyond stove top chemistry. I suppose this is driven by a piston or a pump. But I am still not quite sure that I would need to go that high since after the thread has been started - it might be pulled as well as pushed by back pressure. The temperatures do make it quite important to get thermal control right. From what I have read, it may be reshaped with a die downline from the intial extrusion nad that die can also be temperature controlled.
The fact that a real pressure vessel is involved makes me a bit wary in pursuing this.
PLA is readily available in all sorts of waste here. I suppose I should just start out with a tuna can and see how it melts and what it does.
The 3D Printing machines are quite fascinating. And I see that the operating software - EMC2 - is placed on a Linux CD that allows it to do production runs while never touching the underlying software on your computer. In face, EMC2 can do 3D routers, 3D milling, and a lot of other useful devices.
The above link is to a DIY extruder for HDPE. It looks as though a large wood augur bit was used as a screw to create a ram.
FYI
The auger in our large machine is driven by a 50 HP electric motor that drives a hydraulic pump which in turn drives a 50 HP hydraulic motor at a varable low speed of 10 to 20-ish RPM. The bulk of the heat to melt the plastic comes from the friction of the auger process, with the final temperature tweaked up by multiple kilowatt electric heater bands at the end of the 4 ft long screw barrel.
Not a trivial process to be sure, but for do-it-yourself-ers much smaller non commercial approaches might be feasible.
Cheers,
Peter (pjv)
The link I posted is actually quite inspiring if you look closely at it.
His ram appears to be powered by a 12volt automotive window motor that is then geared by the gear train of a 10 or 15 speed bike. The bicycle gears offer a great deal of choice in terms of experimenting with feed rate and torque.
The actual ram appears to be heated inductively by a hand wound coil around what is likely a section of steel water pipe. And the ram itself appears to be an 18 wood augur bit - maybe 1" dia or larger.
And at the output, he built a post-processor out of Legos.
Oh, and there is a tiny micro-controller monitoring temperature. Could that be a Propeller?
Heat sensing and motor control are easy tasks for micro-controllers. And if you have enough thermal mass, the process is easy to manage.
I wasn't thinking about large scale productions, just a small feed in plant for DIY 3D printers as the materials are listed at about $80-90USD for 5 kilos. It would also allow you to explore other thermoplastics than ABS and PLA - though investigating toxicity is a first priority.
I'd like to consider Nylon and Polypropylene.
One can buy an 18" augur bit on EBay for less that $10USD. The working end would just be ground square: the other end fitted to the bicycle gear.
Regarding the tube, a section of 1" ID water pipe with threads on each end may do quite well. The ends would be capped with pipe nipples. One would be drilled to fit the augur shaft; the other would be sized to the extruded filament - 3mm or 1.75mm. The augur bit would be either 15/16" or 7/8" diameter to allow for movement. Cutting the opening for the hopper might best be done by a machine shop, but it is possible to grind one yourself.
Heat in interesting. I suppose one could wrap the pipe with an appropriate insulator and use nichome wire; but I've looked into inductive heating as well. It seems that 3000 to 50,000 hertz is appropriate for induction heating. If one were to build a solid-state 25watt - better yet, a 150 watt - audio amplifier and attach a op-amp oscillator to its input; an 8 ohm or 16 ohm winding of copper would offer a good inductive heating set up. The temperature would be controlled by the frequency of the oscillations and the audio volume control.
The output end might do best with a water bath to cool the filament extrusion before winding on to a spool.
I like the idea of video monitoring and would use a Propeller to monitor temperature control on a VGA screen. It could also adjust rate of feed.
http://www.lindsaybks.com/dgjp/djgbk/inject/index.html
The main goal of what I have laid out is to produce plastic filament for a 3D Printer as the cost of 5 kilos of the stuff is about $80-90 USD. This extruder l0ooks like it can be easily build for about $120 USD.
http://www.reprapcentral.com/
For the inductive heating feature, Elliot Sound Products has ready-made boards for solid-state audio power amps and op-amp preamps that are quite reasonable and excellent quality.
http://sound.westhost.com/
The idea would be to use the filament for both a CNC printer and for Arbor press type injection molding. I don't know it it reaches 10,000 psi, but Ihave heard Arbor press can exert some force, at least enough to get the plastic into the mold.
The water bath idea is good, they use it after the plastic leaves the extrusion die, and it makes the extrusion cool straight(er) and gives it some properties from the tension of the thermal stress (which I will learn in detail later, now I only know that this is what they do).
I'm preoccupied with tweaking the prusa, but I'll be watching this thread.
Good hunting!
Nichrome wire would be a lot easier if you have something, like thin mica wrapped around the steel tube.
When I look into the actual cost of a 3D Printer and compare it with machine lathes and milling machines, I am strongly attracted to getting a Sherline lath that is CNC ready instead. I can create plastic gears and pulleys with that. And those offer me the means to realize all sorts of mechanical motion that is micro-controller controlled.
But some people are really into CAD design and the DIY 3D printer offers the choice ot create very unique objects that are not necessarily mechanical. It certainly could be used for 1/5 and 1/10 scale models of items that you want to present to investors for getting into production. And it would prove that your CNC code is good, ready for production.
Maybe you could re-purpose a heating element from a coffee maker or a toaster? If you want something more industrial, cartridge heaters arent that expensive. We used one from McMaster Carr for our toy http://www.mcmaster.com/#die-cartridge-heaters/=f8we0g
I can't say that I know much about 3D printing, but I think your idea is a good one if you stick to the same plastic. I don't know if empty milk jugs will work for this purpose, but just for example.....
If you drink a lot of milk, you probably have a regular super market that you get it from, and therefore most likely, you will consistently buy the same brand. Therefore you should consistently have a plastic with the same melting point. Perhaps milk jugs won't work, in which case, find something that you consume regularly.
But alas, pressure for extrusion is still an issue.
Bruce
Just as important is to keep the scale relatively small. In this way, the thickness of pipe walls is not an issue and the screw is able to exploit leverage. I do wonder if an 18" screw is necessary, but it is easier to start with excess length and capacity.
American Science and Surplus has a giant spool of nichrome wire folks use for the reprap hot end. For the recycle project, I was thinking of the wire from this toaster and run it from the mains AC.
The recycling number on the plastic gives a clue, just make each batch all has the same number, and set the temperature as appropriate?
Concerning pressure, I saw an article where the guy would melt the plastic, pour it into a cartrige, and force it into the mold using a press. I was thinking of going this route for injection molding.
I think this is way they folks in the video did it, and the type of plastic is sufficiently liquid to flow from just screw pressure.
It fairly simple to do at home but you will need a decent amount of pressure alone to melt the plastic to a pliable point, do not melt it to a liquid or runny point. You will need a hopper to load the plastic into your pipe with the screw. The back end of the pipe should be completely sealed, the other end of the pipe should be sealed as well, but with a small opening in the center for the pliable plastic to squeeze out. Use a screw similar to a drywall screw but one that does not taper to a point.
with a machine that can make a diameter of plastic tubing like the 3D printer has with any success, you will need to use a water cooled, and heated, tube connected to the area the pliable plastic will come out that has the same inner diameter of the plastic tubing your printer uses. the reason it should be heated water is because if you stop the machine with any plastic in it, the machine will seize up. You will need to find to right temperature at which the plastic starts to harden and gradually cool it as it escapes into the final product.
If you haven't seen it already, take a look at http://en.wikipedia.org/wiki/File:Injection_molding.png as well as the article http://en.wikipedia.org/wiki/Injection_molding.
You will need to chop up the plastic somehow, but not to fine, more like bead size and not a powder. If you have a factory in your area with this kind of machine, give them a call and see if they would be willing to give you a tour.
again, just for safety, make sure you don't melt the plastic, just make it a consistent pliable temp all the way through. It usually takes about an hour for these machines to come up to temp. The actual tube on the machines that does the work is about 3 feet long and about 1/2 foot diameter. Maybe a bit less on the diameter.
Is this due to fire risk? The PLA in 3D printers is runny enough to flow out of the heating chamber, it requires no pressure besides gravity.
PLA melting point is around 160 c, and the machine runs between 180-200 c.
If you are using a new plastic, it might be best to do a test melt outdoors in something like an old tuna can. This would allow you to measure melt temperature, observe noxious fumes, and other properties - both useful and hazardous.
Also heating to a runny flow might cause the plastic to flow back toward the hopper/fill hole. Just be cautious as to everything that can go wrong and take steps to prevent it. Don't want to see you get melted plastic on your hands, the only way to get it off is to let it cool or it will smear and spread the burn.