PVC as extruding material?

I was wondering if PVC would work for extruding. Harbor freight has plastic welders for PVC, and I noticed in another post that someone said weed eater line is made from PVC. This weed eater line can be bought on ebay for $16 per 7 lb! That is 2 dollars/pound. Here:
[www.amazon.com]
Plus you get free shipping if you buy $25 worth. Also, the diameter of the filament is only .08 in, or about 2 mm. This would decrease the pressure needed to extrude. If the plastic can be welded, can't it be extruded?
Also, the strength of PVC is a bit higher than ABS. It could make some very robust prints.

I don't think anybody has tried it yet, but yes in theory it should work. It has a very high melting point and a low glass transition so you would need a sharp transition zone like you do with PLA.

Edited 1 time(s). Last edit at 01/10/2011 04:26AM by nophead.

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[www.hydraraptor.blogspot.com]

Perhaps, but if PVC breaks down due to heat or fire, you could possibly end up with dioxins (which are not nice at all), or potentially HCl gas (nastier).

Thanks, but no thanks.

Weedeater line is made from nylon. Vinyl isn't very tough.

Maybe some is made from nylon, but I am pretty sure the cheaper stuff is PVC. Who would be crazy enough to sell nylon for $2 a pound?

As for breaking down into HCl gas, I know it is a risk, but when PVC burns, you can smell it right away. Small amounts of HCl are not enough to do anything to you. You would have time to put the machine outside and turn the heater off.

Does anyone know the temperature that PVC burns? I don't think a reprap will get anywhere close to burning it.

As for the melting temperature, wikipedia says it can be anywhere from 100 C to 260 C. ABS is 105 C. So basically you just need to find the right kind of PVC. I am hoping the trimmer line will have a low melting temperature. I will see if I have some to test.

If this works, you could just use a 2mm heater barrel instead of 3mm, and use it on your existing reprap. Everything else will be the same, and it will be 5 times cheaper than ABS.

Ok, I just melted some nylon line and some unknown blue line. They both melted fairly easily on a hotplate, without burning. I am not sure what post i saw that said weed eater line is PVC, but anyways, it seems like the plastic would work well for extruding, if you knew the temperature to set the extruder to.

The problem with nylon is that the trimmer line is very floppy and the nylon plug offers a lot of friction as it moves through the barrel. The plug will jam up and because nylon trimmer line isn't very ridged, it will tend to bow and kink rather than push the plug. Its like trying to push something with a rope.

If you have a tapered or extremely short melt zone, it might be possible to use it though. This was one of the first experiments I tried when I got makerbot's MK4 runnning. I tried numerous shapes and sizes but I could not extrude much more than 10cm before it jammed.

Don't the UP! printers use 1.75 mm line? That is smaller than this. I know Nylon has a high melting point, so it will be harder to get flowing. I did use my lathe to make a test nozzle, and i heated it over the hotplate and pushed the line through. The problem is, when the melted plastic comes out, it is full of bubbles. It doesn't come out cleanly. Of course i could only push it through about a half inch before the aluminum nozzle got cooled down too much. So it could be just the first few inches that do this. Does anyone know why this happens?

I was thinking of using a 100W, 200 ohm resistor rated up to 350 C. I would run 120VAC through it, and it would give me around 60W of power. This would be either around the nozzle, or next to it in an aluminum block. I think this would be plenty to get up to the temperature needed for nylon and keep it there. Here is the digikey page for it:
[search.digikey.com]
Here is the relay I will use to control it:
[www.crydom.com]

This is a expensive way to do it. Anyone know something better?

galaxyman7 Wrote:
> The problem is, when the melted plastic comes out,
> it is full of bubbles. It doesn't come out
> cleanly. Of course i could only push it through
> about a half inch before the aluminum nozzle got
> cooled down too much. So it could be just the
> first few inches that do this. Does anyone know
> why this happens?

Nylon _loves_ moisture and will absorb a significant amount of it. The bubbles you are seeing are most likely the absorbed water trying to boil off.

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[haveblue.org]

Well that just ruins everything doesn't it! Does anyone know a way to release the steam?

I saw someone suggest stuffing PLA into an oven on low heat to bake it out, but I wouldn't want to do that with nylon since it smells nasty, releases toxic fumes, and might taint food. Maybe a solar oven could be used instead?

Another possible explanation is that you are applying too much heat and the filament is decomposing into (toxic!!!) gases. If it is also brittle, then you are using too much heat.

As for the up printer and your extruder...
It uses 1.75mm filament, but it is ABS. I don't see any mention of printing with nylon.

Unless you need higher power heaters due to thermal mass, I think 60W will be overkill for the extruder. A normal reprap printer uses more like 16 to 24W. More powerful heaters may be more difficult to control unless there is greater thermal mass to smooth out the temperature swings. Personally, I would feel safer using 12V too. Lower voltages generally do less harm when something goes wrong. If you do need more power, then using 120V may be the most economical or easiest to build way to get it. This is why I have resorted to running my heated build plate on 120VAC despite the hazard of using higher voltages.

Ok, I just found a post that describes exactly why nylon won't work:
[groups.google.com]
Didn't realize how many other people have tried this.
Many of them said it was sticking to the nozzle and forming a plug. I wonder if this is because they didn't have the temperature up high enough, or if there is some byproduct of melting nylon that won't melt.
Still, the $2/lb price is so tempting. I will try to find out how large companies extrude the stuff in the first place, and maybe we can try to copy it.
Meanwhile, I will try using my toaster oven (not the one for food) to dry out some filament. I just need it to stay at a temperature just below its melting point for an hour or two.

Just found a book on google that is all about extruding plastics! In the preview, it says Nylon must be dried at 230-248 F for 10 hours before being extruded. This isn't a very high temperature so it wouldn't be dangerous to leave the oven on for that long. It seems like this would be worth it if you did a whole spool at once in a toaster oven. The problem would be preventing it from absorbing moisture again. Maybe a plastic container that has the spool inside and a small hole for the filament to come out. A rubber grommet could keep a good seal. You could also drop in a couple of those water absorbing packets that come with beef jerky. The rest of extruding should be almost the same as ABS
Here is the book:
[books.google.com]