Cleaning recycled plastic

Audiobull,

I am also trying to recycle (in my case) Eastar 6763 PET and eventually PET drinking bottles. Have you had success actually extruding the recycled particles with Filastruder? (I don't mean to distract from your request on cleaning).

Audiobull,

I use a paper shredder ($150 Amazon Basics 17 sheet microcut paper shredder - awesome) to shred left over prints and filament into pieces or chunks about 5 mm in diameter.  I have to pass the ground plastic through the shredder about 6 times to get consistent sized pieces but the shredder has a very powerful motor and does it all very quick. 

The thing is,  the Filastruder extrudes about 3-4 times slower with the regrind PET than the virgin pellets - I can't figure out why.  I hope someone pops in and helps me to fix this.

I extrude the virgin Eastar 6763 PET normally at 205C and I don't use a melt filter because my printer has a 0.6 mm nozzle and I haven't had a problem with clogs.  I tried raising the temperature up to 230C and lowering to 200C but the flow is still weak and inconsistent.  I sieve off the dust from the regrind with a kitchen strainer and remove the moisture by heating it in the kitchen oven at 170 F for 3 hours.  There is a lot of static electricity after passing it through the paper shredder 6 times so I take a piece of aluminum foil and swish it through the regrind, occasionally discharging the foil on a ground. I even download several hopper designs off Thingiverse and noticed a the vertical hoppers have a more restrictive opening at the screw which I tested just last night (my extruder is usually horizontal but I have also tried vertical but horizontal is best).  The hopper with the narrower opening seems to work a little bit better and also if I continuously, lightly tap on the hopper with a hammer the flow is still slow but at least doesn't sporadically crawl to a stop.  By the way, I let the filament fall to the floor and coil and this doesn't work now with the extrude flow so slow. 

I don't think the melt flow properties of the regrind material are so much different than the virgin pellets.  I put  a pile of regrind and a pile of virgin pellets in the oven at 210C and they both melted identically to my eyes but I don't have a way to do a melt flow test to tell for sure.  I think the problem is in the auger somehow but I know there are people on this forum who are say they are successfully extruding the regrind Eastar PET, ABS, and PLA.  How do these guys do it?

Genesat1, I have tried 20% and still have problems.  I have done a lot of experiments lately.  Virgin PETG (I use Estar) pellets extrude great.  Regrind has rough edges.  My theory is that the regrind rough edges melt easier and stick to the drill bit near the hopper and impede the regrind from being carried down the drill bit to the melting chamber.  If you look down into the hopper you can see regrind coming back out.  The regrind must primarily move along the bottom of the drill bit due to gravity but the stuck pieces block the flow and it comes back out along the top of the drill bit. 

So I changed the barrel insulation and wrapped only the heating chamber so the barrel (and hopefully drill bit) would cool off bear the hopper.  I even had a fan blowing on the pipe right next to the hopper.  But this didn't seem to do much.  But I still think it is a good idea and plan to experiment more.

But what I am doing now seems to have somewhat positive results.  I redesigned the hopper with an overhanging wedge above the entrance to the drill bit.  The wedge helps to stop the regrind coming back out the drill bit. 

Also,  I borrowed a Filabot from work and it could handle 100% regrind perfectly.  I see a few design differences from the Filastruder like 1) higher RPM,  2) more drill bit exposed in the hopper (4 traces vs 2 for Filastruder), and 3) more insulation on the barrel.  I don't see how the extra traces on the drill bit can help especially if it all gets pushed back out again.  Incidentally, the Filabot isn't working that great with the regrind now.  I think if I flush it with virgin PETG pellets then it will work again.

I bought a Filawinder and designed a 45 degree hopper so I can put the Filastruder at a 45 degree angle.  I was able to extrude 100% regrind PETG at a good rate.  The only problem is that every 10 - 20 feet of filament there is a small bulge.  I guess this is due to the less homogeneous regrind compared to the virgin pellets.  I tried extruding ground up PETE water bottles - WHAT A NIGHTMARE!  I think the PETE has a much higher melting temperature than PETG and a bad melt flow rate.  It would extrude an inch, and get plugged over and over again until I purged it all out with 1/2 cup of PETG.  But I would like to know how others handle the regrind.  Does anyone get the >>2mm bulges in the filament?  How do you fix it?

Genesat1,

Actually I am having very good success with regrind now that I have the filawinder.  I have spun about 2 Kg now (not all at once) of PETG filament consisting of 70% virgin pellets and 30% regrind. The microcut paper shredder grinds failed prints but also nicely grinds up failed filament.  I admit, there are still some extrude imperfections and I have to cut the filament and I have to regrind the bad sections and splice together the good filament.  My latest hopper is designed to prevent the plastic particles from getting stuck which should allow a better constant flow into the auger and so far it appears to be doing.  It is important to get constant flow into the auger to keep the extrusion as constant as possible.  If the auger feed slows then the extrusion slows down and the filament diameter goes below 1.60 mm and I have to later cut it out which isn't so bad but it would be nice to have a "hands free" roll of filament.  I'm pretty sure I will have no problem if  I went back to extruding virgin pellets, especially now that I have the filawinder.  But there is something really addicting about using reground pellets!