1 Topic by jamesshuang (edited by jamesshuang 2014-05-30 18:41:27)

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Topic: Polycarbonate

Hey guys,
I've been trying to extrude PC with my filament extruder, and I figured I'd share my experiences / get some help.

I bought PC pellets from here: http://www.ebay.com/itm/POLYCARBONATE-P … 35b282a25f

Unfortunately, the seller did not have a specsheet for the stuff, other than the brand name "Jupilon / Iupilon". Searching around on the Mitsubishi site gives me this very large list of materials with the same brand name: http://www.m-ep.co.jp/en/product/brand/ … select=100

Anyways, I set the heater to 250 and started it extruding, and this is clearly the extremely low viscosity polycarbonate. The MFI is astronomical, way higher than MG94. I'm probably getting close to 20-24" / min. Setting the temperature any lower clearly puts way too much pressure on the motor. Unfortunately, the combination of extremely low MFI and PC's extremely high stiffness once it's cooled means that this stuff is nearly impossible to handle. It ramens with the slightest provocation. I couldn't get it to spool on my winder at all, since even the smallest kink means that the filament jams in the PTFE tension tube. After trying to get it working all morning, I've temporarily given up.

I haven't tried extruding PLA yet, but I suspect it has similar issues. Anyone have any recommendations on how to avoid the nasty kinks?

*edit: In case someone searches and finds this entry, MAKE SURE YOU PREHEAT. The first time I restarted the extrusion, I only preheated for 15 min, and I suspect the plastic was still solid partway up the barrel. The barrel twisted a full 90 degrees, despite dozens of hours of successful extrusion with ABS. Preheat at least 30 min at 250C!

2 Reply by elmoret

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Re: Polycarbonate

First of all, you are the first user I know of that has tried Polycarbonate. Congrats! Be sure you're handling it safely, as PC can offgass toxic fumes. If you want to drop temperature and snot overload the motor, you could reduce motor voltage.

Couldn't you go vertical and higher off the ground if stiffness is a problem? Are you running vertical now? If you're using a winder, fully vertical is best.

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3 Reply by jamesshuang

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Re: Polycarbonate

Yep, it's all done outdoors so the fumes shouldn't be too bad. It does emit a rather pleasant sweet smell, and I'm sure it's probably something horribly toxic and dangerous to my health, haha.

I was originally using a vertical setup, but my feeder tube was softening from the heat of the barrel. At 250C, the metal was probably hovering around 80-90C at the feeder and made the tube slide down and melt! Thus, I had to switch back to my horizontal feeder for now. I might try printing another vertical feeder with something that has higher heat capacity, perhaps nylon. For the brief moment where the vertical setup was working, the extremely low viscosity of the PC actually stretched the filament way too thin.

Perhaps I should find some lower MFI PC...

4 Reply by elmoret

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Re: Polycarbonate

You could cool the barrel with a fan. Are you still powering the heater with 12v? Have you added barrel insulation?

Running horizontal, did you try moving the filament guide closer to the nozzle, and possibly cutting off an inch or so of the base? That should make ramen less likely.

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5 Reply by jamesshuang

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Re: Polycarbonate

I think I just had a minor breakthrough. With the extruder propped up about 30 degrees, I let it extruder about 1 coil's worth of filament down onto the ground. Then I took the coil and fed it through the winder, which doesn't cause any kinks. I let the winder do its thing until it catches up. This seems to successfully allow both extruding and coiling!

Downside is, since I have to let extrude off a table, the filament is very thin, 1.35mm or so. However, it remains very glassy. I will print with it very soon and see how it goes! Also, the filament is very very stiff, to the point that my winder is having trouble winding it. It makes a rather odd crackling noise as it winds. I might have to jack up the voltage on the winder a bit...

Tim, I don't actually have a real filastruder -- I built mine back when the filastruder still had a 6 week lead time and I was impatient. It's very close to your design, except I used a pair of leftover cartridge heaters held against the coupling with a metal zip tie. This design is much less elegant, but it does have plenty of power. It doesn't need any additional insulation or voltage to hit 260 C. I might try cooling the barrel with a fan though.

6 Reply by adam

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Re: Polycarbonate

I ran a batch recycled ABS/PC mixed at 80/20 after my initial purge. It came out fast at 220C, prone to kinks, was was very stiff and almost burnt looking once cooled. It came slow at 180C (3 in/min), but the pressure was too much. First it pushed the auger out thru the back. So I refortified it, and it twisted the barrel like taffy at 190C. So then I mixed a new batch of virgin/recyced at 50/50 by volume and it comes out very well (7 in/min) at 195C..

7 Reply by elmoret

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Re: Polycarbonate

Glad it worked out for you after its trip south of the border, back, and down again!

What you mean mean "pushed the auger out through the back"? That's a 1/4" steel flange...

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8 Reply by IanJohnson

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Re: Polycarbonate

If the shaft collar isn't up against the beginning of the auger flutes, it relies on the set screw to hold it in place.  If that is the case, the auger can get pushed hard enough to slide through the shaft collar and either try to push the motor out the back or push the barrel out the front.  I struggled with the Randolph case trying to destroy itself in that manner until I got everything positioned just right.

9 Reply by elmoret

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Re: Polycarbonate

IanJohnson wrote:

If the shaft collar isn't up against the beginning of the auger flutes, it relies on the set screw to hold it in place.  If that is the case, the auger can get pushed hard enough to slide through the shaft collar and either try to push the motor out the back or push the barrel out the front.  I struggled with the Randolph case trying to destroy itself in that manner until I got everything positioned just right.

v1.4/1.5 uses full clamping shaft collars, no more set screws. Actually the shaft collar is undersized slightly so it grips even harder. If one of those is sliding then it either wasn't tightened or I'd guess thrust loads are exceeding 300lbs.

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10 Reply by adam

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Re: Polycarbonate

What happened to me was that as the pressure in the barrel grew, the auger slide back toward the motor and the plywood uprights bent out into a 'V' shape. It is completely possible that I had some or many misconfigurations, but the design is pretty straight forward. I have v1.5 and thinking about it now, there must have been some space between the nylon bushing and the rear flange in order to have pushed out without moving the shaft collar.

The recycled ABS/PC pellets are irregularly shaped and a good portion of them are ~10mm on one side, which also added to the increased pressure. So it is no mystery to me that I tore it apart. When the barrel twisted, i took it down the block to a machine shop. They cut it apart, checked the auger (not bent!), and made me a new barrel with a slightly smaller opening for the hopper to give it a little more strength. So two hours and $12USD later I was up and running again.

11 Reply by elmoret

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Re: Polycarbonate

If there's some space in the thrust bearing stack, what you described would happen. Also, the nylon bushing "beds in" to the flange, and will allow a few mm of axial translation. This is why it is recommended in the instructions to leave a few mm gap in the hex socket.

Also, I am jealous that $12 gets you a single new barrel, machined and all.

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12 Reply by adam

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Re: Polycarbonate

$12 got my twisted barrel removed and new barrel made!

13 Reply by IanJohnson

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Re: Polycarbonate

Pulling out an auger jammed in a bent barrel with hardened plastic is almost worth $12 by itself, without getting a new barrel in the bargain.

14 Reply by jamesshuang

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Re: Polycarbonate

Well, I'm happy to report that printing this extruded PC looks great! It comes out very clear (far more clear than the transparent PLA i've printed with), and it's SUPER strong. I needed pliers to break a piece that was less than 1mm thick.

I initially had problems getting it to stick. I tried it on PET tape, blue tape, with and without raft, and they all lifted up after just a few layers. However, on suggestion here: http://reprap.org/wiki/Polycarbonate, i put down some superglue over the blue tape, and it's looking pretty good. I'm printing at 270 C, 120 C bed right now. I will take pictures once this print is finished!

15 Reply by elmoret

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Re: Polycarbonate

Nice! Looking forward to pictures.

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16 Reply by jamesshuang

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Re: Polycarbonate

https://imgur.com/a/Pgpjn Here's some pictures of my print as well as the setup I found that works.

17 Reply by mlhmail

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Re: Polycarbonate

Did you figure out which grade of PC you were using?
I am looking at buying some PC and was wondering if you would recommend that grade or another?
Thx

18 Reply by jamesshuang

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Re: Polycarbonate

Unfortunately, there was no additional documentation on the type of PC, other than the Jupilon label. If you know of another source of PC, please let me know!

Also, I haven't been able to get it to print without warping. I managed to get it to stick to the bed using superglue on blue tape, but it just ended up pulling up the tape. I tried superglue on glass, and it didn't stick at all. I tried higher strength adhesive green tape, and it still pulled up the tape. I'm going to give garolite one last try, but I'm about to give up on this particular batch of PC...