Filament separation issue

Help with printing with specific plastic filaments.
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eussrh
Posts: 41
Joined: Fri Jul 31, 2015 5:35 am

Filament separation issue

Post by eussrh » Mon Aug 01, 2016 6:31 am

Does anybody know what causes a problem like this? The initial layers went down fine, but the walls of the channel turned into a stringy blob. The model is fine as it has printed ok before. I am using PETG at 240/90 and the walls should be 4mm thick.
failed nft channel.JPG
failed nft channel

eussrh
Posts: 41
Joined: Fri Jul 31, 2015 5:35 am

Re: Filament separation issue

Post by eussrh » Mon Aug 01, 2016 7:38 am

After some thinking, I'm pretty sure it is heat creep. It tends to occur on large models about 2/3 of the way in (which is really annoying). The amount extruded isn't enough to account for the remaining parts of the model, so I suspect the extruder slowed down partway through the model and then managed to resume. The blob started about when it would have been doing lots of retractions. I've been cleaning the radiator fins, but that apparently isn't enough. It looks like I need to figure out a beefier replacement for the little radial fan.

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piercet
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Location: Battleground, WA
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Re: Filament separation issue

Post by piercet » Mon Aug 01, 2016 8:06 am

The little fan tends to partially fail as well. it still spins, but not at full RPM. You may be encountering that.

kcchen_00
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Joined: Thu Feb 19, 2015 12:42 am

Re: Filament separation issue

Post by kcchen_00 » Mon Aug 01, 2016 11:38 am

I'm not so sure that looks like heat creep to me... but I wouldn't rule it out.

Typical heat creep ends in no extrusion from the nozzle. In your case, it looks like the filament continued to extrude... hence the birds nest. That looks like a possible issue with the gcode... possibly no supports where needed or a void in the gcode.

If you can upload the gcode or STL, we could validate...

eussrh
Posts: 41
Joined: Fri Jul 31, 2015 5:35 am

Re: Filament separation issue

Post by eussrh » Mon Aug 01, 2016 11:47 am

ok. I figured it out. I had set the flow % too low (90% and I had a batch of thinner than normal filament). I upped the flow rate and now it works ok.

In any case, I plan to replace the radial fan. Unless I am diligent about cleaning off the heat sink and cleaning out the inside of the fan, then heat creep is a problem. Plus over time, the radial fan seems to collect a bunch of dust inside that is really hard to get off. My plan is to use this http://www.thingiverse.com/thing:1461335. I'll use a 12v fan and a small buck converter to downstep from 24v aux to 12v.

killacycle
Posts: 38
Joined: Mon Apr 04, 2016 2:14 pm

Re: Filament separation issue

Post by killacycle » Mon Aug 01, 2016 5:26 pm

If it is heat creep, then you can put either my hot-end cooling duct & 25mm fan, (or a Taz6 hotend cooling duct & 40mm fan) in place of the wimpy stock blower.

Part and installation instructions:
http://www.thingiverse.com/thing:1461335

No stuck nozzles, no spaghetti, no "lace" layers, whatsoever since I replace the little blower this nifty new duct and fan.

Bill D.

eussrh
Posts: 41
Joined: Fri Jul 31, 2015 5:35 am

Re: Filament separation issue

Post by eussrh » Mon Aug 01, 2016 6:43 pm

If it is heat creep, then you can put either my hot-end cooling duct & 25mm fan, (or a Taz6 hotend cooling duct & 40mm fan) in place of the wimpy stock blower.

Part and installation instructions:
http://www.thingiverse.com/thing:1461335

No stuck nozzles, no spaghetti, no "lace" layers, whatsoever since I replace the little blower this nifty new duct and fan.

Bill D.
I like your design. I've ordered the 25mm fans and will install as soon as they arrive. Although the birds nest happens some of the time, the most common problem is that the extruder just jams after printing a while. When I remove the filament, it is usually bendy which I figure is a sign of heat creep. I also have some copper foil which I plan to use to coat the inside of your funnel.

eussrh
Posts: 41
Joined: Fri Jul 31, 2015 5:35 am

Re: Filament separation issue

Post by eussrh » Thu Aug 04, 2016 9:39 am

If it is heat creep, then you can put either my hot-end cooling duct & 25mm fan, (or a Taz6 hotend cooling duct & 40mm fan) in place of the wimpy stock blower.

Part and installation instructions:
http://www.thingiverse.com/thing:1461335

No stuck nozzles, no spaghetti, no "lace" layers, whatsoever since I replace the little blower this nifty new duct and fan.

Bill D.
Thanks for your design. I installed the new fan to prevent heat creep and it is working perfectly. I just finished a 15 hour print that had been failing consistently after about 10 hours in the past. That is good because my supply of cuss words was running low.
improved fan.JPG

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