burnt plastic dropping into print

[n108bg]

So i wound up having to replace every part of my printer hat touches filament. The extruder was upgraded to a printed unit for tpu, the bowden tube was replaced, and the nozzle was also replaced. So now i am running an e3d v6 on a 3d printed gantry, including an upgrade to the hotend platform with built in fans. Anyways, i'm noticing bits of burnt plastic, some as big as the end of a q-tip, dropping into my prints and messing up the looks of the normally clear parts i print.. I am running petg at 230c, because at any higher temperature, the stuff starts to bubble and cook in the nozzle. Any idea what's going on here?

[Qdeathstar]

Take pics?

Your platform isn't melting is it? Have you verified your thermistor temperatures with a meter?

[n108bg]

The platform is not melting, no. the plastic seems to just be coating the underside of the printer. I have not verified the temps with a meter.

[U.S. Water Rockets]

The platform is not melting, no. the plastic seems to just be coating the underside of the printer. I have not verified the temps with a meter.

It could just be excess plastic buildup on the sides of the nozzle tip. Once they get big enough they fall off and by then it is discolored from heat. Better retraction and z-lift settings can help keep the buildup from happening.

[n108bg]

Ok, i recently switched over to cura from mattercontrol for comfort reasons. I turned on z-hop to .1mm, and moved retraction from .7 to .8. it'll take me a bit to figure out whether it changes anything, but i'll update if print quality improves. Thanks!

[Windshadow]

Thoroughly clean the tip and its hex facets of the nozzle before each print I heat it up and wipe with a piece of leather belt to get it all off but if there is too much of it I know some folks Remove the nozzle and take a more physical route to cleaning off burnt plastic but if you do this with tools you want to polish off any scratches that may have been caused as they will be a place to catch and cause build up again.

[n108bg]

Ok, so i've tried thoroughly cleaning everything, increasing the z-hop to .1mm, retraction to 12mm, made sure there was a locking clip on the extruder bowden connector, and the only change is that now the plastic is clear instead of black. There's also a LOT of stringiness. Not sure what's going on, because i'm at 230 on esun PETG that has a temp range of 230-250, made sure the correct thermistor settings are correct, increased retraction, increased z-hop, and i'm still winding up with spider webs in my prints, and big globs of plastic.

[nebbian]

What is your travel speed?

I increased this to 300 mm/s on my printer yesterday, which seems to have helped with stringing quite a bit.

As for the blobs, I think that what happens is that on long travels, the petg flows down the sides of the chamber and on the next extrusion it blows out in a bubble. Of course then this sticks to the nozzle the next time it passes by. This suggests that a shorter retraction is better: just get it right. I haven't got it right yet. I do know that blobs only seem to happen on long travel moves.

I hope this helps.

[n108bg]

My travel is at about 100 at the moment. I will probably try 250 or 300 on my next print to see what happens.

[Rolffeof6]

I had this same problem. My nozzle had loosened and melted plastic was oozing out somehow and collecting on the sides and bottom of the heater block and then dropping onto my prints (burnt plastic).

I fixed the problem by unmounting my e3dv6, heating the hotend to 250C and tightening the nozzle onto the heater block. It hasn't leaked since.

I could not tighten the nozzle enough when cold- couldn't budge it- the solidified plastic was gluing the threads together, like Loctite. Tightening it while hot took care of that problem. Unscrew the nozzle a half-turn or so, ensure the cooling tower is screwed snugly (finger tight) into the heater block, THEN use two wrenches on the heater block and nozzle to tighten the nozzle into the block.

Before I did thus, I watched Thomas Sanladerer's Youtube about putting the e3d together at
https://www.youtube.com/watch?v=xr02pG58gaU

[Nylocke]

You can probably run retraction up to 2-3mm (I assume you mean 1.2mm and not 12mm), though I'm not certain where it should be for PETG. Also I use 1mm z-hop. Since were on deltas its no big deal. Even on a cartesian I run around .3 or so. How fast are you retracting? That would also play into things. Most of the settings I'm familiar with are for PLA, JFettig would know best since he exclusively prints with PETG at this point.