old burnt filament extruding long after filament change

Hi I'm new to 3d printing and even newer to the forums so I apologize if this question has been answered. I found nothing with a quick google and a search of the forum. So far I've had pretty good luck with my first prints. I'm running a 10" makerfarm with hexagon hot end and printing mostly abs. Tonight I switched from orange abs to clear. I ran the extruder till it ran clear and started my print. Looked great for the first half hour then black burnt filament started extruding. At first I thought it was burning the clear filament but with a closer inspection this crud was orange. It weird cuz at this point my print was about 8mm tall on the bed. Why would it take so long to clear? I was having some layer separation issues so I have been printing at 240 to 250 degrees. I know that's kinda hot but it seems to have worked in solving my layer separation. Could It be the cause of this new problem? Any insight would be greatly appreciated thanks in advance.

Dripfree

Most likely came from the hobbed bolt of your extruder, make the habit of cleaning it once in a while, specially when changing from solid colors to clear ones.

Your delamination problems are related to open frame printers and cold drafts hitting the hot printed part, increasing the temperature helps keeping the part warmer, also 250 is still within the limits so you are OK.

Quote
ggherbaz
Most likely came from the hobbed bolt of your extruder, make the habit of cleaning it once in a while, specially when changing from solid colors to clear ones.

Your delamination problems are related to open frame printers and cold drafts hitting the hot printed part, increasing the temperature helps keeping the part warmer, also 250 is still within the limits so you are OK.

Thank you for the response but I don't think it did come from the hobbed bolt. I actually cleaned it real nice before I started. This crud was also very burnt (only slightly able to tell it was orange) so my guess was it was burnt onto the inside of the nozzle. But it seemed like quite allot perhaps 15 to 20 mm of extrusion before it ran clear again. I hope I don't need a nozzle cleaning after every filament change. I did also just "upgrade" to "improved hexagon cooling". It uses a much smaller fan to cool the hot end. I am now just considering this issue as I type perhaps I should look further into this.

My hexagon has self cleaned when purged of the previous filament without any problem.
I swap between different size nozzles and between abs, ninjaflex and now nylon.
Ive never had to manually clean the inside of the hot end or nozzle.
And apart from cleaning the outside of the nozzle, crud can build up especially the ninjaflex, ive not had any contamination like that.
As to cooling the hexagon. it doesnt seem to take much. Ive got a tiny 20mm fan squeezed into the y carriage of a prusa i2 not much room to pull air in and its been fine.

250 is very hot for abs.
I use 230 for most if not all of my abs without adhesion problems.
I use ikea mirror tiles covered in kapton tape with the bed between 90 and 110C and for larger taller prints i cover the printer to keep the heat in a bit more.
But most stuff prints fine at 230C without lifting or layers not adhering.

Could it be specific to that filament provider?
Maybe theyve got an additive in the filament that can cause this at the higher temps you use.

Gordon

My hexagon has self cleaned when purged of the previous filament without any problem.
I swap between different size nozzles and between abs, ninjaflex and now nylon.
Ive never had to manually clean the inside of the hot end or nozzle.
And apart from cleaning the outside of the nozzle, crud can build up especially the ninjaflex, ive not had any contamination like that.
As to cooling the hexagon. it doesnt seem to take much. Ive got a tiny 20mm fan squeezed into the y carriage of a prusa i2 not much room to pull air in and its been fine.

250 is very hot for abs.
I use 230 for most if not all of my abs without adhesion problems.
I use ikea mirror tiles covered in kapton tape with the bed between 90 and 110C and for larger taller prints i cover the printer to keep the heat in a bit more.
But most stuff prints fine at 230C without lifting or layers not adhering.

Could it be specific to that filament provider?
Maybe theyve got an additive in the filament that can cause this at the higher temps you use.

Gordon

If it wasn't in the extruder, the only other probable place is a gap between nozzle and barrel, I also have an hexagon and once you clear previous filament it will be fine, so take your nozzle out and check the top where it meets the barrel for residue.

I didnt know they made clear ABS. Are you sure it isnt PLA? You can tell by the temperatures. heat up a PLA part on the heated bed and it should soften at 60 degrees.

[www.ebay.com]

now you know.