Suspect some charring using white ABS

[JohnFox 25]

I am using white ABS supplied by 3D Prima, running on an UM2 at default temperature settings of 260C. From time to time I get brown colouration on the bottom two or three layers. I suspect that this is due to the ABS starting to char.

Is it worth trying to drop the temperature at bit or will this lead to other problems?

Oddly, this doesn't seem to occur elsewhere on the print.

thanks

John

[gixxer 1]

Hi John,

I sometimes get small inclusions of dark char like deposits within a white print. Whenever I've watched this happening it's source has been the outside of the nozzle and not from within.

Check the nozzle surface is clean before starting a print. Any small pieces of filament that are stuck to the outside can release after its gone through a few heating and cooling cycles which then get embedded in the print.

This is far more noticeable on a white print due to the contrast.

[JohnFox 25]

Thanks, sorry I didn't respond sooner.

I've changed to PLA and am getting the same charred bits. It isn't from the outside as I keep the nozzle pretty clean but I now see them fairly frequently at the start of a print, they usually are all out by the time it has printed the brim. They seem to build up within the nozzle and are disturbed when the nozzle cools down and heats back up again.

I've started to do a dummy print in the same run before any important ones in order to get hem out.

 

Hi John,

I sometimes get small inclusions of dark char like deposits within a white print. Whenever I've watched this happening it's source has been the outside of the nozzle and not from within.

Check the nozzle surface is clean before starting a print. Any small pieces of filament that are stuck to the outside can release after its gone through a few heating and cooling cycles which then get embedded in the print.

This is far more noticeable on a white print due to the contrast.

[swordriff 119]

@gixxer

totally agree.

Also this: IF you printed PLA before, some PLA is left in nozzle. It is released (at least some of it) when you print at a much higher temperature with ABS. The higher temperature destroys the PLA.

Edited May 16, 2015 by Guest