Hi gr5,
Thank you for your help with this.
You were spot-on, it was indeed it seems a temperature issue.
My guess is that Ultimaker have made some significant changes to the makeup of the chemical composition of their ABS, to ensure that it sticks well to the glass. Combined with my effective oven of a thermal chamber, it seems clear now that I was cooking the material during the print.
I have now upped the fan speed to 100% on both the Cura setting and the printer setting, dropped the nozzle temperature from 250 to 230 degrees and reduced the plate temperature back down to 80 degrees (from 100) and the change is staggering.
I'm printing the parts with no skirt, no brim, no raft - nothing! The prints are sticking and the finish is loads better.
I also increased the top layer thickness and this seems to have helped with the pillowing issue.
All in all, a surprise but welcome result.
To summarise
Material: ABS Ultimaker, White
Nozzle temperature: 230 degrees
Bed temp: 80 degrees
Fan speed: 100%
Glue: White ABS and acetone slurry (note, pretty thin - the new ABS also does not seem to dissolve in acetone like the old ABS
Print speed: 50mm/s
Enclosure: Fully enclosed in 25mm kingspan foam insulation
cheers,
Chris