Up until now I've been printing exclusively in PLA. Last night I started experimenting with ABS. The first time I tried a print, it failed miserably because I was using all default settings. Not know where to start, I copied all of the PLA settings over to the ABS profile except for the obvious things like temperature. Feed rates and flow rates are exactly the same as for PLA.
This time, the print came out quite nice, but it was also a very small item - a 608 bearing guide. I was so happy with the quality, I decided to try something bigger - an extruder body for the OB1 printer I am building. This wasn't such a success. First I had some curling even though I was printing on Kaptan tape. I attribute this to two things 1) I lowered the bed temp from 110 to 100 after the first few layers, and 2) I have a small fan constantly running pointing at the thermal break of my J-Head. I plan on eliminating both of these when I make my next attempt.
The other issue with my print was much more perplexing. It seemed that on layers where I slow things down - like the bottom layer and any bridging layer, that the flow rate is much too high and I end up flooding the print to the point where I can hear rumbling as the head passes over previously printed areas. When I copied my settings from PLA, my flow rate was already 10% less that my feed rate, so that't currently what I have for ABS. I don't think this needs to be changed though since the sparse-filled layers are coming out beautiful. I think I need to change my bottom layer and bridging layer ratios so that the flow ratio is less than the feed ratio in both cases. I just didn't know if this was extreme. The base numbers are already 10% apart; now I'm going to make them perhaps 20% apart on these slow layers. Do other people have similar experiences?
Thanks
