ABS from 3D extrusion type printers CAN be cast successfully.
I've been using an UP! printer with a 0.2mm nozzle which produces a good but visibly grooved surface finish. There is an easy solution to get a very good surface finish.
I used standard red sprue wax and a wax worker. I dripped hot wax onto the ABS surface and the used the wax worker to spread the wax around and coat the ABS surface as evenly as I could. A standard domestic hair drier helped spread the wax evenly over the whole surface and gave a really smooth, almost polished finish.
I've just cast 4 Silver skulls and they have all come out well. The photo was taken after pickling and ultrasonic to remove the investment residue and then 10minutes in a magnetic polisher.
The printer takes about 7 hours to 'grow' 6 skulls of this size. I used a 6mm round ball burr to remove the support structure from inside the skull so it could be cast completely hollow. The wall thickness is about 1.3mm
For those interested I used the following burnout in a Paragon Kiln, Ramp up to 300 C, Hold for 35minutes. Then ramp up to 925 C Hold for 50minutes then drop to 485 C to cast Sterling Silver.