Howdy
Shortly said: one can use ABS on Z18, but with a lot of patience and knowledge of course.
Heated chamber can heat up to 55dc. This alone is obviously not enough for successful preventing warp at ABS.
I was successful with non-MB filaments of special ABS.

There is third party heated bed on market with proper size (30cmx30cm). Can be installed as add-on. Then you get much easyer way to print ABS all together.
Therefore, If you stick with ABS then i would strongly recommend this heated bed.

Otherwise, Z18 is great machine.
With new extruder even better