I've been very happy with my Mendel90, but attempting to print larger parts in ABS resulted in the inevitable warping of the part as the ABS cools. Nophead has done a load of work on this subject, and my original printer uses a chamber also. So I designed some corner brackets to allow me to make a chamber for the Mendel90 from 6mm MDF. As there are no spare temperature inputs on the Melzi controller, I bought a cheap PID temp. controller off ebay, and wired it into a hot air gun. My '90 is in the garage and needs much more heat than cooling:
Below are the results, keeping the chamber at 45C makes a major difference to the warping. The right hand side shows the same part printed without heating:
This is using ABS juice to glue the parts to the bed. I'm going to try a combination of kapton tape and ABS juice next.