Some plastic materials such as ABS, have a tendency to shrink as they cool down. This shrinkage can occur during printing, which can result in warped or bowed parts.
This warpage can be reduced or mitigated by keeping the printed parts warm during printing. This is typically achieved using a printer inside an enclosure. The Z603-S has a good frame that is fairly easy to seal up with cardboard or other cheap materials, but for a little more money, a much nicer enclosure can be fabricated using laser cut acrylic sheets.
Here is a simple design you can download and take to a laser cutting facility to be fabricated in 3mm acrylic. You can glue it together, but even just some masking tape will be sufficient for holding it together well, thanks to the tabbed design.