ABS warps because it cools unevenly. That is the whole story. The first layer sticks, the top keeps shrinking as it cools, and the part peels itself off the bed at the corners like a sad sandwich curling in the sun. I spent weeks blaming my bed adhesion, my brim, my Z offset, my slicer. None of it was the real problem. The real problem was that my workshop is draughty and the part was cooling far too fast.
So I built an enclosure. Not a clever one. A box.
The first version was a cardboard packing box with a hole cut for the filament and a sheet of acrylic taped over the front so I could watch it. It looked ridiculous. It also worked, immediately and obviously, which was annoying because I had spent so long on everything else. A 30°C ambient inside the box instead of an 18°C draught outside it was the difference between a cracked part and a clean one. The chamber does not need to be hot. It needs to be still and a bit warm.
The cardboard lasted about a fortnight before I admitted it was a fire risk sat next to a 240°C hotend, and built the proper one out of aluminium extrusion and 4mm acrylic panels. I kept it passive at first: no active heating, just the bed and the hotend warming the trapped air. For a 60mm tall part that gets you to the low 30s and that is genuinely enough for most ABS.
Where it stops being enough is tall prints. Anything over about 120mm and the top of the part is in cooler air than the bottom, and the warping comes back in a more subtle, layer-splitting form. That is the bit I have not properly solved yet. I have a small ceramic heater and a cheap PID controller sat in a box waiting for me to wire them in, and a nagging worry about thermal runaway venting fumes into a sealed cabinet in a room I sometimes sleep near. So it waits.
A few things I would tell my past self:
- The electronics do not want to be in the hot box. Move your control board outside, or duct cool air to it. Stepper drivers throwing thermal warnings at 40°C ambient is a miserable way to lose a 9 hour print.
- PTFE in the hotend path degrades faster when the whole assembly runs warm. An all-metal hotend is worth it before you enclose, not after.
- Vent it. ABS is not lovely to breathe. A small extractor on a timer, ducted out the window, is not optional in a room you occupy.
The "eventually" in the title is doing some heavy lifting. The passive box has been good enough for nine months and I keep not building the active version. Sometimes the right amount of engineering is a cardboard box, replaced by a slightly nicer box, and the wisdom to stop there until a tall print genuinely demands more.