I’ll sometimes preheat the chamber by turning on the bed heater at the same time I set the nozzle to 255 C to manually unload the filament and load new filament, then leave them both on while I’m slicing the part that I want to print. The tiny Zero heats the chamber quickly with most of the heat seeming to come from the nozzle heat break forced convection cooling rather than the heated bed.
The Zero is an ABS-CF printing wee beast. I finally have a printer that’s optimized for small precision high temperature structural prints. I set the exhaust fan to kick on at 60 C and it blips on briefly after maybe 30 minutes on a new print, and when the chamber was preheated by a previous print it reaches 60 C in 10-15 minutes. Prior to that, the print is usually short enough that it’s in a static heated air bubble close to the bed so I don’t feel the need to get the chamber up to temperature before I start printing. It warms up as needed while I’m printing.
I recently printed some custom ABS-CF slip cases that are approximately 50 mm in diameter, with a 2 mm thick base and 1 mm thick wall (2 layers) above that. By the time the base finished printing and the walls were quickly rising, the passively heated chamber was already warm enough to avoid any warping.
While I was waiting for my Zero to arrive, I ordered some foaming PLA-LW filament and magnets to make insulating tiles for the inside of the Zero to improve the passive chamber heating, based on my experience trying to passively heat larger chambers, but after receiving the Zero, the small chamber heats so quickly that insulating tiles seem completely unnecessary.
The temperature gets a bit high for PLA, even with the lid off and the door open. I need to use the noisy full width curtain fan on the rare occasions that I want to print PLA quickly so it will cool fast enough. The free 40 C chamber seems to help when printing PETG.