I’ve been doing some testing around pre heating the chamber to help with ASA print consistency and came up with a simple pair of macros to use the printers own hardware to preheat the chamber, I can get the chamber temp to +40 degrees in a 21 degree room within about 30-40 mins, I know that’s a fairly long time to preheat but it makes for some nice consistent ASA prints and its more about
[gcode_macro START_CHAMBER_PREHEAT]
description: Preheat the chamber before printing high temp filaments
gcode:
G28
SET_HEATER_TEMPERATURE HEATER=heater_bed TARGET=120
SET_FAN_SPEED FAN=fan2 SPEED=0.5
G28 X
G28 Y
G90
G0 Z0
[gcode_macro STOP_CHAMBER_PREHEAT]
description: Turn off the heat bed and fan
gcode:
SET_HEATER_TEMPERATURE HEATER=heater_bed TARGET=0
SET_FAN_SPEED FAN=fan2 SPEED=0
G28
UPDATE: It heats up quicker than my earlier tests, I forgot to install the exhaust fan block off! This time I captured and plotted temperature data:
What is the “power” graph look like for your bed heater? More airflow against the underside of the bed will “cool” the bed causing higher duty cycle for the bed heater and reduce your preheat time.
Under the bed pointed straight up. Remove for tall prints.
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.
Why do you have fan2 running, isn’t it pulling room temperature air from behind the printer to the chamber and cooling the chamber as a result?
If you want to mix the warm air inside the chamber then fan0 could be more effective.
Another thing you may want to try for comparison is to move Z to 150 so that the bed is at the bottom of the chamber where the colder air will be instead of trying to heat from the middle.
I’ve tried a few different things over the last week or so and so far the most effective has been moving the bed to Z0 and using fan2 to circulate the heat from the bed, the idea is the high air volume and the wide outlet move a lot of air over the bed causing it to cool and apply more power to reheat.
Yes fan2 does draw air in from the outside yet it reaches around 40 degrees within 20 mins. I guess you could block off the grill on the back to make it more effective, but I’m looking for ways to use the factory printer configuration while I wait for parts to build a chamber heater.
I will test your suggestion and graph the results.
Bed at 120°C, Z height = 0mm, Fan0 @ 100%, toolhead in centre of bed. Results are pretty similar to the first test, although the bed power is much lower compared to using Fan2. I’ll repeat test 1 and run another test with Z at 150mm.
Bed heater is averaging <25% power after about 4 minutes.
More “circular” airflow would speed things up. That USB desk fan pointed straight up with the bed down close. Fan can stay for all but the tallest prints. Unplug it when you start to print.
Been looking at the step model of the Zero. It looks like Sovol tried to limit heat loss from the bottom of the heated bed. 2 layers of “stuff” cover most of the bottom.
If you really want to heat the chamber with the bed heater mods to the plastic “hotbed edge plate” would likely do the trick
Air blown into the front (blue arrows) would be heated and exit around the existing opening for the heater wires (red arrow). Bed plate removed for clarity. The red box on the right is an alternate location for a fan. The front fan does clear the floor when bed is fully down.
If anyone wants to punch a hole in their edge plate let me know and I’ll model up a printable duct and a cutting template.
I would NOT run this fan full speed while printing as it would drive the PID controller for the bed heater nuts. If you get the fan hooked into the MCU you could set the fan to a low PWM and PID tune in a hot chamber. Run the fan at that constant speed while printing. Chamber temp would be (at least partially) self regulating as bed heater power would increase if the chamber cools and decrease if the chamber heats up.
