Absorbing heat ?
Can someone explain what this step is doing ? Is this trying to get the internal print chamber to the target temp ?
This is new for me - I don't have this stage on the MK4S
Best Answer by sfcgeorge:
Absorbing heat seems quite misunderstood, I feel the name and UI isn't very clear. It's specifically about the heatbed and achieves 2 things:
- It allows the whole bed to reach even temperature. The temperature sensor is on the bottom of the bed so it takes a bit longer for the top to reach the same temperature. Moreover the corners and where screw holes are take longer to heat up. If you skip absorption some of the bed may be too cold so a print won't stick properly - warping or popping off.
- It allows thermal expansion to settle as Geoff said. This is important for even probing. The nozzle probes the bed before printing to calibrate a consistent first layer. If absorption is skipped the bed may not have finished expanding so the probe calibration will be uneven. You might notice ugly uneven first layers, or again warping and prints popping off.
Prusa recently released an update to make the heat absorbing delay smarter and potentially faster https://github.com/prusa3d/Prusa-Firmware-Buddy/releases/tag/v6.3.4 and here's an example (on the XL though so more extreme) of the difference when skipping it https://www.reddit.com/r/prusa3d/comments/17pqxny/psa_for_prusa_xl_users_dont_skip_the_absorbing/
I can't find official support advice but personally I don't skip it, I'm happy to wait a few extra minutes for a perfect first layer (especially if a print is hours long overall anyway). Of course it's your machine so do what you want with it 😄 Perhaps you're in a hurry, or run a print farm where time is money, or are just printing prototypes where first layer quality doesn't matter.
There is a separate wait time for chamber temperature but you likely won't encounter this. In PrusaSlicer the setting is Filaments > Filament > Temperature > Chamber > Minimal. For filaments like PLA and PETG this is zero so it won't wait. Only things like TPU, ASA etc have a minimal chamber temp to prevent warping (which you could skip for smaller organically shaped models less prone to warp).
Prusa Core One, MK4S w/ MMU3 (formerly MK4 / MMU3, MK3S+/MMU2), 2 Prusa MINI+, Octoprint. PETG, PVB, (some) PLA.
RE: Absorbing heat ?
My presumption is it's allowing the chassis of the printer to get to temperature, so any expansion of the metal is complete and therefore stable for the duration of your print
RE: Absorbing heat ?
I added some gcode to skip this step for low temp filaments like PLA and PETG. Not my code originally, but don't remember where I got it from.
G28 ; home all without mesh bed level
;
; Added - No chamber heater for PLA/PETG
;
{if chamber_minimal_temperature[initial_tool] > 36}
; CHAMBER HEATING AND WAIT FOR MATERIALS THAT NEED >36 °C CHAMBER
M104 S{idle_temperature[initial_tool]} ; set idle temp
G1 Z10 F720 ; set bed position
G1 X242 Y-9 F4800 ; set print head position
M191 S{chamber_minimal_temperature[initial_tool]} ; wait for minimal chamber temp
M141 S{chamber_temperature[initial_tool]} ; set nominal chamber temp
M107
M140 S[first_layer_bed_temperature] ; set bed temp
{else}
; SKIP CHAMBER HEATING FOR MATERIALS WITH MINIMAL CHAMBER TEMP ≤ 36 °C (E.G. PLA, PETG)
M141 S0 ; disable chamber heater
{endif}
{if first_layer_bed_temperature[initial_tool]<=60}M106 S70{endif}
G0 Z40 F10000
M104 T{initial_tool} S{if is_nil(idle_temperature[initial_tool])}100{else}{idle_temperature[initial_tool]}{endif}
M190 R[first_layer_bed_temperature] ; wait for bed temp
M107
;
; Added - No soak for PLA/PETG
;
{if chamber_minimal_temperature[initial_tool] > 36}
G29 G ; ABSORB HEAT FOR HIGH-TEMP MATERIALS
{else}
G4 S5 ; SHORT PAUSE INSTEAD OF SOAK FOR LOW-TEMP MATERIALS
{endif}
RE: Absorbing heat ?
Absorbing heat seems quite misunderstood, I feel the name and UI isn't very clear. It's specifically about the heatbed and achieves 2 things:
- It allows the whole bed to reach even temperature. The temperature sensor is on the bottom of the bed so it takes a bit longer for the top to reach the same temperature. Moreover the corners and where screw holes are take longer to heat up. If you skip absorption some of the bed may be too cold so a print won't stick properly - warping or popping off.
- It allows thermal expansion to settle as Geoff said. This is important for even probing. The nozzle probes the bed before printing to calibrate a consistent first layer. If absorption is skipped the bed may not have finished expanding so the probe calibration will be uneven. You might notice ugly uneven first layers, or again warping and prints popping off.
Prusa recently released an update to make the heat absorbing delay smarter and potentially faster https://github.com/prusa3d/Prusa-Firmware-Buddy/releases/tag/v6.3.4 and here's an example (on the XL though so more extreme) of the difference when skipping it https://www.reddit.com/r/prusa3d/comments/17pqxny/psa_for_prusa_xl_users_dont_skip_the_absorbing/
I can't find official support advice but personally I don't skip it, I'm happy to wait a few extra minutes for a perfect first layer (especially if a print is hours long overall anyway). Of course it's your machine so do what you want with it 😄 Perhaps you're in a hurry, or run a print farm where time is money, or are just printing prototypes where first layer quality doesn't matter.
There is a separate wait time for chamber temperature but you likely won't encounter this. In PrusaSlicer the setting is Filaments > Filament > Temperature > Chamber > Minimal. For filaments like PLA and PETG this is zero so it won't wait. Only things like TPU, ASA etc have a minimal chamber temp to prevent warping (which you could skip for smaller organically shaped models less prone to warp).
RE: Absorbing heat ?
I never had problems with PLA/PETG prints on my MK4S and since skipping this step on the C1, I don't see any issues with PETG even on large prints. Don't see the point of it for filaments that don't require consistent high temps during the print.