"Absorbing heat", before printing  

You can skip it if you wish but you risk compromising print quality and adhesion.

Cheerio,

RE: "Absorbing heat", before printing

How do you skip it?

Whats it doing?

Posted by: @diem

You can skip it if you wish but you risk compromising print quality and adhesion.

Cheerio,

The XL has a lot of mass to bring up to a stable temperature.

Cheerio,

RE: "Absorbing heat", before printing

I typically skip the bed heating "absorption" stage if I'm doing a smaller print that uses less than three tiles. On bigger prints, I let it go all the way.

One thing I've found. If letting the absorption stage go to the end, sometimes a small blob of filament will ooze out during that time, throwing off the bed calibration and causing the print to fail. This is not a fire and forget printer. It requires babysitting to get a perfect first layer.

RE: "Absorbing heat", before printing

Posted by: @eastmemphis

[...] sometimes a small blob of filament will ooze out during that time, throwing off the bed calibration and causing the print to fail. This is not a fire and forget printer. It requires babysitting to get a perfect first layer.

One trick that saved me my first layer problems - turn down the pre-heat temperature in the machine GCODE. Search for this M109:

M109 T{initial_tool} S{((filament_notes[initial_tool]=~/.*HT_MBL10.*/) ? (first_layer_temperature[initial_tool] - 10) : (filament_type[initial_tool] == "PC" or filament_type[initial_tool] == "PA") ? (first_layer_temperature[initial_tool] - 25) : (filament_type[initial_tool] == "FLEX") ? 210 : (filament_type[initial_tool]=~/.*PET.*/) ? 175 : 170)} ; wait for temp

For PLA, change the final 170 to something lower, say 160. For PETG, I change 175 to 165. That's the temp that'll be used during bed probing and for some reason, the stock defaults in the slicer are all just a bit too high resulting in ooze from the nozzle which is throwing off the first layer calibration cycle. Lowering that number means no ooze means perfect first layers like you'd expect.

Here's a breakdown of that temperature command in case it's not clear what's going on:

((filament_notes[initial_tool]=~/.*HT_MBL10.*/) ? (first_layer_temperature[initial_tool] - 10)

This part checks if the filament notes for the initial tool contain the string "HT_MBL10". If true, it subtracts 10 from the first layer temperature. 

(filament_type[initial_tool] == "PC" or filament_type[initial_tool] == "PA") ? (first_layer_temperature[initial_tool] - 25)

If the filament type is PC (Polycarbonate) or PA (Polyamide), it subtracts 25 from the first layer temperature.

(filament_type[initial_tool] == "FLEX") ? 210

If the filament type is FLEX, it sets the temperature to 210°C.

(filament_type[initial_tool]=~/.*PET.*/) ? 175

If the filament type contains "PET", it sets the temperature to 175°C.  I find 165° to work better without oozing.

170

If none of the above conditions are met, it sets the temperature to 170°C. This is the number to change for PLA or ASA etc, 160° works for me.

RE: "Absorbing heat", before printing

turn down the pre-heat temperature in the machine GCODE

Just to clarify for anyone unfamiliar with this—this means the start gcode in the custom gcode section of Prusaslicer's Printer Settings; no need to edit gcode produced by Prusaslicer. 

RE: "Absorbing heat", before printing

Posted by: @fuchsr

turn down the pre-heat temperature in the machine GCODE

Just to clarify for anyone unfamiliar with this—this means the start gcode in the custom gcode section of Prusaslicer's Printer Settings; no need to edit gcode produced by Prusaslicer. 

I am going to give this shot. I am using only Prusament.

Also I might just start increasing temperature for PLA and PETG to see when to ozing starts and go a but lower compared to the test.

RE: "Absorbing heat", before printing

Posted by: @griffcomm

Hi, tried to do 10 min prints, seems like an extra 8mins with "Absorbing heat", whats that about?

On my machine, the "absorbing heat" delay is 2 minutes.

I think that it is the delay between the moment where the lower side of the heating plate (where the temperature sensor is sticked on) reaches the required température and the moment where the upper side of the printing plate is at required temperature.

The sandwich between those 2 surfaces is about 3 mm in thickness, and most of it is PCB, a poorly heat conducting material.

If I'm right, skipping this delay will start printing at a temperature lower than required (how much Celsius ? I don't know, but Prusa might).

RE: "Absorbing heat", before printing

I think the delay is longer depending on the material. E.g. PETG is 7 or 8 min. 

RE: "Absorbing heat", before printing

And I think >10 min for PA11-CF

RE: "Absorbing heat", before printing

I'm super late but, if you add HT_MBL10 to your filament notes, should decrease of 10°C the filament first layer temperature for the bed mesh.

RE: "Absorbing heat", before printing

I can see this making the perfect first layer issues worse.  The nozzle grows as it heats up and especially on large prints on anything but PLA I raise the nozzle when it starts printing.  A better option would be for automatically texting the filament back and letting the nozzle ooze for a few minutes.  After it stops probe the bed at full temp. 

For small prints it doesn't seem to matter.

Now theoretically you should be able to calculate how much the nozzle will grow at probing temp vs. printing temp, but the default values seem to favor PLA.  I would think the printer could automatically compensate based on the difference between probing and printing temp. 

I did notice that the probing temp for PC is 250, I'm sure due to the high printing temp. 

Anyways that's my 2¢.

RE: "Absorbing heat", before printing

it shouldn't, it takes down the nozzle temperature, actually pursaslicer with prusament pla for example, has the temperature go down to 175° when doing the bed mesh.

First layer temp is 230 and 225 for other layers.

This means that the nozzle will be at 175° when doing bedmesh, then will go up to 230° to print first layer, and then will go to 225° to print the rest.

I actually tried HT_MBL10, but it had the nozzle at 220 for bed mesh and started to oozing. so I will be using, like adviced before here, 160° for PLA for bed mesh.

The nozzle temp will not change as much and migh have been already compensated by Prusa on their printers (I have an XL and my first layer are always perfect, exept for my test with MBL10), the most important is the bed temperature, that will change drastically the bed mesh if done cold and then heat it.