Pre-heating Gcode due to excessive extrusion  

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llangley27
(@llangley27)
New Member

Hi everyone.

 

I'm really excited to be joining these forums as I've had my i3MK3S assembled for a few days now and I absolutely love it. That being said, I'm having some pretty excessive extrusion issues when I start prints as the nozzle heats up.  This is happening before the mesh bed leveling.  Quite a bit of filament comes out straight and either breaks off when mesh bed leveling starts or I quickly grab it off and then as mesh bed leveling is executing, more comes out and curls around the nozzle causing a significant amount to break off just barely before the print starts on the first line.

 

This is happening at normal temps of either 215 or 225.  I've recently had to adjust my first layer temp to 225 and bed temp to 55 as I was having adhesion issues (225/55 fixed those issues).  My live Z adjustment is locked in pretty well as I've been using life adjust z and I noticed that the life adjust gcode has the extruder pre-heated to 170 for mesh leveling instead of 225 which is the first layer and I'm receiving no excessive extrusion during the life adjust z prints.  

 

I'm using Prusaslicer and I don't see any options either in advanced or expert to pre-heat the extruder/bed PRIOR to mesh leveling.  I do see custom code options, but I'm honestly a bit nervous to play with that as I don't know what I should be putting in and where to get the pre-heat before mesh results I want without messing something up.  I've opened up life adjust z PLA in textedit as well and it still makes me nervous to make those changes, so I thought I'd ask here for some direction if anyone knows for sure!

 

Just for clarity, I'm looking to get a pre-heat temp of 170/55 before mesh leveling, 225/55 first layer temp, and 200/55 regular print temp.  My machine is the i3MK3S and I'm using Hatchb0x 1.75mm White filament.  Any thoughts or recommendations?

 

 

Thanks!

 

-Loren

Posted : 31/05/2020 8:11 am
Loak
 loak
(@loak)
Estimable Member

Hello Loren,

 

You can achieve this with two modifications : 

 

First in the start-gcode :

 

M862.3 P "[printer_model]" ; printer model check
M862.1 P[nozzle_diameter] ; nozzle diameter check
M115 U3.9.0 ; tell printer latest fw version
G90 ; use absolute coordinates
M83 ; extruder relative mode
M104 S170 ; set preheat extruder temp here 170 or what ever you want
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
G28 W ; home all without mesh bed level
G80 ; mesh bed leveling

M109 S[first_layer_temperature] ; wait for final extruder temp
G1 Y-3.0 F1000.0 ; go outside print area
G92 E0.0
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E12.5 F1000.0 ; intro line
G92 E0.0
M221 S{if layer_height<0.075}100{else}95{endif}

and second in the "Filament setttings" tab of PrusaSlicer, where you can set the first layer extruder temp and bed temp, and other layers extruder temp and bed temp. I've attached a picture of the tab, It's in french ... nobody is perfect

 

 

This post was modified 4 months ago by Loak
Posted : 31/05/2020 9:18 am
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