Print head offsets in Machine Settings

[stolowma 1]

I'm a bit confused about the function of printhead offset settings. Since I changed control boards on my Ender 3 Pro I have an issue I'm trying to resolve where ABL and printing is offset from where it should be on about 25mm on the X and 35mm on the Y axis. While I was doing research on Marlin settings I saw in an article that this could be caused by the settings in firmware not matching the settings in the slicer. What is the function of the settings in Cura and how do the two correlate with each other? Should the "Apply offsets to Gcode" be checked? 

[GregValiant 1,251]

Cura has no idea how big your build plate is or where it is.  The Machine Settings explain "how big" to the software.

Your printer has no idea where it's own build plate is.  When you Auto-Home then the X Y Z switches are hit.  That is the only position where the print head is positively located (any other position is measured in "steps" from that location).

You need to set your home offsets because that's where 0,0,0 of a Cura gcode file will be located.  The Home Offset location is what synchronizes the virtual build plate in Cura to the physical build plate of the printer.

 

 

 

The Ender 3 Pro definition file should put your X(width) = 220, the Y(depth) = 220 and the Z(height) = 250.  Creality puts a 7.5mm "safety area" around the periphery of the build surface so yes, it measures 235 x 235 and the "build area" is smaller.  You can cheat that by setting Cura to 230 x 230 x 250 and moving your Home Offset to 2.5mm in from the left and 2.5mm back from the front edge.

The Print Head settings define the shape of the print head and are measured from the centerline of the nozzle.  MinX and MinY will be negative numbers.

The "gantry height" is the distance from the tip of the nozzle to the bottom of the X beam.  Yours should be 25mm.

The Print Head settings and the Gantry Height only come into play if you have multiple models on the build plate and elect to print them in "One at a Time" model.  Those numbers give Cura an idea of the interference space as it prints a particular model.

The Extruder tab has settings for the X and Y offset.  These might be non-zero for a multiple extruder printer, but yours should both be "0".  Since they are zero, whether or not you check the "Apply Extruder Offsets to Gcode" doesn't matter since there is just one hot end.

Now Cura and the printer are in sync, the 0,0,0 of the gcode file will be at your Home Offset location.  The mid point of your physical bed should match the mid point of Cura's virtual bed.

The nozzle is at Z = 0 and the bed must be brought to it using the knobs on the underside.  Once you have it there, the "Z offset" will be the adjustment between the tip of the sensing probe and where the nozzle is during probing.

At least that's how I think it works.  I use a piece of paper.

 

[stolowma 1]

Sorry it took so long to respond. I had no idea Cura needs to know that for collision avoidance. The hotend cooler I'm installing says the hotend will have a Y offset of -9mm, how does that fit in with this? 

[GregValiant 1,251]

I don't know how the new parts mounted.  It sounds like the centerline of the nozzle moved further towards the front of the printer.  If that is true then the only thing that should be affected is the Home Offset of the printer.

The printer will put the 0,0,0 origin of a Gcode file at the Home Offset 0,0,0.  That point has to be over the bed and not somewhere off the build plate.

 

If the parts made the print head bigger, then you might want to change the Print Head settings.  Use a ruler and measure from the center of the nozzle to the left most part of the print head (MinX) and that will be a negative number in the settings.  Measure from the nozzle to the right-most part of the print head (MaxX) and that will be a positive number.

In front of the nozzle is negative Y and the behind the nozzle is positive Y.