Can we add disallowed areas?

[DarkShaderz 0]

my printer homes outside of the build surface where a i kept a sponge to clean the nozzle before print. now the problem is , if I put an object in the centre of my buildplate in cura, it prints actually  around 20mm to the left of it. Any ideas to fix this ,I want it to print in the same place specified in cura.

 

this is a custom printer which I made from scratch.  

Edited May 17 by DarkShaderz

[GregValiant 741]

Most model files don't specify a location.  Some 3mf files do.

Cura calculates the mid-point of it's virtual build plate from the numbers you have in the Machine Settings "X(width) and Y(depth)".  Those should represent the true "printable area" of your build plate.  In the case of my Ender 3 Pro - the build plate physically is 235 x 235.  It has a 1mm bevel around the periphery so that can't be printed on.  I wanted another 1.5mm safety area around the periphery as well.  So in Cura I've entered X(width) = 230 and Y(depth) = 230 (235 - 2.5 "non-printable" area on the left - 2.5 "non-printable" area on the right = 230).  That makes my Cura mid-point X=115 and Y=115.

 

In the cases where there is no location data (STL files mostly), Cura gets the "Center-of-Geometry" of the part in the XY and puts that at the midpoint of the Cura build plate.  When the gcode is created the origin point of the gcode is the 0,0,0 of the Cura virtual build plate.

Then the gcode shows up in the printer.

The printer will put that 0,0,0 origin of the gcode file at the printer's defined Home Offset 0,0,0.  If you haven't defined a Home Offset location (M206) then it will be the Auto-Home location.  That is probably what is going on with your off-center prints.

My Auto-Home location is just off the build plate.  I move the nozzle to a point 2.5mm in from the left edge of the glass and 2.5mm in from the front edge of the glass (the dimensions of my "non-printable area") and at a Z=0 and select "Set Home Offsets" on the LCD followed by "Save Settings".  Now the printer matches Cura.

 

If your firmware doesn't have a "Set Home Offsets" option on the LCD then you can do it in a gcode file that you "print".  That's another lesson if the above method can't or doesn't work.

 

Another lesson would be for "Disallowed Areas".  For those you need a printer definition file.  If you are using "fdmprinter.def.json" as your base file for your custom printer - that file should not be altered.

 

Edited May 17 by GregValiant