Print is not centered correctly on Bed

[Brassovits 0]

Hi
I have encountered a problem with the bed in Cura not matching the actual bed on my Tevo Tarantula Pro?
When I load a model (.stl) into Cura it appears fine within the bed, there are no error messages and review indicates that it looks fine.
When I then pull the gcode onto an SD card and start printing, it hits next to the bed, ie the print head runs towards the end stop.
the print is pushed on the bed approx. 1 cm to the right and approx. 1 cm backwards. The home position looks fine, hitting the left front corner of the bed. I have not encountered this problem before, as it is the first time I utilize the size of the bed all the way to the edges, about 2 mm in from all sides.
Hope there is someone who can give a hint where I in Cura need to adjust for it to hit correctly?
The black square in picture 2 is the bed and the blue transparent is where the print is in relation to the bed.

[gr5 2,004]

This is a complicated subject.  I believe the Tevo uses Marlin firmware which probably has an offset from the homing switches in order to print over the build plate (and not off the edge).  Maybe?  All printers are different.  So 0,0 might be inward a bit.

 

Anyway in the PREPARE mode of Cura go into the machine settings for your particular printer and in there you can set the width and height of your print bed.  Whatever numbers you put in there - cura divides those 2 numbers by 2 to get the center.

[Brassovits 0]

Problem solved! I have changed the extruder settings in Cura, (Machine Settings Extruder). Now the print hits exactly 120 mm in from all sides.
After some measurement, adding and subtracting, I ended up with Nozzle offset, X = 15, and Y = 6, in Machine Settings in Cura, and my test print (sight grain), now hits exactly in the middle.

[Brassovits 0]

On 3/3/2022 at 9:59 PM, gr5 said:

This is a complicated subject.  I believe the Tevo uses Marlin firmware which probably has an offset from the homing switches in order to print over the build plate (and not off the edge).  Maybe?  All printers are different.  So 0,0 might be inward a bit.

 

Anyway in the PREPARE mode of Cura go into the machine settings for your particular printer and in there you can set the width and height of your print bed.  Whatever numbers you put in there - cura divides those 2 numbers by 2 to get the center.

If this is correct, Cura is not very good at calculating, bed size was correctly stated, but the print still did not hit the middle of the bed. 🙂

[ahoeben 1,766]

46 minutes ago, Brassovits said:

If this is correct, Cura is not very good at calculating,

No, your firmware is not good at homing.

[GregValiant 982]

The printer will take the coordinates of a gcode file and place that "origin point of the print" at the Home Offset position of the printer.  If you have not defined a Home Offset location in the printer then the default is the Auto-Home location.  That location is often in space just off the build plate.  It is the main reason prints are not centered.  If your build surface is 240 x 240 then the mid-point of the print will be X120 and Y120 from the Home Offset origin.

 

When you define a Home Offset location then Marlin will assign that Home Offset location as 0,0,0.  The Auto-Home location will be related to that 0,0,0.  When you Auto-Home and look at the LCD it will show its location to be the same as your Home Offsets.  The X and Y values will often be negative because the Auto-Home location is often in the negative quadrant of the ordinate system that is centered upon the Home Offset position.  For reference, my home offset is:

M206 X-1.00 Y-5.00 Z0.00

 

And that is why gr5 says it's complicated.  I don't understand the comment about the Extruder Settings though.  They aren't involved in this even for a multiple extruder machine.

Edited March 7, 2022 by GregValiant