# How can I calculate the actual pritable area and set it in Marlin 2 ??

Posted by tolisn
 How can I calculate the actual pritable area and set it in Marlin 2 ?? February 26, 2020 02:31PM Registered: 6 years ago Posts: 25
Hi
I'm new to this 3D printing hobby so be easy.\
I have generic reprap printer with the X,Y endstop located on the LEFT and BACK of the printer so I asume that the 0/0 position of the printer is located on the Left/Back of the print bed.
Now all the examples that I have found use the 0/0 position as the Front/Left of the print bed and that has gotten me confused. I also have a bltouch probe locate to the right of the nozzel.

How do I go about calculating the the auto bed leveling touch points and the actual printable area ? I'm using Marlin 2.0
 Re: How can I calculate the actual pritable area and set it in Marlin 2 ?? February 26, 2020 03:56PM Registered: 3 years ago Posts: 253
By LEFT/BACK you mean that the X carriage is to the left and the bed is at the back? In this case the home position is actually LEFT/FRONT since you care about the location of the nozzle with respect to the bed.

Or do you mean that the nozzle is at the back of the bed (i.e. the bed is all the way forward)? In this case, there's a problem.

Marlin needs the 0,0 position to be either at the LEFT/FRONT or RIGHT/BACK of the bed (in the latter case, it just acts like the printer was rotated 180 degrees). If this is not the case with your setup you'll have to configure Y to home to MAX instead of MIN.
 Re: How can I calculate the actual pritable area and set it in Marlin 2 ?? February 26, 2020 11:45PM Registered: 6 years ago Posts: 25
When I press HOME, the bed moves to the left and to the back. Is this normal?
 Re: How can I calculate the actual pritable area and set it in Marlin 2 ?? February 26, 2020 11:59PM Registered: 10 years ago Posts: 6,119

The bed on most machines only moves in one direction, Normally front to back or up and down.
But there are some oddball machines that move the bed in left/right and front/back. But if this is the case it is not a generic reprap printer.

If it is actually doing as you say then it is homing to X-max and Y-Min

Edited 1 time(s). Last edit at 02/27/2020 12:02AM by Dust.
 Re: How can I calculate the actual pritable area and set it in Marlin 2 ?? February 27, 2020 12:24AM Registered: 6 years ago Posts: 25
Sorry for the misunderstanding, what I meant to say is during the home stage the extruder assembly moves to the left (that is where the endstop is) and the heat bed moves to the back (that is where the endstop is).
 Re: How can I calculate the actual pritable area and set it in Marlin 2 ?? February 27, 2020 07:01AM Registered: 4 years ago Posts: 1,719
My Hictop 3DP11 Prusa i3 Clone moves the exactly the same. I understand you are referring the the Nozzle moving left and the bed moving to the rear.

Computer Programmer / Electronics Technician
 Re: How can I calculate the actual pritable area and set it in Marlin 2 ?? February 27, 2020 10:25AM Registered: 6 years ago Posts: 25
Yes, that is how it is. Where do I make changes in marlin2 to center the print area and to set the auto bed leveling positions?
 Re: How can I calculate the actual pritable area and set it in Marlin 2 ?? February 27, 2020 12:53PM Registered: 3 years ago Posts: 253
OK. If the bed is moving to the back, it means that after homing the nozzle ends up near the front left of the bed, so that's fine.

Here's how I would adjust the limits:
• Take a ruler and measure the bed. Set X_BED_SIZE and Y_BED_SIZE accordingly in your Configuration.h file
• Set X_MIN_POS and Y_MIN_POS to 0,0 - this is just temporary, we'll change them after we've worked out exactly the dimensions.
• Upload the firmware, and using a program such as Pronterface, execute "G28 X0 Y0" to home just X and Y (we don't want to home Z yet).
• It's likely that the nozzle will end up to the left and in front of the bed, but your printer LCD should show X=0, Y=0
• Use the printer's LCD to jog the nozzle until it's just over the front left corner of the bed.
• Take a note of the X and Y coordinates displayed on the LCD. For example, it could say something like X=12, Y=5.
• Make the two values negative and set X_MIN_POS and Y_MIN_POS to these values. In the example above you'd set X_MIN_POS to -12 and Y_MIN_POS to -5
• Upload your firmware again. Execute the "G28 X0 Y0" again and the nozzle should end up in the same place but the LCD should show the coordinates you set as X_MIN_POS and Y_MIN_POS (-12, -5 in the example).
• Execute "G0 X0 Y0" and the nozzle should end up right over the front left corner of the bed.
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