Burning Area is smaller than project

Hi. Im Using Arduino Nano with GRBL 1.1.
I have a problem with burning in Lightburn.
My workspace is set for 650mm x 650mm.
I want to burn round pattern (diameter 600mm)
when i start burning diameter is smaller (ca 550mm)
is there any margins i shoul set or what??
Please help

Have you calibrated your axes?

$100, $101 and $102 – [X,Y,Z] steps/mm

Grbl needs to know how far each step will take the tool in reality. To calculate steps/mm for an axis of your machine you need to know:

  • The mm traveled per revolution of your stepper motor. This is dependent on your belt drive gears or lead screw pitch.
  • The full steps per revolution of your steppers (typically 200)
  • The microsteps per step of your controller (typically 1, 2, 4, 8, or 16). Tip: Using high microstep values (e.g., 16) can reduce your stepper motor torque, so use the lowest that gives you the desired axis resolution and comfortable running properties.

The steps/mm can then be calculated like this: steps_per_mm = (steps_per_revolution*microsteps)/mm_per_rev

Compute this value for every axis and write these settings to Grbl.

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Yes those are set correctly. but final shape is 4cm smaller than planned

i already burned square 20mm x 20mm and its fine. But when i want to burn circle (600mm x 600mm) then its smaller

That’s odd. So you’re saying the 600x600 mm circle is 40 mm smaller than expected but that the 20x20 mm square is perfect to dimension?

Some followup questions:

  1. What happens if you burn a square of 600x600 mm?
  2. Does the 600x600 mm circle look perfectly round?

Normally any issues with dimensions not coming in correctly are going to be caused by calibration issues or a binding issue. If you were getting binding I would expect your burns to look distorted in some way, especially if it’s 6-7% deviation like you’re describing. However, it’s possible that there’s little or no obvious distortion. Check that your belts are not overtightened and especially check that the wheels are not overtightened to the rails.

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