Could anyone please help me with sizing problems. In this example, the first photo shows an image - the size is 185mm across and the px resolution is 144. The next photo shows my Laserweb settings for images - set at 144. The next photo shows the Laserweb image on the screen and the size set at 185mm across. My question is, why when I do a ‘Check Size’ does the ‘square’ only go across 155mm. When engraving, the engraved image is the same as the check size area. Can anyone tell me what I am doing wrong please? I am using a Laseraxe 7W 65cm x 50cm engraver

Is the set up of your step motors correct, in your firmware?
If you move x axe 100 mm it moves 100 mm exactly?.

I’ve checked and it isn’t. If I jog 100mm (using the software), it physically moves about 80mm. That is both up/down and sideways. I don’t suppose you know how I fix that do you? Kindest regards and many thanks for getting back to me. Paul

@Max_Shadow first of all, fix the firmware set up of your board.
wich version of GRBL has it? 0.9; 1.1 …
check \$100,\$101and \$102. your steps/mm are not correct.

\$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.

@Roberbike You were absolutely spot on Roberto. The \$100 and \$100 were out. Now on \$98, they match the distances perfectly and the images are the right size. Kindest regards and many, many thanks. Paul