Use this test-file to check your machine mechanical accuracy and laser spot thickness.

The best results are obtained by running this test file on a piece of anodized aluminum, laser perfectly focused, using maximum power and F500-F800 speed (for a 5.5W optical power model, 20W electrical power). Speed and power should be adjusted for different laser power and material.

Test file loaded in LaserGRBL
In this video you can see this test-file in action
Results of this test on anodized aluminium heat-sink using Ortur LU1-2 laser module