It is very simple to adjust the steps/mm to get precise movement of the axis. You can use the laser if already mounted… but I’m often building a new machine before any tool is mounted. So as soon as I can move an axis under power – and it moves consistently/repeatably the same amount (even if wrong) when commanded to do so – I like to rubber-band a wooden skewer (or other pointed object) to my tool mount, lay a ruler on the work surface in line with the axis, and lower the skewer point to a point as close as possible (without touching) above a major division on the ruler. Then enter a gcode command from the console to move a safe amount (start small… say 50mm, 100mm, etc) and observe where the skewer tip moves relative to the ruler’s scale.
For example, if you commanded 100mm and actually only moved 98mm and your current steps/mm setting is 80… that setting needs to be increased to add enough steps to make up the 2mm it fell short. Use the following to determine the new steps/mm setting…
(Commanded movement / actual movement) * current steps/mm setting
so, plugging in the values… (100/98) * 80 = 1.02040816327 * 80 = 81.63
Adjust the steps/mm setting to 81.63 and rerun the test… you should see very close to 100mm actual movement for a 100mm commanded move. You can do this as many times as you need to… and greater accuracy will be gained with as large a movement as your axis will allow.
I often print/engrave rulers with my machines and then visually compare them to a good metal ruler to see how well I’ve done. It’s very satisfying to know that 1" is really 1" on all the machines in my shop.
– David