Close

Focus

A project log for MultiBot CNC v2

A low cost 3D printed CNC that can be built with minimal tools yet is capable of great things.

david-tuckerDavid Tucker 03/26/2021 at 01:210 Comments

I found focusing the laser to be confusing at best, but eventually hit on a bright idea.  Others have done a trick where you tilt a piece of wood at an angle then draw a series of lines at right angles to the slope.  Then by carefully looking at the lines you can work out what one is the thinest and therefore what height is an optimal focus.

I don't like this trick, it is too complicated and not very accurate.  However I decided to try a different method that seems to work much better.  I used a board at an angle and manually jogged the laser up and down the ramp while adjusting the speed/power till I only burned a line when the laser was roughly in focus.  Then by measuring the line and marking the center point I have a very precise record of the optimal focus point.  Finally I set the laser to a very low power and manually jogged it to that focus point and then measured the height to the base of the laser housing.

I came up with an optimal laser height of 15 mm to the bottom of the housing.  NEJE says 5mm is a more optimal height, so I need to play with the lenses a bit, but I will save that for another day.

Discussions