Calculating Proper Laser Z Height


(Eirik H) #1

The preface to this is, I recently purchased a Red & Black ebay 100w CO2 laser (ruida) but when the package arrived it didn’t come with a z-height guide.

To calculate the z-height I used a thin piece of balsa wood 1/8" thick and then using calipers moved the laser down starting at 20mm and incremented down in 1mm segments and cut a square 20x20mm and a line 30mm long. I then reviewed the cut and measured the kerf. I ran at 55% power and 25mm/s this might not be optimal power and speed but since I kept it the same across all tests I feel it provided consistent benchmark.

Based on my testing it appears that about 6.5mm is the optimal position for z-height above the piece.

What I am curious about is;

  1. Was this be the appropriate methodology to accomplish this or is there a better way?
  2. Is there any settings in the DSP that could have provided me with information? I looked and found none, and the “manual” didn’t even cover z-height.
  3. Based on your experience does this sound to be around the correct height?

Thank you for taking the time to read and respond.


(Isaac Barbary) #2

A good way to sort this out is a technique known as a Ramp Test. Whether 6.5mm is a good height or not depends on the focal length of your lens and the length of the laser head cone.

Tech Bravo’s Laser Focus Ramp Test


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(Eirik H) #3

@chaoticmind, I took a quick peek at the video and ran a similar test as described. It appears I was right in the ballpark give or take .5mm. Thank you so much.

Now I just need to make my tip-up gauge and I should be rocking away.


(Isaac Barbary) #4

The way you went about things will certainly work but the ramp test is a lot easier and faster.


(Eirik H) #5

Yeah I see that now. Using the method you provided on getting the correct height has gotten me down to a 0.25mm kerf for cutting acrylic.

Thanks again.