Relationship between cut speed and power

When trying to optimize the parameters for non proofgrade materials, I am playing a guessing game and I wanted to know if there is some math rules I can apply to hone my guesses.

Anyone have any good info on the relationship between laser power and speed? From my CNC router background, I think of them as analogous to spindle rpm and feed rate. Essentially, the two combine to give you a tool tip velocity or material removal per revolution. Depending on the material being cut, the cut depth, and the bit diameter, a combo of rpm and feed rate will give you the optimal cut. But the two parameters are related.

With the laser, is there a corollary? Is there a swapping procedure where a if you double the power, you can double the speed and get the same material removal rate and end results? Or is it a different relationship - like square or cube? And what other things should you be thinking about?

On a related note, when you switch an operation from Proofgrade to manual, there appear to be pre-selected speed and power values. Are these the actual values from the Proofgrade-calibrated operation that can be used as starting points, or are they just random values? For example, if I have my own hardwood slices, am I doing a good thing by starting with the closest species in the PG list and then switching to another material?


These are actual values that can be used as a starting point.


Moving to Beyond the Manual. The relationship between speed and power is nonlinear and varies by material - for example, you can’t cut through 1/4" material by halving the speed for 1/8" material. Careful experimentation is the order of the day.


Well, it is not linear, and I don’t think anyone has figured out the formula if there is one. Pews and zooms are like feeds and speeds in that there is a relationship. Power is proportional and speed is inversely proportional.
The best thing I’ve found it to find the most similar :proofgrade: and then make an educated guess on which way to go. After that, it is like trying to find a square root by hand. Guess, try, guess again… Go ahead and figure on wasting several square inches of any new material getting things dialed in.


And remember to write down what works for what substrate!!! (Something I keep forgetting to do…:neutral_face:)


This bears repeating. I often get caught up in the project and…


A tracking spreadsheet is a handy tool, if you keep enough information in it. These days, I never hit the little blinky button until I have all the applicable information in the sheet. (And I keep finding new things I should track.) An added bonus is I am tracking hours usage, when it was last cleaned, and how many hours remaining to the 40 hour mark. (I find some materials generate the need for a cleaning in a lot less time, though.)


Haha! I love that.

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The energy density delivered to the material will be the same, so it is a good starting point for a trade off. It won’t give exactly the same results because the time it takes for heat to spread laterally comes into play. When you go slower, with less power you might get less depth and more char as the heat applied to one area is there for longer and so can spread more.

Taken to extreme if you go very slowly with very little power you would get to a point where there is no effect at all because the heat can be conducted away as quickly as it arrives. This is why you can never cut metal with a 40W laser no matter how slow you go but you can with a 400W laser.

However since GF speed units are not really speed any more because they have an offset as well as a scale you need to convert to real speeds before you can double or half, etc.

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We sort of agreed on that a short time ago. My spreadsheet is even labeled ‘pews’ and ‘zooms’.


If you cut 1/8 or 1/4 in, slices perhaps halfway across the material or less and then mark what settings made that cut, thus you have an actual case to look at all in one place hopefully hanging in a place where you can refer to it.