you have a material - wood or heavy cardboard, leather, acrylic, whatever and your cut did not go through, and your engrave burned. For the moment you have a lot of detail so you don’t want to change the LPI or the depth of the cut.
You can change the speed, the power (assuming the cut was not full power before), or make up to two more cuts making it 3. Which will have more effect? Which will increase the amount of burn more than help? as much as I have experimented with various settings I don’t think I have more answers.
For hypothetical example - going from one pass to two cutting power by 45% gives you the same depth but more burn, or increasing speed by 40% will give less burn but the same depth… I doubt that is true but similar idea with more accurate numbers/ percentages.
Very general rule - the longer the hot little laser beam is in contact with the material, the more material is ignited and burned away, and the more it chars. So the slower the speed, the more the burn, and the deeper it goes.
Two passes in the same place just doubles the exposure of that spot to the pew - same principles apply.
More power, more pew.
As to which is better - none of them. Use any or all at need. (My personal favorite is to just knock the speed down a little.)
Interestingly enough - this morning I had a full bed engrave - I don’t usually do them - and I had to slow down the speed to reduce the size of the engraving no-go zones to even allow it to process. Even with the overlapping cuts set to ignore it wasn’t gonna happen.
When I slow it down, I like to also knock the power back a bit to keep from charring the engraves so badly, so the two of those go hand-in-hand for me. If you’re engraving and you cut speed, cut the power back too.
As you lay out the general (cut speed means cut power etc) I get. But how much speed equals how much power. You said you usually cut speed first, but is there a point that multiple passes and lowered power would burn less? I am thinking that having time to cool might help the area surrounding the cut burn less. Or that three passes with 10% power might go deeper nut burn less than one pass at 50%.
No matter what having the laser on a point longer will cut deeper and burn more, but does that mean that the fastest speed that works at full power one pass only, is the best system?
From the standpoint of optimizing the time spent waiting on your cut to finish, yes, it’s better. It’s likely going to be quicker to slow it down by 15% and just do one pass if you almost had complete cut through than it will be to run a second complete pass.
I think the best answers are obtained by experimenting on a piece of scrap material. Then you can find out what works for you, and you’ll have it around as a reference.
Often (but not always) a fast pass (500-1000) at low power (10-20 percent) will take off much of your existing char without doing a lot to depth. So you can sometimes save that for last.
