Step by step
Set the power and speed for a material
Numbers you measured on the material in front of you, instead of numbers somebody posted about a different machine.
Before you start
Anybody cutting a material for the first time, or getting different results from the same settings as last month.
- An offcut of the material, about 100 mm square.
- The machine warmed up, the lens clean and the focus set.
Understand what the two numbers do
Power is how hard the beam fires. Speed is how fast the head moves. What actually decides the cut is how much energy lands in one place, which is power divided by speed.
That means the same depth can come from high power moving fast or low power moving slowly, and the two are not the same. Slow and gentle burns a wider, browner edge. Fast and hard cuts cleaner but is less forgiving of a sheet that is not flat.
Set the focus before you set anything else
A focus that is out makes every reading wrong in the same direction, so you will end up with settings that are compensating for it. Then you fix the focus and nothing works.
Run the focus test first. It takes one small piece of scrap.
Burn a grid, do not guess
The material test grid cuts one small square at every combination of power and speed you give it, on the material in front of you. Give it a range either side of what you think, not a range around what you hope.
For 3 mm ply on a 60 watt machine, 40 to 80 percent power against 8 to 20 millimetres a second is a sensible first grid.
Read it with your hands
Turn the piece over. The squares that fell out cut through. Of those, take the one with the fastest speed and the least brown on the back, because it is the fastest clean cut, not merely a cut.
If nothing fell out, the whole grid was too gentle: raise the power range or lower the speed range and burn another. Do not add passes yet.
Write it down where the next person will find it
Save it against the material name, and it is offered the next time anybody picks that material on that machine.
Say what happened after the job too. A setting that worked in January and is marginal in June is a tube getting tired, and you only see that if somebody recorded both.
Every setting, and what it does
10In the order you meet them. The second line on each is what goes wrong when it is set badly, which is usually the more useful half.
The gentlest setting in the grid, as a percentage.
Starts at 20
The strongest setting in the grid.
Starts at 80
Power steps across the grid
Starts at 4
The slowest pass in the grid. Slower burns deeper.
Starts at 10
The quickest pass in the grid.
Starts at 100
Speed steps down the grid
Starts at 4
Size of each test square (mm)
Starts at 10
Gap between squares (mm)
Starts at 3
Left edge (mm)
Starts at 10
Top edge (mm)
Starts at 10
How to know it worked
- The square you chose fell out of the sheet on its own.
- The back of that square is barely marked.
- The same settings cut a second piece of the same sheet the same way.
When it goes wrong
4Nothing on the grid cut through.
The grid was too gentle, the focus is out, or the lens is dirty. Check the focus and the lens first, because a grid burnt through a dirty lens teaches you nothing.
It cuts through but the edge is very brown.
Too slow. Take a square further along the speed axis that still fell out, and check the air assist is actually blowing.
It cut yesterday and will not today.
Same material, different sheet, or a tube that has aged. Burn a small grid again rather than nudging the old numbers.
Can I just use the settings from a forum?
As a starting range for the grid, yes. As final numbers, no: they were measured on a different tube, a different lens and a different sheet.