When trying to cut small (2mm) holes through 1/4" baltic birch, I found that they came out much smaller on the backside of the project. I tried focusing into the wood and that did not seem to help. It did work better when I focused out, or away from the wood. I used Z Offset for this layer, but the Z axis moves down, does the cut and then moves back up before moving down again for the next cut. I need to cut numerous small circles and would like the axis to move down and stay there until the entire layer is complete. Is there a way to do this other than stopping and manually lowering the bed before I run this layer?
Assuming you enable your Z axis on Edit > Device settings
You can set a Z movement on each pass here:
That was the first thing I tried. The work table moves down, the laser performs the cut for the first circle, the work table moves up while the laser moves to the next circle. Then the pattern repeats itself. Lots of wasted time with the table going down and up on each cut circle.
Okay, I whipped up a quick test on a gcode-output device. I found interesting results.
The Steps:
- In “device settings”, turn on “Optimize Z moves” in the “Z Control” box.
- Draw two rectangles.
- Set the layer mode to “Fill”.
- Set the number of passes to “2”.
- Set the “Z step per pass (mm)” to something – I chose “7.00” to make it easy to find in the gcode.
- Set the layer to “Fill all shapes at once”.
- Save the gcode.
The Z moves in the gcode are optimized, with a first pass, a Z move, a second pass, and a Z move to restore the original Z. - Change the layer mode to “Line”, leaving everything else the same.
- Save the gcode.
The Z moves in the gcode are not optimized, with the first shape having a first pass, a Z move, a second pass, and a Z move to restore the original Z before moving the to the second shape and doing it all again.
So, it appears that it optimizes Z moves for Fill mode, but since Line mode doesn’t have an equivalent to “Fill all shapes together”, it doesn’t optimize the same way. The only way I can think of to do it is to duplicate the Line mode layers and have each with its own Z offset.
(If you have “Optimize Z moves” set and two layers each with their own Z offset, it does give optimized results – basically, it’s using layers to do the equivalent of to fill mode filling all shapes at once.)
This is well known and discussed behavior among regulars. Whether it’s intended, unintended, or a bug is (to my knowledge) unknown to the masses.
The easiest and cleanest workaround is to clone your cut layer into multiple nearly identical copies with the exception of the Z offset. Done this way, it will cut one pass on all shapes within the layer, move z, repeat all cuts, move z, etc. I use this technique when appropriate and find it quite beneficial. You can also save the specifics to your material library for easier setup in the future.
To my knowledge, majority (or entire) credit for this game-changing technique goes to @parsec.
An example I made:
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