Levelled, but still air cuts

[Mr Mayhem]

Same thing happened running the new file generation method; gcode generated using the saved log file from Linuxcnc. The error looks like 1.8mm or so. Now I am thinking to try a free version or older free version to lose this air cut bug. This time, I also tried a second time after shutting off and restarting Linuxcnc to see if the error went away. No luck. Now I am wondering what would make the cnc cut high by 1.8mm or so, for both file methods? I used a probe wire clip on the v-cutter, and the other wire to the copper on the pcb, not a probe, and I did not remove the v-cutter at any time. Probing seemed to work fine with no glitches, from start to finish.

[Mr Mayhem]

I also loaded the Autoleveler version 0.7.8 leveled gcode file into cambam and I see arcs. Is this a sign of not being processed at all? I also noticed that rather long spans (the pcb outline cuts) do not show any z variation; looking at these few lines of code that cut an outline of the board, they are the same depth as the original gcode file from Cambam, across many inches of travel in both x and y. So, maybe the code is not being chopped up and z converted at all. Just a first guess. I will try to email the original files to the developer to see if the bug can be duplicated.

[Mr Mayhem]

I may have goofed by setting the top of the waste board under the pcb to zero z in Cambam. So the top was then 1.5875mm Oops. I will reconfigure to use the top of the pcb blank to z=0 instead. That would make sense. I will try this now. I am still wondering why there was no Z correction visible in the earliest engraving cuts that do the board outline in the copper. Maybe it was out of the z correction scope in the program due to the board top being considered 1.5875mm rather than zero? I try again now with the pcb top at zero z.

[Mr Mayhem]

Ok, I fixed the air cutting issue for myself. Yes, duh, the top of the pcb (or workpiece) needs to be z=zero for this to work. And yes, the file is now tokenized and leveled, whereas before it was not, because it was out of z scope. My cnc is cutting as I type this, and it looks very good so far, not too deep, not too shallow. When I open the leveled gcode file in Cambam and look at it from the edge, I can see the z variations which look like noisy lines between the z extremes. This reveals the changes made by Autoleveler to level it. The original file is very crisp and straight. So I am happy again and making pcbs. I plan to use Autoleveler on non-conductive parts with a real probe next.

[Country_Bubba]

Glad to see that you have it sorted out. Sometimes it is the obvious that will mess us up and be easily overlooked.

Will be interested to see how your "probing" of a non-conductive material works and what your going to probe it with.

I use a touchoff pad to set my Z heights for the various work offsets as I use G54 for the top of the board and G55 for the bottom.

[daedelus]

Just to add.

You may have seen on the AL homepage my twitter feed shows a PCB I milled earlier. This looks perfect to me but what I didnt show was the failed previous attempt. The failed attempt contained a very uneven cut including plenty of air cuts. I swapped the bit because I had damaged it before and I think the tip was dirty, replaced the copper board and probed and levelled again. This time all was good. Im not entirely sure what went wrong in the first attempt but I came to the conclusion that either I messed up the probing stage somewhere or I accidentally loaded the original un-levelled file into LinuxCNC. So yes, it is not unheard of for me to do stupid things like that but I am confident AL does its job well and any errors I find are more likely to be on my part than with AL.

Great that you sorted everything though,
Happy Star Wars day all