With Z=0 aet at the wood’s surface, why would a cut start with a rapid move into the wood?
This happened after an operation failed mid-cut. After (again) having to Retract, Extend and Tension I began the cut again. The first thing the head did was dive into the wood and start moving toward where the cut was to begin. Nothing sours a CNC experience worse than damaging your stock.
What could account for this behavior after a failed cut happened?
I’ve recalibrated my Maslow 4 in hopes that would fix things. I’ve reset Z Stop. I’ve tried to understand the Zw and Zm in an attempt to diagnose the problem. So far, nothing has solved this for me so I’m asking for help.
The same g-code cut just fine until the project stopped midway.
It was only after trying to restart the job that this problem occured.
As for setting Z, I positioned end mill on the surface and Define Z Home.
The head axis position would say it was set at Z=0 and I’d begin the cut again.
It remains a mystery to me as what you suggest are indeed the obvious causes.
Is there something wrong with my workflow to set Z-0?
It’s good to re-check your z position if you have a cut fail in the middle. I’ve had it happen more than once where after re-starting from a mid-cut fail, the z-home is off. My suspicion is that upon restart, it has forgotten where the z was when it was suddenly stopped and sets the value at something it last stored. If you don’t reset the z home then it thinks that it is well clear of the piece. If it happens again, take a quick moment and see what it says it believes the z is set to. Most likely, it will be a positive number (i.e., it believes that it is well above the work piece).
Thanks @Andith but I reset Z=0 each time.
However, you hint at something I’m suspicious about.
“Something happens” when it fails that still throws off depth of cut.
Since I still don’t fully understand Zw and Zm I was suspicious of them …
Do you understand exactly what they define? How they’re measured?
There is Z for the machine (where Z=0 is the router all the way down against the
stops). This is important for maintaining the proper belt lengths. If this is
wrong, then the belt lengths will be wrong (too tight if the machine thinks it’s
lower than it is, too lose if the machine thinks it’s higher than it is)
Then there is Z for the workpiece, (where Z=0 is the end of the bit is at the
top of the workpiece). If this is off, then the machine will not cut at the
correct depth. I believe this is stored internally as an offset from the machine
Z
I had the exact same issue and it had to do with the material and travel heights that I set in Fusion. I think what fixed it was the post processing settings was set to “G28” and it needed to be on “Clearance Height”
I am definitely not an expert. But it looks like David laid it out pretty well. When I was referring to the “z home”, I was referring to the “Z for the workpiece” as David put it.
Also, as Kyle mentioned below, it’s good to check the clearance in the CAM software you are using. I believe this is called different things depending on the software (e.g., “safety height”) and it is a height that the bit will be raised to between cuts in order to ensure the bit won’t drag along the surface.
So if Zm is zero against the bottom of Z travel (against the stops) and
if Zw is zero where end mill meets the stock surface then as the end mill
travels along Z, should Zm and Zw change in equal amounts?
For instance, if Zw is 30mm above Zm then if the end mill is raised 10 mm will
both Zw and Zm change accordingly? Zw going to 40 mm and Zm going to 10 mm? (I’d check this myself but I’ve loaned out my Maslow to a friend.)
I’d like to understand what I read for these variables in the FluidNC UI.
This is a good point and something I always take for granted.
On other CNC I avoid clamps so I leave my retract height at 0.2 in.
That said, my failed/aborted cut could have corrupted Maslow’s gcode.
I’ll look into that when I get my Maslow back. Thanks.
