I’ve started experimenting with 2-stage carves, and it looks like the roughing pass is carving just a bit deeper than the detail pass.
I used a 1/4" upcut for roughing, and a 1/2" 90 degree V bit for detail, both at a depth per pass of .09375. Between passes I am probing for Z only with the Onefinity touch probe.
I found a thread on Inventables that looks like a similar issue, but I did not see a definitive answer as to how they solved the problem.
Any advice on what could be causing this?
Do you have the depth of cut the same? Are you placing the probe block on the same part of the material for each Z-probe?
If I understand the issue correctly, the roughing pass is cutting a small amount deeper than the finish pass?
If yes, does the gcode for the two passes have the same Z-depth in simulation? That would separate it into a CAD/CAM problem versus a gcode sender/mechanical problem - such as what Jim asked.
-Mark
Yes, my depth of cut for the entire pocket is .05.
I am starting with the probe on the bottom left corner, probing for XYZ. After I change bits, I flip the probe over, touch the recessed side to the bit and set it on the corner, then let it probe for Z.
You can verify that the settings for the probe block are correct by probing on the underside (the recessed Z-only side) for both bits. There may be an error in the machine setup vs the block’s construction that results in a different resulting “top of material” calculation when probing the different sides.
The other thing to do is check the GCode like @YXYJack suggests to see if it’s a CAM issue.
Hi Mark - I am completely new to the CNC world. Could you explain further how I can compare the 2 gcode files to determine if they have the same z-depth?
Try a ball nose bit and see if that cleans up better than the vbit.
Blockquote I am completely new to the CNC world. Could you explain further how I can compare the 2 gcode files to determine if they have the same z-depth?
Your CAM program should have a simulation feature. I’d use it to show both toolpaths together, then zoom in on the section where you are getting a step in Z-height and see if the step is shown in simulation (you can also use a gcode viewer like ncviewer.com).
-Mark
