I've encountered a Z-axis problem that I can't seem to make go away. I'm running a Buddy BT32 using a PC router. The spoiler board has been resurfaced. All the electronics have been shut down, unplugged and restarted. And the problem remains.

I'm cutting a 3D model from Vector Art. I've setup the model to be, at most .46" at its deepest point in to the material. In Partworks 3D I established the top surface of the materials as the z-zero location. I've gone through the rough-cut SBP file and seen the Z-axis commands and they are correct.

Here comes the part that's driving me crazy. I've run the same SBP file 3 times on an MDF sheet (don't want to ruin perfectly good wood) and the z-axis actual depths are different (but consistent) from the commands in the SBP file. All electronics were turned off and unplugged between each test. X,Y,Z axis points were set to the center of the material at the surface of the material.

The table below has the SBP file depth command, the actual cut depth, as measured by dial calipers, and the depth difference.

SBP file Actual depth Delta
-0.125 -0.15625" -0.03125"
-0.25 -0.3125" -0.0625"
-0.375 -0.46875" -0.09375"

It seems that the deeper the programmed cut, the greater the delta in depth of cut.

I reset the z-zero to 0 at the surface of the material I'm cutting, in this case the MDF sample board. My process is to use the keyboard control to lower the router until the tip of the bit just touches the surface of the material. Then I use the menu option to set the z-zero. I get confirmation of this action by the fact that the Z setting on the ShopBot control program resets to 0.

If any one has suggestions on eliminating this problem I would greatly appreciate it. I can send SBP files if needed.

Thank you,

Don Thomson
Diamond Lake Custom Woodworks, LLC
www.diamondlakewoodworks.com