Z axis skipping

I am having a problem with the Z axis skipping during 3D contouring. It doesn't lose count but doesn't keep up with the motion of the X and Y axis. I am using V3.5.1 software with NC code generated from MasterCAM. The machine is a newer PRS Standard. I have tried taking the feedrate down to 40IPM/.66IPS and still have problems. If I run a contouring routine where I am stepping down and running just the X and Y axis it makes a perfect cut at speeds up to 3IPS. The slides on the machine are clean and there doesn't seem to be any binding or roughness.

Any Ideas?

Type in VR to SB3. Post a pic of the values you are currently running. Also, tell me what the Move Speeds are for this file - EG MS,2,1

You can easily get a snapshot of the VR screen by holding down the Alt key + Pressing 'PrintScreen' key. Then open up your favorite photo editing software (or MSPaint) and paste it in as a new image.

-B

I am running the G-Code directly as a .nc file.

Here is the screen shot of the setup. Standard as I haven't played with it.

Attachment 9312

Bump. Anyone have any ideas

Frank,
The relation between the XY speed and the Z speed is important when cutting 3D reliefs. The intricacy of the design & level of detail you need to pick up, will ultimately set the 'speed limit' of the tool when cutting. Smaller and more intricate designs (that maybe have a background texture etc) require slower speeds than larger smooth/undulating moves. If nothing else, it is a matter of physics as to how fast the Z axis can move up & down - carrying the weight of the spindle/router.

Here are a few XY,Z speeds that I have found helpful for cutting most 3D parts:
1,0.5
1,1
2,1
3,2
5,3

It is important that you be realistic about the speeds you select, as you must consider what you are asking the tool to do. A speed of 5,3 is not going to be good on a 3D relief that is only 3" in diameter.

In regards to your VR settings, try adjusting the following, which should give you a smoother running tool under all conditions:

Change the 3D Threshold to 150 - This will reduce slowing/ramping in 3D
Change Slow Corner Speed to 45
Change Min Distance to Check to .08
Change Fast Stop Threshold to .8
Change KeyPad Ramp Rate to .2

The last 2 settings only apply to keyboard mode. Drive the tool around in Keyboard mode - Note how much more responsive & smoother it is.

Try messing with the speeds listed above for 3D cutting. One of these combos will get you in the range for what you are cutting.

-B