HI everyone,

I am in the process of surfacing my table on my 3DRouters.com 4x8 gantry CNC machine. I went into the Rectangular pocket wizard and gave it the dimensions of the travel limits and to mill down to a depth of .01" (delta of high and low points on the table).

My question is this: It mills along just fine from the inside-out but on two corners it seems to "get ahead of itself" and runs a diagonal from say, the long travel from the X axis to the Y travel when approaching the corners. This only happens on two corners and they are opposite of each other.

It is almost like it doesn't complete the run down the X axis before it wants to run up the Y axis (as an example). Here is a crude ascii art of what I'm talking about:

 /------------------------------------------------------------------|
|                                                                                  |
|                                                                                  |
|                                                                                  |
|                                                                                  |
-------------------------------------------------------------------/

(Where the "/" are the corners being missed).

I wonder if there is something in setup (ramping?) that is set to fast?

Any and all suggestions would be appreciated

New to Mach 2 in Houston 

Is it just at the last (outside) corners or does i happen on each pass as it moves out?
 Have you checked for backlash or loosness in your y axis?
Hood

Hood,

Thanks for the help. It happens on each pass as it goes out, always on the same corners. I don't have any slop in any of the axis and the other two corners cut just fine.

What does your code look like for the corners, is it a G2 or G3? It is just that it looks like backlash on one axis and backlash would only affect two of the corners.
  What kind of size is this diagonal?  Have you tried cutting a circle to see if it comes out round or squint?
Hood

Hi Pegasus,
I don't see why It would only do it on 2 corners but with high feed speeds, CV mode and settings can cause this. Does it do it in Exact Stop Mode?

It happens when transitioning during G1 mode from a long cut down the X axis to an immediate Y cut, i.e;

G1X0Y0
G1X10
G1Y10  (arc happens during this transition)

Looking at it closer I wouldn't call it an actual slant or diagonal, It is more like a smooth arc to join the Y axis intended direction. X never fully gets to G1X10 before it begins the curve to join the Y axis.

Thanks again for your help

Have you tried it in exact stop mode. Allso, g 61 is Exact Stop And g 64 is CV.

Let me give that a shot and see what happens.

Thanks!