Peculiar Motions

[MetalMarvels]

I have run into a minor peculiarity when contouring an arc. Create an arc some distance from the origin (any convenient distance), then transform, rotate, and copy a new arc 45 degrees from the original arc. Contour the interior of both arcs and post it with MPFAN12. On a Fadal VMC 3016L, the rotated arc will have distinct pauses as the contour is cut, the "normal" arc will cut smoothly with no pauses. As best I can determine, this is because the natural breaks in the 2nd arc (the rotated arc) are no longer at 0, 90, 180, or 270 degrees (they are shifted 45 degrees in the example given). As a remedy, I now create and rotate a point and then individually create an arc at each point. This is not a Mastercam problem per se, but the "rotated" contours were taking twice as long to cut and had a blemish where the pauses occurred. A peculiarity of the Fadal controller??? This is probably the case since a variety of post processors produced the same results (with reasonably similar code).

[KMaynard]

Have you tried using the fadal post?. also I have mine defaulted to output a G8 ..

Kev

[Guest CNC Apps Guy 1]

if you change the start/end angle or the rotated arc in Analyze do you get the dwells still?

[MetalMarvels]

If you rotate the arc start/end back to a 0, 90, 180, or 270 degree position (using analyze), the problem goes away. The problem occurs only when the start/end of the arc is at other than the 0, 90, 180, and 270 position (even a 1 degreee rotation will cause it). I have tried several different posts (Mpmaster, Mpfan, Mpfdl12, etc - had to edit the starting and ending blocks on some of the code outputs so that the 3016L didn't choke on it). The big difference is that the "normal" arc code consists of a G3, X##, I-## line followed by an X## I## and the rotated arc has a G3 X## Y## I## J## followed by X## Y## I## J## (## are the associated distances). I haven't tried a G8 move. The issue seems to be how the Fadal deals with an I/J move for a full circle. I haven't tried it on a partial arc with start/end points not at a "normal" entry angle. Hmmmmm.

[ERIC14779]

I have had a simular problem with a Techno 3 axis router that we have (it starts cutting the arc then part way thru it slows 50 to 75% of the feedrate untill it reaches the end of the arc)

this machine uses a hexadecimal code for a program. NOT G code and has a special post program that techno bundles with the version of mastercam that they OEM bundle with the machine.

this sure is wierd

[KMaynard]

The only reason I mention the G8(Decelerate off) is because G9 (accelerate off) is on by default.. I was told by the fadal applictions engineer that in this mode it will cause the control to dwell eradically in arcs .. by turning it off in the begining of the program it will prevent this problem..

Kev

[MetalMarvels]

Ahhhhhhh!! Not the first peculiarity of Fadal machines. I will check this out. According to the sheets on the Fadal 3016L, the G8 is Accelerate with no feed ramps, and G9 is Decelerate with feed ramps. I will see what this does for (or to) me. Thanks.

[Christian Raebild]

G9 mode will cause your Fadal to pause for a minute period of time at the end of each motion command (G1/G2/G3), and may also cause it to do so at the quadrant and/or octant points of a circle move (G2/G3). I believe the more recent Fadal controls can be set not to do this, but I do not remember the codes needed. You should contact your machine reseller on this point.