MCAM 2018 isn't posting out 3D arcs - how to do it?

[Corp6]

I am drip feeding my machine at 9600 baud, so when I am 3D surfacing, the thousands of tiny line segments cause data starvation and the machine to stutter and give jerky motion.  9600 is the max baud rate and the program is too big to fit in the control, so nothing I can do there.  I am doing curved surfaces and using surface finish parallel to make two passes at 90 degrees to each other to put a 'crosshatch' type surface finish on the part.  Problem is that the part is oriented straight, so the two surface finish parallel operations are at -45 degrees and +45 degrees - in other words, they are not in the XZ or YZ plane.

I cannot figure out how to get MasterCAM to output 3D arcs.  Is it possible?  There is an "output 3D arc entry motion" checkbox on the Arc Filter/Tolerance page, but it's grayed out.  I have the boxes checked for XY/XZ/YZ, but I see nothing else for 3D arcs.  I have the In my control definition, under the "arc/mill" tab, "all planes supported" is checked under the Helix Support section, and I have all the boxes checked for XY/XZ/YZ at the top.  I don't see anything else in this section of the Control Definition that would allow 3D arcs.  Am I missing something, or is this just not something I can do?  

Any help would be appreciated... I am essentially machining a half-egg shape, and the surfacing is the bulk of the code size, so if I can get MCam to output arcs, my code would shrink massively.

Thanks!

Mark

[huskermcdoogle]

If you aren't in XY YZ or XZ planes you can't filter for arc output.  It is possible per say to command the machine to do a "3D Arc" using three points but the filter inside mastercam and the post aren't setup to generate them.  I don't know of any way to get mastercam to do it as it isn't possible to define an off plane arc in the NCI without defining a new tool plane, or GCode class.  

The "output 3D arc entry motion" is for filtering a helical approach from point to point into a arc/helix.  It is not creating a "3D" arc.

[Colin Gilchrist]

Hi Mark,

In order to get "3D" arcs, the arc must lie in the G17, G18, or G19 plane. Simple as that. If the surface isn't perpendicular to one of these planes, you'll never get arcs.

Typically, a "3D" arc is a helix. The "circular" part of that helix must still lie inside one of the 3 planes that are planar to 2 of the machine's linear axes.

Now, it may be possible to use G68 or G68.2 to "rotate" the Coordinate System of the machine's control, so that those "arcs" now lie in the imaginary planes dictated by the G68 or G68.2 rotation, but you'd likely have to do some "fudging" to get that output from Mastercam.

[nickc]

i would try the Raster toolpath,basically a parallel finish with a arc on and off,and set your filter to create arcs in xz,yz ( g18 g19)

[Guest]

If you can share a file, someone can get a look and determine if it's settings or if it just won't happen because of the geometry