Mesh settings and Rhino

Steven DAntonio · Post by **Steven DAntonio** » Mon Mar 12, 2007 1:12 pm

Lets say I have a large model. In one area it has some very small intricate curves and in another area it has some large flat areas.

If I set my mesh parameters through properties, that sets the mesh globally and I may potentially result in a huge file (in the case of the file I'm working with now I'm up to 130M.

How does the mesh settings effect the CAM operation. I know a small or large mesh isn't going to make me have any more lines of gcode. That is dependent on the surface size, tool size stepover rate etc. If however, I use a larger mesh size so that I see faceting on the computer screen, will I potentially see faceting on the actual part cut on the mill? In the extreme, if I have a 1mm ball mill and see 4mm faceting on the screed due to the meesh settings am I going to cut 4mm facets on the surface or does RhinoCAM smooth the surface? Of am I better off making the smallest, tightest mesh I can and let RhinoCAM work with that?

Thanks

Post by **MecSoft Support** » Mon Mar 12, 2007 10:02 pm

In RhinoCAM the intol/outol affect the meshing parameters. We do on the fly meshing and so the tighter these tolerances the better the finish will be - at the expense of resource usage and performance.

If you see facets on the screen using flat shading then you will see the facets on the cut part. RhinoCAM does smoothing when you do arc-fitting but otherwise it will stay true to the part you are machining.

nscott · Post by **nscott** » Wed Mar 14, 2007 10:44 am

If I could butt in on this thread...I am interested in using arc fitting to smooth faceted models. does this work the way shading does for display purposes? If the arc tolerance is equal or less than the intol would the cutting remain outside the polygon boundary?
We frequently cut polygon models of terrain on a cnc router and there are often problems with faceting. I never thought of arc fitting as a solution.

TIA,

Nick Scott

Post by **MecSoft Support** » Wed Mar 14, 2007 11:15 am

Hi Nick,
Arc fitting tries to fit an arc to successive points if they lie on an arc within the specified tolerance. So the arc will in effect go through the points are being fitted. There is no guarantee that the arc will inscribe or circumscribe the points. The only criterion used is that the points will not lie away from the arc more than the specified tolerance. (This is true of interior points as well. So if you arc fit square you will not get a circle going through the vertices.)

nscott · Post by **nscott** » Wed Mar 14, 2007 12:23 pm

I'm afraid I don't quite understand. I'll try a few examples to see what happens. thanks anyway.

Nick

DareBee · Post by **DareBee** » Wed Mar 14, 2007 1:12 pm

nscott

Arc fitting is fairly easy to visualize once you have generated your toolpath.
Linear movements are light blue in colour and circular movements are dark blue.
I like to keep loosening my arc fitting tolerances untill I see the right amount of dark blue in my toolpath.

nscott · Post by **nscott** » Thu Mar 12, 2015 1:11 pm

Just looking through old posts...
would it be possible for 3d finishing paths e.g. Parallel, to have arc fitting. They would have to be fitted outside the surface but for many of our topo models the inaccuracies of extra material left would be worth the smoother result and faster and smoother machining.
Nick

Post by **MecSoft Support** » Fri Mar 13, 2015 4:39 pm

Yes, you can fit arcs to 3 axis toolpath in the 3 principal planes XY (G17), XZ (G18)and YZ (G19).
To do this you would need to use the toolpath editor (select a operation, double click on the toolpath to launch the editor). select Fit arcs to toolpath under global edits. This feature is available in PRO & Premium configurations.

MecSoft Corporation