Problem- Elipse edge not smooth

[Mikeee]

I'm trying to determine what would cause an elipse edge to not be smooth. Tested with various size circles and edges are smooth but trying to cut an elipse the top/bottom or large radius of the elipse has obvious steps in the curve. Is this caused by the cam software? Or hardware? Tried drawing an elipse in ViaCad and Vectric Cut2D with the same result. The gcode generated by Vectric is many short lines rather than a series of arcs to create the elipse. Could someone point me in the right direction to solve this problem? I don't think Mach3 is the source of the problem.

[ger21]

I just checked in Aspire, and it looks like Ellipses are output as a series of short straight movements.

In Aspire, I can fit arcs to the ellipse, which gave me G2/G3 moves. But, I don't think Cut2D has this option, though.

Another option is to find a CAD program that can draw an ellipse as arcs, and import it into Cut2D. I can do this with AutoCAD.

[Mikeee]

That makes sense. When drawing the elipse in ViaCad the same steps are visible. Cut2D has an elipse draw function but it doesn't use arcs. I'll have to look for another CAD/CAM program to generate elipse gcode with G2/G3 moves.

[Andre' B]

Every CAD program I have used provides some way to specify the number of line segments or the length of the segments or a max error that the line segment can get from the curve.
I other words figure out how to get more (shorter) lines.

[christinandavid]

If the effect is more on the stretched radius it sounds like the software is working in fraction of a degree increments (the same way you would program an ellipse at the controller).

Unless you have a very fast/feedrate limiting controller then smaller moves/usin arcs could have an adverse effect at the tighter squashed radius, with the machine pausing once in a while so the controller can catch up.

Saying that, the controller will process an offline program faster than an online one...

DP

[Mikeee]

ViaCad 2D has settings in the Dimension area for Angular and Angular Tolerance. I've changed them to 00.000 instead of 00.0. There doesn't appear to be a setting for length of line segments or max error of line segments. I have an autocad dxf of an elipse that when processed by Vectric Cut2D it generated gcode with G2 commands. With the change in ViaCad tolerance Vectric Cut2D still generates a series of lines instead of G2/G3 commands. The edges are much smoother though with these changes. It appears that I need to change CAD programs to get Arcs instead of lines. Vectric Cut2D will generate the arcs if the elipse is drawn using arcs.

[ger21]

What size Ellipse do you need? I can whip one out in a few seconds.

[Mikeee]

Thanks for the offer. I cut some templates this evening using the new dimension settings in ViaCad 2D and each elipse was real nice and smooth. Just as they should be.

[Mikeee]

Thanks for the offer. I've cut a few elipses this week with the dimensional changes in ViaCad and the edges were nice and smooth. Still cut as multiple short lines rather than arcs. The bottom line is the machine did exactly what it was told to do. The operator (me) was the problem.

[skmetal7]

I have this problem too. I use Pro/engineer and when doing splines or curves in the z axis I get a bunch of lines. I export in .iges, or .stp. I use mastercamx to gen toolpath. I've tried making mastercam do arcs but still outputs lines. Haven't seen any settings in Pro/e to change line size.

[crane550]

Could you please provide a photo? Chatter and backlash show up most on your corners and ellipses. You might be dealing with one of those issues.