Mastercam toolpath not following radius

[Swamer]

Why doesn't the cutter path follow the geometry as drawn? All other radii in the same file work OK. See attached pic.

[Oscar R.]

Swamer, it's really hard to tell from your picture what is what. Is the blue rough tool or your part, or vise versa?

 

From what I see though, you may just be seeing a graphic error.

[Swamer]

The cutter path is created by 4 straight lines as it makes the radius. When I backplot and step through the path, each straight line is clearly defined as it makes its way around the radius (but not following the radius with an arc). I have redrawn the radius and still have the same problem. Sometimes it even makes one straight line out of it, ignoring the radius completely by going from the end of the line prior to the radius to the start of the next line.

[gms1]

That could be any number of things as its hard to tell from looking at that pic.

 

Did you cut your part and the results were poor? Are you just zooming way in and seeing poor mismatch from loose screen tolerance settings? Is that trying to cut lines without filter settings turned on?

 

 

edit:: geez im slow! posted after

[djstedman]

Looking at the pics that's a VERY small radius.. I am just guessing since I haven't seen your settings but my thought would be that that is being caused by your Arc / Filter tolerance being too large.. if the filter setting is larger than the radius you are trying to cut it will turn it into a straight line..

[Colin Gilchrist]

All cutter paths in Mastercam are linearized during toolpath creation.

 

You need to enable the "Filter" in the toolpath. This has options to "fit arcs" to the toolpath. My guess is that the Filter is not even enabled here.

 

I recommend enabling the Filter on every toolpath you create.

[Swamer]

When I chain another arc on the part (of the same radius (0.415mm)), it works fine. This particular radius is the only one out of 4 identical radii that has this issue.

G20G0 G17 G40 G49 G80 G90T1 M6G0 G90 G54 X.6581 Y-.196 A0. S8556 M3G43 H1 Z.3602M8Z.3102G1 Z.0402 F6.2X.6195 Y-.1416X.5952 Y-.1279X.5642 Y-.1256Z.2402G0 Z.3602M5G91 G28 Z0. M9G28 X0. Y0. A0.M30

[Guest]

If you analyze it, is it a spline or an arc?

[Swamer]

It is an arc.

[Oscar R.]

If you analyze it, is it a spline or an arc?

That's most likely the case, I think.

Filter would absolutely help. Sometimes I will even go so far as to make my own three point arc from the spline in I feel I need to.

 

Filter, filter, filter.

[Oscar R.]

Also might want to check to make sure that your don't have overlapping entities right there.

[Colin Gilchrist]

Try changing your Analyze Precision to 6 decimal places. My guess is that your arc endpoint does not quite lie on the machine grid, and the rounding is causing the arc to be linearized.

[Swamer]

Thanks for the ideas everybody. A friend suggested that I try the following and it worked.

 

Project all geometry to zero. At this point what had previously been the problem arc became a Nurbs Spline.

Edit, Simplify all geometry to 0.00002.

The Nurbs Spline was converted back into an arc and the cutter path now follows it nicely.