[Donkey Hotey]

I was struck by the appearance of what appears to be triangle facets on the surface of your part. Did it really look that way, or is that a camera/pixelation phenomena?

No, that's exactly what I was pointing out. That was Mastercam's surface tessellation and the VF-2 cut it so accurately that it was visible in the final product. Remember that this was with straight line cutting paths.

The trick is that with the arc substitution, it turned those straight lines into smooth curves. Without short line segments, the facets are impossible to recreate so you get a more natural looking surface.

Haas applications manager John Nelson has explained several key points much better than I could here:

That was a very good link. Thanks for posting it. It's been awhile since I read that. It is a good primer on what affects surface finish.

[HuFlungDung]

Ok, so now I've seen the effect of surface tessalations Your machine must be really tight to make those show up that clearly.

Because I use OneCNC, and it uses NURBS as a basis for surface toolpaths, the facetting I have seen is more....chordal in nature, and is never triangle shaped. Guess I haven't been around this biz long enough to see everything, but this helps. Thanks for the info

It would be interesting to compare the program length and smoothness of the same part under both types of CAM systems, if one had the time and inclination to make the comparisons.

[Donkey Hotey]

Ok, so now I've seen the effect of surface tessalations Your machine must be really tight to make those show up that clearly.

The machine had about 100 in-cut hours when that was taken. I don't use it for production yet. It's essentially new.

I'm not sure about the basis of Mastercam surfaces. It might convert them to some other form depending on the cutter path method chosen. I can tell you that it was actually kind of neat to look at the whole surface with those little triangles all over it when it was done. Yeah, I was impressed by it too, even though that's not what you want in a finished product.

When I changed to arcs, the effect was different. I got what looked like a fishing net, with rounded contours. It still had some lines running vertically. I assumed they were from the cutter rotation.

[ktm666]

tighten the calculation tolerance of your toolpath in mastercam and those triangle will get less noticeable. I've not used mastercam, but changing the tolerance in WorkNC from .005 to .0002 makes the path much more fluid on a HSM equipped HAAS. The toolpath will take longer to crunch but on a finish path its needed.

also. rough your parts with G187 P2, which will speed up the machine through all of those "tiny line segments" and make finish passes with G187 P3.

adding G2 and G3 can be a bad move if your going for absolute dimensional accuracy.

another way to get rid of the triangles is to use different software like CAMTOOL. it cuts to the surface, not a projected mesh. its expensive though, and not needed for most stuff.

Also, the spindle rpm is not the only, or maybe not even the most deciding factor in surface finish. spindle growth, machine rigidity and other factors play a huge role.