faceting on machined surface

[ScottC]

Hi Guys,

Leaning Gibbscam and I've run into a problem I cant solve using the manual...
Im cutting a test program of a hemisphere (30mm in dia) and the cut surface off the mill is faceted. The part surface in gibbs is very smooth (imported parasolid file out of Inventor) but the facets show up in the cut part render when the stock is cut.

Im running a surface flow cut as the finishing pass after a contour rough, Im sure there is a global tolerance setting that im missing, but every tolerance box I change ends up with the same result..

Any advice?

regards,

Scott

[txcncman]

Just because it is showing in your computer graphics to be faceted does not mean the G-code produced will make a part that is faceted. Most likely the problem is your graphics card. Check the software requirement against your hardware.

[Species8472]

Also take a look at "Flash CPR Settings". "Cut Part Chord Height" and "Body Chord Height" Be aware that as you reduce these settings it will require more and more resources to render the cut but will smooth the rendering.

[ScottC]

Thanks Guys, but the faceting is actually coming out on the part when I machine it, identical to the facets showing in the cut part renderer....

[txcncman]

"facets show up in the cut part render". That is graphics.

Ok, now we have to look for smoothness and resolution settings. I will come back and check into it after dinner.

[ScottC]

Yep, im following you now. Species mentioned chord height settings which I recall reading about in the manual somewhere. Ill post up a pic of the cut part shortly. Thanks for the help.

Scott

[txcncman]

Ok. I have GibbsCAM 2004+. I built my own. Here are a couple of screen shots. 001 is the settings. 002 is the render.

[ScottC]

Struggled to take a clear picture, but you can see some of the faceting artifact near the light reflection. Im doing a contour rough followed by a finish contouring path in the surfaces tab, not a lace cut. Out of interest, how woud you guys aproach roughing and finishing a pocket? Contour or lace?

Scott

[txcncman]

As you should be able to see in my sample (done in inches, not mm), I used the Lace method with no apparent faceting in the render.

For pockets, depends on the final results needed and the surfaces involved. As you can see with your sample, the render graphics must be pretty accurate. Why GibbsCAM would cut this part this way, I have no clue. But it seems from your sample that WYSIWYG.

I hope this helps you find the answer to your problem. If not, post back here and we can explore other possible solutions.

[blowlamp]

It looks more like a coarse .stl mesh file than a nurbs solid or surface to me.

Martin.

[ScottC]

Attached is the solid file I'm using to generate the toolpaths. (Parasolid exported out of Inventor).

[ScottC]

Hey All...

Found the problem... I added an extra zero to the global tolerance settings AND THEN re-processed the finishing path and all the faceting has gone.

My mistake was that I didnt re-process the finishing path after changing the values, for some reason I thought it would automatically update but in hindsight...

Ill recut the path shortly and post the results...

Thanks for the help

Scott