Tolerance settings for surface finishing in Fusion 360??

[aarongough]

Hey all!
For the longest time I thought that my 'old' Fadals simply weren't capable of creating really high quality surface finishes, I would always get small inconsistencies in between passes when doing a finishing toolpath, and that would leave divots and so on that I'd have to hand finish out...

However I recently found out Fusion 360 does not create toolpaths directly from the solid model, instead it creates a mesh of the model first and then makes the toolpaths from that. Apparently this is fairly common with CAM software, I just didn't realize that was how it worked...

After that revelation I started paying a lot more attention to the 'tolerance' setting in the Fusion toolpath dialog as it directly impacts how finely the mesh is generated, and found that setting it to very small values (0.00001mm) drastically improved the quality of my surface finishes, at the expense of much longer times for computing the toolpaths.

Just today I found out that Fusion has a bunch of 'hidden' tolerance settings that can be accessed by right-clicking on a toolpath and then choosing 'compare and edit' and filtering the parameters by 'tolerance', which gives you this:

Some of these I understand:
Surface Triangulation Tolerance - Maximum error between generated mesh and solid model
Contour Linearization Tolerance - Maximum error between contour and generated linear segments
Smoothing Tolerance - Maximum error allowed when fitting arcs to generated mesh

However I have no idea what the 'Chaining Tolerance', 'Thinning Tolerance' and 'Calculation Tolerance' settings do, and it seems that they are not documented officially anywhere which is frustrating.

Does anyone have any tips/tricks/experience for utilizing these settings to produce really high quality machined surfaces? My application is similar to mold/die work where I'm hard-milling and need to produce REALLY high quality surfaces with minimal error in order to reduce/eliminate the need for hand/bench work.

I am happy for a toolpath to take hours to generate if that's what it takes to get the results I need!

Any and all input greatly appreciated!

-Aaron

 

[hahn_rossman]

Hey all!
For the longest time I thought that my 'old' Fadals simply weren't capable of creating really high quality surface finishes, I would always get small inconsistencies in between passes when doing a finishing toolpath, and that would leave divots and so on that I'd have to hand finish out...

However I recently found out Fusion 360 does not create toolpaths directly from the solid model, instead it creates a mesh of the model first and then makes the toolpaths from that. Apparently this is fairly common with CAM software, I just didn't realize that was how it worked...

After that revelation I started paying a lot more attention to the 'tolerance' setting in the Fusion toolpath dialog as it directly impacts how finely the mesh is generated, and found that setting it to very small values (0.00001mm) drastically improved the quality of my surface finishes, at the expense of much longer times for computing the toolpaths.

Just today I found out that Fusion has a bunch of 'hidden' tolerance settings that can be accessed by right-clicking on a toolpath and then choosing 'compare and edit' and filtering the parameters by 'tolerance', which gives you this:

Some of these I understand:
Surface Triangulation Tolerance - Maximum error between generated mesh and solid model
Contour Linearization Tolerance - Maximum error between contour and generated linear segments
Smoothing Tolerance - Maximum error allowed when fitting arcs to generated mesh

However I have no idea what the 'Chaining Tolerance', 'Thinning Tolerance' and 'Calculation Tolerance' settings do, and it seems that they are not documented officially anywhere which is frustrating.

Does anyone have any tips/tricks/experience for utilizing these settings to produce really high quality machined surfaces? My application is similar to mold/die work where I'm hard-milling and need to produce REALLY high quality surfaces with minimal error in order to reduce/eliminate the need for hand/bench work.

I am happy for a toolpath to take hours to generate if that's what it takes to get the results I need!

Any and all input greatly appreciated!

-Aaron

Aaron-
I'm a fan of your work!
Autodesk has some blogs about trying to achieve better surface finishes:
Hey Machinist! So what smoothing and tolerances should I use for my machine anyway? - Fusion 360 Blog
I'm curious about whether you have smoothing turned on or not for your surfaces?
And 'çhaining' tolerance is probably how well curves meet in the model.
John Saunders has this:
List of Fusion 360 CAM Parameters, Expressions & Formulas - NYC CNC
Which probably came from here:
CAM Expression Variables in Fusion 360 | Fusion 360 | Autodesk Knowledge Network
Siemens defines chaining like this:
Provides for the chaining of objects which do not intersect or do not have end points which are coincident.
Which makes the most sense to me.
Keep up the good work and let us know which tolerance helped with your toolpaths.
Hahn Rossman

 

[triumph406]

In Surfcam if cutting 2D splines you adjust the Curve Tolerance, .001" would give you a segmented finish depending on the curvature, that's what I would use for roughing. For finishing I might change to a curve tolerance of .0001" or .00005". That gives a much finer finish, a much larger file size, and in the case of my Makino it'll mean I might be limited to 25ipm to avoid the machine hesitating.

For 3D surfacing SurfCam has a setting for surface tolerance, again finer values give a better finish.

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For the parts you do the CAM program should generate the gcode in a matter of minutes regardless of how tight you set the curve/surface tolerances

 

[couch]

The biggest one is changing the triangulation tolerance to something way smaller. Instead of tolerance*0.5 make it tolerance*0.05 or tolerance*0.005, or whatever. As far as I understand it, it will create a much finer tessellated model on the back end and almost always results in a much smoother surfacing toolpath. Just takes longer to generate.