Anomaly in STEP file

[billostratum]

I have an .stp file, exported from Rhino and opened in Fusion.

There is one surface that appears to be completely flat, but Fusion finds one portion of that flat surface that is at a different height than the rest of the surface, by a millimeter or so. Only this bogus portion is at the proper height and the rest is higher.

I've used an extreme Adaptive toolpath to illustrate the section. Pocket clearing results in the same pattern.

I've looked at the original Rhino wireframe and don't see anything that could possibly be related to this oddly-shaped section.

I've included a simulation result highlighting the properly-milled odd section in green (and the rest of the same, flat section still in blue).

Any ideas about how to investigate or repair this section or work around it somehow (i.e., to mill the higher part that is remaining too high).

Tia,
Bill

.f3d attached

[HughesTooling · Accepted solution]

I think the problem is you have the top height set to stock top and the fine stepdown set to 5.5 so the height you get the toolpath is governed by the stepdown from the top. If you edit the bottom height and set it to selected and select the face you want to machine it produces the toolpath on the face. You could use Flat Area Detection but that will take longer to calculate rather than just selecting the bottom height.

I should also point out select just the face under model could be a problem as Fusion will ignore the rest of the model. On this fairly simple part you get away with it but if there were islands in the way Fusion would just put linking moves through the model. You are safer to select a boundary curve to restrict the area for the toolpath and leave the whole model selected. See attached file with the bottom height set to the face and the boundary selected to restrict the area.

Mark

[HughesTooling]

@billostratum Are all the surfaces supposed to be at the same level? 

The biggest difference in height I can see is only 0.031mm (the long surface in the middle), some are at the same level and the big surface on the other side is only 0.004mm out.

[billostratum]

Thanks. That worked.

It is still a little worrisome that a random shape somehow appeared on the surface of my flat.

[billostratum]

Yes. The surfaces are supposed to be at the same level, and will be in our final model.

Thanks for the illustration of the utility of Measure. I'd been trying to make that work for me, without much success. Your example was great.

Bill

[billostratum]

@HughesTooling 

Because you nicely suggested a couple of options, I decided to use this as a case study.

First I increased the Fine Stepdown so I could easily see only the problem areas.

My original toolpath is obviously bad. Your suggestion to select the Bottom as the flat area worked perfectly.

I tried a variety of parameter changes to see if anything else worked. The only other option that worked was to set the option to Machine Shallow Areas to True.

The Flat Detection option produced a really odd toolpath and was not quite right.

Bill

Below are the original Bad toolpath and the Machine Shallow toolpath.