Tool path not following selected geometry

[Anonymous]

Hi everyone,

Having a little trouble with a contour toolpath that doesn't seem to be following the selected path accurately.  Please see screenshots below.  You can see that the toolpath line seems to stray away from the middle arcs in the middle of the seat shape.  Is this happening cause I'm doing something wrong or there's a setting that needs to be changed?  Thanks for any help you can provide, project file is attached.

[HughesTooling · Accepted solution]

I've seen this before where there seems to be a problem using an edge of a solid constructed from a conic spline. A workaround is to use a sketch instead, here's what I get after projecting the bottom face to a sketch and then selecting the sketch profile, image shows both toolpaths.

file attached

Mark

[Lambodesigns]

Seems as if several of us are having this issue and it seems to come from using a conic curve. I've tried other curves/arcs/etc that seem to work ok but not a lot of testing.  Selecting the sketch might help with a 2d operation but using a 3d operation gives you a bad tool path and not sure how you get around it other than using a different type curve since selecting the sketch isn't an option.  Large curves are easy to detect because they are so far off but mild ones may not be detected by someone.  I also exported a dxf from a file I was having problems with so no CAM was involved and the dxf matched the tool path so it looks like a CAD issue and not CAM related.  

Link to an additional thread I first found researching the problem:

http://forums.autodesk.com/t5/cam-discussions/tool-trajectory-doesn-t-match-contour-selected/td-p/62...

[HughesTooling]

I've only seen this on 2d, here's the file above done using the 3d op Contour, as you can see it works OK off the 3d model. The only place I've seen this as a problem is picking edges for boundaries. Have you got an example where a 3d op produces the wrong toolpath.

Mark 

[Lambodesigns]

Mark,

Thanks for the relplys.  I didn't save it but I did a simple 4 sided sketch (one side a conic and 3 straight lines) and then pulled it up a bit and put a 1/4" radius on the top for a test the other day.  Then applied a parallel 3d operation seleccting the bottom contour and it seemed to follow the same toolpath as the 2d contour.  I idid the same thing using a spline and it seemed to follow the right contour. Not a lot of testing but it did seem to have issues in 3d mode and since it should be fixed in 2d mode I didn't look at it much but made a note to myself to never use a conic curve for anything until it is fixed.  I'm tied up with work today so I won't have any time to play with it until tonight.  I also haven't done a lot of 3d CAM so I may have just been looking at it wrong but the toolpaths between the 2 different paths did look diffenet to me.  

Regards,

Jim 

[Lambodesigns]

Turns out I hadn't saved the file but it was still up on my engraver pc so I saved it off.  I've tried to attach the file so hopefully that will work to show what I'm talking about.  Basically, I just did two quick sketches with the first having a conic and the second having a spline.  I think the toolpaths should look similar as I attempted the same 3d paths on both of them.  Again... I'm a rookie at this and could have done something wrong but with my limited knowledge it looks to me like there is a difference in the 3d  paths between the 2 with the conic looking odd.    

[Lambodesigns]

Here's a quick screencast to show what I'm seeing when I look at it.  

[Anonymous]

That did the trick Mark, thank you! I'll either use that trick or avoid conic curves all together for now after reading some of the other problems folks are having. Do we know if the Fusion team knows about this issue as well?

[HughesTooling]

The problem you see with the toolpath in your screencast is because you have not selected the model\body in the set up. You need to always select the part or parts you're machining in the set-up or you'll get unexpected results!

The only problem with the 3d is with boundary selection, the toolpaths are correct you just might have problems containing the toolpath to the correct area.

Here's the 3d and 2d toolpaths.

File's attached.

Mark

[Lambodesigns]

ahhh... now I see what you mean by selecting the model in setup.... my version of selecting it and the right way were not one in the same.

The boundry setting... pretty obvious now that I see it and what it does.   The more I use 360 and see what it does the more I'm impressed with it.  Of course, I still think they should fix the conic issue in 2d though:)  Thanks again for your help and not sure how any of us rookies would ever get past the frustration of figuring out all the little things that make it all work without forums like this and the experts that keep us going.   If you're ever in Steamboat give me a yell and I'll buy you a beer.... speaking of beer... I need to get to work.  I'm building benches, tables and bar top for a new brew pub that is going in just down the street from the house.  Should be pretty cool when it is all done.