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2D pocket generates different tool paths for the same parts

Message 1 of 9
228 Views, 8 Replies

2D pocket generates different tool paths for the same parts


I'm trying to pocket out the parts as shown above.  I'd prefer to use the slot operation, so that is does it in one pass, but that fails to generate a tool path when your slot has any intersections in it (At least that what I think from my testing of the slot operation).


If I use a 2D pocket operation (with zero stock to leave) I get partial tool paths on each part. All of the slots are atleast the width of the bit. There are only two parts in this design (as you can see in the browser) and they are linked parts so they are identical and yet the generated tool path is different for each part.

The above generated tool path has the geometry selected with pocket selection and "Select same plane faces ticked".



I can get closer to the correct tool path if I select the four geometries as open chains like this 


but this still leaves out part of the tool path for the operation on the right most piece and doesn't fully run the slot to the end for the 1st and 3rd piece.


What I can't work out is why it generates the correct tool path on one instance of the part but not the others.  I know I could hack around it by reducing the size of the bit until it generated the path, but that doesn't alert Autodesk to the 

issue.  It would also be nice if the slot operation could somehow handle the T junctions, so that I didn't waste all the time with the two passes in each slot as it comes back along the opposite edge.


Message 2 of 9

Update: If I try to machine this pocket using the contour operation I get the following tool path.



And I cant select the last remaining material as an open chain contour, because as soon as I select the contour (you cant see the cursor in the screen grab but I'm selecting the contour where the red arrow is pointing).  It selects all 16 contours (at the bottom of the pocket) even though open chain is selected (as shown in the green circle). Also doesn't matter if I click the contour again (like you used to have to do to create an open chain) it keeps the 16 edges.


Screen shot before selecting the single contour


Screen shot after selecting the single open contour at the position shown by the red hand drawn arrow in the previous screen grab.




Message 3 of 9

Would you be able to share your Fusion file here?
File > Export > Save to local folder, return to thread and attach the .f3d/.f3z file in your reply.

Seth Madore
Customer Advocacy Manager - Manufacturing
Message 4 of 9

Sorry, I thought I attached the file when I posted.  I did export the file at the time I made the post, I'll attach the file tomorrow. 

Message 5 of 9

File Attached now.

Edit: Linked files also attached.

Message 6 of 9

When using a tool that is the same size as the slot/pocket to be cut, it's always a crap-shoot as to whether you have success. If you either slightly reduce the size of the tool or add a bit of negative stock to leave (in this case, it was -.001mm), you'll get this:


Seth Madore
Customer Advocacy Manager - Manufacturing
Message 7 of 9

Yep, the negative stock to leave does make it generate a tool path that will remove all the material.  Unfortunately everything is cut twice as pocket is now .002 mm bigger than the tool, which doubles the time it should take. The cut along the return edge does nothing and is a waste of time. It would be nice if the pocket operation was smart enough to know if the slot is the same size as the bit to only cut it once. (sort of like a slot operation)  Or alternatively have the slot operation handle slots with Junctions, then we wouldn't have to use a pocket operation. 


Maybe a checkbox could be added to force the pocket operation to only do one pass if the return pass is less than 0.XYZ mm from the previous pass along the opposite edge.


It could be done in a single pass using an open contour operation if the open contour selection worked correctly.  With this model the open contour either has no edges or 16 edges, nothing in between.  I'd even call this a bug that should be looked at.

Message 8 of 9

No, it's not a bug. The Pocket toolpath simply doesn't work well with features that are the same size as tool. Since we calculate geometry to a fixed tolerance, there's a floating decimal error that shows up.

One potential workaround (in this case) is to draw a sketch line down the middle of the features and use the Trace toolpath or 2D Contour (set to "Off" for compensation)

Seth Madore
Customer Advocacy Manager - Manufacturing
Message 9 of 9

The bug I'm referring to is trying to select an open contour for a contour operation. I use open contours all the time, bit for what ever reason with this model I couldn't create an open contour. 

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