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Top Height using Slot Mill

Message 1 of 8
148 Views, 7 Replies

Top Height using Slot Mill


A) I'm milling an undercut groove with a KeyCutter classified as a Slot Mill Using 2D Contour.

B) From Model Top to top of groove is -.074 in.

C) The Width of the Cutter is .125 in. (So we're shooting for an NC File dropping tool Z-.199, for the top cut, if you follow)

D) In order to achieve this to work correctly in NC File and Simulator I've had to reduce my Top Height Calculation by .060in. (-.139)

E) My brain can't figure out where this top height reduction number is coming from.  Looking for a Logical answer.

F) The bottom height works as intended Z-.599=Z-.599 In NC and sim.


Thanks in advance, I'm baffled, but tried to add lots of visual references for you to see what exactly is going on.


Matthew M.



Message 2 of 8

I dont see a file, but my guess is that your WCS is NOT set directly on the top of the part. 

Please click "Accept Solution" if what I wrote solved your issue!
Message 3 of 8

Heres the File. Double checked and WCS is in fact set to top of part.

Message 4 of 8

Your top height should be Model Top -.074, not sure where .139 is coming from? 

Keep in mind that right now Contour does not calculate the top of the tool flutes like you desire. You can just modify the Top Height with Origin offsets to make the first pass at -.199, or do a separate pass entirely at this height. 

Please click "Accept Solution" if what I wrote solved your issue!
Message 5 of 8

This is getting a little frustrating.

Now its throwing it down .100 below the target



Message 6 of 8


I ended up setting it Top height-.099 to get it to work correctly which is .025 below Z-.074.



Not sure why this is acting funny.  I would like a logical explanation, to set my mind straight.  


All the other heights on this job came out as expected.  That's why we double check things. 


Thanks- Matthew


Message 7 of 8

as I said, Fusion doesn't compensate off the top of the flute when undercutting, only the bottom where it is touched off. If you wanted it to, you'd have to use 3D contour instead. 

Please click "Accept Solution" if what I wrote solved your issue!
Message 8 of 8



The thickness of the tool is .125.


Where does top height Z-.099 make sense.  Thats just the  number I found worked to get it to Z-.199   

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