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How do I cut a groove the way a machine would ?

R-man

Senior Member
I want to cut a 3mm wide 'groove' that is 1mm deep but with the bottom sloping inward toward the centre. Think of shape of the end of a drill bit. I tried using a profile to do a sweep cut along a path. The problem I run into is that where the radius of a turn in the path is smaller that the width of my profile the 'inside' edge of the profile goes backwards, thereby potentially creating a folded surface. Alibre doesn't allow it.

I can sketch the two edges and simply ExtrudeCut a flat bottomed groove (see attached part), but would like to have a better representation of what will eventually be milled.

Is there anyway I can make a virtual cutter that just evaporates whatever is in its path, with regard to folded surfaces?
 

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Ken226

Senior Member
Are you talking about the pattern in the Z - face of your part, as highlighted in blue in my screenshot?

1657938446413.png



If im understanding your question right, your wanting to radius the bottom as if it were cut with a ball mill, or chamfer mill?

Something like this, which i did with fillets?

1657938572984.png






or this version, using chamfer?

1657938771083.png








Or perhaps by using a draft angle on your extrude cut? Which allows sloping the entire wall inside the cut, as would be done using a 60 degree V cutter, like a chamfer mill or similar.

1657938915303.png





Each of those methods will have limits. For example, using a draft with your extrude cut, it wont angle the walls inwards more than about 30 degrees with your existing sketch width and depth. So a 60 degree V cutter (30 per side) would do it, but Alibre wouldn't let you model the wall as would be left using a 90 degree V (45 per side).


If thats what you had in mind. As if, you made a first 2d pocket operation using a 3mm end mill, leaving the island. Then after, machined the wall bevels using a 60° chamfer mill.

I've done similar in the past with ball mills making lead molds for a company that manufactures leather blackjacks.

 
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R-man

Senior Member
Wow! Thanks guys! So many ways to approach this. The chamfer version is the basic shape I am looking for, but with a shallower angle - 1mm straight wall with centre less than 1mm more. A cutter with a 120 degree included angled end will be used.

FYI there is a part with two 3mm diameter ball bearings attached. Both bearings engage this cam wheel in 180 degree opposition to create an almost linear motion when the wheel is rotated. I say "almost" because where the cam slot curvature is too small the 'corners' are cut away (folded surface in alibre) and the slot is unable to constrain the bearing. I went from linear motion just enough so that the outer corner will constrain the bearing.

The reason that this is in the script department is because since python scripting became available I've used it exclusively to interface with Alibre.
 

idslk

Alibre Super User
the file only for the "completeness"...
"cutter" 3mm diameter and ~120° tip angle (see EquationEditor)

Regards
Stefan
 

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