3D machining profile, Boundary Taper negative value.

[Bob La Londe]

Ok, First, please do not take offence. None is intended here. Sorry if I did so.

At the risk of offending, did you read the whole sentence? 

I can't make it do what isn't there, but an alternative might be to use several 3D waterline finish MOPs starting with a large roughing clearance and eventually finish with zero roughing clearance. 

[dkemppai]

At the risk of offending, did you read the whole sentence? 

I can't make it do what isn't there, but an alternative might be to use several 3D waterline finish MOPs starting with a large roughing clearance and eventually finish with zero roughing clearance. 

Yes, I did read the whole thing. And I will play with this option also. My concern is DOC may be harder to control than what the automatic code in the Waterline Rough does. Visualizing what's actually being cut with a ball end mill is a bit difficult without a simulator, so checking for a DOC too deep would be hard to do manually.

As you said, it'll will take more time to get a working solution than just letting it cut air. Of course, at this point it has become an academic exercise. The tool has been made, heat treated, tempered, and used to finish the job already!

I will also play with Eddy's plugin. (Which is very cool, BTW). I haven't played with it enough to realize the limitation existed in code.

If the boundary taper could be made to work both positive and negative, it would be a neat solution. I just never figured it would only grow the toolpath in +Z.

Thanks, and Merry Christmas. Hopefully Santa brought you lots of goodies to make chips with!

Dan

[Dragonfly]

I think what you are talking about is some kind of combination between 'Side Profile' with a slope and '3D Waterline roughing'.  With side profile you can control whether the tool makes clearing passes to remove excess material or not, but you can't control it to follow the vertical curvature of the 3D object. Roughing on the other side follows the object curvature but assumes there is material to be removed and cuts air if it has been removed by other means.
But if we look outside the particular odd case of the shape in your project I don't think it is an easy task to make a MOP algorithm which will work on varying 3D shapes. Because it's difficult to describe set the parameters of the material which has been removed. I think this is implemented to an extent in the high end CAM packages but still it is the program which plans and programs the removal and keeps track of the cleared zones.
It has been suggested already that keeping the outside boundary circle and playing with roughing clearance is the best available approach to reduce empty cuts.

IMHO the 'Boundary Taper' has different purpose - to allow some tiny angle on vertical walls, or 'draft angle', either to allow material separation if it is a mold or to prevent the tool rubbing the material.

[Bob La Londe]

Well, you have the geometry of the part, you created, and you have to have some idea of the geometry you created by turning off the bulk of the material off on the lathe before hand.  Sure you have to pull some dimensions and do some math, but you CAN reduce your air time by using finish operations, but with roughing clearance and a roughing depth increment.  There may be a problem with the total depth because I believe roughing clearance with all 3D operations also leaves material in Z if the mesh is below the last passes.