Helical milling non-cylindrical shapes

[SamuelMoses]

Is there a way to machine the side walls of a non-cylindrical shape (tear drop) in a helical motion? I don't want to machine a depth and then plunge to the next depth but helix down to the full depth and make a finish pass there.

Thanks

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[DanielSantos]

Samuel,

Mastercam and HSMworks fully support this programming approach, what is just great for some situations. I've opened a enhancement request a year ago at PTC to ask them to support this for 2D trajectory milling (I complained about this with Mr. francois Lamy - PTC Director for Tooling/NC Solutions) and they told me they do not plan to implement this... sadly PTC does not listen us when we ask for simple things that makes differences in the shop floor... ramp countouring is one of such features... it can save a lot of time and improve substancially the surface finish/tool life...

This strategy is also very useful to machine plates with very thin plates glued to each other. Since there are no lead in/out moves between successive depths, the tool moves continuosly to the Z negative direction, keeping the material layers to keep glued to each other. Without this strategy, the lead-in / lead-out moves causes the scraps of some parts...

Well, I was told back then that you can do it using volume milling with the options "Profile only" and "S Connection"... never tried this way though...

Would you mind to test this and let us now if it works for ya?

Good luck,

Regards,

Daniel Santos - Sr. NC Programmer / CAM Support

Liebherr Aerospace Brasil

[DanielSantos]

Terry is absolutely right, I missed this one...



This is also a valid approach... however it will not generate arcs at all..
Only point-to-point moves. however you can turn on arc-fitting in G-Post to
filter the moves and convert them to arcs/lines.

I particularly don't like to use this method due to the point-to-point
toolpaths. simple contours will have thousands of points. and G-Post
arc-fitting (as any post-processor arc fitting solution) will be very
dependent of the tolerance you use. and even with tight tolerances sometimes
you get small discontinuities at the surfaces due to the rounding issues.
the calculation time and regeneration time will increase dramatically.
that's why I asked PTC to implement this as a true solution in trajectory
milling, since trajectory milling sequences based on sketches will output
arcs as precise as your sketches (since in fact Pro/NC is just offsetting
your tool radius). it would be awesome if they could allow you to helix down
these "geometrically true" contours. go figure out why they don't want to
implement this. I think that it's because they already offer this point to
point solution. and then they sell to everyone that G-Post can fix their
mess. maybe, at the cost of toolpath calculation/regeneration time once
tight tolerances will decrease your performance. imagine a hundred of
sequences with such tight tolerances.



"These additional scan types appear only after the cutlines are defined"



This is also a important note. You have to chain the two contours first
(Upper and lower) and then switch back to the parameters dialog. Then you
are going to see the option helical, which is only available when you do
this.



Daniel

[DanielSantos]

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