[marbles]

I’ve been doing lots of 2.5 axis CNC carving but recently added a 4th axis, which is widening the possibilities but also the learning curve.

In short I would like to be able to machine below the rotational axis when using the 4th axis, here is an example of a spoon to illustrate. I understand some of the softwares can do it and increasingly I’m being asked to work with sort of sculptural forms which curve either side of the rotational axis and sometimes have voids as well. At the moment i’m not sure how to do do this but i’m sure it can be done.

My question is which CAM software and strategies will help me understand and work out methods to mill out forms like this (not spoons).

Thanks

Attachment 417606

[awerby]

The easiest way to cut something like that spoon would be to do it with an "indexing" 4th axis routine; cutting the top side first, then rotating 180 degrees and doing the bottom. You'd set the Z and Y axis zero points in the middle.of the part, so that they don't change when you rotate around the A axis. Deskproto would be a good CAM software to use for this; and we offer a good price on it, especially if you're a student or hobbyist.

[marbles]

The easiest way to cut something like that spoon would be to do it with an "indexing" 4th axis routine; cutting the top side first, then rotating 180 degrees and doing the bottom. You'd set the Z and Y axis zero points in the middle.of the part, so that they don't change when you rotate around the A axis. Deskproto would be a good CAM software to use for this; and we offer a good price on it, especially if you're a student or hobbyist.

Thanks I understand the indexing principals of flipping the part 180 and back again. I'd certainly consider doing roughing like that but I really want to be able to do true 4th axis finishing in which there is a choice to have the 4th in constant rotation and able to mill below the middle of the part.

[marbles]

I should perhaps be calling the process 4th Axis Continous Machining..

[Lennings]

DeskProto can indeed do that: the part rotates while cutting.
This is even possible using a helix-shaped toolpath: one long path around the complete part.

[awerby]

The Original Poster was talking about toolpaths that would dip below the Z zero line (set as the rotational axis) in the course of a continuous routine. I'd love it if DeskProto could do that, but any time I've tried, it refuses to write any moves that send the tool tip into Z-negative territory. Is there a trick to this I haven't discovered yet? If so, please show us how it's done. If not, can you explain why the math is so difficult that it's not possible?

Andrew Werrby
https://computersculpture.com

[Lennings]

Hi Andrew,
DeskProto can surely dip below zero when rotary machining.
When checking "Use rotation axis" the minimum Z limit for the Z by default is set to 0.0 (Part parameters, Material block size). Then indeed the cutter will not go lower. For most rotary projects that is the best choice.
You can however set a lower minimum Z value for the material block: then the cutter will go below zero.
For more details see the tutorial video on this subject: https://www.youtube.com/watch?v=0Xg0HIMWdMk
Lex.