Dead CNC lathe -> EMC Special purpose machine

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08 Aug 2010 18:53 #3635 by andypugh
Gregor wrote:

Have you tried, or would you mind trying if you have a minute, a profile with a flat section? I'm a little concerned that it will be difficult to produce an actual flat facet like in my sketch. Precise flatness is probably not critical for my application, but it would need to at least look right. What are your thoughts?


Flat facets should be possible (they make cams using vaguely similar machines) but you will need to do some clever maths to figure out the axis position for each angular position.

The end-mill as you show it is equivalent to a flat cam follower. A shell mill running axially would be equivalent to a roller follower. I have seen the equations for both types in books. Your end-mill would need to be at least as wide as the flat.

With the single-point lathe tool it should still be possible to create a flat, but tool clearance angle will be an issue. If you consider the point where the tool it at the very beginning of the flat, if the angle of the flat to tool is greater than the tool clearance, then it can't be cut.

I think that the maximum flat width is twice the base length of a triangle with the tool clearance angle at the apex, and the hypotenuse being the material radius.
Tools with large clearance angles do exist though, as they are needed for boring tools. I have not found any with an angle >20 from a cursory inspection though.

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08 Aug 2010 21:52 #3636 by Gregor
You raise some good points that I hadn't considered. Using a radial live tool is going to require an instantaneous reversal at the point where the tool is perpendicular to the flat, could have problems there. A turning tool or an axial live tool will result in a more gradual decel/accel through the flat facet. On the specific profile in question I don't think the flat is steep enough to cause clearance problems with a turning tool, and it would be a non issue obviously with an axial live tool.

Time to do some reading up on EMC2. Hopefully I will have some hardware ordered in the next week or two!

Thanks for your help!

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09 Aug 2010 13:07 #3655 by andypugh

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14 Aug 2010 04:29 - 14 Aug 2010 04:32 #3733 by M4MazakUser
I'm pretty impressed with the functionality of cam turning, and I'll have to look into this as it would suit a few jobs I do. Sure there is the clearance angle problem with flats, but live tooling would solve this, if this was accessible from a "gui cycle" it would be unreal. - though cam profiles are hard to define other than by points.

I'll look at this in a couple of weeks as I only just started making things on my lathe yesterday. - a three week retrofit!

The gui pgm I refer to is "Dewey's tcl" program.
Last edit: 14 Aug 2010 04:32 by M4MazakUser.

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