How to generate Lathe GCode from a drawing?

[Jonathan]

Looks like there is no alternative to DIY.

Over a couple of hours this afternoon I have put together a short JRuby program that will produce GCode from an array of Z,X values that represent the profile (or half cross-section) of the finished piece.

If anyone wants a copy of my code (which is very basic) let me know. (No charge ! )

...R

Have you included tool tip radius compensation? If not your code will only be accurate for moves parallel to X and Z, or with very sharp tools with no tip radius.

[birchy]

Maybe dxf2gcode? I'm going to be using LinuxCNC (cos I'm a Linux geek) and have briefly tried dxf2gcode. Seemed to work OK. Try searching the LinuxCNC wikis and forums as well, the members always seem to be willing to help and will probably suggest other programs.

[Robin2]

@Jonathan, thanks for the tip !

@birchy - thanks I will look at dfx2gcode

...R

[Robin2]

@birchy, I've now had a very quick look at dfx2gcode. It seems only to produce code for milling.

Have you used it to generate Gcode for a lathe? If so perhaps you could explain what I need to do.

Thanks

...R

[birchy]

@Robin: Sorry, I've only done some quick tests on milling machine programs and assumed it would also convert dxf files to lathe gcode. You'll find this an interesting read... LinuxCNC Support Forum :: Topic: lathe programming (1/3)

[Robin2]

@birchy, thanks.

I had seen that LinuxCNC link.
The final bit about using Blender got me looking at the internals of some of the data formats. SVG files seem fairly simple and I might experiment with using them as input to my JRuby GCode generating program. But it may actually be simpler to devise a piece of program that would produce a series of short straight lines for an arc.

Truth is I'm at the very beginning and I'm not sure what I will want. The purpose of my enquiry here was to ensure that I'm not re-inventing the wheel because I missed something simple, good and free.

I will probably try to do some milling on the lathe using a vertical slide as the Y axis and (just to make things complex) it will be the Z axis for 3D printing.

...R

[m_c]

The lack of Lathe CAM options is down to the limited number of CNC lathe owners, and I'd guess the larger majority of those are professional users where paying for good CAM is not a major issue.
There are far more mills and routers than there are lathes, and lathe CAM is alot more complex than standard mill CAM.

One thing that sticks in my mind is Art Fenerty mentioning that writing LazyTurn was essentially a lesson in collision detection. External turning you have to deal with avoiding all the tool edges colliding on the profile, and internal turning you have to deal with the non cutting edge having enough clearance in the bore.

Have you had a read through the main thread about LazyTurn on the Mach forum?
I'm pretty sure that's where Art mentioned alot of the issues he had to work with, and I'm sure it would provide you with a good insight into what's actually needed to get a good lathe CAM.

[Robin2]

Thanks @m_c.

That LazyTurn thread is verrryyyyyyy loooonnnnnnnnnggggggggggg

I will keep it in mind.

...R

[m_c]

It is a long thread, but you'll probably find the final half is all about getting it to work/working around issues that never got sorted. I'd concentrate on mainly reading Art's posts. I can remember him mentioning the main issues somewhere, and I'm sure it was in that thread, although it could of just as easily been on the Mach yahoo group, as quite a few of his side projects overspilled on it aswell.

It's a shame he never developed LazyTurn more, but Gearotic Motion is his current project.