Ballscrew articulation, has anybody had success?

Has anybody replicated a 'port block' style of milling machine?

More info?

Didnt think they used this on cnc machines, but I guess you can get a whole 120 degrees outta it so not bad. I figured control would be something linear like (ballscrew travel/total degrees)/steps per mm

tommy, it looks like centroid has a 5 axis mill that uses linear ballscrews for rotary motion, like those fancy laser adjustment stages.

Thats if I understand it correctly. I havent seen any diy implementations before but my interest is piqued now.

Ok, that explains a lot.
A balscrew and some good bearings can get pretty good tolerances compared to cheap gearboxes, so that might be one of the reasons for using this.

It would need some maths in the kinematics file to convert linear motion to the final angle, but it seems simple enough.

I think this is cooler:

I have designed a few iterations, 8 degrees plus and minus (16 total) can be done with just ballscrew mapping on Mach3 using an 80mm water cooled spindle held in a pillow ball.
Bigger ambitions require more forethought.

That's a good point, ballscrew mapping would probably work for LinuxCNC too.

Hi

I am new to CNC and specifically LInuxCNC. I am trying to build something like this for my B axis except I use the ball screw to turn the spindle rather than turning the workpiece. So it is possible to write a math function to relate the linear motion to the angle of the axis. It is similar to the formula used to find the crankshaft angle when the piston has travelled x distance. Like this

But how do I enter this into LinuxCNC? I am ok with the math I need help on the implementation into LinuxCNC

Normally you get better answers on a forum if you show you've put in some effort yourself, and then ask more specific questions.

You can start by reading about Kinematics in LinuxCNC

linuxcnc.org/docs/2.8/html/motion/kinematics.html

In short: You write your custom kinematics in C, and "halcompile" compiles it into something compatible with LinuxCNC.