Developments on my Home built 5C CNC Lathe - Polar interp. and Live tooling

besriworld wrote:

It seems quite complicated. Has anyone done it with +-10v control? I want to try it on my lathe.

It's been a while since that post, and my lathe project has been stalled for a few months... but I had to give up on C-axis.comp.  I didn't get far enough to try the polar kinematics.

The insurmountable problem I encountered with caxis.comp was that it interfered with synchronized spindle moves (threading).  I wasn't able to figure out how/why it was causing problems, but once I abandoned it for a spindle/axis scheme proposed by @Aciera and @PCW, threading started working properly.

There is still an issue with threading in LCNC - thread start point varies with RPM - but that's not related to caxis.comp.

Thanks for the update. Then I will try without polar coordinates.I would be happy if you could share the configuration. Because I did not find an example of a spindle and C axis with +-10v control.
My lathe doesn't have an index yet and can't make threads. Because I want to install a hydraulic chuck first.

I don't have copy on hand, but if you search through my posts you should find some of the later caxis.comp configs attached.  Maybe 4-6 months ago or so?

I tried step/dir and pwm, so there may be examples of both attempts somewhere in the forum.

Something to keep in mind is that for rotary axis work you want the highest resolution encoder (or resolver) you can get.  NoJo (OP) I think reported problems with C-axis milling and feature alignment due to a moderate-count encoder.

Of course, high counts and a high-speed spindle means problems with max input speed.  I wound up with a 10k-line encoder on my 3500rpm spindle... which works but I had to turn off Mesa input filtering.

Another issue I think I encountered with NoJo's polar kinematics was that he hard-coded the live tool offset in to the component.  He only had a single live tool so that worked for him, but a re-write which uses a tool offset from the tool table might be wise.

At a later stage, I plan to add an additional 1kW servo motor, which will operate in torque mode to act as a dynamic load on the main 7kW motor. This will increase the system's rigidity. Currently, I'm using the encoder from the main motor

besriworld wrote:

At a later stage, I plan to add an additional 1kW servo motor, which will operate in torque mode to act as a dynamic load on the main 7kW motor. This will increase the system's rigidity. Currently, I'm using the encoder from the main motor
 

That sounds interesting.  How are you planning to couple the secondary motor to the spindle?

I’ve bought a hydraulic chuck closer for the lathe chuck, but in order to mount it onto the spindle shaft, I need to cut a thread on the spindle. After that, I’ll add an additional gear on the spindle, which will be connected by a belt to a second servo motor with a 1:2 gear ratio. The motor will be mounted on top of the spindle housing