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

VFD is what I meant.
I guess the best would be to have some kind of gear (low for c-axis and high for lathe work) with some way to electrically switch from one to the other.
13deg and damp is not nice to fiddle with things. I remember reading something about a beetle in some coastal desert that can gather it's drinking water by catching the mist on it's body.

I tried to come up with a geared arrangement with a servo activated pawl that slid a locking gear between 2 gear trains - a 1:1 and a 5:1, but since that had not been thought of from the start, my layout, mechanics and structure was just too small to accomodate the concept. I suppose had there been a purpose for the machine then I may have maintained the interest!
You are right about the beetle - does hand stands on the dune windward side and the mist condenses on the trailing edge of his wings and runs down the central ridge to his mouth...Mother nature is a smart Cookie....

Aciera wrote:

VFD is what I meant.
I guess the best would be to have some kind of gear (low for c-axis and high for lathe work) with some way to electrically switch from one to the other.

 

My commercial lathe has a big gear on the spindle, and a servo with a pinion.  Servo is mounted on a swinging bracket connected to an air cylinder.

Engage the C-axis and the main spindle motor is deactivated and the air cylinder shoves the servo (actually a 5-phase closed-loop stepper) against the spindle gear.  Once they're engaged the C-axis immediately homes before anything else happens.  Looking at the gears, I think it's about 40:1 reduction.

Main spindle motor is a 5kw, 7k rpm 3-phase induction motor with a Lenze VFD, driven via a 1:1 10-rib micro-V belt.  The main motor and the stepper both have encoders, but there's also a separate shaft encoder with a 1:1 timing belt connected to the spindle.

The two motor encoders are fed in to the respective drives, but my guess is that the spindle encoder is what the control uses for velocity and positioning control.

As an alternative configuration, there's a guy on YT who's been doing some interesting stuff with his lathe and a Centroid Acorn.  Specifically, he's got a standard VFD/induction motor, and separate servo connected via a timing belt.  The servo has an electric clutch to engage/disengage when the C-axis is active.

I considered going that route, but toothed electric clutches are very not-cheap new.  And I don't want to depend on an ebay score only to have a scorchingly expensive replacement bill if it dies int he future.

@NoJo -

Thank you very much for the updates and files.  This will go a long way towards a number of us making progress.

-Ralph

Ralph,
I think your lathe's spindle motor/C axis drive servo mechanism is fairly standard in the industrial machine world. My little lathe was one of those things that grew beyond my control. The cost of the lathe at the end was quite stupid and could have bought a really nice small Emco machine! And as these things go, the final result would have been better thought out had the original idea encompassed the end product! The original idea was a MACH2 cnc control, and a SMALL lathe using a small (5NM) Clearpath servo on the spindle ( 4000rpm), with an ER40 spindle. The bed was to be maybe 350mm long, no C axis......And the idea got out of hand. I really enjoyed the mechanics though, and using all the other machines to build this one ( an 85 year old shaper, for instance!).

If you need any of the other software let me know - the tool changer deviates substantially from the LCNC examples, but is very specific - also with the live spindle and so on..The live spindle is driven by a 500watt (1.5KW peak!) RC Brushless motor ( about 80mmOD 100mmLong), to which I fitted 3 hall sensors and wrote some Vector control SW to drive it. That works well - good torque @ 100rpm, max rpm of around 8000 @ 40VDC source drive.

You will have noticed I am running V2.9Pre - Dgarret updated that to a next release I believe - the Pre included fixes for a bug my Wife found in the LCNC code, but I am to scared to update to the latest build - who knows what else is different and what stops working on my machine!
Joe