Re: [CAD_CAM_EDM_DRO] dual function lathe spindle

I am (re)building just such a system.

The servo does not hunt at all.
Of course, is use 10.000 count encoders at a 3:1 mechanical advantage
for 30.000 count positioning.
This necessitates the use of a hw step generator, in my case a
smoothstepper (SS) with mach3.

The mach3 SS plugin is late, buggy (spindle steps/per) and missing
features (SwapAxis, RunAsSpindle), which were estimated to work january
2010.
I am evaluating my options, but the SS is just so good (for teh price)
if only the (small but vital) functions could be gotten to work.

Where the servo position holding is or proves to be inadequate, I will
add an electro-mechanical brake.

> Gents
>
> Tried searching this forum & the web, haven't found the answer to a
> nagging question. Hope someone here can help.
>
> Depending on what machining operation you want to be doing, a lathe
> spindle could be either rotating at various speeds (vfd w/ an
> induction motor, pwm with a dc motor, or perhaps servo drive), or
> fixedly maintaining particular radial positions, similar to a 4th axis
> (which generally use worm gear reduction driven by a stepper).
>
> An Emco CNC lathe with live tooling that was in a school shop I had
> access to a few years ago seemed to mechanically switch between these
> two drive systems to alternate functions, perhaps with electromagnetic
> clutches. However, lately there seem to be videos on the web showing
> both lathe and 4th axis spindles making this switch between functions
> seamlessly. The only sort of drive that I can possible imagine doing
> both would be a servo drive, but holding a static position would be
> problematic, as the servo motor, unlike a stepper, would be constantly
> hunting, wouldn't it?
>
> What am I missing here?
>
> TIA
>
> Steve
>

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