Re: [CAD_CAM_EDM_DRO] 4wire vs 6wire step mtrs also Taig mill S&D conversion

Ken Jenkins wrote:

> I recently bought a "preowned" Taig CNC mill and I've
> already decided I want to convert it to Step & Direction
> for a number of reasons (which I won't go into here).
> I would really appreciate some advice/comment from
> those of you out there who have experience in stepper
> drive systems. I know how to use them, and basically
> how they work, but some of the electrical requirements
> and connection considerations I'm a bit weak on.
>
> Q1: Have any of you other Taig CNC mill owners out there
> converted your system from the LAMDA phase controller to
> Step & Direction and what was your approach. Did you
> use any part of the LAMDA controller (ex: the power
> supply, case and connectors) or did you just set it
> aside and put in a new front end?
>
> Q2: I am looking at Stepperworld's FET-3 product which
> looks great for what I want to do (I think).
>
> http://209.41.165.153/stepper/fet3.htm
>
> has anyone else used this board with the Taig motors
> which are 6 wire steppers from Shinana Kenshi Co. Ltd. (SKC)
> model # SST57D5101 / 1.8 deg/step / 9.2v / 1.0A / 200 oz/in
> holding torque with the following wiring which I assume
> makes them unipolar:
>
> Phase 1 ------+
> |
> +------Common---(13)
> |
> Phase 3 ------+
>
> Phase 2 ------+
> |
> +------Common---(24)
> |
> Phase 4 ------+
>
> Noting that they are 6 wire motors and assuming they are
> unipolar is an integral part of my befuddlement and the
> questions that follow.

The current ratings on unipolar stepper motors are intending that the
rated current flows through only one half of the winding at one time.
You have the choice of running 1/2 the rated current through the full
winding (motor runs a little cooler, but performance suffers) or
running the rated current through only one HALF of the winding
(either half is fine) from one end to the common or center tap terminal.
In this mode, due to the full power supply being applied to the
winding to reverse the current flow, the motor performance at high
speed is greatly improved over unipolar systems.

>
> (about here is where the waters begin to close over my head :-)
>
> Q3: Can I use my PacSci 6410 drivers?
>
> Another way I can go in doing the conversion to S&D is to
> use a bank of (4) Pacific Scientific 6410 drivers I have all
> powered up/wired up/ and ready to go (this has the advantage
> of letting me add a rotary "A" axis later and keep everything
> the same). I am using the 6410's to drive steppers which I am
> installing on my Taig lathe (these are 4 wire motors and work
> just fine). My question is can I treat the Taig motors
> as (4) wire motors by just tying both commons together back
> at the 6410.

No, I think you DON'T want to do that. Assuming the 6410 is a
bipolar drive, connect one end of each winding and the common
to the bipolar drive, leave the other winding end disconnected.

Jon