Re: [CAD_CAM_EDM_DRO] Lathe Encoders

John Mesh wrote:

>Hi all,
>Once again I need your expert advice on encoders.
>I have 2 small Hercus Compulathes - CNC lathes that I am trying to
>convert
>over to PC control. Currently, both of them have resolvers.
>Would like to put 320 Gecko's and encoders on them.
>My question is, what CPR for the encoders.
>Here is the encoders that I would like to buy . (H1 series)
>http://www.usdigital.com/products/h1h3/
>On the X axis (cross slide) the encoder is attached direct to the
>screw.
>About 6.125 turns moves the crossilide 1"
>

So, 6.125 turns/inch. For 10000 counts/inch, you need 2500 cycles/inch, or
2500/6.125, which gives 408 cycles/rev. They make a 400 cycle/rev encoder,
which will give a resolution of 400 * 6.125 * 4 = 9800 counts/inch, or
.00010204".

I could not come up with any combination that makes a nicer number.

>On the Z axis (carriage) the encoder is mounted on the end of
>the servomotor. About 12.25 turns gives me 1" of travel, as the motor
>drives the screw with 2:1 ratio with a cogged belt.
>
>Also, I need some information on the servomotors.
>Electro-Craft model # E 586-SA Part # 0586-24-024
>I think these are 24 Volt. I have a 30V transformer from
>the old control. Will this work, or should I get a 24V?
>
>

The 30 V AC RMS transformer will give 42 V DC when full-wave rectified.
This is probably the minimum you should use. The Gecko drive will take care
of the applied voltage. Only if you command greater than the rated
motor RPM
would voltage greater than 24 V be applied. Anyway, these ratings are
pretty
soft. the important one is instantaneous peak current, and the Gecko
limits that,
too.

Jon