Re: CNC power supply question

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "snagglexr650"
<snaggletto@c...> wrote:

> Hello,
>
> I'm trying to get the 'big picture' on designing my own servo
> based cnc control using a Gecko based system. I'm currently trying
> to tackle the power supply issue; Why some kinds are better than
> others and how to determine PS size from the motor specs in

general.

>
> I've read here and elsewhere that the varying loads associated
> with CNC motor control is a problem for commonly available
> regulated/switched power supplies.
>
> What makes a 'homemade', unregulated(?), PS (Jerry's PS, or Doug
> Fortunes 1kw/1.5kw monsters) better at handling varying loads than
> the 'comercial/professional' grade regulated PS you see on Ebay or
> other retailers?

First you need to get the horse, then the cart ;-) The power supply
voltage and current are in relation to the motors you plan on using.
Even the choice of motor controller (Gecko, Rutex, etc) hinges on the
motor specs. You can of course shop for motors that will fall into
the spec range of specific components but the current requirments
will vary all over the place.

Sit down and decide what kind of machine you are building or retro-
fitting. Determine the type of machine and work envelope. Is it to
be moving table or moving gantry. What kind of drive approach will
you take: rack and pinion, toothed belt, ballscrew, acme screw, etc)
Decide how fast you want it to go and roughly how much you think the
moving parts will weigh. In other words design the machine first.
If you already have some components run your numbers using those
items and see if you can get there. Once you have a pretty good grip
on what you want to move and how fast, you can shop for motors. IF
you want to use servo's and hobby level motor controllers (not to
infer that hobby grade controllers are any less capable than
commercial units but they will not drive certain motor types) then
you need to shop for DC brushed motors with either encoders or a way
to mount an encoder.

Once you have your design and motors THEN it's time to start thinking
about a power supply. Rather than go into the technical aspects of
regulated VS unregulated or Switched VS Linear approaches at this
point you need to have the actual voltage and current specs you will
need in hand and then look to see what is out there to match. There
have been multitudes of threads about the pros and cons of different
types of supplies. In the grand scheme of things in the hobby CNC
life the power supply is one of the less critical aspects.

What you will find is that under most circumstances the voltage and
current you will need to run your motors at optimum speed and torque
will not be one of the standard 12, 24 or less common 48V regulated
supplies so the question will answer itself. If you do find a
regulated or switching supply at the voltage and current you need
then post a question and we can tell you how to safely use it with
your motors.