Re: [CAD_CAM_EDM_DRO] Re: DRO: USDigital new resolutions 250cpi x 4

It makes one wonder about the 'elasticity' of the machine
when doing small steps. I suppose if the cutter is going
fast, there shouldn't be much force. I'm aiming for a
work area of 2.4m x 1.2m. I'll use DC servos and chain
drive. I haven't seen very long lead screws.

How cheap can you get 1000 pulses/rev encoders (or 250 pulse
encoders if you can count edges)?

ballendo wrote:

>
> Russell,
>
> There are a lot of machines out there based on 5TPI (.200"lead)
> screws. When driven by a "typical" 1.8° stepper, which has either 200
> (fullstep) or 400(halfstep) SPR(Steps Per Revolution), you get a
> SYSTEM resolution of .001 or .0005 inches/step.
>
> Another factor is that you generally want a resolution at least
> double your intended accuracy; so for a machine designed to make
> parts of .001 tolerance, the scales of .0005 are a minimum.
>
> Now to your router: There are many commercial (and expensive) routers
> which have only 500 SPI (Steps Per Inch). This is often a trade-off
> to get the higher top speed this type of machine needs. Modern
> technology is making some of these trade-offs less demanding than
> they used to be, due to things like fast block times and pulse trains
> from the controllers, affordable microstepping drives, and more
> powerful magnets, which translate into more compact and electrically
> efficient motors...
>
> Beware of "empty" resolution. This is where your machine makes
> several steps without moving. Also beware of equating resolution with
> accuracy; they are NOT the same thing!
>
> Hope this helps.
>
> Ballendo