Re: Pulse Gen

Alan Marconett KM6VV <KM6VV@a...> wrote:

> hi Wally,
>
> Good points. No, actually I was only thinking of the PulseGen

hardware

> for my software efforts. No driver for EMC planned. A TSR for DOS

would

> be a possibility, as would be "sharing" the driver (function call or
> subroutine) code for other users.
>

Allan i am confused what your sofware efforts are. I do not
understand what you are writing software for and what you are trying
to do.

> I hadn't stopped to consider the speed issues, as I am thinking

from a

> "small mill" mentality. Probably nothing bigger then a FB-2 or

Grizzly,

> or perhaps a "Dream Machine" of similar proportions, from what I

gather.

> 200 IPM! In my current mindset, 20 IPM is fast! But yes, I
> understand.
> I recall seeing the 14 I.C. figure too, I need to see what Mariss

has

> for a schematic, or study the block diagram a little more.
>
> The 5tpi is something to think about. I have 20 tpi on the little
> Sherline, and a few pairs of what I think are 8tpi. x 3/8". I think
> they may possibly be metric, as the shaft end was not a simple

English

> dimension, and some of the 3/16" (?!) hardware associated with them
> turned out to be metric! Anyway, I am just realizing that the belt
> reduction used with ball screws must also be to get more

steps/inch, not

> just for power as I originally surmised. Would have been nice to

drive

> them direct with a flex coupler. What steps/in should I be shooting
> for? And what's realistic?
>
> I'd appreciate your input.
>
> Alan KM6VV

First, i do not follow the small mill stuff to closely. I think many
people use the existing screws and direct drive them. It would not
be realistic to change these screws to 5TPI from 20TPI for several
reasons. First reason cost. Second reason Larger steppers would be
required as more force would be needed to turn the screw. Third no
performance gain. My calcs show that a 20 tpi screw directly driven
to 20ipm with half steps will take 2.67K PPS. This number of pulses
is easly obtainable with software. If you use full steps you only
need 1.33K PPS and will get a step resolution of .00025" per step.

It seems to me with this resolution there is no need for further belt
reduction and you should directly drive the 20tpi screw with a zero
backlash flex coupling.


Wally K.