RE: [CAD_CAM_EDM_DRO] Re: What makes step and dir?

Hi Afogassa,

You asked about acceleration/deceleration.

Build a table of rates to implement ramping. Start out at the low rate,
then increment up through the table to the rate wanted. The table is
basically the periods for each rate. They increase faster as you go through
the table.

Determine steps needed for move.
Determine how many steps are needed for ramp up/down. If move is short, may
not be able to accelerate up to full speed (trapezoid or triangular
acceleration/deceleration).

A "slope" multiplier is also applied to the calculation to control; you
guessed it, the slope of the acceleration/deceleration.

ACCELERATE
Get starting rate.
Take a step.
Get next rate.
Take a step.
...
Don't get any more new rates if at feed rate.
...
DECELERATE
Get slower rate.
Take a step.
Get slower rate.
...
We're stopped.


This is a sample of a table I use.

5, //steps/sec, [ 5], 300 steps/min = 0.0375 IPM, 200.000 ms

10, //steps/sec, [ 5], 600 steps/min = 0.0750 IPM, 100.000 ms

20, //steps/sec, [ 10], 1200 steps/min = 0.1500 IPM, 50.000 ms

25, //steps/sec, [ 5], 1500 steps/min = 0.1875 IPM, 40.000 ms

50, //steps/sec, [ 25], 3000 steps/min = 0.3750 IPM, 20.000 ms

75, //steps/sec, [ 25], 4500 steps/min = 0.5625 IPM, 13.333 ms

100, //steps/sec, [ 25], 6000 steps/min = 0.7500 IPM, 10.000 ms

125, //steps/sec, [ 25], 7500 steps/min = 0.9375 IPM, 8.000 ms


The TurboCNC project (group) can be quite useful. Need more hints, contact
me. I love to talk about CNC controller programs!

Alan KM6VV

> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of afogassa
> Sent: Tuesday, June 21, 2005 2:56 PM
> Subject: [CAD_CAM_EDM_DRO] Re: What makes step and dir?
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "dharhay" <dharhay@h...> wrote:
> > Hi, I have only posted a few times and was asked a question that I
> > couldnt answer: I was wondering if I wanted to make a machine that
> > made one move in the X direction then back to cut slots. What could
> I
> > use to make the step and direction to Geko drives that power steppers?
> >
> > In the past I have always used a PC based CNC, but I really wouldnt
> > need to have the features and flexibility of a CNC because I want to
> > go one direction and a fixed amount and then back.
> >
> > Can a plc do step and direction or is there another simple way to do
> > one move and back? Thanks for any input.
> >
> > Dave Harhay
>
>
> You could use a atmel 90s2313 chip it outputs a very fast stepping
> signals, I've used it in the past, you can use free bascom for
> programming in basic language.
> The only thing I could not do on the code was implementing the ramp
> up or down necessary to achive top speed at the motors.
> BTW if anybody knows howto do it in Basic( ramp up or down)reply to
> this.
>