Re: Plasma cutter

[Jon Elson <elson-at-pico-systems.com>]

Luc Vercruysse wrote:

> Hi list,
>  
> I want to use EMC to control a plasmacutter.
> As the XY table measures 2 X 3 meters, I want to make G0 movements 
> with a speed of 500 mm/sec.
> I will use:
>     200 step/rev steppermotors.
>     5KHz step rate =>  5000pls /sec 
>                                  -------------------  = 25 revolutions 
> /sec  
>                                  200 puls/rev  
>  
>     500 mm/sec 
>     ------------------    20pulses /mm
>     25 rev/sec              
>  
> In my ini file I set both SCALES on 20, UNITS = 1
>  
> I always get a following error.
>  
>  
>  
> Is it inpossible to reach such a speed ? Do I have to adjust settings ?

5000 pulses/second is no problem for a reasonable CPU to do.  I would 
use at the very
minimum, a 133 MHz Pentium classic, but a 200-300 MHz machine gives you more
CPU resources to get a little better pulse train timing.

You probably  need to increase the P gain term (at least with freqmod.o, 
you don't say
which you are using).  You probably want to reduce the max_acceleration 
value.
Note that the velocity and acceleration settings are in user units per 
SECOND,
while the feedrate you specify for moves are in user units per MINUTE.

Note also that the following_error settings are in user units, in your 
case mm, so
a setting of 0.050 means any error greater than .05 mm causes a 
following error.
If the following error setting is less than, or even close to, your step 
resolution, you
are in BIG trouble.  Since you have 20 steps/mm, a MIN_following_error 
of .050
almost guarantees a following error, as it is only one step!  So, 
increase the
min_following_error to at the very least, 5 steps or so.

Jon