Re: [CAD_CAM_EDM_DRO] Re: cnc pc board question

turbulatordude wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Marc Wullaert"
><marc.wullaert10@y...> wrote:
>
>
>>Try http://www.jraco.com
>>
>>Greetz,
>>Marcus
>>
>>
>
>
>In these links it seems they call the card a controller card and have
>an external ampliphier or what we often call a driver.
>
>Seems the parallel port is free and you only need to buy the driver
>such as a Gecko. and that would be much less expensive.
>
>Am I missing something here ?
>
>

Yes. If you need encoder feedback to the PC, the parallel port doesn't
have enough pins, and not a fast enough sampling rate, either, in most
cases. If you want to run many axes, have limit and home switches and
control
auxilliary I/O (spindle forward and revers, coolant, etc.) you just run
out of
signals. Also, if you want step pulse rates above about 25,000 steps a
second for fast routers or mills with high microstepping factors, you
can't do it with software-generated step pulses.

If you don't need all these features, and open-loop stepper drives at
modest speeds will work for you, then there's no need for the
"controller" board.

Jon