Re: Why is the push to such high step rates (Grex and Arc100)?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "lcdpublishing"
<lcdpublishing@...> wrote:

>
> No pain felt here, so not sure what you mean by that question.
>
> As for the cost, well, yes it does cost more and that is what I am
> trying to figure out along with a practical application. See, for the
> hobby folks here, they can use a PC with MACH software and a parallel
> port (which is free) and get upwards of 45,000 SPS. On the other hand,
> they could buy one of these new devices and get 45,000 SPS at a price
> of around $500.00 give or take. The 45,000 SPS is in reality beyond
> the need for the vast majority of CNC machines people talk about in
> these forums.
>
> Both of the devices, the GREX and the ARC100 promote some very
> intresting features and performance specs. At first glance I thought
> I might be able to utilize these features but after looking at the
> numbers a bit more closely, I couldn't see a practical application for
> hobby use. So, that got me thinking about commercial applications
> and, well, I just couldn't think of one so I had to ask.
>
> I know from the posts by people in the various groups that there are a
> number of these units out there. What is it that they are building
> that utilizes such amazing performance?
>
> Chris
>

It is not only a matter of how high a pulse rate a device can produce.
It is also how much jitter the pulse train has. While a PC may be able
to reach 45KHZ. The pusle train can have severe jitter if you try to
go just a bit higher and that causes difficulty in building systems
that push the PC's limits and run in production environments even at
bellow 100KHZ.

Having a stable pulse train allows running the same motor/driver/load
combo at higher pulse frequencies without missed steps or stalls in
long production runs. That also applies to hobby use if you make a
part that takes days of machine use like it often happens when using
software such as DeskProto for example.

That is where products such as te ARCNC100 come in. And once you have
solved the jitter issue, it doesn't cost any more to make it go up to
4 MHZ or even 20 MHZ for that matter. Any solution that solves the
jitter issue involves hardware and for hardware, 4 MHZ or 20 MHZ is
pretty much the same ball park.

Patrick Robin