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

I don't quite see the point you're trying to make here. I mean, if
someone wants 45k SPS and no more, then they're welcome to go with a PC
and parallel port.

If someone wants more, they can get a GREX. If a GREX was limited to 45k
SPS it would not suddenly become hundreds of dollars less. The cost
penalty to add 350k SPS to the GREX is probably pennies. I expect that
most people are buying GREX for the added I/O and other features
associated with it rather than because they are limited by the 45k SPS.

That said, when I first put together my NC retrofit, I had (free)
encoders that were 1024ppr, at 45k SPS, I was limited to roughly 50ipm
which was insufficient, so I had to go out and buy 500ppr encoders at a
cost to me of $180. Even with the 500ppr encoders, I am not reaching the
RPM limit of my servo's and could get even faster rapids with a GREX.
And yes, increasing my rapid speed by 30% (difference between my 45k SPS
max and my RPM max) would make a difference that would be worth the
extra money.

Oh, one more thing - the PC that I'm using (which I had laying around
and was pretty much 'free') is only really reliable at 35k SPS, at the
time I was putting everything together, a 45k capable PC would have cost
me around $200-250. The GREX wasn't available at that time. If it was I
would have bought one in an instant

The price difference would have gone something like this:

3 encoders @ $180
New PC @ $200
Parallel Port Breakout Board (I don't have one, mostly because I didn't
know what one was at the time and just hardwired everything, but if
you're going to compare Apples to Apples...) @ $50-125.

Total for 45k SPS limit ~$450-500.

Or I could have just bought a GREX...

--C.S.

>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