Re: [CAD_CAM_EDM_DRO] Bridgeport CNC Mill???

On 10/02/2011 05:33 PM, Jon Elson wrote:

> David G. LeVine wrote:
>> Since the Mesa stuff (and I only chose that as an example) can do most
>> of this in the FPGA, EMC2's speed is not a question.
> Well, no. Both the Mesa and Pico Systems boards close the servo loop in
> the PC, at
> least when using EMC2.

The point is that the hardware is there, the programming may not be. I
do bow to your superior knowledge here.

And, as you pointed out earlier, how many machines can respond quickly
enough that even a 1 KHz rate will matter?

>> It is not normally
>> significant if there is a 1 mS delay between the end of one move and the
>> start of the next EXCEPT when doing cuts with many straight line
>> segments.
> Well, even still, if you are doing close to 1000 vector segments per
> second, that is
> a really hard thing to do, and it may be more due to a poor G-code
> program in many
> cases than an actual need to break the path in that many segments. I do
> have a torture
> test that I set up for EMC2 to find out how many G-code blocks it could
> handle.
> It consists of a 3" diameter circle broken into 10,000 G01 vectors. It
> handles it
> in about 13 seconds, so better than 750 vectors/second. That test was
> performed on
> a 600 MHz Pentium III, so it will do even better on a faster computer.
>
> Jon
>

Again, the point is that the small delay between the stop of one segment
and the start of the next is not a real issue, as you just pointed out.

Back in the days when I was working on photoplotters, we found some
people who complained about how slowly the machine was plotting had made
the traces from (literally) thousands of segments. The segments were
made of multiple widths and the photoplotters would do an aperture
change for each size, so they put it through an optimizer which sorted
by size. The optimizer they used did not sort based on line endpoints,
only on line widths.

You can see what the problem was with no other information, the random
walk was painfully slow.

Dave 8{)

--
/"Political Correctness is a doctrine, fostered by a delusional,
illogical minority and rabidly promoted by an unscrupulous mainstream
media, which holds forth the proposition that it is entirely possible to
pick up a turd by the clean end."/
(quoted from http://www.wattflyer.com/forums/showthread.php?t=30060)

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