Re: [CAD_CAM_EDM_DRO] Re: Max feedrate

knives01us wrote:

>I'm kind of new to Flashcut & CNC myself, but when I was setting up
>my machine I discovered that it will only tolerate about 1/3 the
>seperate axis feedrate when doing a 2 axis move.
>

(snip)

>I got the circular interpolation
>figure much the same way, having the machine do a 2" circle drawn in
>Cad and converted to G code until I found a speed that didn't drop
>steps, which was only about 1/6 of the fastest single axis move
>possible.
>

Boy, there is soooo much to this really... I find the "1/6th" issue to
be quite a difference than I ever saw. Even the "1/3" concept has been
a stretch for me, where I would say "1/2 the speed" more accurate for
linear. Case being, I can get any single axis to 600ipm, but with all
axis running and using valueable steps from the softwares maximum
available steps, 300ipm is about the max without step loss.

In the Circular example, I might conclude that that "1/3rd" area is a
reasonable conclusion rather than 1/6th....... I know that I could hit
200ipm on a 2" diameter circle without step loss ( it will "hammer"
pretty good !) but I do not run that high. THAT is exactly what the "Max
Arc Feedrate" setting questioned earlier lets you limit. I set mine to
150ipm.

Much of each individuals experience with any controller will come down
to the mechanical details of the machine. I've noticed the biggest
challenges to acheive maximum capability are distributing the "available
step" output, *effectively* across multi axis'. I think in some cases,
we have overly fine "lead" screws, ( what do those Sherlines have ?) and
then we have the tendency to "microstep the thing to death" just so we
can gets some rediculous resolutions.

We must realize that even if we have some astronomical resolution
....It is more than likely we will >never< benefit from that fine
resolution without very special, and mechanical machine considerations.
I shoot for no finer than .0003 for my machine because that in itself
seems to be the common denominator for the Cherry snap switches I use
for seeking home.

What we WILL DO in trying for astronomical resolutions is USE UP all of
the control programs capability in "maximum step output", making it
impossible to perform at a more impressive level. So, I guess what I
get curious about when I see those type of losses, is if one is "Running
Out" of the "available step output" from the program. If you are
using ALL of the pulses up unecessarily, It will ACT as if it just can't
go any faster, because it is OUT of pulses to "push it" any faster.

If you really need the resolutions, then its all you can hope for in speed.

Chris L