Re: Max feedrate

Isn't max feed rate a calculation of cutter tip speed, material, and
depth of cut ?

Thre is not sence in going 375 ipm when you are spinning a 3" carbide
hogging mill at 300 RPM. most motors can't handle 1/4 deep cuts per
flute.

max feed rate is better determined by part being cut, the sharpness
of the cutter and as was stated, 80% of the speed where steps are
lost.

Setup on steppers is typically done dry, with rapids to see how fast
the table can be moved without the additonal force of the cutter.

Dave

--- In CAD_CAM_EDM_DRO@yahoogroups.com, CL <datac@l...> wrote:
> andrewyslee wrote:
>
> >Hi,
> >
> >What are the factors that determine the max. feedrate?
> >
> The short answer here is that Max feedrate is limited by your
mechanical
> design ( motors, drivers, gear ratio's etc.), provided that you are
not
> "Using up" all of the step capability of the program. Some designs
will
> run faster, some much slower.
>
> > The max.
> >steps/sec that can be output by the computer or the driver (max.
> >volt, amp. etc.)?
> >
> This can consist of a few things. First and foremost, it helps to
know
> what the particular programs capabilities are. Most current
versions of
> what is available and discussed on this list comes near or around
> 25,000-30,000 steps per second ( someone may know what some of the
> available programs really are). You can contact the Developer of
your
> program to find out the "possible" step output, keeping in mind
that an
> older Processor could have an effect on your possible output.
>
> One must realize that depending on your driver settings, and actual
> distance traveled per 200 motor steps via your drive mechanism, you
> might need to divide that step "availability" properly across your
> multiple axis.
>
> I'm working on a clear comment.............
>
> Ok, Say you have 5000 steps per second to "appropriate" to a
particular
> axis.
>
> If you were driving motors at "full" step, one step per pulse,
you'd
> (in theory) get your motor to move 5000 "Motor Steps" (1.8 degree -
200
> steps) PER Second.
> In reality, your motor may not be able to run that fast, especially
with
> a load applied.
>
> Now, on the other side of the coin, If you had your drivers set
to "10"
> stepping, like a Gecko, you would immediately divide that 5000
steps by
> 10, dropping your capability to only 500 Motor steps per second.
>
> As you can see, those 10 microsteps can burn up a whole lot of
> capability, especially across 3 or more axis.
>
> Lead screws have a similar effect. If you have a screw that
moves .500",
> compared to .100" per turn, you will use only 1/5 of the "Available
> steps" with the .500" screw. Whether your motors can "pull" the
larger
> screw is another question.
>
> So, machine design has a lot to do with things as well. One should
> consider what is "necessary" in your design, and build around those
> needs. I am pretty convinced that I would have a hard time watching
a
> machine like a Sherline conduct rapids at 30ipm or so ( someone
tell me
> what they do hit ).... I think I would bolt the thing down, and
shoot
> for 100ipm with larger motors and Faster screws. You could
certainly get
> close, if your target resolution was kept in the neighborhood
of .0005,
> instead of what they must be getting with those fine screws and 10
> microstep drivers.
>
> Chris L