Re: [CAD_CAM_EDM_DRO] Minimum reasonable computer speed?

Hi Jan,

Are you talking about a complete hobby controller, or simply some
experiments with steppers? When you mention changing "delay loop
numbers", I wonder if you are running a complete controller.

What kind of feed rates do you get? can you select different feed rates
(F words, G0, G1 words)?

Can you move all three axis at once? Interpolated motion is required
for a controller. Without interpolated moves, you can't do anything
other then vertical or horizontal lines. What does your controller do?

Can you do arcs? All controllers can do arcs. If not, then it would be
good to state so when you declare that "NO reason to have speed faster
than a couple megahurts clock for CNC purposes" is required. Otherwise,
you are misleading readers! Interpolated motion and arc calculations
demand floating point math, and that takes a LONG time at "couple
Megahurts".

How do you set various feed rates using delay-loop constants? And how
do you do acceleration/deceleration? Anything faster then about 4 IPM
needs acceleration/deceleration. Can you rapid? Then you need acc/dec!
a fixed "delay-loop constant" will not give you acc/dec.

What "flavor" of Gcode do you parse? A controller program must be able
to parse (read and break down) a CNC or "motion control" language. This
language gives coordinates and control words that the program needs to
do it's job.

An extremely limited subset of a controller program might just READ a
list of coordinates for drilling. This limited controller would be able
to do Manhattan (just horizontal and vertical) motions in the XY plane,
but this is a special case. Is that what you're talking about? You
should specify. And the "drilling program" would still have to READ the
coordinates from a file. Adding lines of code to a program to define
the coordinates you wish to drill at is NOT the type of controller most
of our list members are going to want. A worthwhile experiment perhaps,
but it should be stated as such so as not to confuse readers.

All of these topics must be addressed for a reasonable controller
program. As the machine requirements for your experiments are not
typical, you should state so when you discuss your work.

I suggest the reader below check the requirements of TurboCNC or one of
Art's Mach programs to determine his machine requirements.

Alan KM6VV


JanRwl@... wrote:

>> In a message dated 1/27/2005 5:28:52 P.M. Central Standard Time,
>> codesuidae@... writes:
>>
>> I've got an old 486 (about 33mhz), which I think should be sufficent, but I
>> just want to double check.

> My first home-brew CNC stuff ran off a '286 PC with only 7 mHz. clock. I
> use a nice old '386 in my lab, and it's clock is around 20 mHz. The 33 mHz
> '486 is MORE than sufficient! You only have to change the "delay loop numbers"
> in your software to maintain the desired OUTPUT-rate.
>
> I now have a Pentium3 Compaq which came with Win.95 running my home-brew
> lathe, but that '95 got corrupted, and updating to '98 would have cost as much
> as a new computer, so I just FORMATTED it and loaded ONLY MSDOS and GWBASIC,
> and it works fine, so long as I put in HUGE delay-loop constants in the
> step-subroutines.
>
> I can see NO reason to have speed faster than a couple megahurts clock for
> CNC purposes, so long as you know how to jiggle the output-rate by changing
> constants in your op.sys.
> Jan Rowland
>