Re: EMC AND GECKO'S G210

RICHARD (comments mixed in)

>    From: "armartinus" <armartin@...>
> Subject: EMC AND GECKO'S G210
>
> EMC puts out some raged steps,

Has this raggedness caused machine failure for you or is this statement a
reflection of some previous posts or concerns expressed on this list?
FUD?

My personal experience is that the raggedness of the pulse train for
steppermod or freqmod cause no problems with my 100 ounce inch steppers
running my grizz at 36 ipm. In this example the EMC is running on a slightly
overclocked gateway 166 and driving Gecko 210's. My INPUT_SCALE for that
machine is 6k.

> will the gecko's g210 with the
> multiplier chip help me? freqmod also seems to put out raged steps at
> higher feed rates. I get clean steps from cncpro but no continuous
> contouring. Jon Elson is working on a board for EMC to put out clean
> steps but it is not finished yet( Jon i will send you coffee if you
> work late).If any one has experimented with EMC and the G210 at high
> speeds. my goal 200 ipm carving.

Yes the 210 will be an advantage but not because it banks pulses and smoothes
out the train. It's advantage is that it can drive your motors a full step
for each pulse put into it. (see calculations below)

Now you say that you want 200 ipm but are afraid that you can't get that with
the EMC. Let me share the experience of a fellow who called me the other
day. He is getting 600 ipm on a rather large router table cutting 3d foam
molds and fillers for the US military. (That might say something about
accuracy and repeatability.) Seems he sits in his air conditioned room
watching this thing work through the window. And he is making mega-bucks 12
hours a day with it.

How does he do it? Well he did some planning for the cutting speeds he
wanted and simply built the table for the number of steps per unit to achieve
that speed at a known good ppr from a reasonable computer. So the answer to
your question about someone EXPERIMENTING is probably no, but I know of
several who are RUNNING consistently at multiples of the speed you want using
the existing software.

The following design calculations assume inch as the unit. You should not
assume that this calculating is correct as it was done at the end of a very
long day.

1 - Start your design with the desired speed. (200 ipm)

2 - Make a conservative guess at pulse rate (8KHz) for PC times 60 for ppm.
8000 * 60 = 480,000 ppm

3 - Find stepsize by dividing ipm by ppm and ask yourself if you're happy.
200 / 480,000 = 0.00042

4 - Multiply ppm by the turns-per-inch of your leadscrew. (assumed 5)
200 * 5 = 1000 rpm (watch the whipping on long screws)

4 - Divide ppm by pulses per revolution for motor.
480,000 / 200 = 2400 rpm

5 - Divide rpm by 10 microsteps for gecko 200 series.
2400 / 10 = 240 rpm (this is top speed if driven by gecko 201)

6 - Multiply by the 210 pulse multiplier factor.
240 * 2 = 480 motor rpm
240 * 5 = 1200 motor rpm
240 * 10 = 2400 motor rpm

7 - Compare motor rpm and leadscrew rpm.
480 / 1000 = 0.48 belt ratio
1200 / 1000 = 1.2 belt ratio.
2400 / 1000 = 2.4 belt ratio.

Now it is time to consider cutting and acceleration forces and study Mariss's
motor sizing post.

Ray