Re: EMC freqmod.o question

> Date: Mon, 01 Dec 2003 02:44:17 -0000
> From: "earla13" <earla13@...>
>
> I have been using EMC steppermod.o for some time to control a
> Sherline Mill with a simple Stepper Word step direction controller.
> When I try using freqmod.o the motors run much smoother, but I
> eventually loose control of the Y and Z axis expecially when homing
> or sometimes when starting up EMC. The parallel port appears to be
> locked up and completely shutting down and turning off the PC power
> corrects the problem. It is not the parallel port...changing it to
> another brand has no effect. Could it be that my PC is not fast
> enough for freqmod.o ? (450 Mhz Pentium, Intel BX Motherboard, 512
> meg RAM.) I have experimented with the Sherline Mods and played with
> their freqmod.ini files and get exactly the same result. Does anyone
> have any ideas?

The first batch of Sherline PCs used a 1.2 GHz processor and the INI file
for frequency stepping is set up for that. It is also set up for 1/4
microstepping and the standard direct connection between the 200 steps
per revolution motor and the 20 tpi screw. This means a value of 16000
steps per inch of travel.

The first thing that you will need to do is set INPUT_SCALE and
OUTPUT_SCALE so that the distance you command with the EMC matches the
actual distance traveled by an axis. If the commanded distance is the
same as actual distance moved then a value of 16000 is okay. If not you
will have to change these scale values to match your setup.

You'll need to increase the time allowed for one period and adjust the
trajectory max velocity variable. The Sherline values are;

PERIOD = 0.000016
...
MAX_VELOCITY = .36

As a first guess, I'd try

PERIOD = 0.00004
...
MAX_VELOCITY = .2

That will reduce your rapid travel to about 12 ipm but should let it run.
You may gradually reduce period until you see noticable delay in the way
that the mouse pointer moves over the mini interface.

From there you can gradually increase max_velocity until you get following
errors on long moves. When you've found a good max_velocity you should
change that parameter in each of the axis definitions as well as in the
traj section. You don't need to have the motors powered up when you do
these tests and adjustments -- except for the actual vs commanded
distance.

The home thing is a puzzle, do you have real home switches? If yes, you
can NOT use the "Joe" or "All Zero" button. You'll have to use the
individual home button or keyboard <home> instead.

Hope this helps.

Ray