Re: EMC setup questions

Anders

One thing that you want to think about when setting an EMC's ini file for
metric is that several of the variables are in units per whatever. Accel
is units per sec per sec so you would want to run higher than we do in
inches. Also following error is in percent deviation per unit so it
becomes very small when you switch to mm. I'd multiply it by 25 at least
so that you get back to where it would be with inches.

I believe that the reason that following error trips out quicker in one
direction than the other is that when something in the equasion changes
sign, it does one computation or comparison ahead of another. I've seen
this behavior fairly often and most of the time, changing following error
for metric will cure the problem.

I'd agree with the several other posts that say that 80 sounds right for
input scale.

Ray

>    From: "awallin25" <anders.wallin@...>
> Subject: EMC setup questions
>
> Hi All,
>
> Thanks for all the answers to my previous questions. I have now got my
> system up and running with EMC.
> I am still looking for the right settings to get my units correct:
> Now EMC works in mm and shows mm on the screen, but my table moves
> lots more than 1mm when commanded to move 1mm. This is when I have
> input_scale=1000 and the emc-gui shows a feedrate of around 20-60
> units?/s
>
> I am using steppermod.o
>
> I have linear_units =1
>
> I have tried to calculate input_scale as follows:
> my steppers are 200step/rev driven with halfs steps => 400steps/rev
> my ballscrews give me 5mm movement for every rev.
> => input_scale should be 80 ??
>
> when I set input_scale to 80 on one axis for testing it, it seems to
> work when jogging in the + direction, but I immediately get a
> following error when pressing the - button.
> The FAQ tells me to reduce feedrate when this happens. I have
> max_velocity set to 20 on all axes.
> If I understand correctly the parallell port whould be able to do
> around 5 kHz which would be equivalent to a feedrate of over 60mm/sec
> on my system (5000steps/s / 400 steps/rev * 5 mm /rev > 60 mm/s)
> even with a very low feredrate I get the following error when trying
> to move in the - direction.
>
> thanx for any help,
>
> AW