Re: [CAD_CAM_EDM_DRO] EMC Acceleration

ab2pn wrote:

>
> I have been fighting with EMC, My Mill, and My Cad software trying to
> get a decent PC Board or engraving out of it all.
>
> I would lose steps and the z axis would drift down while engraving or
> while making a pcboard.
>
> I called Sherline (my Mill manufactures) and they said to hook up a
> counter weight. So after building a counter weight and pulley system
> I still had the same error of the bit drifting down (My weight and
> the head are almost perfectly balanced).
>
> I was having some trouble with EMC and WinQcad and the programmer of
> WinQcad said to use TurboCNC, so I set up TurboCNC using the .ini
> file from the group. It worked perfectly!!!
>
> I to have read up on and made changes to the EMC .ini file I have
> come to the conclusion that the problem in in the accell/decell
> movements.
>
> When TurboCNC runs you can hear the motors Ramp-up move then ramp
> down, unlike EMC where it is a fast move and steps get lost (because
> of inertia?).
>
> I have not been able to get a good cut out of EMC due to the Z axis
> drifting down, but would love to see it work since it suits my need
> better than TurboCNC.
>
> Please let me know if you find any more details or a solution.
>
> Thank you.

**************************

Hello ab2pn,

At any given computer clock speed, EMC will not run steppers as fast as
TurboCnc will. TurboCcn runs my Sherline 5410 axes at 20ipm max
velocity, 20ipm/sec acceleration, 8 microsteps, on a 200MHz Pentium
laptop. I did this for a year on my previous laptop with a 66MHz 80486.

EMC on my 200MHz laptop tops out at about 4 or 5 ipm with 8 microsteps.
I can get 8 to 10ipm if I use 4 microsteps.

The bottom line is that TurboCnc will run steppers faster than EMC will
if computer clock speed is the limiting factor. If you got the computer
from Sherline then it is setup for 4 microsteps and the clock is fast
enough (600MHz?) to get you up to 20ipm or so on all three axes with EMC
but you will probably be at about the limit of EMC on that computer. On
the same computer, TurboCnc won't even be breathing hard.

Tom Hubin
thubin@...