Re: Steppers and lead screws

[Ray <rehenry-at-up.net>]

Lucas

Glad that you have joined and have a running system.  Sorry to take so
long getting back to you on your problems with setting up the EMC for mm
rather than inches.  I will mix my comments into your post.

On Tue, 20 Feb 2001, Lucas wrote:
> Hi everybody
> 
> We have a compiled 11Aug2000 EMC running with the new interpreter, and
> since we want to work in mm, and the stepper- lead screw combination we
> use, has a ration of 200 steps/mm, we made the following settings in the
> ini file:
> 
> LINEAR_UNITS=1
> INPUT_SCALE=200  0
> OUTPUT_SCALE=200  0 (since we are using freqmod)

In order to make my system work like you are thinking, I edited my ini file
like this.  (I put stars after the things I changed in the list below, not
in the real ini file)

-----snippet of my ini-----
; Trajectory planner section --------------------------------------------------
[TRAJ]

AXES =			3
; COORDINATES =		X Y Z R P W
COORDINATES =		X Y Z
HOME =			0 0 0
LINEAR_UNITS =		1.00000000  *****
ANGULAR_UNITS =		1.0
CYCLE_TIME =		0.010
DEFAULT_VELOCITY = 	0.42418  *****
MAX_VELOCITY = 		30.48  *****
DEFAULT_ACCELERATION =	5.0 *****
MAX_ACCELERATION =	5.0  *****
...

; Axes sections ---------------------------------------------------------------

; First axis
[AXIS_0]

TYPE =				LINEAR
UNITS =				1.0000000000  *****
HOME = 				0.000
MAX_VELOCITY =			30.48  *****
P = 1000.000
I = 0.000
D = 0.000
FF0 = 0.000
FF1 = 0.000
FF2 = 0.000
BACKLASH = 0.000
BIAS = 0.000
MAX_ERROR = 0.000
DEADBAND = 0.005  *****
CYCLE_TIME =			0.001000
INPUT_SCALE =			200.0	0  *****
OUTPUT_SCALE = 		200.0 	0  *****
MIN_LIMIT =			-1000.0  *****
MAX_LIMIT =			1000.0  *****
MIN_OUTPUT =			-10
MAX_OUTPUT =			10
FERROR = 25.400  *****
MIN_FERROR = 0.254  *****
HOMING_VEL =			0.1
HOME_OFFSET =			1 ***** (I use 0.1 inch)
ENABLE_POLARITY =		0
MIN_LIMIT_SWITCH_POLARITY =	0
MAX_LIMIT_SWITCH_POLARITY =	0
HOME_SWITCH_POLARITY =		1
HOMING_POLARITY =		1
JOGGING_POLARITY =		1
FAULT_POLARITY =		1
-----end of ini snippet-----
 
> With EMC in MDI-mode, the following command resulted in 18 steps in
> stead of 2:
> 
> G0 G21 X0.01

With this command, I got 2 steps.  My system seems to work the way that you
would like yours to work.  If your ini file is set up the same as mine
above, the only difference is that I used the january 17, 2000 binary from
sourceforge.  

> My second question is also related to G21.  Is it correct to say that if
> I enter G21 in MDI-mode, and change back to manual-mode, that the jogs
> will be in mm?

If you set all of the linear units to 1, you will always get manual motion
in mm rather than in inches.  G20/G21 only affects auto and mdi modes.  In
G21 (default in the new interpreter) cds.ngc will cut a very nice metric
sized model.  It will also show it using backplot from the view menu.  

In G20 it will cut the inch sized model.

Tkemc will always display axis position in mm.  I suppose that we should
remove the last zero since it isn't used at all. 

Hope this helps.  It was interesting to try it here.

Ray