Re: EMC ini file questions.

[Jon Elson <elson-at-pico-systems.com>]

Lee & Chris studley wrote:

>
> Hi, Does anyone have definite explanations these items under the
> axis setup sections:
> [AXIS_0]
> .
> HOME = 0.000 

This is the offset between the mechanical location where the home switch
closes a contract and the position called home.  In other words, you can 
have
the hope position located some distance away from the actual home switch
position.  When you home, it finds the switch, moves the HOME distance
specified on that axis, and then the display will read 0.0000

>
> MAX_VELOCITY = 1.2 ?????????????? 

If you have defined the user units to be 0.03937xxxxx, your "user units" are
inches.  If you've set them to be 1.00000, then your user unit is mm.
MAX_VELOCITY is that many user units per **SECOND**.  So, if
your units are inhes, the above setting is 1.2 IPS, or 72 IPM (a more
familiar unit for machinists.)

>
> BACKLASH = 0.000 

Sets the amount of backlash to be compensated for in software, again, in 
user units.

>
> BIAS = 0.000 

A steady offsetting force applied to an axis.  This is only meaningful for
real analog servo systems, in most cases.  It will help offset the weight of
a machine head, for instance.

>
> MAX_ERROR = 0.000
> DEADBAND = 0.000 

This sets a region close to the commanded position where no effort will 
be made
to correct the difference between actual and commanded position.  Since 
freqmod
and other open-loop stepper drive schemes simulate a servo system in 
software,
this can help stop jittering digits or chattering motors when the 
machine is supposed
to be at rest.

>
> CYCLE_TIME = 0.001000 

This sets the time, in seconds, between evaluations of actual and commanded
position.  It also sets the rate at which the current path is 
interpolated.  The above
setting is 1000 times a second.

>
> .
>
> And under the section[TRAJ] just above the Axis setup, how do these
> interact with same items defined in each of the [AXIS-..] sections:
>
> ; Trajectory planner section ------------------------------
> [TRAJ]
>
> AXES = 3
> COORDINATES = X Y Z
> HOME = 0 0 0
> ;LINEAR_UNITS = 0.03937007874016
> LINEAR_UNITS = 1.0
> ANGULAR_UNITS = 1.0
> ; CYCLE_TIME = 0.025
> CYCLE_TIME = 0.025
> DEFAULT_VELOCITY = 2 ???????????????????
> MAX_VELOCITY = 3.0 ????????????????? 

Default is the current jog rate when EMC starts up, and MAX is the
highest you can set the jog rate, and also the highest feed rate that will
be attempted by the software.  These work out to 120 and 180 IPM,
assuming user units are inches.  (settings are user units/second, again.)

>
> ;1.3
> DEFAULT_ACCELERATION = 0 ???????????????????
> MAX_ACCELERATION = 0 ??????????????????? 

These would not be good settings to use.  I'm not exactly sure of the
meaning of the two settings, only one of them (forget which) is
meaningful for EMC.  (Robot motion control through RCS
has distinct meanings for both, I think.)  So, set both the same for
EMC, and it is again in user units / second / second.  2 to 3 is good
for many small and stepper machines, somewhat higher for powerful
servo machines, when using inches.  50 to 75 might be good for user
units of mm.

>
> ;1.3
> ;PROBE_INDEX = 0
> ;PROBE_POLARITY = 1

These apply when using the probing option of EMC, to tell it which I/O bit
is wired to the touch probe, and whether a 1 or 0 means the probe is 
touching
the workpiece.

Jon