Noobie needs Z-Axis Help Please!

[titaniumw41]

Hi All,

I am new at this so hopefully there is a simple answer to my problem. I have a fine line automation FLA-100 with a g540. I wired in 3 "floating" hall effect switches on the moving axes that trip using magnets on each end. I have everything figured out on the x and y axes but am having quite a time getting the z-axis figured out. It wants to home in the "down" position and I need it to home in the "up" position. When I click the inverse buttons it functions the way I want it EXCEPT that the AXIS representation is inverted as well as the page up / down keys. I tried inverting, using a negative sign in front of the lead-screw pitch, and both (inverted the invert) but I just can't get it right. I also tried tweaking settings in the .ini file but I still end up with the same issue. I have been reading forums and checking the emc2 docs but I can't seem to find anything. Any ideas?


Here is my .ini

# Generated by stepconf at Thu Jan  6 04:00:58 2011
# If you make changes to this file, they will be
# overwritten when you run stepconf again

[EMC]
MACHINE = my-mill
DEBUG = 0

[DISPLAY]
DISPLAY = axis
EDITOR = gedit
POSITION_OFFSET = RELATIVE
POSITION_FEEDBACK = ACTUAL
MAX_FEED_OVERRIDE = 1.2
INTRO_GRAPHIC = emc2.gif
INTRO_TIME = 5
PROGRAM_PREFIX = /home/cnc/emc2/nc_files
INCREMENTS = .1in .05in .01in .005in .001in .0005in .0001in

[FILTER]
PROGRAM_EXTENSION = .png,.gif,.jpg Greyscale Depth Image
PROGRAM_EXTENSION = .py Python Script
png = image-to-gcode
gif = image-to-gcode
jpg = image-to-gcode
py = python

[TASK]
TASK = milltask
CYCLE_TIME = 0.010

[RS274NGC]
PARAMETER_FILE = emc.var

[EMCMOT]
EMCMOT = motmod
COMM_TIMEOUT = 1.0
COMM_WAIT = 0.010
BASE_PERIOD = 50000
SERVO_PERIOD = 1000000

[HAL]
HALFILE = my-mill.hal
HALFILE = custom.hal
POSTGUI_HALFILE = custom_postgui.hal

[TRAJ]
AXES = 3
COORDINATES = X Y Z
LINEAR_UNITS = inch
ANGULAR_UNITS = degree
CYCLE_TIME = 0.010
DEFAULT_VELOCITY = 0.50
MAX_LINEAR_VELOCITY = 5.00

[EMCIO]
EMCIO = io
CYCLE_TIME = 0.100
TOOL_TABLE = tool.tbl

[AXIS_0]
TYPE = LINEAR
HOME = 0.25
MAX_VELOCITY = 4.75
MAX_ACCELERATION = 30.0
STEPGEN_MAXACCEL = 37.5
SCALE = 4000.0
FERROR = 0.05
MIN_FERROR = 0.01
MIN_LIMIT = 0.0
MAX_LIMIT = 24.0
HOME_OFFSET = 0.125000
HOME_SEARCH_VEL = -0.500000
HOME_LATCH_VEL = 0.125000
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = 1

[AXIS_1]
TYPE = LINEAR
HOME = 0.25
MAX_VELOCITY = 4.75
MAX_ACCELERATION = 30.0
STEPGEN_MAXACCEL = 37.5
SCALE = 4000.0
FERROR = 0.05
MIN_FERROR = 0.01
MIN_LIMIT = 0.0
MAX_LIMIT = 36.0
HOME_OFFSET = 0.125000
HOME_SEARCH_VEL = -0.500000
HOME_LATCH_VEL = 0.125000
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = 2

[AXIS_2]
TYPE = LINEAR
HOME = -.25
MAX_VELOCITY = 4.75
MAX_ACCELERATION = 30.0
STEPGEN_MAXACCEL = 37.5
SCALE = -4000.0
FERROR = 0.05
MIN_FERROR = 0.01
MIN_LIMIT = -6
MAX_LIMIT = 0
HOME_OFFSET = -.125
HOME_SEARCH_VEL = -0.500000
HOME_LATCH_VEL = 0.125000
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = 0

Thanks for your time!

[chester88]

From the manual:
Home Search Velocity
The velocity to use when moving towards the switch. If the switch is near the end of travel, this velocity must be chosen so that the axis can decelerate to a stop before hitting the end of travel. If the switch is only closed for a short range of travel (instead of being closed from its trip point to one end of travel), this velocity must be chosen so that the axis can decelerate to a stop before the switch opens again, and homing must always be started from the same side of the switch.
If the machine moves the wrong direction at the beginning of the homing procedure, negate the value of Home Search Velocity.

so get the axis and the GUI to agree on jogging direction, then if it homes in the wrong
direction negate the home search velocity entry
The other possibility is the home switch needs to be inverted but usually you get a 'on limit switch error ( if your limit and home is shared).

Chris M

[titaniumw41]

Yeah, I should have caught that. I'll report back tomorrow when it works

Thanks for your help!

[titaniumw41]

Yes, that fixed it after some frustration. Turns out I forgot I edited some things directly in the .ini file. Then when I switched the sign on HOME_SEARCH_VEL I did it in stepconfig. Stepconfig isn't aware of anything you did to the .ini file so it over wrote it with some things I had in there previously (it even warns you about that.) In the end, after switching the HSV sign and setting my HOME and HOME_OFFSET to what they should be, all was well.

Another question though: Does everyone typically have their z completely negative? I have mine set to 0 to -6 (6 inches of travel.) What is common for this? 3 to -3? 6 to 0?

I tried the obligatory "shove a sharpie in the collet and draw" test today. After error upon error, I learned I have a lot to learn about offsets. Maybe I'll have better luck tomorrow!

Thanks,

Michael

[chester88]

When the tool travels closer to the work holder (either the table or a chuck eg lathe)
then the axis is moving in the negative direction. This is a standard.

When setting the table travel limits in stepconf you are actually defining the origin of the machine coordinates.

As far as I can tell it really doesn't matter where the origin is as long as moving the tool towards the work holder is in the negative direction.

The reason it doesn't matter is you don't run the machine using machine coordinates you set user coordinates (G 54 etc) . These are referenced from machine coordinates.

I lied a little actually - there is a G 53 command that directly uses machine coordinates.
programming G 53 x0 will move the axis to the 'absolute' x 0 which is the machine c0ordinate x 0 which you defined in stepconf. so if using G 53 then the defining of the origin would be important. You might use this for a tool changer position .

To answer the other question about machining with z negative.
if you set your user coordinate to be zero at the top of your table the all you z moves will be positive.
I'm pretty sure most people set Z zero at the top of the work piece.

Chris M