Auto-Squaring with LinuxCNC v 2.8

[Kitwn]

Clive,
Well, yes it does say that but before this update I always used stepconf to make minor adjustments having never got my head round the inner workings. I was always careful to use the 'update existing file' option. Keeping safe copies of software before making changes is part of my DNA so it was only the mechanical effects I was worried about.

I'm sure I'm not the only user of LinuxCNC who is more interested in cutting wood than learning the intricacies of it's file editting, and I say that as someone with several years experience of designing and building assorted projects involving some quite complex Arduino code (never got as far as writing all of anything in C++ though).

Anyway we're all back to normal now with everything squared up again. Altering the homing squaring doesn't need alterations to the software, just a tweak of the microadjustable switch actuator shown here:

[Clive S]

Anyway we're all back to normal now with everything squared up again. Altering the homing squaring doesn't need alterations to the software, just a tweak of the microadjustable switch actuator shown here:

Yes that is one way. But is far simpler to just edit the ini file as you can get very fine adjustments. . (This is for the benefit of others to see that the config files are just plain text)


# Generated by stepconf 1.1 at Sun Jul 1 16:50:39 2018
# If you make changes to this file, they will be overwritten when you run stepconf again
# This file has been edited

[EMC]
MACHINE = test_for_slaved_axis
DEBUG = 0
VERSION = 1.0

[DISPLAY]
DISPLAY = axis
EDITOR = gedit
POSITION_OFFSET = RELATIVE
POSITION_FEEDBACK = ACTUAL
ARCDIVISION = 64
GRIDS = 10mm 20mm 50mm 100mm
MAX_FEED_OVERRIDE = 1.2
MAX_JOG_OVERRIDE = 1.2
MIN_SPINDLE_OVERRIDE = 0.5
MAX_SPINDLE_OVERRIDE = 1.2
DEFAULT_LINEAR_VELOCITY = 2.50
MIN_LINEAR_VELOCITY = 0
MAX_LINEAR_VELOCITY = 25.00
DEFAULT_ANGULAR_VELOCITY = 2.50
MIN_ANGULAR_VELOCITY = 0
MAX_ANGULAR_VELOCITY = 25.00
INTRO_GRAPHIC = linuxcnc.gif
INTRO_TIME = 5
PROGRAM_PREFIX = /home/clive/linuxcnc/nc_files
INCREMENTS = .5mm .1mm .05mm .01mm .005mm
PYVCP = custompanel.xml


[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 = linuxcnc.var

[EMCMOT]
EMCMOT = motmod
COMM_TIMEOUT = 1.0
COMM_WAIT = 0.010
BASE_PERIOD = 100000
SERVO_PERIOD = 1000000

[HAL]
HALFILE = wal_slaved_axis.hal
HALFILE = custom.hal
POSTGUI_HALFILE = postgui_call_list.hal

[TRAJ]
COORDINATES = XYZ
LINEAR_UNITS = mm
ANGULAR_UNITS = degree
CYCLE_TIME = 0.010
DEFAULT_LINEAR_VELOCITY = 2.50
MAX_LINEAR_VELOCITY = 25.00

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

[KINS]
KINEMATICS = trivkins coordinates=XXYZ kinstype=BOTH
JOINTS = 4

[AXIS_X]
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
MIN_LIMIT = -0.001
MAX_LIMIT = 200

[JOINT_0]
TYPE = LINEAR
# final home position machine-unit/sec
HOME = 70
MIN_LIMIT = -0.001
MAX_LIMIT = 200
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
STEPGEN_MAXACCEL = 937.5
SCALE = 320
FERROR = 1
MIN_FERROR = .25

HOME_OFFSET = 0.1 # use this to square the gantry

# machine-units per sec next 3 lines
HOME_SEARCH_VEL = 10 This is the speed it searches for the home switch use a -ve number to revervse
HOME_LATCH_VEL = -6 This the the speed it use to back off the switch use a -ve to reverse
HOME_FINAL_VEL = 20 This is the speed it will travel to the final HOME position

HOME_USE_IIDEX = NO

HOME_SEQUENCE = -1 # has to be -ve for gantry

[JOINT_1]
TYPE = LINEAR
# final home position machine-unit/sec
HOME = 70
MIN_LIMIT = -0.001
MAX_LIMIT = 200
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
STEPGEN_MAXACCEL = 937.5
SCALE = 320
FERROR = 1
MIN_FERROR = .25

HOME_OFFSET = 0.5 # use this to square the gantry

# machine-units per sec next 3 lines
HOME_SEARCH_VEL = 10
HOME_LATCH_VEL = -6
HOME_FINAL_VEL = 20

HOME_USE_IIDEX = NO

HOME_SEQUENCE = -1 # has to be -ve for gantry

[AXIS_Y]
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
MIN_LIMIT = -0.001
MAX_LIMIT = 200.0

[JOINT_2]
TYPE = LINEAR
HOME = 0.0
MAX_VELOCITY = 25.0
STEPGEN_MAXACCEL = 937.5
SCALE = 80.0
FERROR = 1
MIN_FERROR = .25
HOME_OFFSET = 0.000000
HOME_SEARCH_VEL = 0
HOME_LATCH_VEL = 0
HOME_USE_IIDEX = NO
HOME_SEQUENCE = 0

[AXIS_Z]
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
MIN_LIMIT = -100.0
MAX_LIMIT = 0.001

[JOINT_3]
TYPE = LINEAR
HOME = 0.0
MAX_VELOCITY = 25.0
STEPGEN_MAXACCEL = 937.5
SCALE = 80.0
FERROR = 1
MIN_FERROR = .25
HOME_OFFSET = 0.000000
HOME_SEARCH_VEL = 0
HOME_LATCH_VEL = 0
HOME_USE_IIDEX = NO
HOME_SEQUENCE = 0

[Kitwn]

Thanks Clive, I didn't know about that way of setting the squaring.
I have plans to make some new homing switches using latching Hall effect sensors and two magnets attached to the moving gantry. Using latching sensors will overcome the problems associated with the gantry overshooting the sensor while decelerating and might be more accurate/repeatable than conventional Hall sensors. That design may be less able to use the microadjustable switch actuator shown above so your method may well become necessary.

Kit

[michaelrommel]

Hi folks,
I am building such a gantry with two Y-axis motors/joints. I want to use these typical chinese proximity sensors as limit switches and homing switch.

In order to have the gantry square every time, the two sensors on the Y-Axes need to be precisely repeatable. So I wondered if any of you have experience whether it is better to approach the limit axially or radially (the cutout in the metal in the lower image shall act as an "open" of a NC sensor - with the axial approach this is not possible, of course.)

Where to those sensors detect more reliable?



Thanks for your insights!

Michael.

[Clive S]

Welcome to the forum Michael

I prefer the target going past the end of the sensor PNP NO as it is quite easy to break the sensor head on. PNP are easier to use with standard Mesa cards like 7i96 7i76 7i92 etc.

Of course as you probably know with linuxcnc 2.8 you adjust the home offsets to square the gantry in the ini file.

[Kitwn]

Michael,

I hope this thread will help you get LinuxCNC 2.8 up and running without any problems.
One thing to watch out for that is mentioned on the LinuxCNC forum regarding the auto-squaring is that the sensors must stay triggered until the software tells the gantry to move again. If the cutout in your drawing were too narrow there is a risk of overshooting the slot during deceleration and resetting the sensor too early.

Kit