THC qtplasmac 2.9 is moving UP when it should be moving DOWN

Hello
I'm having a weird Qtplasmac 2.9.238.315 bug where my torch goes down when it should be going up - but only during THC corrections.
Normal Z axis movement is OK as it should, with homing, probing, etc.

THC is being used from voltage (THCAD-2) and arc OK signal is present. 

I tried reversing the Voltage Scale (from 0.009 to -0.009) and no changes. - it still is correcting in the reverse way. how weird is it!

Where could i start?

Thanks everyone

Does the torch go down when pressing the PgDwn button on keyboard or - sign with jog buttons on screen?
If that is incorrect, nothing will help.
Also, what are the min_limit and max_limit set for the Z axis in the ini file?

Yes, that’s the weird part. It is correct.




INI for Z it’s like this:



[AXIS_Z]
# MAX_VEL & MAX_ACC need to be twice the corresponding joint value
MAX_VELOCITY = 66.66666666666667
MAX_ACCELERATION = 1500.0
OFFSET_AV_RATIO = 0.5
MIN_LIMIT = -0.0
MAX_LIMIT = 250.0

[JOINT_2]
TYPE = LINEAR
HOME = 250.0
FERROR = 10.0
MIN_FERROR = 1.0
MAX_VELOCITY = 33.333333333333336
MAX_ACCELERATION = 750.0
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.
STEPGEN_MAXVEL = 41.67
STEPGEN_MAXACCEL = 937.50
P = 1000.0
I = 0.0
D = 0.0
FF0 = 0.0
FF1 = 1.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 0.0
# these are in nanoseconds
DIRSETUP = 10000
DIRHOLD = 10000
STEPLEN = 3000
STEPSPACE = 3000
STEP_SCALE = -1000.0
MIN_LIMIT = -0.0
MAX_LIMIT = 250.0
HOME_OFFSET = 260.000000
HOME_SEARCH_VEL = 16.666667
HOME_LATCH_VEL = 5.000000
HOME_FINAL_VEL = 0.000000
HOME_USE_INDEX = NO
HOME_SEQUENCE = 2

Try:
min_limit = -250
max_limit = 0
home = 0
home_offset = 0 or -3 due to not stopping at the switch
Notice there are two instances of min/max limits to change.

To add to what Tommy said ...

From: linuxcnc.org/docs/devel/html/plasma/qtpl...ml#plasma:z-settings

[AXIS_Z] MIN_LIMIT should be just below top of the slats with allowances for float_switch_travel and over travel tolerance. For example, if the user’s float switch takes 4 mm (0.157") to activate then set the Z minimum to 5 mm (0.2") plus an allowance for overrun (either calculated using the equation below or allow 5 mm (0.2") below the lowest slat).

[AXIS_Z] MAX_LIMIT should be the highest the user wants the Z axis to travel (it must not be lower than Z HOME_OFFSET).

[AXIS_Z] HOME should be set to be approximately 5 mm-10 mm (0.2"-0.4") below the maximum limit.

There's a nice diagram there too.