Z Axis Home - Gantry Router
- Project_Hopeless
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15 Mar 2020 01:09 #160241
by Project_Hopeless
Z Axis Home - Gantry Router was created by Project_Hopeless
On my Z axis (vertical) I'm using the top switch as the home/limit. Made sense to have the tool clear all parts and fixtures during homing.
After the homing and latch functions are complete the axis moves to the Home_Offset (towards the table). This leads me to believe the Home_Offset should be a small value so it doesn't approach the table.
However Home _Offset sets the machine zero after it executes according to the DRO. If I use a small Home_Offset does the Z axis work in the negative quadrant? The table is not zero?
I did hand edit the HAL file in one location to reverse the Z axis motor. This shouldn't cause a problem should it?
What setting would you recommend for a Z axis with 185mm of travel hard stop to hard stop?
After the homing and latch functions are complete the axis moves to the Home_Offset (towards the table). This leads me to believe the Home_Offset should be a small value so it doesn't approach the table.
However Home _Offset sets the machine zero after it executes according to the DRO. If I use a small Home_Offset does the Z axis work in the negative quadrant? The table is not zero?
HOME = 170
HOME_OFFSET = 150
HOME_SEARCH_VEL = 15
HOME_LATCH_VEL = -10
HOME_SEQUENCE = 1
HOME_USE_INDEX = False
HOME_IGNORE_LIMITS = TrueI did hand edit the HAL file in one location to reverse the Z axis motor. This shouldn't cause a problem should it?
setp hm2_[HOSTMOT2](BOARD).0.stepgen.03.direction.invert_output trueWhat setting would you recommend for a Z axis with 185mm of travel hard stop to hard stop?
HOME = ?
HOME_OFFSET = ?
HOME_SEARCH_VEL = ?
HOME_LATCH_VEL = ?
HOME_SEQUENCE = ?
HOME_USE_INDEX = False
HOME_IGNORE_LIMITS = TruePlease Log in or Create an account to join the conversation.
- tommylight
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15 Mar 2020 01:45 #160246
by tommylight
Replied by tommylight on topic Z Axis Home - Gantry Router
Easiest :
home offset 0
touch the material with the bit, touch off in the GUI (near the home button) and that will be your material 0.
home offset 0
touch the material with the bit, touch off in the GUI (near the home button) and that will be your material 0.
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15 Mar 2020 02:27 #160251
by pippin88
Replied by pippin88 on topic Z Axis Home - Gantry Router
Yes, the Z travel will be negative in machine coordinates (G53).
You are correct to have your home switch at the top of the Z.
Example:
Z axis travel 200mm
Machine coordinates (G53) will be -200 to 0.
Once homed, you usually deal with work coordinates (most commonly G54).
You then 'zero' the work coordinates where you want, commonly the top of the work, or the table/spoilboard.
www.linuxcnc.org/docs/html/gcode/coordinates.html
There is no problem at all with working with negative travel values in GCode. It is by far the most common method to have Z working in 'negative' space.
You are correct to have your home switch at the top of the Z.
Example:
Z axis travel 200mm
Machine coordinates (G53) will be -200 to 0.
Once homed, you usually deal with work coordinates (most commonly G54).
You then 'zero' the work coordinates where you want, commonly the top of the work, or the table/spoilboard.
www.linuxcnc.org/docs/html/gcode/coordinates.html
There is no problem at all with working with negative travel values in GCode. It is by far the most common method to have Z working in 'negative' space.
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15 Mar 2020 02:28 #160252
by pippin88
Replied by pippin88 on topic Z Axis Home - Gantry Router
Also, given tools are different lengths, it is not feasible to have the table as zero in machine coordinates.
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- Project_Hopeless
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15 Mar 2020 14:17 #160303
by Project_Hopeless
Replied by Project_Hopeless on topic Z Axis Home - Gantry Router
And axis limts are based on machine coordinates, so I should have 0 to -175mm for Z limits?Yes, the Z travel will be negative in machine coordinates (G53).
You are correct to have your home switch at the top of the Z.
Example:
Z axis travel 200mm
Machine coordinates (G53) will be -200 to 0.
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15 Mar 2020 14:26 - 15 Mar 2020 14:31 #160305
by pippin88
Replied by pippin88 on topic Z Axis Home - Gantry Router
First to check:
What direction does your Z axis move when you job up (Page Up on keyboard or + button on GUI)?
(Another way to invert an axis direction is to make the step scale negative. In my ini below, you'll see "STEP_SCALE = -250.0")
You can use values like your original post that will result in positive values (though your values, particularly home offset are not correct), however I suggest it is easiest to work with Machine Z zero being at the top of the Z axis.
My INI for Z axis
What direction does your Z axis move when you job up (Page Up on keyboard or + button on GUI)?
(Another way to invert an axis direction is to make the step scale negative. In my ini below, you'll see "STEP_SCALE = -250.0")
You can use values like your original post that will result in positive values (though your values, particularly home offset are not correct), however I suggest it is easiest to work with Machine Z zero being at the top of the Z axis.
My INI for Z axis
#********************
# Axis Z
#********************
[AXIS_Z]
MIN_LIMIT = -195.0
MAX_LIMIT = 0.01
MAX_VELOCITY = 333.333333333
MAX_ACCELERATION = 2000.0
[JOINT_3]
TYPE = LINEAR
HOME = 0.0
FERROR = 0.5
MIN_FERROR = 0.05
MAX_VELOCITY = 333.333333333
MAX_ACCELERATION = 2000.0
# 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 = 500
STEPGEN_MAXACCEL = 4000.0
# these are in nanoseconds
DIRSETUP = 5000
DIRHOLD = 10000
STEPLEN = 2500
STEPSPACE = 2500
# 4000 pulses (200x20microstepping) per rev / 16mm pitch screws
STEP_SCALE = -250.0
MIN_LIMIT = -195.0
MAX_LIMIT = 0.01
HOME_OFFSET = 0.25
HOME_SEARCH_VEL = 30
HOME_LATCH_VEL = -0.25
HOME_FINAL_VEL = 0.000000
HOME_USE_INDEX = NO
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = 0
Last edit: 15 Mar 2020 14:31 by pippin88.
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- Project_Hopeless
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15 Mar 2020 14:36 #160307
by Project_Hopeless
I do have a question about your Home_Offset. If the Max_Limit is 0.01, how does the machine Home_Offset to 0.25? Isn't that outside the limits?
Replied by Project_Hopeless on topic Z Axis Home - Gantry Router
I set the axis Invert to True, and +ve Z moves up.First to check:
What direction does your Z axis move when you job up (Page Up on keyboard or + button on GUI)?
(Another way to invert an axis direction is to make the step scale negative. In my ini below, you'll see "STEP_SCALE = -250.0")
You can use values like your original post that will result in positive values, however I suggest it is easiest to work with Machine Z zero being at the top of the Z axis.
My INI for Z axisMIN_LIMIT = -195.0 MAX_LIMIT = 0.01 HOME_OFFSET = 0.25 HOME_SEARCH_VEL = 30 HOME_LATCH_VEL = -0.25 HOME_FINAL_VEL = 0.000000 HOME_USE_INDEX = NO HOME_IGNORE_LIMITS = YES HOME_SEQUENCE = 0
setp hm2_[HOSTMOT2](BOARD).0.stepgen.03.direction.invert_output trueI do have a question about your Home_Offset. If the Max_Limit is 0.01, how does the machine Home_Offset to 0.25? Isn't that outside the limits?
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15 Mar 2020 15:19 #160314
by pippin88
Replied by pippin88 on topic Z Axis Home - Gantry Router
Do you have a shared home/limit switch?
If so, HOME_OFFSET must be outside the soft limits or you will trigger the limit switch during normal use.
HOME_OFFSET is the physical location of the home switch in relation to the axis coordinates.
It tells LinuxCNC where the allowed axis travel (soft limits) is in relation to the home switch.
See this thread: forum.linuxcnc.org/49-basic-configuratio...ading-possibly-wrong
If so, HOME_OFFSET must be outside the soft limits or you will trigger the limit switch during normal use.
HOME_OFFSET is the physical location of the home switch in relation to the axis coordinates.
It tells LinuxCNC where the allowed axis travel (soft limits) is in relation to the home switch.
See this thread: forum.linuxcnc.org/49-basic-configuratio...ading-possibly-wrong
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15 Mar 2020 18:18 #160324
by Project_Hopeless
I'm going use your example as a template see how that works, Thx!
Replied by Project_Hopeless on topic Z Axis Home - Gantry Router
Yes I have shared home/limit switches like your router example in the link you provided. I agree the shared home/limit condition is not thoroughly explained in the manual. What I find confusing also is whether the sign matters or if only absolute value is used.Do you have a shared home/limit switch?
If so, HOME_OFFSET must be outside the soft limits or you will trigger the limit switch during normal use.
HOME_OFFSET is the physical location of the home switch in relation to the axis coordinates.
It tells LinuxCNC where the allowed axis travel (soft limits) is in relation to the home switch.
See this thread: forum.linuxcnc.org/49-basic-configuratio...ading-possibly-wrong
I'm going use your example as a template see how that works, Thx!
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15 Mar 2020 18:22 #160325
by pippin88
Replied by pippin88 on topic Z Axis Home - Gantry Router
The sign (positive or negative) does matter
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