Homing problems on Z-axis
18 Nov 2018 20:07 #120962
by jnp1968
Homing problems on Z-axis was created by jnp1968
Gents!
First off - i'm a total newbie to LinuxCNC but have been dreaming of owning a cnc mill for nearly 20 years.
So finally - I recently purchased a chinese 3040 mill/router and couldn't be happier.
I thought of it as an fast and cheap way to get started and learn something about this wonderfull world.
Before doing any actual work on it i installed and configured home switches on all three axis.
"Home" is set to be front left corner with Z all the way up - and got it working like a charm!
But this morning when moving the machine to a temporary box/enclossure something happened and i can't figure out what went wrong.
First of all the z-axis moved the wrong way i got the message "cannot unhome while moving joint 2" which i traced down to a broken wire on the Z-axis home switch.
But even now, with the home switch working again, LinuxCNC does not recognize it when homing.
It just moves past it and rams the z-axis right into the top - Not a nice sound, i might add!
The home switches are all installed in NC mode and break the connection when triggered.
I can meassure the home switch breaking when the z-axis hits it, but this does not stop the axis from moving.
Only pressing F2 prevents the axis to hit the mounts but then i again get an "Cannot unhome while moving, joint 2" message.
My guess is that the the home switch signal is not received by LinuxCNC (damaged break-out board?), and to verify that i would like to learn about a method to read the input signals real-time.
Meaning seing the home switch signals change real-time.
I have tried using HAL Scope without succes,- that is, i can see the signals, but they don't change real-time.
I would be very happy if you could help me out here.
My ini file for this axis says:
Hal file for axis 2 says:Any suggestion would be greatly appreciated ![:) :)](/media/kunena/emoticons/smile.png)
Best Regards
Jesper
First off - i'm a total newbie to LinuxCNC but have been dreaming of owning a cnc mill for nearly 20 years.
So finally - I recently purchased a chinese 3040 mill/router and couldn't be happier.
I thought of it as an fast and cheap way to get started and learn something about this wonderfull world.
Before doing any actual work on it i installed and configured home switches on all three axis.
"Home" is set to be front left corner with Z all the way up - and got it working like a charm!
But this morning when moving the machine to a temporary box/enclossure something happened and i can't figure out what went wrong.
First of all the z-axis moved the wrong way i got the message "cannot unhome while moving joint 2" which i traced down to a broken wire on the Z-axis home switch.
But even now, with the home switch working again, LinuxCNC does not recognize it when homing.
It just moves past it and rams the z-axis right into the top - Not a nice sound, i might add!
The home switches are all installed in NC mode and break the connection when triggered.
I can meassure the home switch breaking when the z-axis hits it, but this does not stop the axis from moving.
Only pressing F2 prevents the axis to hit the mounts but then i again get an "Cannot unhome while moving, joint 2" message.
My guess is that the the home switch signal is not received by LinuxCNC (damaged break-out board?), and to verify that i would like to learn about a method to read the input signals real-time.
Meaning seing the home switch signals change real-time.
I have tried using HAL Scope without succes,- that is, i can see the signals, but they don't change real-time.
I would be very happy if you could help me out here.
My ini file for this axis says:
[AXIS_2]
TYPE = LINEAR
HOME = 0.0
MAX_VELOCITY = 30.0
MAX_ACCELERATION = 200.0
STEPGEN_MAXACCEL = 250.0
SCALE = 400.0
FERROR = 1
MIN_FERROR = .25
MIN_LIMIT = -70.0
MAX_LIMIT = 0.001
HOME_OFFSET = -70.000000
HOME_SEARCH_VEL = 10.000000
HOME_LATCH_VEL = 1.250000
HOME_SEQUENCE = 0
Hal file for axis 2 says:
net home-z <= parport.0.pin-12-in
net home-z => axis.2.home-sw-in
![:) :)](/media/kunena/emoticons/smile.png)
Best Regards
Jesper
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19 Nov 2018 02:14 #120974
by alan_3301
Replied by alan_3301 on topic Homing problems on Z-axis
Use the halmeter to check your home-z signal, while triggering the switch manually.
Halscope is good for fast changing signals, but halmeter is better for simple checks or slow changing signals.
Halscope is good for fast changing signals, but halmeter is better for simple checks or slow changing signals.
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19 Nov 2018 15:50 #121000
by persei8
Replied by persei8 on topic Homing problems on Z-axis
See section 3.6 of linuxcnc.org/docs/html/config/ini-homing.html#_home_offset
Your ini would indicate that the homing switch is at the bottom limit of travel. If that is the case, it might be that it is searching for the switch but not finding it because it has already passed it. If that is not the case, you need to adjust the home_offset value.
Your ini would indicate that the homing switch is at the bottom limit of travel. If that is the case, it might be that it is searching for the switch but not finding it because it has already passed it. If that is not the case, you need to adjust the home_offset value.
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19 Nov 2018 21:23 #121025
by curtisa
Replied by curtisa on topic Homing problems on Z-axis
Your HOME_OFFSET value looks to be wrong, although if it was working beforehand maybe it's not the issue. The description for HOME_OFFSET in the documentation states that:
What happens when HOME_OFFSET is the equal to the MIN_LIMIT value (as you have in your INI file) isn't clear, so perhaps LinuxCNC just ignores the value set in HOME_OFFSET and homes Z as if it had no offset. Ie, your previously-working homing of Z-axis perhaps only worked by pure chance.
I'd be more focusing on the reason as to why you can't see the limit switch being triggered manually in Halmeter or Halscope. If it was previously working and you've since discovered issues with the wiring of the home switches on that axis since the machine was moved, I'd be looking at more wiring or circuitry issues on that axis' limit switches.
The home switch location, as indicated by the HOME_OFFSET variable, must be strictly within the soft limits. That is, MIN_LIMIT < HOME_OFFSET < MAX_LIMIT.
What happens when HOME_OFFSET is the equal to the MIN_LIMIT value (as you have in your INI file) isn't clear, so perhaps LinuxCNC just ignores the value set in HOME_OFFSET and homes Z as if it had no offset. Ie, your previously-working homing of Z-axis perhaps only worked by pure chance.
I'd be more focusing on the reason as to why you can't see the limit switch being triggered manually in Halmeter or Halscope. If it was previously working and you've since discovered issues with the wiring of the home switches on that axis since the machine was moved, I'd be looking at more wiring or circuitry issues on that axis' limit switches.
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20 Nov 2018 14:57 #121060
by andypugh
Replied by andypugh on topic Homing problems on Z-axis
Can you jog the Z axis in both directions before homing?
My suspicion is that what has actually happened is that you have broken or displaced the Z stepper DIR wire.
My suspicion is that what has actually happened is that you have broken or displaced the Z stepper DIR wire.
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20 Nov 2018 18:20 #121078
by jnp1968
Replied by jnp1968 on topic Homing problems on Z-axis
Thanks,- exactly what i need!
Ill be looking into that and figure out how to use it![:) :)](/media/kunena/emoticons/smile.png)
Br Jesper
Ill be looking into that and figure out how to use it
![:) :)](/media/kunena/emoticons/smile.png)
Br Jesper
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20 Nov 2018 18:32 #121079
by jnp1968
Replied by jnp1968 on topic Homing problems on Z-axis
Good point about the home offset ![:) :)](/media/kunena/emoticons/smile.png)
Actually i figured out what the problem was just when i went to bed,- and it was far worse than a broken cable.
When disconnecting the machine to put it in a box, i did not have the common sence to just unplug the plug from the breakout board.
I actually unscrewed all...
And then - the next day putting them back in - i put the common ground to all three home switches into an unused input port - and not in the ground port - in essence leaving all home switches floating.
So the problem was my mind not understanding what my eyes where seing.
Worked just like supposed again![:) :)](/media/kunena/emoticons/smile.png)
Br Jesper
![:) :)](/media/kunena/emoticons/smile.png)
Actually i figured out what the problem was just when i went to bed,- and it was far worse than a broken cable.
When disconnecting the machine to put it in a box, i did not have the common sence to just unplug the plug from the breakout board.
I actually unscrewed all...
And then - the next day putting them back in - i put the common ground to all three home switches into an unused input port - and not in the ground port - in essence leaving all home switches floating.
So the problem was my mind not understanding what my eyes where seing.
Worked just like supposed again
![:) :)](/media/kunena/emoticons/smile.png)
Br Jesper
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20 Nov 2018 18:34 #121080
by jnp1968
Replied by jnp1968 on topic Homing problems on Z-axis
Yes - actually i was able to jog Z both up and down, and in the direction that i wanted.
The error message ("cannot unhome while moving joint 2") itself actually hinted that the link from the home switch was broken.
I just failed to see that actually all three home switches where triggered as being active - since i didn't know how to use HAL meter![:) :)](/media/kunena/emoticons/smile.png)
/Jesper
The error message ("cannot unhome while moving joint 2") itself actually hinted that the link from the home switch was broken.
I just failed to see that actually all three home switches where triggered as being active - since i didn't know how to use HAL meter
![:) :)](/media/kunena/emoticons/smile.png)
/Jesper
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