Can't get home!

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05 Jan 2012 23:21 #16362 by fgauder
Can't get home! was created by fgauder
Hurco MD3 4 axis mill with Mesa 5i20, 7i48, and 2 7i37TA boards using EMC2 2.5, configured with PnCConf. Z axis has pos and neg limit switches plus a home switch and it homes perfectly. I have to replace the X axis scale so it's not in the picture right now.

The Y axis is configured to have the pos limit also be the home switch. The .ini file is set to "HOME_IGNORE_LIMITS = YES". When I try to home Y it hits the pos limit and throws a joint 1 following error. I can override the limit and back off of it, but the control is not ignoring it. I have read all the helps and instructions and changed the all the variables until I can't think of another combination. I just can't seem to get home.

I've attached the .hal and .ini files as of my last attempt. Please show me the error of my ways. Thanks

File Attachment:

File Name: Hurco_MD3-...42a6.hal
File Size:14 KB
Attachments:

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05 Jan 2012 23:23 #16363 by fgauder
Replied by fgauder on topic Re:Can't get home!
I couldn't figure out how to attach 2 files so here's the .ini.

File Attachment:

File Name: Hurco_MD3.ini
File Size:4 KB
Attachments:

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06 Jan 2012 00:02 #16365 by andypugh
Replied by andypugh on topic Re:Can't get home!
fgauder wrote:

The Y axis is configured to have the pos limit also be the home switch.


I vaguely recall that homing to the positive limit switch is slightly harder than a negative limit switch.

I am fairly sure you would need a negative HOME_OFFSET. I would suggest ignoring the numbers initially and work through the signs.

Sorry not to be much help, but it's been a while since I configured homing.

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06 Jan 2012 17:14 #16380 by fgauder
Replied by fgauder on topic Re:Can't get home!
Well I'm still lost. After trying all the combinations of signs I could imagine, I switched my home switch to the negative limit and went through the same process just as unsuccessfully. By making changes to the Z axis parameters I came to the following conclusions concerning the terms in the .ini file:

Home = where you want to end up after homing.

Home Offset = the value given to the Home limit switch position.

Min and Max Limits = the soft limits.

Based on the above, my .ini file for Y looks like this:

#********************
# Axis Y
#********************
[AXIS_1]
TYPE = LINEAR
HOME = 0.0
FERROR = 0.01
MIN_FERROR = 0.005
MAX_VELOCITY = 3.33333333333
MAX_ACCELERATION = 2.0
P = 15.0
I = 0.125
D = 0.007
FF0 = 0.0
FF1 = 0.12
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
ENCODER_SCALE = 25400.0
OUTPUT_SCALE = -1.0
MAX_OUTPUT = 10.0
MIN_LIMIT = 0.0
MAX_LIMIT = 18.0
HOME_OFFSET = -.1
HOME_SEARCH_VEL = -0.166667
HOME_LATCH_VEL = 0.016667
HOME_FINAL_VEL = 0.166667
HOME_USE_INDEX = NO
HOME_IGNORE_LIMITS = YES

This says that Y0.0 is home and the minimum soft limit, Y18.0 is the maximum soft limit, and Y-0.1 is the position of the home and minimum hard limit. The latch and final velocities are in the opposite direction from the search velocity.

When I try to home Y, it goes to the negative limit, sets it's value to -0.1 and throws an error. I can override the limit and back off of it. It appears to me that EMC2 is not ignoring the switch as it should. Can someone post an .ini file from a combination home and limit switch that does work? Is there something in Hal that needs to be connected that PnCConf might not have?

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06 Jan 2012 17:59 #16382 by andypugh
Replied by andypugh on topic Re:Can't get home!
Have you seen this page?
www.linuxcnc.org/docview/html/config_ini_homing.html
Especially the pictures.

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06 Jan 2012 19:13 #16385 by fgauder
Replied by fgauder on topic Re:Can't get home!
Andy,

Yes, that's one of the resources I used. I started out as the first diagram and now I'm it's reverse. If I put those exact figures in my .ini file, however, it still doesn't work.

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07 Jan 2012 00:50 #16389 by andypugh
Replied by andypugh on topic Re:Can't get home!
fgauder wrote:

Andy,

Yes, that's one of the resources I used. I started out as the first diagram and now I'm it's reverse. If I put those exact figures in my .ini file, however, it still doesn't work.


Oh. That's disappointing.

You don't have something odd like shared limit switches and simultaneous homing?

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07 Jan 2012 02:27 #16393 by captain chaos
Replied by captain chaos on topic Re:Can't get home!
Happy new year Andy, fgauder,
had a similar problem on my Z axis, you may try

Home = 18.0
Min_limit = 0.0
Max_limit = 18.0 or = 18.1
Home_offset = 17.9 or = 18.0

and I'm not too sure, but you might have to invert the HAL Y Dir (direction) pin as well.

cheers Paul

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07 Jan 2012 02:32 #16394 by captain chaos
Replied by captain chaos on topic Re:Can't get home!
Geez Andy that was quick, echoes of my little problem, you are quite rite, I forgot about that

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07 Jan 2012 23:37 #16422 by fgauder
Replied by fgauder on topic Re:Can't get home!
Thanks for the help guys. It turns out that the original Hurco control had the over travel limit switches wired to both the servo drives and the controller. The servo drives have a built in feature that inhibits travel in the direction of the tripped limit, but allows free travel in the opposite direction. I thought the redundancy to be a good thing. Disconnecting the the limit switches from the drives allows EMC2 to home as it should.

Thanks again.

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