Author Topic: Best method for mastering after replacing wiring harness...can't all reach zero  (Read 2357 times)

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Offline Archer

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I guys,
Yes, I tried the search, but I ended up with pages of information that wasn't usefull.

Situation:
We have cells with 3 M-20ia robots.
We need to change wiring harnesses on all of these every 1.5-2 years.
1 of the robots can not be moved to all zero degree positions.
We CURRENTLY use quick master, and the quick master reference point is set to all zeros save for one robot that is at all zeros, but 1 axis set to 45 degrees.
Quite normally, they end up a little bit off (brakes slipping while changing harnesses?), we we are left trying to zero degree master the 2 robots that can reach zero (these are very important to get accurate setting on) and just seeing how it runs.
Touching up the programs is a monumental task as we have over 100 recipes for running different parts, each would need touching up...and usually do.

I would like to make a end of arm tool that has 3 points that I can touch to a plate and master it in that position... this position would not be anywhere near zero for most if not all axis (imagine the plate is on a table in front of the robots, 2 of the 3 would share the same plate (mastered separately of course).
To me this sounds like mastering to a fixture, but how do I tell it that the positions I am setting it to are not zero degrees without using quick master?

Thanx!

Offline rafahil

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Use Single Axis Master

Using this type of mastering, below the column (MASTER POS), you can write the angle where you are mastering the axis or axes.

Offline Archer

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Thank you. Can all 6 axis be done at the same time?
Also, can one axis be RE-mastered in single axis master if you didn't quite get it right (i.e.I have a #2 in the [ST] column, but I think it needs to be adjusted anyway)?

Thanx 1,000,000    :applaus:
« Last Edit: August 29, 2017, 03:03:07 AM by Archer »

Offline Racermike123

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This is a procedure I have used to master robots when a pulse cable is replaced that has worked for me 100% without touching up points.
It only works on a robot with brakes or if it doesn't have brakes you will need to move the robot to a position where no axis can move.
Move the robot to zero or to a position to enable the robot to be repaired. Note all of the joint angles. Use these to restore the mastering.
Replace the cable. Reset all of the pulse coder alarms and cycle power.
Again note all of the joint angles, they will have changed. Use these to establish the pulse.
Move each axis enough to reset the pulse not established and then move back to the joint angle recorded on the second set of joint angles.
After all of the pulse errors are cleared, single axis master each axis to the positions recorded on the first set of joint angles.
Done.

Offline Archer

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Thank you!
Last detail: Can I master all 6 at once? Or do I have to cycle power for each axis? Thanx!

Offline rafahil

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Using Single axis master you can master all 6 axes at the same time, you have to only put a (1) in the SEL column for all axes.
Those axes with a (1) in SEL column will be mastered when you press F5 Execute.

Offline Archer

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Awesome!
Thanx again all! :bravo: :bravo: :bravo:

Offline Archer

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OK....1 last confirmation.
Racermike123, in another thread you posted "The only rule for mastering a Fanuc is that axis 2 must be at zero to master axis 3 at zero."
If I do single axis mastering as mentioned above, does this not apply? My plate would not have axis 2 and 3 @ 0 degrees.  I will know the positions of 2 and 3, but they just won't be zero.
Thanx again!!! (and again, and again. I want to change how we do things here but the guy "in charge" (who isn't involved with the mastering after a wiring harness job) is quite stubborn, and I HAVE to have this right before I bring it to management. He thinks quick master is the best way to go....we always have problems when we do that)
« Last Edit: August 30, 2017, 12:10:03 AM by Archer »

Offline Robtics

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OK....1 last confirmation.
Racermike123, in another thread you posted "The only rule for mastering a Fanuc is that axis 2 must be at zero to master axis 3 at zero."
If I do single axis mastering as mentioned above, does this not apply? My plate would not have axis 2 and 3 @ 0 degrees.  I will know the positions of 2 and 3, but they just won't be zero.
Thanx again!!! (and again, and again. I want to change how we do things here but the guy "in charge" (who isn't involved with the mastering after a wiring harness job) is quite stubborn, and I HAVE to have this right before I bring it to management. He thinks quick master is the best way to go....we always have problems when we do that)

Axis 1, 2, 3 possible single mastering

but Axis 4~6 must have to same zero angle and execute mastering.

becuz related reduction gear and pulse code refer each axis 4 ~6
ABB
FANUC
KAWASAKI
HHIR

I Can handle it!

Offline Racermike123

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That's right but in this case we are manually putting in the known values for the joint angles so that doesn't apply.

The rule applies to Fanuc robots where axis two and axis three are perpendicular to each other when the robot is at zero. So it doesn't apply to M3 robots.
If you are single axis mastering axis 3 to zero, then axis 2 must also be at zero.

Offline robotero

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What I do to master ONE axis is
1 Engagage the brakes
2 make a mark on the arm (I use an an x-acto to make a hairline mark)
3 I write down the joint angle value at mark
4 then after repair or replacement Clear all encoder/servo errors BZAL, establish pulse, cycle power, etc.
5 Move back the robot to mark
6 Finally master usin single axis master (you have to input the original joint position value)
7 Calibrate

You can do the same simultaneously in more than one axis or in your case ALL axis

QUICK MASTER is even faster

First you need to create a QUICK MASTER REFERENCE POSITION
You need to make marks in all axis to bring the robo back to this position later

Make your repair and clear all servo/encoder errors
(Arm is moved off marks to establish pulse)

Now, move the arm back to the reference position,  do master using the QUICK MASTER and finally calibrate
 

From servo data the number of pulses per revolution and the angle change per pulse is known

When QUICK master position is created, the joint angle value is stored and also the number of complete motor turns plus a remaining fraction of a turn (relative pulse distance)

To restore a LOST calibration it ONLY requires to move the arm NEAR the QUICK reference position (within a half turn of the motor????)
Then the controller computes the TOTAL pulse distance with the known number of complete turns and computes the joint angle value to do the masterization


This is the FASTEST method possible






« Last Edit: September 02, 2017, 05:55:00 AM by robotero »

Offline pdl

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When quick master is successful, which it isn't always, it's also the most accurate way to re-master.

Offline Archer

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Update:
Sorry to bring back old thread, but the information is still valid. Just want to pass on what I have been doing and the results I have been getting.

I have been doing single axis master 2 ways.

1. I have an end of arm tool that I attached 3 dial indicators. I also center-punched 3 spots on a large section of steel on a nearby wall.
I set my indicators to all read zero when the robot is in position (mastering to a known point). When I need to check zero, I can move it to this position and check the position of each axis and compare it to my master numbers. (Useful for confirming master or when master is lost and the robot is in an unknown position). If the numbers are different, I just punch in my master numbers on the axis that are off and I'm good to go. I have this master saved as a position.
This position is a stretch for the robot...it couldn't be much farther away. My MAIN concern is Axis 1-3 and 5. This distance from the robot exaggerates any errors in position.

2. When replacing harnesses, I will put the robot in the most ergonomic position I can (usually straight out horizontally), and record the position of each axis. After replacing the harness, and clearing all alarms (rotating each axis etc), I will punch in the numbers I just recorded (I just take a pic of the screen with my phone), and single axis master it right where it sits.
Once that is complete, I move it to my mastering position described above to check the accuracy of the mastering.

Results:
Method 2 will get me to within .005" on each gauge.
Touching up with method 1, I find that if I move the robot to the same position a number of times (and at different speeds), it will vary by .002-.003" So my initial master was really only off by .002" when the accuracy of the robot is factored in.

I wrote a small program that moves the robot to the main master position, and 4 other positions that I marked out in my robot cell, then I also have it stop basically at zero for each axis to show positions in relation to alignment marks (yes, very redundant) in total I check it at about 7 different positions to be sure. Both of these methods have worked exactly the same after mastering the robot over 20 times from all sorts of positions, never caring if 2 and 3 were at zero or anything else.

This proved invaluable when someone accidentally moved 1 robot to all zeros, and then did a zero axis master.....on the wrong robot! (it was not anywhere near all zeros). I just eyeball it to what looks like zeros. Run my mastering program, and touch up the first position, enter my saved numbers, and single axis master. NO touch-ups were needed.

This all might not be anything new to some of you, but for others this might help.

Offline bagged2drag

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If you have your original mastering sheet from fanuc, or an old backup, you can manually enter the original master counts if the mechanical attributes haven't changed (ie, you didn't have to take any of the motors off or anything).  This is the most accurate method of mastering in my experience.  If you are going to use an old backup for the master counts, you would need to build a cell in Roboguide to get those values.   

I document master counts on any robot I work on as a "first step."  Master counts reside in the system variables in DMR_Group.   


Offline petrim

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If you have your original mastering sheet from fanuc, or an old backup, you can manually enter the original master counts if the mechanical attributes haven't changed (ie, you didn't have to take any of the motors off or anything).

Can I actually do this once the robot has been moved?

We had a battery mishap and lost the mastering on our little 10i and it has never quite been the same. It never occurred to me that I might just be able to recover the mastering from a backup.