June 18, 2019, 03:14:27 PM
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 Staubli RX60 Microswitches, homing?

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August 24, 2018, 09:50:39 PM
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RossL


Hi

I appreciate this bot is obsolete by a country mile or ten, but as a project I am working on one. I have just the arm and have an open source controller for it.

At the moment I am manually homing it. How was homing done with the original controllers (CS7M for this bot)? Was it still manual or did the bot somehow know its limits?

On the same topic, I note that the schematics show serial-wired NC limit switches for the first three joints, and the loom has 2 wires labeled LS1+ and LS2-. There is continuity on these wires but no change in resistance, continuity or any other value when a joint is brought into its full travel. Were they functional on the RX60s? If so how did they operate?

Cheers

Today at 03:14:27 PM
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August 25, 2018, 04:53:13 AM
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TygerDawg


Homing was done semi-manually.  The user would use the teach pendant to drive the robot axes to the little machined divots in mating axes, or the riveted pointer/indicators, or the machined alignment marks.  Doing this would position the arm in a vertically-pointing pose.  It was explained to me that positioning to the index marks would put the axis was within one revolution of the axis encoder home index at that point.

Then the user executed the "cal" program to complete the process.  Once the robot was calibrated, then the position data was maintained by battery backup.

LS1, LS2:  don't know, can't remember.
TygerDawg
Blue Technik
Virtuoso Robotics Engineering
www.bluetechnik.com

August 25, 2018, 04:00:45 PM
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RossL


Hi TygerDawg

Thank you, that seems to chime with the divots on each of the joints. There are a number of interesting factors I am still trying to understand.

Quote
It was explained to me that positioning to the index marks would put the axis was within one revolution of the axis encoder home index at that point.

The bot has resolvers, do you know how these would indicate the home index electronically? I am running them via open source controllers which are capable of processing the feedback signals (sin / cos), what might I look for in terms of the index?

Do you mind if I pick your brain on some other topics?

I am trying to find someone who has taken a wrist apart on any of the staublis. I am trying to understand the coupling between the final joint and its preceding brother (J5 and J6). When J5 moves, J6 does an equivalent rotation in the opposite direction. However, when you rotate joint 6 alone, J5 does not move.

Taking it apart (minimally, see pics) I can see that J6 backdrives its wormgear, and J5 backdrives J6 and then I assume the controller would compensate the rotation of J6 via its servo. I can write a script to do that but want to make sure there's nothing mechanically preventing it. However I do not have the confidence to completely dismantle the wrist as I am not convinced it will ever go back together again. Do you know what is behind the spur gear to couple to Joint 6? I am guessing either a bevel gear or other right angle gear mechanism?

One final query, are the wrists sensitive to the oil you give them? The recommended spec is extremely expensive and only available in 20L drums minimum, so if I can replace with a cheaper type that would be great.

August 26, 2018, 04:50:02 PM
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TygerDawg


Sorry, I won't be much help.   

Those RX60 wrists were as delicate a fine porcelain teacup.  They could be broken by sneezing loudly in the same room.   :icon_wink:    I was very good at breaking them, and never had the task of repairing them.  Don't know the construction.   I suspect that specific fixtures were mandated for wrist gearing assembly.

If they specified a specific oil, I would not change if my job depended on it because Staubli was always so particular.

However, those arms are relatively ancient in robot-years, most likely no longer supported, and superceded by more robust designs.  So changing the oil would probably only generate more torque that the tiny motors would have to overcome before faulting.

August 26, 2018, 06:46:34 PM
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RossL


OK cheers TygerDawg

Much of the oil has spilled out on the floor due to a faulty joint 6 o-ring lol. I may have to bite the bullet and buy some of the oil listed in the manual.

I guess playing about with a long obsolete bot means I can dig around much deeper without a boss yelling at me. Its interesting though, as I dont think the staubli wrist design has changed so much in the last 15 years. Its impossible to find drawings or schametics of it, so perhaps they are still very protective of it. The curiosity is maddening lol.

They are 100% obsolete sadly, I have just been lucky enough to get my hands on one and am self-teaching robotics :) We are building an open source controller and have it running from linuxcnc, capable of doing gcode programs from Fusion360. Is a lot of fun for sure, but everything is like solving a mystery!

Anyway cheers for your thoughts, if anything else pops into your head please do let me know, even little tidbits of info can be amazingly helpful : )


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