What is causing Irregular Movement in our FANUC R2000iB/165F

    Hi,


    This is about our R2000iB/165F with an R30iA controller and operating the SpotTool+ 7DA7/26 and Software edition V7.70P/26. It is getting 1 or 2 bumps along its travel path when I am jogging it in World and when jogging the J2 axis in Joint mode. It will be moving smoothly, and then will have a sudden bump of roughly a 1/10 to 1/4 of an inch. It seems to happen at similar J2 and J3 axis interaction angles (somewhere between -16 and -18 degrees)(it has also occurred near -50deg J2/J3 interaction). The bump also will not occur when moving the J3 axis, but it will when moving the J2 axis in Joint mode. After the bump, it will continue moving smoothly.


    Question(s):

    * What advice or potential causes for the bump would you recommend?

    - Is there anywhere we can get info or dimensions on the R2000iB/165F's guide pins so we can machine them ourselves in case it is a mechanical issue?)

    - After finding the pattern at the J2/J3 interaction, could there be a software side issue causing this? and if so, is there a way to change the way the J2 and J3 interact, besides the Joint Interaction Limits?



    Background Info:

    * I am new to working on robotics. I've been working on this and we've only had the robot for the last 3 weeks. So, a bit of a learning curve.

    * Bought 2nd hand through a surplus company. This is our first robot, and are trying to get this thing running for the least amount of money possible. We are not a large company, and this is not directly impacting our operations yet

    * Our software came with it, and has not been repurchased through FANUC.

    * This robot is eventually meant to be used with OLP software to assist in 3D path planning to route and trim plastic parts.


    Things we have tried:

    * Remastering: (Reloaded back up position reference and master count variables, and have re-zeroed using the witness marks. The robot came with the Pulse Encoder batteries dead, so old mastering data was lost. Created an all system files back up and IMG backup, before doing an INIT start, to get around built in password protection)

    * Rotated Pulse Encoders: (We wanted to test if the pulse encoder disc could be damaged, but it showed no effect)

    * Set Payload: We were told that Payload settings can potentially disrupt movements, so it was set as low as 30kg compared to the default setting of 165kg. No inertial values were placed in. (It does currently have an old tool attachment point left on, that is roughly 15kg.


    What we wanted to Check:

    * Is there mechanical wear on a gear tooth or on the reducer of the J2 or J3 joint? (We have the mechanical unit maintenance manual for this machine)

    - If we did that, would we be able to remove the upper part of the armature without the guide pins? We would like to make them ourselves, but we have no information on their dimensions. We know where they should roughly go for J2, and their part numbers of A290-7324-X921 and A290-7324-X923.

    * Now that I know that it is happening near J2/J3 interaction points, I feel like it is a software issue, but I don't know where to begin to figure out the J2/J3 interaction on the software side. I'll be looking in that further, but any recommendations would be very helpful.


    Note:

    This is my first post and I am just getting started in the field. Does this format work for making posts, or should I shorten it up like the others I've seen here?

    Thank you

    That's one of the nicest post I've seen, nice work.


    Sounds like you have a bad gear reducer. How many hours are on the robot?


    This could be pricey. I would try to find a local integrator to look at it. Fanuc won't touch it without re-licensing it, which is $$$.

    Thank you, that makes me feel better about the long post.


    Info: So, it has a production date around 2012 and it's got about 10,000 hours of run time on it.


    Possible Solution: Thank you, we were thinking it could be the gear reducer. Since we're trying to save as much money as possible, so we even considered taking it apart ourselves. After looking at it more though, the set of guide pins would be 700 alone, so going the integrator route makes sense. The reducer we know is going to be a heavy cost one way or the other. Cheapest I've found so far is 2800, and typical costs closer to 5 to 6k.

    - The reason we're looking for the guide pin dimensions is because both sets can add up to nearly 750 just for these metal pins with a threading that can easily be made ourselves.


    Question: Why doesn't the bump in the travel happen at a consistent spot on the J2 or J3 axes? It seems to be consistent with the J2/J3 interaction angle.

    - I thought that was just the way they were configured on the computer end, and not mechanically.

    Guide pins - buy (4) M12x90 bolts and cut the heads off. Chamfer the edge of the cut end and cut a slot in it to fit a flat screw driver. The slot for the screwdriver helps with loosening. You need 2 but make 4 so you have spares as rookies sometimes bend them.


    Regarding the "bump" - you seem to have narrowed it down to J2. Inspect the balancer rear pivots for wear and the watch the front where the rod couples to the lower arm when this bump happens. It's unlikely to be a balancer issue but worth ruling out before undertaking an RV.

    You can also remove the J2 grease outlet bolt and insert a wire tie in as far as it will go, pull it out and wipe the grease on a clean paper towel. If the grease is dark and has tiny metal flakes, it is the RV.


    Regarding location of the "bump" - if there is play in a worn RV, the bump location could be where the balance shifts the play from + direction to - direction.


    Agree with pdl, a lot more problems would be resolved a lot faster if all posts were as organized and detailed. :applaus:

    Quote from Skooter

    Guide pins - buy (4) M12x90 bolts and cut the heads off. Chamfer the edge of the cut end and cut a slot in it to fit a flat screw driver. The slot for the screwdriver helps with loosening. You need 2 but make 4 so you have spares as rookies sometimes bend them.

    Thank you!! I was looking all over for this kind of information. Can you tell me if the pitch matters in creating the guide pins? And does that mean the both types of guide pins are the same length and diameter?

    All the pictures I have seen of the guide pins seemed to have a short threaded end piece, so I assumed it was meant to fit with the thread of the Armature's base

    When I was looking at the mechanical unit manual, it showed that we would need 2 different types of guide pins. So both sets of guide pins, the general A290-7324-X921 and the J2 specific A290-7324-X923, should be able to be substituted with these new M12 X 90 course thread bolts after some machining?


    Also, thank you! We'll machine these and try them out. We'll see where it goes from there. I'll update the status of the project on here once we've tested them and inspected the J2 gear reducer. This gives us a direction to go in

    Edited once, last by Koe: Add question about J2 guide pins vs general guide pins. (In terms of length and other dimensions) ().

    Quote from Skooter

    Guide pins - buy (4) M12x90 bolts and cut the heads off. Chamfer the edge of the cut end and cut a slot in it to fit a flat screw driver. The slot for the screwdriver helps with loosening. You need 2 but make 4 so you have spares as rookies sometimes bend them.

    You can also buy a 1m long M12 screw and then cut it into pieces how long you need :smiling_face:

    It could be the cheapest way, we always do it this way.

    Quote from neighbour1

    You can also buy a 1m long M12 screw and then cut it into pieces how long you need :smiling_face:

    It could be the cheapest way, we always do it this way.

    Tried that a long time ago. Found they bent easier, the threads collected grease making them harder to keep clean, the threads gave more opportunity to catch & tear glove material, and the threads were 'catchy' when first engaging the pins. Just a matter of preference amongst my colleagues when asked.


    As an alternative to the slot in the end, our not to be outdone machinist did this:

    After cutting off the bolt head, chucked it in the lathe, drilled & tapped a 6mm hole, installed a M6 sockethead cap screw, welded it in place, ground the weld to a nice chamfer.

    If you're working on a Fanuc bot, you're much more likely to have a 5mm hex wrench with you than a slotted screwdriver.

    I have the same issue here about the bump ,

    it is diffenetly not the gear reducer of J2 , as we noticed the following :

    1-it happens with the movement of J3 only and the load is not switching direction ,

    2- it happens in a fixed J2/J3 interaction value regardless of J2 position ,

    3-i have 2 identical robots R-2000IB-210F , and both behaves exactly similar.

    Quote from Skooter

    J3 is very simple, only the motor and RV. Maybe the motor has worn bearings. Press your ear (or other listening device) to the motor and listen for a clunk sound inside the motor.

    Hello skooter ,

    I did what you said exactly

    If you check the videos , i am moving j3 only, and the clunk sound "and movement" happens in j2

    I feel it is a software bug in the motion firmware for example,


    If i move j2 to another angle,it happens in the same j2 and j3 interaction,


    I have 2 identical units and it happens in both of them at the same angle

    I recently had a robot doing something similar. I would move J3 and J2 ,j5 would move also. What I eventually found was the payload Z is in centimeters and someone put 662. 662mm was the correct number but 662cm is like 21 feet. Changed it to 66cm problem went away.

    If you want to rule out an issue similar to ROBOT_G's, use Tool frame 0 and try again.

    Using an improperly defined Frame may explain the motion seen in video.


    Typically a clunk sound comes from excessive play somewhere in the gears,

    Clunking sound around J2 could also involve the balancer.

    Also seen clunking come from loose anchor bolts.

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