Need help NX100 (EA1400N) robot with excessive play in the L-axis.

    NX100, EA1400N robot with excessive play in the L-axis. I cant find the backlash in the gearing. Check the bolts at each end of the shaft going to the T-axis. Belts snug to axi- T L. Need help to fix the problem.

    Could you elaborate on this? Where are you see this backlash at? I'm confused, excessive play on the L-axis but talking about an axis that is 3 axes away.


    The L-axis is a rotary vector drive. Any backlash is from the manufacturer of the drive plus any crashes over the years. The only thing you can do is replace the drive. That requires separating the L-axis from the S-axis.


    The T-axis is a harmonic drive. It is driven by the shaft you are probably talking about. Course tooth gear at the drive. Fine bevel gear at the arm. Bevel gear is driven by a pulley.

    I know a thing or two, because I’ve seen a thing or two. Don't even ask about a third thing. I won't know it.

    Sorry my mistake type-o not the L-axis.


    The backlash is in the B-axis in the Plus direction about 5° movement.

    This is what I checked so far:

    - bolts at the shaft between the B-axis (fine teeth) and the T axis (course teeth).

    - bolts at the belt pulleys at the T and B axis.

    - bolts at the belt pulleys at the T and B axis motor.

    - Tension on the to drive belts for the T and B axis.

    All the bolts are tight and match the paint marks on the bolts the pulleys and gears. The back lash is present with or without the servo power up.

    Now we're cooking. Okay, my directions for left and right will be from standing behind the robot looking towards it. The T-axis side is the left; the B-axis the right. With the right side cover off. Move the B-axis by hand. What do you see?


    Is the belt staying stationary and just the casting moving? If so continue on through this.


    Disclaimer 1: If you follow this you WILL have to grease and recalibrate the B-axis.


    On the right side, remove the belt. Disclaimer 2: Removing the belt the casting with flop around since there is nothing holding it. Make sure if it flops nothing or no one is in the way. Someone could hold it in place. You can do this several ways. Remove the pulley from the B-axis motor, remove the pulley from the B-axis drive, or remove the bolts from the B-axis motor (this would be done from the left side).


    On the right side looking at the pulley opposite the motor (B-axis drive side) the pulley mounts on a shaft. On the back side of the shaft is a bearing that fits into a land in the casting. Important for removing the wave generator section. Still looking at the same area, there are roughly 8-12 bolts that are either M3 or M4, going of the top of my head. Some of those bolts go through a inner piece (circular spline) into the casting. Some of the bolts are on an outer piece (an additional piece of metal that sits on the inner piece, wave generator section). Remove the bolts ONLY for the outer piece. There should be two threaded holes 180 degrees apart. These are the jack bolt holes. Using the correct size bolt slowly jack the outer piece out. The bearing is on the back side so 1/2 turn to 1 turn max on each at a time. Don't want to cock or damage the bearing.


    Once that piece is out, you can look inside after wiping up the grease. There is a circular piece of metal with 12-14 bolts in it and a hole. The bearing goes through that hole. This is the flex spline cup. Move the B-axis by hand.


    What do you see? 1) The 12-14 bolts could be loose. 2) The sides of the flex spline cup should be straight. In a crash the cup will start to develop wrinkles or a fracture. That is no good. If there are wrinkles, complete drive unit needs to be replace.

    I know a thing or two, because I’ve seen a thing or two. Don't even ask about a third thing. I won't know it.

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