After extensive testing and analysis, we have discovered that UR10 Generation 3 (CB3) robots can potentially experience loosening of the elbow joint due to certain programming and a lack of annual joint inspection. As a result, Universal Robots is implementing UR10 (CB3) improvements to prevent loosening of the elbow joint (bottom of this page).  

The elbow joint takes the brunt of the torques for the robot “arm.” This situation could be self-detected under expected operating circumstances; however, units returned to Universal Robots for service have been found to have had thousands of protective stops that were reset within milliseconds of occurrence. 

If protective stops are not understood by the customer or simply ignored, elbow joint failure can happen.  If the robot is used in a collaborative action, such failure can happen when a person is close to the robot and thereby expose the person to the risk of unexpected and unintended contact.  While it can also happen in a non-collaborative application, personnel will have a greatly reduced exposure, thereby significantly lowering the safety risk.  To minimize this safety risk, proper inspection and maintenance is required and customers must follow the steps below and the guidance set forth in the UR Service Manual (https://www.universal-robots.com/download/)

Universal Robots is currently addressing this matter by implementing the use of “plugs” and a “lock collar” in UR10 elbow joint assemblies. UR Manuals are being updated to include specific instructions that programs are NOT to automatically reset protective stops. Programs must also be implemented that result in a minimal number of protective stops. 

We recommend all owners of affected robots, particularly those in a collaborative application, to STOP the robot operation and perform steps a) through e) below prior to continued use of the robot. For non-collaborative applications, the same process should be followed as soon as practicable.

What robots are affected and how to identify the robots?
In order to determine if the robot requires the “PLUGkit”, please check the serial number or production date, as applicable. The serial number and production date are printed onto the robot label and the robot control box. An example is shown below.

What are possible indicators of impending failure?

One possible indicator of this situation is the occurrence of excessive protective stops. Ignoring protective stops is considered abuse of the robot which voids the warranty.

These faults can be hidden from view under the following two circumstances:

1)Personnel simply resetting a fault without review of why the fault has happened.

WARNING: Ignoring protective stops masks fault detection! Pay careful attention to protective stops. Learn why they happen to improve your programs and preserve fault detection!

Protective stops must never be acknowledged and reset automatically, it must always be a deliberate action by a user to resume after a protective stop.

In general, protective stops are designed to inform the user that the robot has stopped due to an external event such as hitting an obstacle or similar. In case the robots are pushed close to the limits, the robots can generate protective stops to indicate that they are not capable of following the desired trajectory.  After a protective stop, the following must be done before resuming operation:

i.   If there has been a collision or similar:
Remove the obstacle and ensure that operators are out of the way before resuming operation. See Section 2 of Service Manual (see link below).

ii.  If there has been NO collision or similar:
The robot is operating too close to the limits, the application should be adjusted to reduce the load on the robot, for instance by reducing accelerations, by correct use of blends or similar measures.

Protective stops are indications of issues, including program or production issues – not only safety issues. An application which results in daily protective stops is not designed correctly and needs to be modified.

2)      If an automatic acknowledgement and reset of a protective stop has been programmed – no one will see the protective stop.

WARNING: Automatic acknowledgement and reset of protective stops masks faults that will lead to a failure condition. When there is a protective stop, verify the cause. If there has been no collision, then adjust the program.

If an integrator has set-up the application program to do automatic acknowledgement and reset of protective stops, the customer should contact the integrator change the program immediately, as such override voids the product warranty and masks fault detection.

Universal Robots requires the following steps be undertaken immediately by owners of affected UR10 CB3 robots:

a)   Check on the number of protective stops and follow the guidance above.

b)   Check if there is an automatic reset of protective stops. 
If yes, remove this portion of the program. 

c)    Inform and train personnel of the value of protective stops and how to make use of protective stops to improve their applications.

d)   Upon receipt of the PLUGkit from Universal Robots or your UR Distributor, install it according to the instructions (see next page).  Use the torque wrench in your UR Service Tool Kit as it is a calibrated tightening tool. 
Guidance on installation of the PLUGkit will also be found in Service Manual. 

e)  All joints should be checked annually, as shown in the Service Manual. 
After implementing the PLUGkit to the UR10 elbow joint, immediate and ongoing routine inspection of all joints and retightening (not overtightening) are highly recommended. This is detailed in the UR Service Manual (https://www.universal-robots.com/download/).
Use this as an opportunity to perform the annual inspection and tightening of the other joints. 

An update on the deployment action for the PLUGkit will be available on the Universal Robots website. 

If you have any questions about this Safety Notice, please contact your regional Universal Robots representative which can be located at https://www.universal-robots.com/about-universal-robots/contact-info/.

Universal Robots A/S expressly disclaims liability for any and all damages or injuries caused as a result of customer’s failure to operate the robot in strict compliance with the User and Service Manuals, follow and implement the recommendations in this Safety Notice.

Instructions for disassembling of the elbow joint, tightening the joint, applying the “PLUGkit”, and reassembling the joint.  ONLY use the torque wrench from the UR Service Tool Kit.

FAQ for Product Alert: Safety notice for CB3 UR10