Universal Robots Forum

Loose screws in joints

I have discovered that there are small screws loosening in the robot joints and then rattling around inside as the robot moves.

Screws have fallen out from the brake solenoid that resulted in the spring, sleeve, and washer also rattling around in the joint. This also resulted in complete joint failure because the brake stopped working. Luckily I was able to find all the fasteners and put it back together again and the joint came back to life. Other small screws within the joint have also fallen out.

Incidentally, the first screw that fell out was noticed just after receiving a brand new robot. We have not used these yet for material removal applications, but are planning to do something similar in the future. Rotating end effector frequency and vibration will certainly become an issue.

The problem is that these screws in the joint are very small, and have only a few threads of engagement. They are also not patched with Nylok to prevent loosening from vibration.

Does anyone have a list of screws sizes and descriptions that are used inside the joints? Better yet, does anyone have a source to buy Torx head, stainless steel screws in the sizes used inside the joints? If I can buy these screws, I will get them patched with Nylok and then replace all the screws in the joints. I have found Loctite to be too messy and prefer to send screws out for Nylok patching.

I think if enough people are having problems with loose screws, UR will solve this problem like they did by placing helical inserts into the tool plate. If enough people voice their concern, we can solve the loose screw issue and make the robots more capable of machine shop applications.

Hi @christian.mackin, please create a service case within myUR detailing this issue or ask your distributor to escalate it to UR Customer Service to ensure that the issue is appropriately addressed.