Plastic rings : The two plastic rings should be in the inner of round rubber cover rubber . Please see the enclosed photo .
Function : The two plastic rings are for supporting the rubber cover only , because the round rubber cover length is longer , so the rubber cover manufacturer add the two rings in the inside to avoid the rubber cover destroyed by the ball screw .
We don’t have rubber cover assembly drawing .
You could put the two rings in the inside of rubber cover and fixed it at about middle position.
The possible reason for a strange noise while Y axis table movement:
We think the noise may cause by the plastic rings of ball screw’s rubber cover. The ring was fallout from the rubber cover .
We suggest you could take off the rings which are out from rubber cover , and check if there is no noise again .