The E-Stop is CAT1. " Robot motion is stopped with power available to the robot to achieve the stop and then removal of power when the stop is achieved."
But, for example, if the robot is static (not move), when I push the E-stop (Teach Pendant Button), the power is removed and the arm of robot falls of several millimetres before the brakes block.
Why the brakes are not active before the power is removed? In my case, in emergency case the falls of my arm of UR3 is impossible (even one millimetre). How I active the brakes BEFORE remove the power? or How I avoid the fall of the robot when I push the button E-Stop?
Thank you for you help.
The reason is the brakes design. The motor Axis on each joint have mounted a spinning arm that locks on a pin which is moved up when the E-Stop is pushed. You can unscrew the caps and take a look inside
The “clicking” sound when you push the robot in braked state is that arm hitting the pin.
To add to what @m.birkholz said the design of the brake is also the reason that you are able to move the joints slightly when the arm is not powered up, you are basically moving the joint between the two fingers of the spinning arm and the pin. As that arm moves it eventually contacts the braking pin and that is what stops the arm, so the drop you see if the arm “falling” until all 6 joint braking arms contact the braking pins. I do believe that power is not pulled from the arm until the brakes are thrown but you will still get that motion regardless because of the design.