Failure analysis of encoder shaft locking and red powder appearance

Failure analysis of encoder shaft locking and red powder appearance

I. Encoder failure phenomenon

The encoder shaft locks up and a red powdery powder appears.

Second, the encoder manufacturer test results

1. Brownish-red powder is found both inside and outside the re-encoder. Absolute encoder is to convert the displacement into a periodic electrical signal, and then convert this electrical signal into counting pulses, and use the number of pulses to indicate the size of the displacement.

2. The following samples and traces were collected from the inside of the bearing.

a. The internal and external bearings of the encoder show obvious signs of wear and tear, and the bearing grease is dried up.

b. The other two bearings also show signs of wear.

III. Causes of failure

1. About bearings

Bearings inside and outside both wear appear, the other two pieces are accompanied by grease degradation phenomenon. Encoder installation installed after the reduction gear, such as the shaft end of the winch wire rope reel or the last section of the reduction gear shaft end, this method has no gear back and forth clearance, measurement is more direct, higher precision, this method is generally measured in long-distance positioning, such as a variety of lifting equipment, feeding trolley positioning, and so on.

2. Brownish-red powder

The powder contains FE,O,C and AL. It is mainly metal oxides, so the color is brownish red. And there is degradation of grease inside, so it can be concluded that the powder is not from grease.

A lot of wear (a basic type of component failure) powder is found inside the encoder, but grease is still present in the bearing, and there are obvious internal and external wear marks on the bearing. The signal output mode of the rope displacement sensor is divided into digital signal output and analog signal output, digital output type can choose incremental rotary encoder, absolute encoder, etc., the output signal is a square wave ABZ signal or Gray code signal, the stroke can be done up to 10,000 mm, the linearity accuracy of up to 0.01%, the resolution according to the different configurations can reach a maximum of 0.001 mm / pulse. Encoder close to the internal wear traces of grease programmed black, this part of the bearing has obvious cracks, foreign objects can easily enter.

To summarize, the foreign matter arises outside the encoder and later enters inside the encoder. It caused degradation of the bearing grease, and the rotation was not smooth. The bearing is too close to the side of the motor, resulting in serious damage to the bearing, and the other two also have this problem, the powdery material is produced outside the encoder and then enter the encoder inside resulting in problems.