Eddy Current Testing of Automotive Air Bag Pneumatic Parts

Automotive air bag pneumatic fittings develop cracks during the manufacturing process. Cracks may be through the entire length of the part, but some cracks will be only partially through the length of the part. Some cracks exist on the outside and the inside diameters of the part, but this is not always the case. Sometimes the cracks exist only on the inside or the outside.

All of these cracks can be detected with Eddy Current Non-Destructive Testing. In order to find all of the cracks, the Eddy Current Probe must have 3 sensors, 1 for the I.D., 1 for the O.D. and 1 for the end. Each pneumatic fitting must be inspected with 2 probes, 1 for each end of the part.

Eddy Current is capable of detecting cracks in the threaded area of parts.

The parts can be tested either manually or automatically.

There are 2 probes with 3 sensors connected to a multi channel Eddy Current Instrument, 1 probe for each end of the part.

There are 2 probes, 1 for each end of the part. The part is placed in 1 of the 2 probes. The part is then rotated well in excess of 360 degrees, perhaps 1-1/2 turns, to ensure that any crack in the part will pass the sensor that is positioned to detect the crack in that location. The part is then moved to the second probe that is used to test the other end of the part, where it is also rotated about 1-1/2 turns.

If there is a crack in the part, it shows up as a large vertical movement on the screen of the Eddy Current Instrument. Also, an alarm tone occurs to alert the Operator. Bad parts are placed in the bad bin, good parts are placed in the good bin.

Automatic testing is very similar, but instead of the part being placed manually in the probe, the machine that machines the part places the part in the probe and rotates it 1-1/2 turns and then moves the part to the second probe, also rotating it about 1-1/2 turns.

The Eddy Current Instrument communicates with this machine using inputs and outputs that are compatible with PLC voltage levels. The machine sends a signal to the Eddy Current Instrument when the part is being rotated in the probe and if a defect is detected, a failure alarm is sent to the machine. The machine recognizes this failure alarm and places the part in the failed bin.

It is easy to tell the good part good-part From the bad part bad-part