Years ago it was easy. Cars were made out of steel, inductive sensors sensed the presence of steel, case closed. Today there are several alternative materials used in the manufacturing of vehicles above and beyond steel. Today’s vehicles are made out of different materials such as aluminum, plastic, and fiberglass.
Within these vehicles you will find several types of alternative materials or patches, for instance, beta patches, black patches, aluminum sound-deadening patches, as well as hardeners and resins.
Let’s figure out what type of sensing technology you can use with each of these materials.
Beta patches are usually plastic patches that are adhered in between panels of the vehicle. These patches expand under heat in the paint ovens to strengthen panels and keep wind out. Beta patches are best sensed using capacitive sensing technology that detects almost all types of material, as the sensors react to changes in capacitance caused by the target. These sensors come in the same shapes and sizes as the inductive proximity sensors we are all used to. Beta patches come in different colors. No problem here since capacitive switches are color blind.
Black patches are usually stuck to one panel before the panel is joined by a mating panel to hold the two panels together as an alternative to welding. These black patches are a nice contrast in color against the unpainted metal vehicle panel. As a result, using a photoelectric sensor with infrared technology or an invisible beam provides a great black/white differential to detect the patch. You can usually mount these sensors at least 2 meters away to give the operator room to load and unload panels.
Aluminum patches are padded pieces of aluminum about 2 mm thick that have a sticky adhesive backing. Most aluminum patches are peeled off of a roll and applied to the vehicle by a robot. Here we need to use a sensor on the end of the robot for a seek-and-find application so the robot knows where the edge of the patch is. In this case, an “all metals” or “reduction factor 1” proximity sensor works great. This proximity sensor is small enough to be mounted on the robot and senses the patch while not sensing the paper it is attached to.
Hardeners and resins:
Plastic car parts are held together using a 2-part epoxy containing a hardener and a resin. These materials are kept in separate containers until mixed together using an epoxy gun. Once these two materials meet, the bond they make will be much stronger than the plastic part they are holding together. The need to detect the level of this material is critical as you do not want to run out in the middle of production. In this case, capacitive sensors work great. They can shoot through the plastic container and detect the liquid material inside because the liquid has higher dielectric properties, which these sensors like.
Hope this gives you a better understanding of the kind of technology that works best with alternative materials in the automotive industry.