How to detect double layers or sheets of material

Doublesheet detection sensors are used in application in which sheets or plates are processed. This involves industries that process labels, use printing machines or work with folding machines. Creases, wrinkles and accumulation of sheets and plates can make a whole process come to a stop. Production errors can be detected early with the use of ultrasonic doublesheet sensors and thus can be detected and solved in time to save time (and money).

The way double sheet detection sensors work

But how does this work? Doublesheet detection sensors are unique ultrasonic sensors that are placed in front of each other. The first sensor functions as a transmitter while the second one is a receiver. The material that has to be detected is led through these sensors. The transmitter sends out an ultrasonic soundwave from one side of the material. The sound wave reaches the sheet. The signal has got through the sheet and is weakened as it reaches the receiver on the other side. The weakened soundwave tells the receiver that there is a sheet present. When a material, paper for example, flaps because of the vibrations from the sent soundwave it has no effect on the detection. There are several sensors available for various detection distances. By detecting this presence other processes can be adjusted to the supply of sheets that is led through the machine which improves the efficiency and prevents or resolves errors faster.

The mounting of dbk+ sensors

The recommended mounting distance from transmitter to receiver is 40 mm (for the dbk+4 /M12/3CDD/M18 E+S this is 20 mm). In exceptional cases it is possible to deviate from this within the range of 20 to 60 mm. This is often in accordance with local terms that apply to the installation of the sensors. With the help of the LinkControl software or teach-in procedure it is easy to configure a mounting distance when using the sensor for the first time.

The doublesheet sensor has to be mounted with a special inclined angle toward the material when working with thicker plates that are made from materials such as cardboard, metal, plastic or foil (e.g. credit cards). The recommended mounting angle for cardboard types is ≥ 35°. For plastic foils it is 27°, while 11° is recommended for (semi-conductive) wafers.

Standard settings or custom configuration

Doublesheet detection can be used for a variety of materials. However, the sensor needs a teach-in beforehand for the material used in the application.

The sensors are equipped with 3 inputs for teach-in. These are inputs that make it possible to configure three different settings for the materials and the thickness of it. The configurations for different materials are based on the grammage of the sheets or plates that need to be detected.

The standard configuration is applied to materials with a grammage from 20 up to 1200 g/m2. For thin sheets and plates the ‘thin’ configuration is used which handles material thickness less than 20 g/m2. For thicker plates and sheets there is the ‘thick’ configuration that is made available for materials such as cardboard. This configuration applies to materials with a thickness starting from 1200 g/m2.

It is possible to switch between configurations during production. It is not necessary to teach-in values for material thickness because of the built-in configurations (standard, thin and thick). If needed, in very critical applications for example, it is possible to teach-in a custom configuration for materials. This is done through the three inputs for teach-in. See the table below for which COM-input to make active to use the desired configuration.