Sensors are increasingly used in the factory and manufacturing environment for production monitoring and quality control. For products such as chipboard, plasterboard or paper, it is crucial to accurately determine the thickness of the manufactured products to ensure that they meet the final product specification. It is also to minimize waste as the amount of raw materials used can be controlled.
The non-contact laser displacement sensors have been popularly used for measuring thickness of manufactured products in the factory. These sensors are generally compact and can be easily mounted in the manufacturing site. The sensors are also capable to communicate with various industrial interfaces for easy integration. In this case, two laser triangulation sensors are mounted at the opposite end of each other. The schematic diagram of the system is shown below.
The board thickness can be calculated using the formula below.
Thickness (C) = H – (B+A), where
C = Board Thickness
B = Measurement from Laser Sensor B
A = Measurement from Laser Sensor A
H = Distance between Sensor B and Sensor A
Users need to synchronize both laser sensors for this system to deliver accurate thickness measurement. The laser triangulation sensors from Micro-Epsilon, optoNCDT series, offer this feature and they can also actively compensate for rapidly changing surface in real-time which is ideal for measuring in production environment. These laser sensors are also capable of measuring at a very high speed with high accuracy and resolution.
Users can also engineer their display panel meter to automatically calculate the thickness based on the input from the two sensors. The WPMZ series digital panel meters from Watanabe Electrics are included with up to 10 arithmetic expressions for calculation of two input parameters which allows the user to calculate the board thickness. The design of these digital panel meters is also optimized for production environment as they are easy to read and easy to use. Refer to the diagram below for the calculation method using the feature from the WPMZ panel meter.
The value of C can be set depends on the users’ preference. For example, if the user would like to display exact result of board thickness, the C constant could be set at 0. The results from the sensors can also be transmitted via relay output to alarm the operators when the deviation exceeds the tolerated limit.
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