Mechanical presses are key elements for forming and stamping metals in highest quantities. These production processes are relevant for industrial mass production, which are typically used in automotive industry, in production of white goods like washing machines, of structural elements for buildings and also the production of components of all kinds of consumer goods.
As presses in many cases are operationg at high speed, the perfect operation of the stamping or forming process is essential for both high production quality and machine protection.
A typical risk is to have two or even more sheets of metal rather than one entering the press. The result of such an occurence in many case is big damage at the stamping die or even at the press.
To avoid this damage quite often sensors are used to detect the material thickness of the metal sheet. A so called “double sheet detection” can prevent from a damage when using two inductive distance sensors with continuous output signal (0..10V, 4…20 mA) and analyzing the signals in a controller.
When using continuous band material for the stamping process the feeding speed needs to be adjusted to the machine stamping frequency.
By using Ultrasonic distance sensors the sag of the metal band which is fed to or from the stamping process is measured as an information to control the feeding speed. Even if there are openings in the already stamped band ultrasonic sensors properly detect the sag as the distance to a band area rather than to a spot is measured.
Hydraulic presses achieve their rated force over the entire stroke travel. Magnetostrictive position sensors handle the position monitoring to optimize the press stroke depending on punching die in use.
The position marker is attached to the moving slide or ram and the profile style linear sensor fixed to a location on the steady part of the press. The sensor is isolated from the mechanical shocks and with its high measurement precision and its update rate in the millisecond range contributing to a efficient and flexible production.
The resulting hydraulic pressure of a stamping process is used to monitor the production and is a good indicator about the performance of the production process (Condition Monitoring)
Therefore it is very popular to use pressure sensors with continuous output signals in presses. The combination of pressure values at defined positions of the stamping process is analyzed. Then by defining permitted deviations of the standard curve of the two dimensions pressure and position, unnormal situations are detected and the press is stopped to find a failure and its cause.
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