Achieve precise positioning of pneumatic systems

In many pneumatic control systems using cylinders, the determination of the piston position alone is no longer sufficient to meet the user's high-precision requirements. Only with continuous position signal feedback and monitoring can high-precision automation tasks be completed without the use of expensive linear motors. Now, SICK has developed and produced MPS electromagnetic position sensors that can detect the movement position of the cylinder piston according to the working principle of analog signals , successfully combining operational flexibility and high positioning accuracy. MPS electromagnetic position sensors can be used for linear motion position detection in pneumatic systems. The sensors in this series can detect lengths of 32 mm, 64 mm, 96 mm and 128 mm, which can be selected by the user according to the task to be completed (Figure 1). This allows for extremely high flexibility in production. On the one hand, it is no longer necessary to install multiple sensors for each detection point on the T-slot of the cylinder; on the other hand, a large amount of sensor mechanical positioning is omitted through the "recording" function, which optimizes production and facilitates the conversion of production processes. The adjustment settings of the zero point and the end point also provide users with maximum clarity within the detection range.

Figure 1 MPS electromagnetic position sensor developed and produced by SICK: Depending on the detection task,
this series of sensors provides four detection lengths: 32mm, 64mm, 96mm and 128mm

Improving the accuracy of pneumatic drives

Different detection ranges also place different demands on the length of the sensor detection part. The detection part of the MPS electromagnetic position sensor adopts a quick-connect structure design, which can be easily installed from the top into the T-slot and fixed with two screws. In the sensor housing with a safety protection level of IP 67, there are two circuit boards, Hall sensors for contactless position signal acquisition, monitors, and recording and feedback components. The recording and feedback button can accurately determine the zero point and the end point, that is, no matter where the piston moves to and how the electromagnetic field is polarized, the required detection range can be accurately determined. The piston position between the zero point and the end point can be represented as an analog signal of 4-20mA current and 0-10V voltage (Figure 2). This sensor can detect the movement position of the piston with high precision at a maximum movement speed of 3m/s. The detection accuracy is 0.05mm, the linearity deviation is only 0.3mm, and the repeatability is 0.1mm. With the help of MPS electromagnetic position sensors, the working accuracy of pneumatic drive systems can be comparable to that of linear motors and cylinders have been used in more applications.

Figure 2 Cylinder with position detection sensor: Piston position between zero point and end point
Can be represented as an analog signal of 4~20mA current and 0~10V voltage

Analog control in the production process of connections

The interconnection of metal materials or metal parts, as well as the bonding or clamping of structural parts related to this connection, can be completed with MPS electromagnetic sensors. In bolt tightening systems, the zero point, screw-in speed and maximum screw-in depth can be adjusted and set using the analog signal data of the sensor. In ultrasonic welding equipment, MPS sensors can accurately provide the relative position between the ultrasonic generator and the workpiece by detecting the linear position of the piston. In the insertion and riveting process, MPS sensors can provide precise parameters of the riveting punch. When bonding, clamping or gripping workpieces, the analog data of MPS electromagnetic sensors can also provide highly accurate production process control data, just like automatic pick-and-place processes.

Blanking process matching material properties

The blanking and shearing production process has extremely high requirements for repetitive accuracy. On the one hand, the blanked parts must be punched out accurately and reliably; on the other hand, the blanking process must not cause damage to the stamping machine and the stamping die. MPS electromagnetic position sensors can be used to precisely control the movement of the punch during the punching and stamping process, and can adjust the punching and blanking production process to match the characteristics of the metal material. At the same time, the sensor can stop the punch in time when the punch reaches the recorded depth dimension. Precise feeding of deformation processing and automated production processes When performing precise feed movements, whether grinding, punching, bending or punching, problems such as the control of the punch movement distance, punching depth or die bending position are often faced (Figure 3). Now, using the analog detection data of MPS electromagnetic position sensors, these problems can be easily solved. Similarly, in die-casting machinery, this sensor can also be used for precise positioning and control of die-casting dies and casting ejection mechanisms. It is precisely in harsh working environments that the high availability of MPS sensors is particularly prominent. In environments such as impact, impact and vibration, it will not affect the fixation of the sensor in the cylinder T-slot, nor the accuracy and repeatability of the piston position detection.

Figure 3 Suitable for demanding automation applications: With
the help of MPS electromagnetic position sensors, the machine can precisely determine the punching depth

Under certain application conditions, the detection data of the cylinder piston position can be used as important data for parts production. For example, based on the position and size of the parts, assemblies or components collected, it is possible to judge whether the product is qualified. In packaging machinery, when processing belt and guide materials, the cutting length can be monitored through the analog controlled cylinder data, and the production data can be adjusted if necessary. In the future, the characteristic data of the instrument, such as programmable switch control points or IO-Link functions, can be improved using powerful MPS electromagnetic position sensors and corresponding pneumatic drives.