Application of Festo Flexible Piston Rod Cylinder on CMM
I believe everyone is familiar with rodless cylinders, so have you heard of flexible piston rod cylinders? Festo (China) Co., Ltd. manufactures this special cylinder according to the needs of customers.
This flexible piston rod cylinder mainly plays the role of a balancing cylinder, which is used as the Z axis of a coordinate measuring machine. The coordinate measuring machine is an advanced measuring instrument that integrates advanced technologies such as machinery, electronics, optics, and software. It can measure high-precision and high-speed measurement of the geometric dimensions and tolerances (especially curved surfaces) of complex parts. Connect with the machining center.
The coordinate measuring machine has three coordinate axes, namely X, Y and Z axes. In order to reduce the resistance and ensure the stability and accuracy in the measurement process, the X and Y axes can adopt the form of guide rails or air floats. The rigidity of the Z axis is poor, and the measuring head needs to be installed, so it is not appropriate to use the same method as the X and Y axes, but the weight balance method. But this increases its motion inertia in the X and Y axis directions. Due to high motion resistance, high cost, and complicated structure, this method has been replaced by a balancing cylinder.
The balance cylinder is characterized by low friction and even no resistance. When a certain pressure is applied to the upper chamber of the cylinder, the gravity of the cylinder barrel and the measuring head can be offset, so that the measuring head is not affected by gravity when accelerating the measurement displacement up and down.
In order to reduce the error of the measuring head (including cylinder parts) and the piston rod in the Z-axis linear direction, most CMM manufacturers use flat bearings and other methods to connect the top of the piston rod when installing the balancing cylinder, so that it is at the X , Y-axis direction floats freely, but this method will cause the measuring machine to vibrate and reduce accuracy during high-speed measurement.
In order to realize the automatic adjustment of the measuring head when moving up and down in the Z axis direction, we need to design a flexible piston rod cylinder. The piston rod is composed of two parts of different materials: the upper half of the piston rod is made of metal material, which has external threads and is fixed to the frame; the lower half of the piston rod is made of plastic PFAN, to ensure that the piston rod has sufficient flexibility, making The deviation of the flexible piston rod in the Z axis movement has nothing to do with the cylinder and the measuring head.
It should be noted that the middle of the plastic piston rod is a steel wire with a diameter of 2 mm, which makes the plastic piston rod stronger. The upper and lower parts of the piston rod are connected into one by a QST-8 joint, and one end of the QST-8 is used as the cylinder air inlet.
The test situation is ideal. The customer believes that the optimized application of the balance cylinder on the Z axis is one of the core technologies urgently needed to be developed by the advanced coordinate measuring machine manufacturers.