The ball screw pair is assembled on a large CNC machine tool

With the ever-increasing requirements for working accuracy of CNC machine tools and machining centers, the high-precision of ball screws has become an inevitable trend of development. In order to meet the requirements of the coordinate position accuracy of the machine tool, reduce the deflection of the screw, prevent radial and offset loads, reduce the heating and thermal deformation of each link of the screw shaft system, minimize the transmission torque of the servo motor, and improve the continuous operation of the machine Reliability, we must fully improve the installation accuracy of the ball screw pair on the machine tool.

    The most commonly used installation methods of ball screw pairs are usually: double push-free method, double push-support method, double push-double push method.

    The large horizontal machining center is a high-performance, high-rigidity, high-precision mechatronics high-efficiency machining equipment. It is an ideal equipment for processing various high-precision transmission box parts and other large abrasive tools. Its three coordinate directions are all driven by a servo motor to drive a rolling screw drive, and the three coordinate directions—X, Y, and Z directions have a large working stroke. Due to the structural characteristics of the ball screw pair, the installation of the three-direction ball screw pair on the host has become a particularly critical issue.

    According to the traditional method, the installation of the ball screw pair always uses a mandrel and a positioning sleeve to connect the two ends supporting bearing seat and the middle nut seat together for correction. Use a dial indicator to align the mandrel axis and the machine tool rail in parallel, and the mandrel can be driven freely The brisk way. This installation method is more convenient to apply to small CNC machine tools and machining centers with small strokes in the three coordinate directions. Because there is a matching gap between the mandrel and the positioning sleeve, the positioning sleeve and the bearing holes supported at both ends and the nut holder hole in the middle, the coaxiality error of the supporting bearing hole and the nut holder hole after installation is often large, causing the wire The increase in the deflection of the rod and the increase in the radial offset load cause a series of serious consequences such as the temperature increase of the screw shaft system, the increase of the thermal deformation, the increase of the transmission torque, and the servo motor overload and overheat, and the servo system alarms. Affect the normal operation of the machine tool. In addition, the actual difference between the bearing holes at both ends and the middle nut can not be accurately measured, which affects further precise adjustment. For CNC machine tools and machining centers with large strokes in the three coordinate directions, since the mandrel required is more than 1500mm, the mandrel with this length is difficult to process and the accuracy is not easy to guarantee. Therefore, the alignment method of the mandrel and the positioning sleeve cannot be used for ball Installation of the screw pair.