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Ball screw assembly in large CNC machine tools

Time:2014-01-19 10:56:03Source:This siteViews:3755

With the increasing CNC machine tools , machining centers, precision work required precision ball screw has become an inevitable trend of development, such as high-speed silent HIWIN ball screw nut rotating ball screw Rolled Ball Screws and so on. In order to achieve the requirements of the machine coordinate position accuracy , reduce screw deflection, radial and bias load to prevent and reduce all aspects of the screw shaft and heat distortion temperature , reduce the maximum transmission torque servo motor , continuously working to improve the machine reliability, we must be fully in order to improve the precision ball screw installed on the machine .

    Ball screw installation is usually the most common are: double push - Liberal way , double push - support the way , double push - push-push mode .

    Large horizontal machining center is a high-performance , high rigidity , high-precision mechatronic efficient processing equipment, processing all types of high-precision gear box parts and other large equipment ideal for abrasive . Its three coordinate directions are rolling screw driven by servo motor drive, three coordinate directions -X to, Y , Z travel to work larger . Due to the structural characteristics of the ball screw vice , so that the ball screw mounted in three directions on the host becomes particularly critical issue.

    According to the traditional craft methods , has been used to install ball screw mandrel positioning sleeve bearing will be supported at both ends and intermediate filaments female correction together with a dial indicator to the mandrel axis parallel alignment with the Machine Tool and mandrel drive with ease brisk approach. This installation method itinerary smaller mini CNC machine tools in the three coordinate directions , the machining center applications more convenient. As the mandrel and positioning sleeve , the sleeve and the bearing bore and locating the middle of the wire mother bore supported at both ends with the gap exists , tends to support the installation of the bearing bore , concentricity error nut larger bore , causing the wire bar deflection increases, the radial offset load increases, causing the screw shaft all aspects of temperature, heat distortion increases, the transmission torque increases and a series of serious consequences , leading to a servo motor overload , overheating , servo system alarm , affect the normal operation of the machine. In addition , the actual difference between the two ends of the bearing bore and short intermediate filaments mother can not accurately measure , which affects more precise adjustments. For the three coordinate directions stroke larger CNC machine tools, machining centers , as required in the multi- 1500mm above the mandrel , the mandrel length processing such difficulties is not easy to ensure the accuracy and therefore can not adopt a positive approach to find the heart and positioning rods were set with ball screw vice installation.

    When reproduction of a horizontal machining center, due to the larger machine of the three coordinate travel , in the traditional craft methods in the process, because the ends of the bearing bore and intermediate filaments mother bore concentricity tolerance , resulting in radial ball screw and bias load increases, often servo motor overload , overheating , servo system alarm and so on, so that the machine can not run continuously . At the same time , seriously affecting the life of the ball screw and driving accuracy and shorten the maintenance cycle hosts .

    We have assembled using other methods, such as : mobile saddle seat so as to shorten the distance and bearing nut , and the nut at both ends of the bearing seat and were looking for a positive way , as is the two were looking for a positive , to be seized rods, check with the gap set of practical effect is not good , the same problem exists . During the installation of ball screw must be strictly controlled axial runout ball screw , this will have a direct impact on technical indicators ball screw drive feed system location accuracy. In addition , HIWIN ball screws during installation , the strict control of the ball screw axial runout , this technology will directly affect the index system of ball screw feed drive position accuracy .

    Pre-stretch the ball screw shaft is also very necessary. HIWIN ball screw feed system in order to improve the rigidity and precision , when the screw shaft to implement an effective pre-stretch , but because various sections of the screw shaft , and it is not easy to accurately set the temperature rise , so the calculation of the relevant literature out of the pre-tension can only be used as a reference volume . In the production practice is often the target of the screw shaft having a negative direction is pre- stretched , so that curves toward positioning accuracy levels close to the machine table .