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CNC machining machine requirements for feed movement
Feb 01, 2019

The feed motion of CNC machining tools is a direct object of digital control. Regardless of point control or contour control, the final dimensional accuracy and contour accuracy of the workpiece are affected by the transmission accuracy, sensitivity and stability of the feed motion. To this end, the feed system of CNC machining tools should pay full attention to reduce frictional resistance, improve transmission accuracy and rigidity, eliminate transmission gaps and reduce the inertia of moving parts.

1. Reduce frictional resistance

In order to improve the rapid response performance and motion accuracy of the CNC machine feed system, it is necessary to reduce the frictional resistance of the moving parts and the difference between the dynamic and static friction forces. In order to meet the above requirements, in the CNC machine feed system, the ball screw nut pair, the static screw nut pair, the rolling guide, the static pressure guide and the plastic guide rail are generally used. While reducing the frictional resistance, it must also be considered that the transmission components should have proper damping to ensure the stability of the system.

2. Improve transmission accuracy and stiffness

The transmission accuracy and rigidity of the feed transmission system are mainly determined by the mechanical structure and the accuracy and rigidity of the transmission clearance and the screw nut pair, the worm gear pair (circumferential feed) and its supporting structure. The transmission clearance mainly comes from the transmission gear pair, the worm gear pair, the screw nut pair and its supporting parts, and the pre-tightening force should be applied or the measures to eliminate the gap should be taken. Shortening the drive chain and providing reduction gears in the drive chain can also improve transmission accuracy. Increasing the diameter of the lead screw and applying the pre-tightening force to the screw nut pair, the supporting member and the screw itself are effective measures for improving the rigidity of the transmission. Insufficient stiffness can also cause crawling and vibration of the workbench (or the carriage).

3. Reduce the inertia of moving parts

The inertia of the moving parts has an effect on the starting and braking characteristics of the servo, especially for parts that are running at high speeds, and the influence of inertia is greater. Therefore, under the premise of satisfying the strength and rigidity of the component, the mass of the moving component is reduced as much as possible, and the diameter and quality of the rotating component are reduced to reduce the inertia of the moving component.

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