The feed motion of a CNC machining machine tool is the direct object of digital control. Regardless of point control or contour control, the final dimensional accuracy (accuracy) and contour accuracy of the workpiece are affected by the transmission accuracy and sensitivity of the feed motion. (Sensitivity) and stability (explanation: stability and stability; no change). For this reason, the feed system of CNC machining machine tools should pay full attention to reducing frictional resistance, improving transmission accuracy and rigidity, eliminating transmission gaps, and reducing inertia of moving parts.
1. Reduce friction resistance
In order to improve the rapid response performance and motion accuracy (precision) of the CNC machine tool (attribute: automated machine tool) feed system, the friction resistance and the difference between dynamic and static friction of the moving parts must be reduced. In order to meet the above requirements, in the feed system of CNC machine tools, ball screw nut pairs, hydrostatic screw nut pairs, rolling slides (TTW guide), hydrostatic guide rails and plastics (structure: synthetic resin, plasticizer) are commonly used , Stabilizers, pigments) guide rails. While reducing the frictional resistance, it is also necessary to consider that the transmission components should have appropriate damping to ensure the stability of the system (explanation: stable and stable; no change) (The stability of).
2. Improve transmission accuracy (precision) and rigidity
The transmission accuracy (precision) and rigidity of the feed transmission system are mainly determined by the transmission clearance and the accuracy and rigidity of the screw nut pair, worm gear pair (circumferential feed) and the supporting structure from the mechanical structure consideration (consider) . CNC machining CNC is also called computer gong, CNCCH or numerical control machine tool. It is actually a kind of name in Hong Kong, which greatly reduces the number of tooling. CNC machining parts with complex shapes does not require complicated tooling. CNC machining is a new type of processing technology, the main work It is to compile the processing program, that is, to convert the original manual work to computer programming. If you want to change the shape and size of the part, you only need to modify the part processing program, which is suitable for new product development and modification. In the numerical control processing, the control system issues instructions to make the tool perform various movements that meet the requirements, and the shape and size of the workpiece are expressed in the form of numbers and letters, and the processing required by the processing technology. It generally refers to the process of processing parts on CNC machine tools. In order to improve the degree of production automation, shorten the programming time and reduce the cost of CNC machining, a series of advanced CNC machining technologies have been developed and used in the aerospace industry. The transmission gap mainly comes from the transmission gear pair, worm gear pair, screw nut pair and its supporting parts. Pre-tightening force should be applied or measures to eliminate the gap should be taken (refer to the solution to the problem). Shortening the transmission chain and setting a reduction gear in the transmission chain can also improve the transmission accuracy. Enlarging the diameter of the screw, and applying pre-tightening force to the screw nut pair, supporting parts, and the screw itself are effective measures to improve the transmission rigidity. Insufficient stiffness can also cause crawling and vibration of the workbench (or carriage).
3. Reduce the inertia of moving parts
The inertia of the moving parts has an impact on the startup and braking characteristics of the servo mechanism (organization), and the inertia of the parts running at high speeds has a greater impact. CNC machining General CNC machining usually refers to computer digital control precision machining, CNC machining lathe, CNC machining milling machine, CNC machining boring and milling machine, etc. The feed route of finishing is basically carried out along the part contour sequence. Therefore, the focus of determining the feed route is to determine the feed route of rough machining and idle stroke. Therefore, on the premise of satisfying the strength and rigidity of the components, the mass of the moving components and the diameter and mass of the rotating components may be reduced as much as possible, so as to reduce the inertia of the moving components.
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