I. Maintenance Methods for Ball Nuts on CNC Machine Tools
CNC machine tools automatically process parts according to pre-programmed machining procedures. We compile the machining process route, process parameters, tool movement trajectory, displacement, cutting parameters, and auxiliary functions into a machining program sheet according to the instruction codes and program format specified by the CNC machine tool. This program sheet is then recorded on a control medium and input into the CNC device of the CNC machine tool, thereby directing the machine tool to process the parts. In July 2023, the 25th Research Institute of the Second Academy of China Aerospace Science and Industry Corporation successfully developed a high-precision optical automated centering CNC lathe integrating optical inspection, fine-tuning, and machining. This technology has been verified through engineering pilot applications and has reached a leading level in China.
Ball nuts are high-precision mechanical components widely used in various mechanical equipment, including CNC machine tools, precision bearing housings, and ball screws. As a crucial component of the feed system in CNC machine tools, the maintenance methods of ball nuts have a significant impact on the accuracy and service life of the machine tool. The following are some suggestions for the maintenance of ball nuts in CNC machine tools:
1. Cleaning and Lubrication: Regularly clean the exterior and interior of the ball nut to remove accumulated dust and impurities. Additionally, periodically add an appropriate amount of lubricant to the ball nut to reduce friction and wear.
2. Inspection and Tightening: Regularly inspect the fasteners of the ball nuts to ensure proper clearance between the nut and the screw, avoiding loosening or overtightening. If any loose fasteners are found, tighten them promptly to prevent further damage.
3. Check the screw: Regularly check the surface of the ball nut screw to ensure it is smooth and free from obvious wear or corrosion. If any abnormalities are found, the screw should be replaced in time to avoid affecting the performance of the entire transmission system.
4. Axial clearance inspection and adjustment: Regularly check the axial clearance of the ball screw and nut assembly on the CNC machine tool. Generally, the clearance can be eliminated through active compensation by the control system. When the clearance is too large, the ball screw and nut can be adjusted to ensure its accuracy.
5. Leadscrew Protective Cover Inspection: Regularly inspect the lead screw protective cover to prevent dust and abrasive particles from adhering to the lead screw's surface, affecting its service life and accuracy. Repair or replace any damaged lead screw protective covers on CNC machine tools promptly.
6. Support bearing inspection: Regularly check whether the connection between the support bearing and the CNC machine tool is loose, and whether the support bearing is damaged. If so, tighten the loose parts and replace the support bearing in time.
In general, the maintenance method for ball nuts on CNC machine tools should be determined according to the actual situation, so as to ensure their normal operation and extend their service life.
II. CNC Lathe Selection Principles
1. Preliminary preparations
Determining the process requirements of typical parts, the batch size of workpieces to be processed, and the functions that CNC lathes should have are the prerequisites for making good preliminary preparations and rationally selecting CNC lathes to meet the process requirements of typical parts.
The technological requirements for typical parts mainly include their structural dimensions, machining range, and precision requirements. The control precision of the CNC lathe is selected based on these precision requirements, namely the dimensional accuracy, positioning accuracy, and surface roughness requirements of the workpiece. Reliability is also a crucial factor, as it guarantees improved product quality and production efficiency. The reliability of a CNC machine tool refers to its ability to operate stably for extended periods without failure under specified conditions. This means a long mean time between failures (MTBF) and the ability to recover and return to use quickly even after a malfunction. It is essential to select machine tools with a reasonable structure, excellent manufacturing, and that are already in mass production. Generally, the more users there are, the higher the reliability of the CNC system.
2. Selection of machine tool accessories and cutting tools
Machine tool accessories, spare parts, and their supply capacity, as well as cutting tools, are crucial for CNC lathes and turning centers already in production. When selecting a machine tool, the compatibility of cutting tools and accessories must be carefully considered.
3. Emphasize the uniformity of the control system.
Manufacturers generally choose products from the same vendor, or at least the same vendor's control system, which greatly facilitates maintenance. For educational institutions, which require students to have broad knowledge, selecting different systems and equipping them with various simulation software is a wise choice.
4. Choose based on performance-price ratio
Ensure that functions and precision are not idle or wasted, and avoid selecting functions that are irrelevant to your needs.
5. Machine tool protection
When necessary, machine tools can be equipped with fully or semi-enclosed protective devices and automatic chip removal devices. The above principles should be considered comprehensively when selecting CNC lathes and turning centers.
