Apart from the gap between raw materials and heat treatment, accuracy and related problems are primarily manifested in part grinding for high-end bearings, with the consistency of batch cnc turning services accuracy and precision being of particular concern.
(1) An example of precision bearings is angular contact ball bearings for machine tool spindles, which are used in many different applications. Bearing rings with P4 or higher precision, for example, have significant machining accuracy differences. A good company's qualification rate for one-time processing is typically around 80% in most cases. The rate of match was 60% in this case. Some types of bearings (for example, tapered roller bearings for cnc milling wind turbine shafts) are also difficult to maintain at a quality level higher than P4 in some circumstances.
In the case of cylindrical roller bearings and tapered roller bearings with a precision of P4 or higher, high-precision class I and Class 0 rollers cannot be mass produced, and the processing quality of class II and class III rollers will fluctuate as a result.
(3) It is not possible to control and guarantee the dimensional stability of parts effectively. It is common for cnc machining service defects such as grinding burns and cracks to occur when the stress and deformation caused by the grinding process are excessive.
Breaking the bottleneck will require a number of key technologies and measures.
(1) Make use of machine tools that have high precision, stability, and dependability. (2)When working with some bearing rings that have complex shapes, it is necessary to use the grinder of a full-function NC system to call the function directly, so that it can be controlled and interpolated in time; however, this is not always necessary. In order to complete high-speed grinding, a high-speed motorized spindle is used for inner surface grinding, while a high-stiffness dynamic and static pressure grinding wheel spindle is used primarily for outer surface grinding to complete the process. It is controlled by a servo system that is both semi-closed loop and closed loop, allowing for accurate micro feed and compensation to be completed. The feed resolution can be as small as 0.25 M or as large as 0.1 m. The accuracy of repeated positioning can be as high as 1 micron or as low as 0.5 micron. Ball screws, guide rails, and other moving parts should be made of high-precision, rigid, and wear-resistant materials; a bed cnc components with sufficient aging stability and a relatively good vibration absorption effect should be employed. High-precision grinding machines will be equipped with granite beds that have excellent vibration attenuation properties and a low thermal expansion coefficient.
(2) The active measurement method is used for grinding dimension control, and the accuracy of the control is 3 M or greater to 1 m in the grinding dimension control. A servo motor is used to drive and control the grinding wheel dresser, which reduces the frequency of grinding wheel dressing and improves the quality of grinding wheel dressing. Alternatively, diamond grinding wheels and CBN grinding wheels with good shape retention are used to ensure consistency and accuracy in shape accuracy when batch processing is performed.
(3) Reduce the grinding allowance by forging, finishing, or precision cold rolling, and fully implement additional tempering and cold treatment between various processes in order to eliminate grinding stress and avoid defects such as grinding burns and cracks caused by excessive feed, as well as improve cnc machining factory accuracy and surface quality.
Fourth, pay close attention to improving the manufacturing quality of rolling elements, cages, and other critical components. Full-automatic production lines are used in particular for the manufacture of high-precision cylindrical rollers and tapered rollers. High-precision rollers must be completely stable and age-proof to function properly.
For precision and ultra precision machining, it is necessary to achieve environmental control. For bearing production, it is necessary to abandon the long-standing practice of operating an open plant or a general air conditioning plant. Construction or transformation of environmental facilities in the processing area must be done in strict accordance with the requirements for constant temperature and humidity, vibration isolation, and cleanliness.
(6) In the production of precision parts, fully carry forward the characteristics of mastery and inheritance, strengthen the skill training and experience accumulation of operators, strictly enforce the process flow and process discipline, strengthen the quality assurance system, match the software with the hardware, and make the excellent hardware perform even better.
