Parallelism guaranteed by simultaneous double disc grinding machine?

In the field of precision manufacturing, the parallelism of workpieces is one of the core indicators of product quality. In the case of piston rings in automotive engines and aerospace bearings, for example, a deviation in parallelism between the two end faces of the workpiece that exceeds the micron level can lead to abnormal wear and tear of the part, or equipment downtime in the event of a serious accident. The traditional single-face grinding process requires repeated turning of the workpiece for two processing, which is not only inefficient, but also prone to cumulative errors due to datum conversion. The double disc grinding machine solves this problem fundamentally through the innovative way of synchronous grinding of two end faces. The core principle lies in the use of upper and lower two high-precision grinding wheels acting on the workpiece at the same time, so that the material removal process of the two end faces to maintain dynamic balance. This simultaneous processing not only eliminates clamping errors, but also compensates for fluctuations in the thickness of the workpiece through real-time pressure adjustment, thus controlling the parallelism accuracy within ±0.002mm, even to the sub-micron level.

To achieve this high-precision synchronised grinding, equipment structure and process control are indispensable. Firstly, the dynamic balance of the double grinding wheel system is crucial. The grinding wheel spindle usually adopts hydrostatic bearing or magnetic levitation technology to ensure that the radial runout when rotating is less than 0.001mm. the spindle of a German brand grinder is even equipped with a thermostatic cooling oil circulation system, which reduces the impact of thermal deformation on the axial offset by 70%. Secondly, stable clamping of the workpiece is the basis for ensuring parallelism. For thin-walled parts that are prone to deformation, traditional mechanical fixtures are prone to local stress concentration, resulting in rebound deformation after grinding. The mainstream programme now uses electromagnetic suction cups with air film floating support, which can firmly fix the workpiece, but also through the 0.1MPa level air pressure adjustment to achieve flexible buffer. For example, a Japanese manufacturer developed a vacuum adsorption fixture, the use of 128 independent microporous zoning control suction, so that the diameter of 200mm ceramic sealing ring in the grinding displacement of no more than 0.5 microns.

In the machining process, the intelligent control system plays the role of the ‘central nervous system’. When the sensor detects an initial deviation of 0.005mm in the thickness of the workpiece, the control system immediately adjusts the feed rate difference between the upper and lower grinding wheels. For example, the upper grinding wheel to accelerate the feed of 5% to remove more 0.003mm material, while the lower grinding wheel to reduce the feed of 3%, through this dynamic compensation to make the two end surfaces eventually reach parallel. A domestic grinding machine enterprise also innovatively introduced machine vision technology: installing high-resolution CCD cameras at the discharge port, automatically shooting end face images for every 10 workpieces processed, analysing light interference fringes through AI algorithms, providing real-time feedback on parallelism data and correcting the angle of the grinding wheel. This system has increased the parallelism pass rate of motor end caps for a new energy vehicle model from 82% to 98.6%.

However, technological breakthroughs never end. Currently, double disc grinding still faces the challenge of difficult-to-machine materials, such as silicon carbide ceramics in the grinding is prone to edge chipping, resulting in a sudden drop in parallelism. In this regard, the industry is seeking breakthroughs in two directions: on the one hand, research and development of new composite grinding wheels, such as diamond micropowder and resin bond made of slotted grinding wheels, not only to enhance the chip removal capacity and reduce thermal damage; on the other hand, explore the laser-assisted grinding technology, with a 200W pulsed laser localised softening of the material, so that the grinding force reduced by 40%. It is foreseeable that with the extension of precision manufacturing to optical components, semiconductor wafers and other fields, the double disc synchronous grinding technology will open a new chapter in nanoscale parallelism control.