The performance ceiling of ultra-precision air-floating motion systems often depends on the microholes and air outlet end faces of granite air bearing bases. Many people focus on the flatness of the stone substrate, yet easily overlook that the consistency of air hole diameter, the morphology of microhole distribution, and the profile precision of the air outlet surface are mutually coupled. Once any of these items goes out of control, uneven air film pressure and fluctuating local bearing capacity will occur, causing slide table jitter and directly reducing the positioning stability of equipment. In scenarios such as semiconductor XY stages, femtosecond laser processing and precision metrology equipment, micron-level deviations in air holes will amplify air film disturbances and ultimately lead to persistent motion errors. In long-term R&D and production of ultra-precision granite components, ZHHIMG has established an integrated quality control scheme for microhole forming and ultra-precision finishing of air outlet surfaces. It manages the whole process from microhole design, stone machining, grinding forming to metrology verification, and addresses the collaborative precision challenges of air holes and air outlet surfaces.
The biggest difficulty in air hole machining lies in the microcrystalline hard characteristics of granite itself. Conventional drilling processes easily cause edge chipping at hole openings, inconsistent aperture sizes and rough hole walls. Chipping at hole openings breaks the continuity of the air outlet surface; large dispersion of aperture sizes leads to unbalanced outflow from each microhole and uneven air film thickness. Rejecting general mechanical drilling methods, ZHHIMG adopts special micromachining processes. It arranges microhole arrays according to load requirements and carries out stress simulation in advance to optimize the distribution density and pitch of air holes, avoiding local microcracks generated in granite after drilling. At the microhole forming stage, feed parameters are fully controlled to reduce impact damage to hard granite during drilling. This ensures smooth inner walls and intact hole openings for every air hole, enabling stable laminar outflow of gas and preventing turbulent flow from interfering with air bearing operation.
The completion of air hole forming does not mean the air outlet surface machining can start immediately. After drilling, the local stress state of the stone changes. If large-area grinding is performed directly, profile deformation will easily occur and damage the flatness precision. ZHHIMG adopts a stepwise stress relief process. After microhole machining, the workpiece enters constant-temperature static aging to gradually release local machining stress brought by drilling and eliminate potential deformation risks in subsequent finishing. This step is often omitted by many manufacturers in the industry. Skipping aging treatment will cause slow micro-deformation of the air outlet surface as stress releases gradually after grinding, and the air film performance will deteriorate over time.
Ultra-precision grinding of the air outlet surface is the core of the whole process. The air outlet surface does not simply pursue flatness; it must guarantee that all hole openings of the microhole array are coplanar with the reference surface. If hole openings sit higher or lower than the stone substrate surface, pressure peaks or negative pressure zones will form at hole openings, resulting in slight ups and downs when the slide table moves. ZHHIMG adopts a zoned fine grinding strategy combined with decades of manual grinding technology. Progressive material removal at submicron level is applied to the air outlet surface. The surface profile is continuously monitored during machining to ensure uniform contour of the whole air outlet reference area, with all microhole outlets flush with the substrate surface, free of steps or depressions. This allows gas to spread evenly and form a stable air film with consistent thickness.
Multi-equipment joint metrology is adopted in the precision inspection stage to realize synchronous verification of air holes and air outlet surfaces instead of separate detection. Measuring flatness alone cannot reflect the actual airflow performance brought by air holes. After machining, under constant-temperature and shock-proof metrology conditions, the flatness and straightness of the air outlet surface are inspected on one hand; on the other hand, sampling and full-area inspection are carried out for the aperture, hole position and hole opening morphology of microholes. Meanwhile, static air film pressure distribution tests are performed to simulate actual working conditions and verify whether gas output in each area of the whole air outlet surface is balanced. All test data is traceable. Once local pressure anomalies are found, the workpiece will return to the finishing process for correction, and potential hidden troubles will not be brought into the assembly stage. 
Many customers only pay attention to the apparent flatness of finished marble or granite bases and ignore the collaborative precision of air holes and air outlet surfaces. Some low-cost products on the market feature rough air hole machining and severe hole edge chipping. Although the static flatness seems up to standard after delivery, the air film becomes unstable once installed, causing motion jitter and attenuation of bearing capacity after long-time operation. Adhering to the basic logic of precision manufacturing, ZHHIMG connects air hole forming, stress control, nanoscale grinding of air outlet surfaces and working condition simulation testing into a complete process chain, and controls the geometric precision of air holes and the profile precision of air outlet surfaces as linked indicators.
Stable and controllable microhole arrays and high-precision air outlet reference surfaces are the foundation for frictionless and smooth movement of granite air bearing bases. Relying on this integrated process, ZHHIMG supplies high-performance granite air bearing bases for linear motor stages, semiconductor optical inspection and precision metrology equipment, continuously meeting the increasingly stringent stability requirements for air-floating moving parts in global ultra-precision equipment.
Post time: Oct-09-2026