Inspection and measurement requirements for granite base: full-dimensional control from appearance to performance
As the "reference platform" of precision equipment, the quality of the granite base directly determines the measurement and positioning accuracy. From factory to delivery, multi-dimensional inspection and measurement are required to ensure that each indicator meets strict standards. The following are the core requirements that must be strictly controlled:
1. Appearance inspection: Do not miss any minor defects
Inspection focus: Check surface quality through the three methods of "see, touch, and measure" --
Visual comparison: Compare with the standard sample to check whether there are cracks, color difference (especially black stones such as "Jinan Blue" must be uniform and free of color), scratches (length > 3mm is judged as unqualified);
Touch feeling: Use the fingertips to gently slide the surface to feel whether there are bulges (> 0.05mm) or depressions, and the edges must be smooth and free of burrs;
Tilt detection: Tilt the base at an angle of 30°, illuminate the surface with strong light, and use light reflection to find fine cracks or bubbles (common in stone defects that are not completely removed during processing).
II. Dimension measurement: hard-core requirements for millimeter-level accuracy
Key indicators: The tolerances of length, width, thickness and hole/slot positions must be controlled within the design value ±0.1mm (precision-level base requires ±0.05mm).
Measuring tools: Use digital display vernier calipers (accuracy 0.01mm) to measure length and width, micrometers (accuracy 0.001mm) to measure thickness, and coordinate measuring instruments to locate the center distance of holes;
Environmental control: The measurement must be carried out in a constant temperature environment of 20±2℃ to avoid the thermal expansion and contraction of stone materials caused by temperature changes affecting the data (the linear expansion coefficient of granite is about 4.6×10⁻⁶/℃, and a temperature difference of 5℃ may produce an error of 0.02mm/m).
III. Flatness detection: the pursuit of "zero error" of the reference surface
Detection standard: 00-level base flatness error ≤2μm/m, 0-level ≤5μm/m (scan point by point with a laser flatness meter).
Operation points: Place the base on the anti-vibration platform, and the laser probe takes a measuring point every 50mm along the X and Y axis directions. After recording all the data, a flatness error curve is generated;
Failure judgment: If the local convexity or concave exceeds the tolerance value, it needs to be returned to the factory for re-grinding until it meets the accuracy requirements.
IV. Hardness and wear resistance: "Durability" guarantee for long-term use
Hardness test: Use a Mohs hardness pen to scratch the non-working surface of the edge of the base, which must reach level 6-7 (can scratch glass but not easily scratched by a steel knife);
Wear resistance verification: Use a standard grinding head (loaded with 50N force) to rub the surface 1000 times, the wear amount must be ≤0.001g, and there is no obvious wear mark on the surface - to ensure that there will be no accuracy degradation when the workpiece is placed for a long time or measured frequently.
V. Extreme environment adaptability test
Temperature stability:
The base is tested in a cycle within the range of -10℃ to 40℃ (heating/cooling 5℃ per hour). After each temperature stabilization, the dimensional change is measured. The total error must be ≤0.01mm/m - simulating the seasonal temperature difference in the workshop or the impact of air conditioning start and stop.
Corrosion resistance:
Drop 5% hydrochloric acid and sodium hydroxide solution on the surface of the base (area 2cm×2cm) respectively, let it stand for 24 hours and then wipe it. The surface must be free of discoloration and pitting - especially suitable for bases in corrosive environments such as chemical and electroplating.
VI. The "last line of defense" before leaving the factory: packaging and transportation inspection
Packaging verification: It needs to be wrapped with solid wooden boxes + EPE pearl cotton double layers, with anti-collision corner guards on the four corners, and filled with moisture-proof agent (humidity indicator card shows ≤40%);
Transportation simulation: The impact resistance of the packaging is verified through vibration testing (frequency 10-50Hz) to ensure that there will be no micro cracks caused by bumps during transportation.
VII. Inspection Report: Data-driven "Passport"
Each batch of bases must be accompanied by a detailed report, including:
Original data of various tests (such as flatness error value, hardness grade, temperature test curve);
Testing equipment number and calibration certificate (to ensure data traceability);
Qualified judgment conclusion (to clearly indicate whether it meets the customer's specified standards, such as GB/T 20428 or ISO 8512).
From microscopic defects to macroscopic performance, the inspection and measurement of granite bases covers the quality control points of the entire life cycle. Only through this rigorous process can it be ensured that it plays the role of "benchmark" in precision equipment and escorts high-precision measurement and positioning.