Why CMM Granite Surface Plates Demand Higher Flatness and Rigidity

In precision metrology, the granite surface plate is the foundation of measurement accuracy. However, not all granite platforms are the same. When used as the base for a Coordinate Measuring Machine (CMM), the surface plate must meet far stricter flatness and stiffness standards than ordinary inspection plates.

Flatness – The Core of Dimensional Accuracy

Flatness is the key factor that determines the accuracy of measurement.
For standard granite surface plates used in general inspection, flatness tolerance typically falls within (3–8) μm per meter, depending on the grade (Grade 00, 0, or 1).

In contrast, a granite platform designed for CMMs often requires flatness within (1–2) μm per meter, and in some cases even below 1 μm over large areas. This extremely tight tolerance ensures that the measuring probe’s readings are not affected by micro-level unevenness, enabling consistent repeatability across the entire measuring volume.

Rigidity – The Hidden Factor Behind Stability

While flatness defines accuracy, rigidity determines durability. A CMM granite base must remain dimensionally stable under the machine’s moving load and dynamic acceleration.
To achieve this, ZHHIMG® uses high-density black granite (≈3100 kg/m³) with superior compressive strength and minimal thermal expansion. The result is a structure that resists deformation, vibration, and temperature drift—ensuring long-term geometric stability.

Manufacturing Precision at ZHHIMG®

Every ZHHIMG® CMM granite platform is precision-ground and hand-lapped by master craftsmen in a temperature-controlled cleanroom. The surface is verified using laser interferometers, WYLER electronic levels, and Renishaw sensors, all traceable to national metrology standards.

We follow DIN, ASME, and GB specifications and customize the thickness, support structure, and reinforcement design based on each customer’s machine load and application environment.

Why the Difference Matters

Using an ordinary granite plate for a CMM may seem cost-effective initially, but even a few microns of unevenness can distort measurement data and reduce equipment reliability. Investing in a certified CMM granite base means investing in precision, repeatability, and long-term performance.

ZHHIMG® — The Benchmark of CMM Foundations

With over 20 international patents and full ISO and CE certifications, ZHHIMG® is recognized globally as a trusted manufacturer of precision granite components for metrology and automation industries. Our mission is simple: “The precision business can never be too demanding.”