Core key advantages of granite as a CMM platform base:
I. Excellent thermal stability, suppressing dimensional drift caused by temperature changes
The linear thermal expansion coefficient is stable (4.5~6×10⁻⁶/℃), far lower than steel, cast iron, and aluminum alloys. The deformation caused by small ambient temperature fluctuations is extremely minimal, reducing the pressure of temperature compensation for the CMM and ensuring continuous measurement accuracy.
The material has good overall thermal uniformity, avoiding the local temperature difference warping issues found in metals; although its thermal conductivity is far inferior to SiC, it fully meets micron-level inspection requirements under normal constant-temperature workshop conditions (20±1℃).
The overall integral molding is free of internal stress, with minimal dimensional creep over long-term use and strong stability for repeated measurements over the years.
II. High damping and vibration reduction, eliminating measurement errors caused by vibration
The dense crystal structure inside granite has damping performance far superior to steel and cast iron:
It can effectively absorb micro-vibrations caused by ground vibrations, air compressors, machine tool operation, and personnel walking;
The vibration attenuation speed is fast, ensuring no table resonance shaking occurs the moment the probe contacts the workpiece, significantly improving repeatability;
For small and medium-sized workshops without independent vibration-isolated foundations, the granite base is the most cost-effective vibration reduction solution.
III. Extremely high rigidity and low deformation, ensuring the reference remains undeformed under load
With a Mohs hardness of 6~7 and high compressive strength, the table surface will not undergo elastic depression when bearing workpieces and fixtures;
The elastic modulus is high, and bending deformation under self-weight and workpiece load is minimal, ensuring the X/Y/Z three-axis motion reference remains straight;
After precision machining, the flatness, straightness, and perpendicularity can achieve 00 / 000 grade sub-micron accuracy, serving as a long-term stable core reference surface for the CMM.
IV. Wear-resistant, non-magnetic, and corrosion-resistant, with good long-term accuracy retention
The overall stone material has no risk of metal corrosion; the reference surface will not rust or corrode in humid workshop environments or from cutting fluid splashes;
The material is dense and wear-resistant, so long-term probe contact and tooling pushing/pulling will not quickly produce scratches. After pore sealing treatment, it can maintain a high-precision working surface for many years;
It is completely non-magnetic, will not attract iron filings, and does not interfere with the CMM’s built-in gratings and optical sensing elements, making it suitable for inspecting magnetic workpieces.
V. Simple machining and forming, capable of complex reference structures, with complete calibration support
T-slots, locating bosses, mounting holes, and weight-reduction cavities can be milled integrally, with all slots and holes featuring R-fillets to prevent cracking, meeting various tooling fixation needs;
It can be mass-produced in standardized batches, with each piece issued an ISO8512 or JJG117 metrological calibration certificate, recognized by European and American customers for procurement and acceptance;
It supports split-piece tenon-and-mortise splicing to create large-sized CMM platforms, solving the size limitations of single raw blocks.
VI. Comprehensive cost advantages, suitable for most industrial CMM scenarios
Compared to silicon carbide (SiC), zero-expansion microcrystalline glass (Zerodur), and carbon fiber composites, the raw material and machining costs of granite are significantly lower;
The lead time is short, with standard-sized platforms always kept in stock, and batch orders of 8 pieces can be quickly scheduled for production;
Maintenance costs are low; minor bumps and micro-cracks can be repaired using stone repair techniques and re-ground to restore accuracy without needing a complete replacement.
VII. Chemically stable, resistant to oil stains and mild acid/alkali corrosion
After the sealing treatment of dense fine-grained granite, the internal pores are sealed:
Cutting fluids, lubricating oils, and small amounts of cleaning agents will not penetrate the interior of the stone to cause expansion or bulging;
It is not easily corroded by mild acids and alkalis, making it suitable for the CMM (Coordinate Measuring Machine) inspection stations in machining workshops.
