In precision measurement, precision machining, and semiconductor and optical equipment, a precision granite surface plate is not merely “a piece of stone,” but the precision reference and physical foundation of the entire device. Its importance can be summarized in one sentence: Platform precision ≈ Final equipment precision; Unstable platform ≈ Zero overall equipment precision.
I. It is the “Reference Surface” for all precision
The precision of almost all precision equipment is measuredtive to this platform:
Coordinate Measuring Machines (CMM)
Vision Measuring Machines, Projectors
Lithography Machines, Bonding Machines, Dispensing Machines
Precision Grindingchines, Lathes, Inspection Platforms
Granite platforms serve as:
The reference for workpiece placement
The reference for guide rail motion
The reference for the coordinate system origin
If tence surface is uneven, unstable, or deformed, all subsequent measurements, movements, and machining will be incorrect.
It is like building a high-rise on soft ground; if the fodation tilts, the entire building tilts.
II. Only granite can simultaneously meet the four major “precision necessities”
This is something other materials (cast iron, aluminum alloy, ordnary marble) cannot achieve:
- Extremely strong thermal stability — Precision does not collapse with temperature changes
Thermal expansion coefficient is only 1/3 to 1/4 tat of steel
With environmental temperature fluctuations of 2-3°C, metal platforms deform noticeably, while granite remains almost unchanged
For instruments, this means:
High precision can be maintained without strictture control; it is accurate upon startup and does not require repeated calibration. - Complete release of internal stress — No long-term deformation
Natural granite, after hundreds of millionsf geological action, has completely released internal stress:
No warping
No twisting
No slow deformation over time
Even with aging treatment, metal beds will undergo slight deformation after few years;
Granite can maintain basic precision for ten to twenty years. - High rigidity High damping — Anti-vibration and anti-interference
High density and rigiit resistant to deformation under force
Large internal crystal structure damping provides far superior vibration reduction compared to cast iron
Machine tool vibrations in the workshop, personnel movement, and fan vibrations ickly attenuate when transmitted to the granite platform.
For precision equipment:
Less vibration = Accurate measurement, bright machining, and high yield. - Rust-proof, non-magnetic,tenance-free
Does not rust, so no need for oil coating to prevent rust
Non-magnetic, does not interfere with sensors, gratings, or probes
High hardness, wer-resistant, almost no wear
Long-term use will not cause precision drift due to rust, wear, or magnetization.
III. Surface precision directly determines the highest precision the equipment ve
Precision granite platforms are not just “a little flat is enough,” but:
Flatness can reach 0.1μm～1μm/m
Surface roughness can mirror-like Ra 0.02μm level
This directly determines:
Whether air-bearing guides can run smoothly
An uneven surface causes air bearings to vibrate and pressure fluctuatiotly reducing positioning accuracy.
The quality of measurement repeatability
If the workpiece has the same posture every time it is placed, repeatability is good.
Whether high-preci sensors can function normally
Laser interferometers, linear encoders, and CCD vision systems all depend on a stable and flat reference.
In short:
Platform precision is the ceiling of equipme precision.
If the platform cannot achieve 0.5μm level, the entire machine cannot achieve sub-micron level.
IV. Without it, high-end precision equipment is simpl impossible
These fields must rely on precision granite platforms:
Semiconductor packaging, lithography machine stages
CMMs, high-precision inspection equipment
Optical experiments, laserng
Precision automation, micro-assembly equipment
Once the platform is omitted or standards are lowered:
Measurement data becomes unreliable
Machined dimensions exceed tolerances
Yield decrea calibration and rework
Equipment life is drastically shortened
Saving money on the platform will result in multiple losses in scrap, rework, downtime, and calibration in end.
Summarize in the most critical sentence: The precision granite surface plate is the “precision heart” and “physical foundation” of precision equipment. It determines ty, stability, and durability of the equipment, serving as the fundamental guarantee for all high precision.
