Silicon Carbide Advantage

CMM-Z-axis-designCOORD3 uniquely offers Silicon Carbide Z rams across the full range of its vertical CMM products. Known as the NT version a COORD3 NT Bridge or Gantry CMM offers a no compromise scanning machine with enhanced accuracy and performances. NT variant has been specifically developed for the higher accuracy scanning applications using the Renishaw SP25 and SP80 scanning probes.

Scanning requires a Rigid CMM

Scanning on a CMM involves moving the stylus of the probe across the component surface contours. For example, measuring a hole requires the probe to be moved in a circular path, causing the moving elements of the CMM machine structure (the bridge and Z ram) to undergo accelerations whilst the measurement is taking place. Accelerating the CMM requires significant forces and inevitably results in inertial deflections at the stylus tip that are not detected by the machine’s position encoders and therefore the inability of a CMM structure to resist these acceleration forces results in structural deformation which has a corresponding effect on the metrology of the measured features. As a consequence of these forces a CMM machine used for scanning applications is required to be significantly stiffer than a CMM used just for simple touch probe measurements.

Stiffness1Modulus of Elasticity is critical for CMM Z Axis

Silicon Carbide (SiC) also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by sintering to form very hard ceramics that are widely used in applications requiring high endurance, such as car brakes, car clutches and ceramic plates in bulletproof vests.  Today Silicon Carbide is also widely used in high-temperature/high-voltage semiconductor electronics.

Silicon Carbide offers much improved Scanning Performance over a Granite CMM

COORD3 has pioneered the use of Silicon Carbide for use as the material for the Z axis across its range of coordinate measuring machines. Silicon Carbide offers the most advanced ceramic material for applications in the field of CMM structural components.

 

  • Excellent Mechanical Properties | Modulus of Elasticity: E = 4500000 N/mm2 | Density: ρ = 3.09 kg/dm3
  • Excellent Thermal Properties | Expansion Coefficient: α = 4.9 µm/m°C | Thermal Conductivity: λ = 160 W/m°C

Thermal-Expansion-Coeffiecient-GraphIn comparison with other materials, the mechanical properties allow higher values of static and dynamic stiffness while offering lower component weight. These properties make Silicon Carbide the material of choice for high accuracy scanning CMMs and is superior to regular ceramic used by other leading CMM brands.

Better Thermal Performance than Granite CMM

Granite has an Expansion Coefficient of higher than 6.5 µm/m°C. 33% greater than Silicon Carbide’s low Expansion Coefficient of just 4.9 µm/m°C.

Rapid Thermal reaction critical for today’s CMM

Silicon Carbide has a rapid thermal diffusion rate of 160 W/m°C; more that 40 times better than slow reacting Granite meaning if the CMM is subject to temperature fluctuations the change is dissipated quickly. This results in less CMM structure distortion and therefore less inaccurate measurements due to temperature fluctuations.

Thermal-Diffusion-Rate-Graph

 

Silicon Carbide is the engineered material of choice for the modern highly accurate CMM. Its stiff, light, stable and reacts fast to thermal change with less physical expansion and distortion.

Granite is yesterday’s CMM structure material

The granite structure CMM first appeared more than 40 years ago, and long before the invention of CMM scanning probes; today the “all-granite” CMM still follow this 40-year-old tradition of “screwing together machined granite blocks”. Under the scientific microscope however the all-granite CMM offers severe metrology limitations when installed in a ’non-perfect’ temperature laboratory and has very poor structural stiffness when used for advanced scanning measurement applications.

 

Silicon Carbide is optimum CMM Z axis material

Silicon Carbide is stiff, light, temperature stable and reacts fast to thermal change with less physical expansion and distortion. Check it out!

Silicon Carbide – the engineered material used in by the most advanced CMM structures. Select an Advanced Technology Coordinate Measuring Machine – the Scientific Engineer’s Choice.