Brittle Fracture Mechanism and Analysis of Cutting Difficulties
The core challenge facing CNC machining ceramics is their extremely high hardness (usually HV1000-2000) and brittle characteristics. Unlike plastic deformation of metals, brittle fracture occurs mainly during cutting. When cutting forces exceed the fracture strength of the material, microcrack propagation occurs. If the crack extends to the surface, it will lead to chipping, spalling or macrocracks, which will directly damage the precision and appearance of the part.
Therefore, CNC machining ceramic process design must focus on "inhibiting crack growth" and "controlling heat affected zone". For engineering ceramics such as alumina (Al2O3) or silicon nitride (Si3N4), it is often difficult to balance efficiency and surface quality by relying solely on conventional cemented carbide tools. Professional manufacturers need to combine material hardness, cutting speed and cooling methods to develop specific CAM path strategies to avoid microstructural damage caused by vibration or thermal stress. Understanding this physical mechanism is the first key indicator for evaluating a supplier's technical capabilities.
Tool Material and Cutting Parameter Selection
For brittle cutting of ceramics, the choice of tool material determines the upper limit of machining. The following is a comparison of several mainstream solutions against which the purchaser can assess the supplier's process maturity:
| tool type | Applicable ceramic type | Cutting speed recommendations | advantages and limitations |
|---|---|---|---|
| Polycrystalline diamond (PDC) | Aluminum oxide, silicon carbide | 200-800 m/min | Long life, high sharpness; high cost, strict monitoring of wear |
| Cubic boron nitride (CBN) | Ferrous cermets, partial oxides | 100-300 m/min | Good heat resistance; slightly inferior hardness matching for some ceramics, tip easy to collapse |
| Diamond coated/coated tools | Low hardness ceramics, glass ceramics | 50-150 m/min | 1.33。
