Types of Chips in CNC Milling

  • The process of milling is to use the high-speed operation of the milling cutter and the contact of the workpiece to process the workpiece into the required shape and size. In the CNC milling process, the milling cutter cuts off the metal material on the surface of the workpiece to become chips, including the cutting effect of the cutting edge and the pushing and expanding of the cutter surface, so that the chip can leave the processing surface.

    Due to the different materials and cutting conditions of the workpiece, the deformation in the cutting process is also different, so different chips are produced. According to the different chip morphology, the chip can be divided into four kinds: strip chip, node chip, granular chip, and chipping chip.

    1. Strip chip: in the process of cutting, if the slip on the final slip surface has not reached the degree of fracture, it will form a continuous strip chip with a hairy outer surface and a smooth inner surface. Strip chip is the most common chip in finish machining. This kind of chip is often produced when the cutting speed is high, the cutting layer thickness is small, the tool rake angle is large and the cutting edge is sharp.

    2. Nodal chip: the nodal chip is formed under the condition that the slip on the final slip surface is sufficient and reaches fracture. The outer surface of the nodal chip is serrated and the inner surface is smooth. This kind of chip is mostly produced when plastic metal material is processed, the cutting speed is low, the cutting layer thickness is large, and the tool rake angle is small.

    3. Granular chip: when the crack runs through the whole chip layer, the chip becomes a ladder-shaped unit body to separate, then the granular chip (also known as a unit chip) is formed. Granular chip is produced when processing metal materials with poor plasticity, low cutting speed, large cutting layer thickness, and small tool rake angle.

    4. Chipping: when cutting brittle metals (such as cast iron, etc.), due to the small plasticity of the material, the metal surface layer will be brittle broken to form chips after an elastic deformation and extremely small plastic deformation under the cutting and pushing of cutting tools. The harder the workpiece material is, the smaller the rake angle of the tool is, and the greater the thickness of the cutting layer is, the easier it is to produce such chips.