The operation of a CNC milling machine (Computer Numerical Control Milling Machine) is a subtractive manufacturing process that uses a computer system to control the movement of cutting tools to produce workpieces with complex shapes and high precision. The working principle is different from a CNC lathe in that the milling machine rotates the cutting tools (milling bits) while the workpiece is mostly held in place.
The working process of CNC milling machine has the following main steps:
1. Programming & Data Preparation:
Design the workpiece (CAD Model): Start by creating a 2D or 3D model of the workpiece using CAD (Computer-Aided Design) software.
Generate cutting paths (CAM/G-code): The CAD file is imported into Computer-Aided Manufacturing (CAM) software to define the toolpath, spindle speed, and feed rate. The software then converts these data into a series of numerical commands called G-code.
Enter command: Enter G-code into the CNC milling machine controller.
2. Machine Setup:
Workpiece Clamping: The material (Workpiece) is firmly clamped on the Worktable using a fixture or vice.
Install the cutting tool: Install a suitable milling cutter into the tool holder and attach it to the spindle.
Zero Setting: Set the zero position references (Work Offset and Tool Offset) so that the machine knows the exact starting point of the workpiece and cutting tool.
3. Milling Operation:
Control system (CNC System): It processes G-code and sends electrical signals to the axis driving motor (Servomotor).
Rotation of cutting tool: The main shaft (spindle) rotates the cutter at high speed.
Axis Movement: A typical CNC milling machine has three main axes of movement (3-axis):
X-axis: Horizontal movement (left-right)
Y-axis: Depth movement (front-back)
Z-axis: Vertical movement (up-down)
For 4 or 5-axis milling machines, an additional rotation axis (A, B or C-axis) is added to allow milling of the workpiece from multiple directions without changing the clamping.
Machining: As the cutter rotates and moves along a specified path, the cutting tool gradually cuts material away from the workpiece until the desired final shape is achieved.
In short, CNC milling machines work by controlling the rotation of the milling cutter and the movement of the tool or workpiece table along axes defined in a computer program to create the desired shapes and details on the workpiece.
