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How CNC machines work? Plastic parts manufacturing

  • Posted On: February 18, 2025
  • Posted By: admin

Computer Numerical Control (CNC) machines are computer controlled automated tools used for precise cutting and shaping, plastic, and composite materials. They are widely used in plastic injection molding.

1. CNC Machines

CNC Machines work on software controlled movements of tools like lathe, mill, router, or grinder. They are equipped with sensors, motors and controls(fully programmed) to allow operation on specific inputs of the operator. they are generally used for designing intricate parts with precise dimensions. CNC machines enable tasks like drilling, milling, and grinding. G-Code programming is used for running CNC machines. This programming instructs the movement of tools along various axis.

The basic structure of a G-code program includes:

  • G-codes: Specific commands for machine movements (e.g., G1 for linear movement, G2 for circular interpolation).
  • M-codes: Commands for controlling auxiliary functions such as turning the spindle on/off, coolant on/off, and tool changes.
  • Toolpath Instructions: These  instructions are prefed and decides how the tool will move along various axes to provide the desired cut and shape of the workpiece.

The G-code is loaded onto the CNC controller which then starts sending signals for operations to the machine

2. Components of CNC Machines

  • Controller (CNC Computer): It is the heart of the system and operates through G-code. It recieves inputs from the program and sends electrical signals to guide the movement of the machine’s parts , tools and workpiece. They help in providing precision, efficiency and repeatability in tasks.
  • Machine Tool set: This is the functioning arm consisting of drills, mills, lathes, or grinders, depending on the type of CNC machine.
  • Axis/Motion System: The most common axes of CNC machines are
    • The X-Axis controls horizontal movement (left to right),
    • the Y-Axis handles vertical movement (front to back), and
    • the Z-Axis manages depth movement (up and down). Some machines are equipped with extra axes, such as A, B, and C, which allow for rotational movements, enabling more complex tasks.
  • Tooling/Workholding Devices: It include cutting tools (drills, mills) and fixtures holding the workpiece in place and ensuring tight holding and precision during cutting or trimming process.
  • Feedback System: They use sensors/encoders/AI systems to monitor the position of the tool,workpiece, the precision of cuts being made, consistency in operations along large number of pieces and provide feedback in real time to the controller of the machines to make any adjustments

 

Functioning of CNC machines

A. Setup

Before CNC machining starts, the workpiece and tool are set up properly.

  1. Workpiece Clamping: The plastic part is clamped on the machine’s worktable and secured firmly to avoid any movement during cutting oir trimming process which may affect the accuracy of operation.
  2. Selection of tool: The required tool (like drill bit, lathe tool etc) is inserted in the CNC machine spindle.
  3. Calibration of the machine: It ensures correct tool’s position relative to the workpiece

B. Program Execution

Once setup is complete, the CNC machine can begin executing the program.

  1. Movement Control: The controller sends electrical signals to motors that drive the machine’s axis. These move the tool or the workpiece along the X, Y, and Z axes.
  2. Toolpath Generation: The cutting tool is guided by the path already pre-fed by the CNC program. This involves straight lines,complex curves or arcs. The position of the tool is continously updated by the CNC controller
  3. Feed/Speed Control: The controller continously adjusts the speed at which the tool moves through the material, also called as feed rate and the rotating speed of cutting tool, also called as spindle rate.
  4. Cutting Action: The cutting process involves
    • Milling
    • Turning
    • Drilling
    • Grinding

Different types of CNC Machines

There are different types of CNC machines, each designed for specific types of work:

  • CNC Mills:
  • CNC Lathes
  • CNC Routers
  • CNC Plasma Cutters
  • CNC Laser Cutters
  • CNC Electrical Discharge Machines