What is a CNC Milling Machine & How Does it Work?

Read our beginner guide to CNC milling machines to learn what the device is, its uses and how it works.

CNC milling machines are widely used both in large industrial enterprises and small companies. Regardless of the complexity and cost of the equipment, the general principle of their operation is the same, i.e., machining of a part with an automated power tool controlled by a program.

What is a CNC Milling Machine & How Does it Work? 1
Read on to learn about the design features of CNC machines and how to work with them.

Features of a CNC Milling Machine

Before we continue, watch the video below to find out more about CNC milling machines.

CNC milling machines are used in the manufacture of different parts from hard materials (plastic, wood, metal, etc.). The devices have numerical control (hence the abbreviation “CNC”), which allows automatic processing of any complexity.

CNC milling machines are more expensive than manual milling machines. However, the advantage of CNC machines is high accuracy, speed and minimum level of errors.

Investing in a CNC machine will quickly pay off, thanks to the high quality products produced from them.

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A CNC milling machine is largely similar to its mechanical counterpart. All units and mechanisms are mounted on the bed (1), while the workpiece is fixed on the work table (2). Depending on the design of the CNC milling machine, the working table moves along the guides (3) in the longitudinal and/or transverse direction.

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To process the workpiece, a milling cutter or other cutting tool is used. The cutter is fixed in the spindle (4). Column (5) is used to move the spindle in the vertical plane.

Cost of CNC Milling Machine

The price of a CNC machine largely depends on how the spindle movement mechanism is implemented. This unit must be accurate and smooth under long-term operating conditions. More expensive CNC machines have increased vibration resistance.

A CNC milling machine has the following features for convenient and safe operations:

  • Door (6) – provides operator access to the desktop
  • Tool magazine (8) – optional element for automatically changing the cutters in the machine
  • Protective covers (7) – protect the working area of the machine, thereby preventing foreign objects from entering the working table and preventing the scattering of chips around the machine

Most machines have a control panel (9), which is usually located on the front of the case. The control panel will be present depending on the cost of the machine and the complexity of the tasks for which it is intended.

Finally, there is a remote control, which consists of a display (touch or conventional) and a button block.

The CNC milling machine can be equipped with various mechanisms, ventilation systems (for removing smoke from the working chamber), air or water cooling of the cutting tool, and other features.

Data Input Devices

CNC machines differ in design features and, accordingly, in price. The most obvious difference is the type of input device. The following technologies are used in the machines:

  • Personal computer or enterprise network
  • Reader of magnetic strips
  • Punched tape reader

The second and third types are more common on obsolete industrial machines and are gradually falling out of use. This is especially true of the third technology.

The RS-232-C format is used to enable the device communicate with the control unit when data is inputted.

Machine Control Unit

The machine control unit is a key element in a CNC machine. The element gives a command to the nodes and analyzes the result of the work. Its roles include the following functions:

  • Processing of data received from the input device
  • Generation of codes for controlling machine units
  • Feedback signal processing
  • Performing additional actions (changing cutting tools, etc.)

Actuating Mechanism

The actuator in a CNC machine is the unit that process the part. The working table moves the part in the horizontal plane, while the spindle moves the tool in the vertical plane. Motors and lead screws are required for this mechanism to work.

Drive System

In a CNC machine, the drive system receives commands from the control unit, after which it adjusts the speed and trajectory of movement of the elements of the actuator. The drive system consists of the following components:

  • Amplifier circuit
  • Drive motors
  • Ball screw bearing.

Feedback System

The machine feedback system analyzes, in real time, the accuracy of the movement of the cutting tool relative to the workpiece. Using data from high-precision sensors, the CNC machine can automatically adjust the toolpath and speed of the cutter.

Remote Control

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The dashboard is used both to enter a task and to monitor the progress of that task. The operator can quickly make adjustments through the control panel, or stop the process if necessary.

Diagram of a CNC Milling Machine

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The above structural elements provide effective interaction between the operator and the equipment. Moreover, operator intervention in the work process is minimized. In the diagram, the operator only has access to the data entry device and the control panel. The technician performs all other processes autonomously.

How Does a CNC Machine Work?

Check the video below for an overview of how a CNC machine works.

Work on a CNC machine consists of several stages, including extensive preparatory work. To download a project to the machine, you must first create a model of the part on the computer in a CAD program. Here are the stages of work on a CNC machine:

  • Designing a 3D part on a computer
  • Using software to transform the 3D model into a list of G-codes that are understandable to the CNC machine
  • Setup the machine
  • Check the correctness of the equipment settings and the presence of unnecessary objects in the working area of the equipment
  • Connect additional devices, if necessary
  • Check inclusion at idle speed
  • Install the necessary tools
  • Install the part
  • Download the project to the machine
  • Test check the operation of the machine with the movement of the cutter at a height of 5 cm above the surface of the part
  • Manufacture the part

Although the mechanical part of a CNC milling machine resembles the old, manually controlled devices, there are important differences. In particular, a CNC machine is operated automatically using a computer. Moreover, it also has sensors and motors, which ensures parts are of high quality and are produced faster in a repeatable manner.

In modern manufacturing industry, a CNC milling and milling-lathe is an indispensable tool.

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