Demystifying the CNC Milling Process

A computer numerical control (CNC) milling machine is programmed with electronic tools including a dial and keypad to control mechanical devices such as drills, saws and lathes. A CNC machine is commonly used to manufacture industrial parts, such as engines. Computer-aided design (CAD) software is used to manipulate mechanical processes.

What CNC Milling Machines Manufacture

  • Products made of metal, plastic, glass and wood
  • Customized machine parts
  • Precision cuts, curves and a wide range of shapes

Key Parts and Machining Process

The CNC milling process starts with a designing a CAD model. This model must then be converted into a CNC program. The operator then prepares the machine and executes the program. The primary components of a CNC milling machine are:

  • Parallels
  • Drill bits
  • Limit switches
  • A spindle
  • Table
  • Vise to clamp the stock in place

Parallels are strips of metal with a series of holes and are used to help mount stock in a vise. The vise should be cleaned with a brush since you need a flat surface for mounting a part. The stock is placed in the device and tightened with a handle.

The machine contains a door that opens and closes so that you can insert the stock. An edge finder tool is used to identify the stock’s location. The operator shuts the door and selects the manual data input (MDI) button from a menu viewed on the digital monitor. This menu allows you to select tool changes. You then type in the appropriate tool number and press the automatic tool change (ATC) button. The red emergency stop button is used when a part gets disconnected from the vise. The green start button resumes where the program left off.

Codes and Functions

A CNC milling machine translates programs identified by letters and numbers. G codes program moving parts while M codes turn devices on or off. Programming involves pressing buttons on a keypad starting with the program button. All programs start with the letter “O” and are numbered. These codes write instructions for the machine to perform specific functions using 16 building block tools. These tools control location, speed and other factors.

Designs can be cut seamlessly in various shapes from straight to circular patterns. At high speed, you can create complex designs in a matter of minutes. Location is determined by an X, Y and Z axis. The X, Y and Z buttons are controls for moving the parts, as X moves the table left and right, Y moves the table forward and backward and Z moves the spindle up and down.

You then set the edge finder,  which works most efficiently at 1,000 rpm, with the door closed. If you want better visibility with the door open, it must be set at 750 rpm or lower. Modern CNC milling machines can get as fast as 12,000 rpm.

Here at Serra Laser, we can use CNC milling either to reverse engineer your part, or to draw specifications from scratch. Contact us to learn more about our capabilities.

 

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