Understanding CNC Milling

Posted on May 9, 2021

CNC milling is suitable for workpieces with various materials, such as metal, plastic, wood, or glass, which are all sturdy and malleable for cutting, drilling, or milling works. The performing of CNC milling includes different methods, conducting at angles, and in multiple directions in order to accommodate the different requirements of the machining works that show the versatile applications of CNC milling.

What Is CNC Milling?

CNC milling stands for computer numerical control milling, which is a process in precision machining. CNC milling is conducted by following the code of the program that is controlled by the computer, in combination with a variety of cutting tools, in order to make the customized products or parts of the products.

Before CNC milling was invented, the making of products could not be as standard as the products that are made by the CNC milling machine. The reason is in the operation methods.
 

What to Notice When Performing CNC Milling?

If the operators of the machining work do not follow the instructions of the computer, which fixes the working angle, speed, or feed rate, then the products would be made without consistent specifications. This may cause the quality of the products to be not consistent and not reliable as well, which decreases the desire of the customers to buy the products.

In contrast, if the machining work is aided by the computer, then the producing process would be standardized, and the products that the machining tools make would be standardized and consistent with the optimal accuracy and precision at the same time, which makes it suitable for the large-scale precision machining works.

CNC milling is suitable for workpieces with various materials, such as metal, plastic, wood, or glass, which are all sturdy and malleable for cutting, drilling, or milling works. The performing of CNC milling includes different methods, conducting at angles, and in multiple directions in order to accommodate the different requirements of the machining works that show the versatile applications of CNC milling.
 

:: Read More: How to Select a Machining Mill?
 

How does a CNC Milling Machine Form?

Depending on the working directions, CNC milling can be differentiated into horizontal CNC milling, in which the machine tool and the arbor along with the workpiece are parallel to each other when being operated, and vertical CNC milling, in which the machine tool is perpendicular to the workpiece.

No matter which direction the CNC milling follows, the CNC milling machine mainly consists of a base, a column, a machine interface, a spindle, a knee, a saddle, a work table, and a work-holding device.

For the horizontal CNC milling machine, there is also an additional arbor that is attached to the spindle, with arbor support that holds the arbor in place. As for the vertical CNC milling machine, there is a ram that provides a downward force, in conjunction with the rotating force of the spindle to the workpiece below the ram.
 

  • Base

The base of the CNC milling machine is set at the bottom of the whole device, which is strong enough to support the components upon it.
 

  • Column

The column is mounted on the base and set on a side, which is extended upward from the base. It can also be arranged with other internal components such as oil and coolant reservoirs that help the procedures of the CNC milling go smoothly.
 

  • Machine Interface

The machine interface is for the operators to do the settings in order to turn on and make the CNC milling machine start to do the works.
 

  • Spindle

The spindle can be set either on the side of the column or under the ram. When the electrical source is powered up, the electric energy would be transferred into the kinetic energy, and trigger the spindle to rotate, in order to execute the instructions from the computer.
 

  • Knee and Saddle

The knee and the saddle on the knee are mounted upon the base, which acts as the support for the worktable and the work-holding device, as well as the workpieces that the whole device is going to work for.
 

  • Work-holding Device

The work-holding device can be either a vise or a chuck depending on the requirements of the workpieces, such as the shapes of the workpieces. It holds the workpiece in place by clamping the workpiece so as not to let it slip off the worktable.
 

What Are the Methods a CNC Mill Apply?

In addition to the different directions of the working of CNC milling machine, there might be, there are also different operation methods of the CNC milling machine that works the machine with the opposite principles, including conventional milling and climb milling.
 

Conventional Milling

Conventional milling is worked when the cutter rotation goes upward, which is against the material feed. This is done due to the backlash or play there might be. The backlash or play is the clearance or lost motion in a mechanism caused by gaps between the parts, which may be occurred when the cutter rotation and the material feed are in the same direction with each other.
 

Climb Milling

Climb milling is worked when the cutter rotation goes downward in the same direction with the material feed. This operation method is more commonly applied in CNC milling nowadays, as most CNC milling machines today are capable of compensating for backlash or equipped with a backlash eliminator.

This operation method not only reduces or eliminates the backlash but also extends the lifespan of the machine tool since the cutting surface between the workpiece and the machine tool is cleaner, which then leads to less rubbing force for the machine tool.
 

Types of CNC Milling


Surface Milling

Surface milling, also known as plain milling, is a type of CNC milling in which the rotation axis and the working direction of the machine tool are parallel. In this type of CNC milling, both narrow and wide surface milling cutters can be applied. 

The narrow milling cutter is able to make a deeper cutting surface, while the wide milling cutter is specialized in cutting a wider area of the surface. When the wide milling cutter is used, it would be coupled with either coarse teeth or fine teeth. The wide milling cutter with coarse teeth provides with slow cutting speed, fast feed rate. In contrast, the one with fine teeth provides fast cutting speed and a slow feed rate.
 

Face Milling

In comparison with surface milling, face milling is used when the rotation axis is perpendicular to the working direction of the machine tool. In addition, the teeth on the cutter in face milling are on the sides and the end, instead of right on the cutter, like that of the surface milling, which makes the cutter be regarded as a side milling cutter or end milling cutter.
 

Angular Milling

Angular milling is used when making chamfers, serrations, and grooves. These shapes cannot only be done with the flat cutters that are equipped with teeth. Instead, the shaped, angled cutter, such as dovetail cutters are used for making grooves, or the cutters with the conical heads are used for making chamfers.
 

Form Milling

Instead of the sharp edges that the above types of CNC milling would make on the cutting surfaces, form milling produces round recesses or round edges on the workpiece. This type uses convex and concave cutters, for example, to make the complex contours of the cutting surfaces, which requires the right parameters in order to make the products precisely and accurately.
 

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