Computer numerical control milling, also known as CNC milling, uses computerized controls and spinning multi-point cutting tools to create a part or product to a specific design. Metal, plastic, glass, and even wood may all be machined with this method, among many other materials, to create a wide range of one-of-a-kind components and finished goods.
Precision CNC machining services provide a wide range of capabilities, from mechanical to chemical to electrical to thermal. Material is removed from the workpiece using mechanical means, such as the actions of the milling machine’s cutting blades, in CNC milling, as in drilling and turning and other machining processes.
The fundamentals of CNC milling, as well as its components and tools, are discussed in this article. Milling operations other than computer numerical control milling (CNC) are also discussed.
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Table of Contents
What is CNC Milling
CNC milling is a manufacturing process that involves the selective removal of material from a block of a raw substrate using a cutting tool mounted on a rotating spindle. The workpiece is fixed on a table that can move or rotate in many planes to accommodate the tool’s wide range of cutting angles. To create more complex shapes or to keep the workpiece from having to be transferred to a different machine, high-end CNC milling machines can contain five or more axes of independent motion.
CNC Milling Process
CNC milling, like other types of computer numerically controlled (CNC) machining, involves computerized controls to operate and manipulate machine tools used in cutting and shaping stock material. In addition, it involves the standard steps in production common to all CNC machining operations, such as:
Creation of CAD Model
The first step in CNC milling is designing the part in 2D or 3D CAD software. The finished design is then exported to a CNC-compatible file format, where CAM software transforms it into a CNC machine program that controls the actions and movements of the machine and its tools over the workpiece.
Transforming the CAD Model into a CNC Program
The operator of a computer numerical control (CNC) milling machine must first attach the workpiece to the machine’s worktable or work holding device (such as a vise) and secure the milling tools to the spindle before running the CNC program. Mills and drills have many cutting edges and are used in CNC milling. The milling machine’s orientation and the milling application’s requirements determine whether the CNC milling operation is performed on a horizontal or vertical axis. When the milling process is ready to begin, the operator initiates it via the machine interface.
Preparing the CNC Milling Machine
CNC milling involves a machine that, once started, can spin the cutting tool at thousands of revolutions per minute. As the tool cuts into the workpiece, the machine will do one of the following, depending on the type of milling machine used and the requirements of the milling application:
- Keep the workpiece moving slowly into the fixed, rotating tool.
- Drag the tool back and forth across the still work
- Rearrange the tool’s position in regard to the workpiece.
In computer numerical control (CNC) milling, the machine feeds the workpiece in the direction of the cutting tool’s rotation rather than against it, as traditional milling does. Climb milling processes are those that adhere to this standard, while conventional milling processes are the opposite.
Performing the Milling Operation
Milling, which provides definition to or produces features like holes, slots, and threads, is ideally suited as a secondary or finishing process for an already machined object. This method is also used to transform raw material into a finished product completely. The milling technique is used to create both forms by gradually removing material to reveal the final form.
The tool begins by chipping away at the workpiece to create a rough outline of the final form. When the milling process is complete, the part will have the exact characteristics and specs for which it was designed. It usually takes multiple runs through the machine for a finished product to reach the required accuracy and tolerances. Several machine configurations may be needed to fabricate more geometrically complicated items successfully.
When the milling process is finished, and the item is made according to the custom-designed specifications, the milled part moves on to the finishing and post-processing phases of manufacturing.
How does CNC Milling Machine Works?
Slots, holes, and other features can be milled into a piece of material using a computer numerically controlled (CNC) milling machine. This machine has a spinning cylindrical cutter that can operate along many axes. Most machines work on three to five axes, which gives them much more accuracy and detail. CNC milling machines today have the versatility to be set up for both horizontal and vertical milling. In addition to metals, you can use plastics, ceramics, and composite materials to make parts. Mechanisms such as automatic tool changers, coolant systems, tool carousels and magazines, and protective housings ensure that machinery operates reliably and efficiently with minimal human interaction.
CNC Milling Machine Types
CNC Milling Machines come in many different shapes and sizes, from simple machines with two to three axes to multi-axis CNC machining centers. In general, the main types of machining centers are either vertical or horizontal.
Some types of CNC milling machines types are as follows:
When choosing the right CNC milling machine for your machining needs, you should consider the size of the part you want to make, how complicated its shape and design are, how accurate you need it to be, and how long and stable the machine is.
C-Frame
Vertical Machining Centers (VMCs) usually look like a C-Frame, their traditional shape. These can only be used on machines up to a certain size because the spindle may stick out too far, and the machine may need too much space on the floor.
Vertical Milling Machine
The table and arm of the vertical milling machine are connected to a vertical column. The spindle is also vertical.
On the one hand, the table moves up and down the z-axis with respect to the arm.
When it comes to the spindle, on the other hand, how the table moves depends on the type of vertical milling machine. For example, in a vertical turret mill, the spindle stays in one place while the table moves along the x-axis. In a vertical bed mill, the table can move along the x-axis, and the spindle can move along the y-axis in the same direction as the arm.
Vertical milling machines are accurate enough to be used for complicated tasks. Also, you can use them to work on vertical surfaces and shapes with angles.
Horizontal Milling Machine
Like vertical milling machines, horizontal milling machines are used to cut metal. On the other hand, the universal ones can turn along the z-axis. So, they are milling machines with four axes. They also have a horizontally placed spindle.
These machines don’t have as many uses as their vertical cousins. Even so, they are better for doing heavy machining.
Multi-Axis CNC Milling Machine
A CNC milling machine with multiple axes can cut in different directions and at different angles. There are different kinds of multi-axis milling machines, which include:
2-axis milling machines
A piece of work can be done on 2-axis milling machines in the x and z directions. So, they can cut in one direction, both vertically and horizontally. They are the most basic type of CNC milling machine.
3-axis milling machines
Milling machines with three axes can move along the x, y, and z axes. So they can cut pieces of work in any vertical direction.
They are the most common milling machine with more than one axis. But they have some problems, like the fact that a uniform angle makes it hard to cut some complicated parts.
4-axis milling machines
The spindle of a 4-axis milling machine can move up and down, side to side, and back and forth without moving the workpiece. It can also turn on either the X-axis or the A-axis. So, it is a good choice for making cutouts and other complicated milling tasks. These machines work quickly and precisely.
5-axis CNC milling machine
The spindle and cutting tool of a 5-axis milling machine move along three axes and can turn along two axes (any of the x-axis, y-axis, and z-axis). They are complete multi-axis CNC machines and can work on many different parts.
High Speed and High Capacity Machining Centers
High-speed machining centers, also called HSC machines, can be used to get the best surface finish on the part being machined and to handle tools with very small diameters, like 0.030 mm or less.
In the same way, high-capacity machining centers are made and designed to work with materials that are very hard. Some examples of these materials are Heat Resistant Stainless Steel, Titanium, and Inconel.
Machining Centers with Pallet Changers and Two or More Spindles
Vertical or horizontal double-spindle or multi-spindle machining centers are the best CNC milling machines. They often come with Pallet Changers. These are made so that they are as productive as possible and can make a lot of complicated parts.
By using automatic pallet changers, downtime is cut down, and productivity and efficiency are increased. They can also be used as part of the process of automating your factory.
CNC Milling Machine Operations
There are different ways to set up and use CNC milling’s various operations. Here are some of the most common types.
Plain Milling
Plain milling is an operation that uses a column and knee to mill flat, horizontal surfaces. The tool for cutting is in line with the workpiece. So, cutting goes from one end of the piece of work to the other. You can feed the table in a longitudinal, cross, or vertical direction.
Face Milling
In face milling, the rotating axis of the cutting tool (a face milling cutter) is parallel to the surface of the workpiece.
The face milling cutter is special because it has cutter inserts that can be switched out. It cuts through things with its many cutting teeth. Face-milled parts have better surface finishing because of this. Also, the process is easy to control, which makes it easy to get the surface you want
Form Milling
Form milling is the best way to make a piece of work with an irregular shape. The shape can be straight or straight with curves. The edges can be either concave or convex, and they are made with teeth that go in the opposite direction. So, if you want to make a product with a concave edge, you should use a form milling cutter with a convex edge.
Form milling is about 20 to 30 percent slower than regular milling because making curved surfaces requires more precise cutting.
Angular Milling
Angular milling is the process of using a cutting tool at an angle to mill flat surfaces. The only difference from plain milling is the way the machine is set up.
Angled milling cutters come in two types: single-angle and double-angle. The single-angle cutters have teeth on the angled side of the cutter and large flat sides. You can use them to cut at angles of 450 or 600.
The double angular milling cutters are better for milling flat surfaces at 45°, 60°, and 90°. Their teeth are shaped like a V, and their surfaces are shaped like cones.
Other Types
You can use different types of milling machining processes. Here are the most important ones:
Straddle Milling
Milling procedures that straddle two or more parallel workpiece surfaces are known as straddle milling. In this method, two cutters are mounted simultaneously on the same machine arbor mill from opposite sides of the workpiece.
Slot Milling
In slot milling, the width of the cutter is less than the width of the workpiece. This is how a slot is made in the workpiece.
Side Milling
It can be used for milling, which is a type of machining that makes a flat, vertical surface in the workpiece. Turning the table’s vertical feed screw can change how deep the cut is.
Profile milling
When a machine tool mills a surface at an angle or vertical plane, the process is known as profile milling. The cutting tools used in this process are held at right angles to, or parallel to, the surface of the workpiece.
Gang Milling
Gang milling is a way to cut horizontal surfaces by putting two cutting tools on the same arbor. The combination has a lot of potentials and cuts down on time it takes to mill
Gear cutting
Milling with involute gear cutters is known as “gear cutting,” and it’s used to make gear teeth. These cutters, a subset of formed milling cutters, come in various geometries and pitch sizes to accommodate any gear design. The procedure can also be used to make gear teeth with the help of a specific lathe cutter bit.
Advantages Of CNC Milling
Because of its benefits, the process is an essential part of many industrial production steps. But it also has some bad things about it. Here are some good and bad things about the process.
Accurate and Precise
The accuracy and precision of CNC milling machines are better. So they can make parts that meet their technical requirements. So, they can mill parts with as little as 0.0004 mm of error. Also, because the process is automated, mistakes made by people are less likely to happen.
Fast and Effective
CNC milling machines are more rapid and productive than their manual counterparts. This is because, depending on the ATC, they may transport a plethora of cutting tools, facilitating rapid tool swaps and streamlined operations.
Large Compatible Material
The method is suitable with numerous compatible materials, e.g., plastic, metals, and composites. Therefore, CNC milling can be the perfect method after you have a block of material.
The Tooling Requirement is Reduced
Tooling complexity is eliminated, and the number of tools needed to process complex parts is drastically decreased. It is appropriate for new product creation, and enhancement since the shape and size of the part may be altered by only adjusting the part processing procedure.
Can Process Complex Profiles
It can handle profiles that are difficult to process using more traditional methods and portions of the processing that are not easily observable.
Affordability
Precision, speed, and a host of other benefits are all well and good, but cost-effectiveness is what really matters to organizations wanting to outsource manufacturing. The computer numerical control (CNC) milling process is one of the most cost-effective methods of making products today. On the contrary, the cost of a CNC-milled product would be far lower than that of a 3D-printed one.
Applications of CNC Milling Parts
Exceptional precision, tolerance, and accuracy can be achieved with milling. Therefore, it can be used for a variety of purposes. Some of the many uses it has in the business world are listed below.
Used in Aerospace
The aerospace sector makes extensive use of the milling process. Metals, polymers, and composites are just some of the many materials that can be milled with a computer numerical control machine. Many different kinds of items could benefit from CNC milling, and the process can be utilized to make a wide range of components.
The aerospace industry is one sector that benefits from CNC milling. CNC milling is an excellent method for producing high-precision and speed metal and composite aircraft parts. In addition, it’s useful for manufacturing tiny components that would be challenging or impossible to produce otherwise.
Used in Agriculture
By rotating the material around a cutting edge, milling can be used to create precise cuts and precise shapes. To achieve this, a machine under the guidance of computer code is used to manufacture complex components to exact specifications. Milling is used to produce parts for various farm equipment, including tractors and fertilizer spreaders. Some examples of how CNC milling is used in farming are listed below.
Parts for Tractors
It might be challenging to make tractor parts that are both accurate and fit together properly using alternative methods. Because of CNC milling, the production of parts is streamlined, freeing up resources that may be used for farming rather than fixing things.
Irrigation Systems Parts
As a means of fostering plant growth, irrigation systems channel water to specific areas. Components that meet these requirements can be difficult to manufacture using conventional techniques because of the high pressure and high temperatures they are subjected to. CNC milling allows for near-perfect replication of components. This means that farmers may rely on their irrigation systems more and have a lower probability of making mistakes.
For Industrial Use in Health Care Production
The applications for computer numerical control (CNC) milling are extensive. CNC milling is widely used in the medical device manufacturing business. Computer numerical control milling can manufacture components without requiring much time-consuming and error-prone human intervention. In addition, components created using CNC milling are typically more precise and uniform than those made via alternative methods.
Used For the Automotive Sector
Complex auto parts can be easily manufactured using the CNC milling method. Metal, plastic, and other materials can all be employed in the process. CNC milling is widely used in the production of automobiles, airplanes, and their many parts and accessories.
Precision, reproducibility, and decreased cycle times are just a few of the advantages of CNC milling above conventional manufacturing methods made possible by this technique. Furthermore, the pieces made by CNC milling are indistinguishable from those made by traditional machining methods.
CNC Milling Materials
There is a large variety of materials that are suitable for use with CNC milling technology, and the choice will depend on the intended use of your design. Once you’ve settled on CNC milling as the method of manufacture, you’ll need to settle on a suitable material, such as metal, plastic, or even wood.
Metals
Metals are one of the most popular CNC milling materials, and there is a wide variety to choose from. Let’s take a look at the most common choices and the contexts in which they are best suited
Aluminum
Aluminum is a famous CNC milling material for mechanical and aesthetic components. Aluminum is the most economically viable metal because it can be machined quickly. Aluminum parts form a protective barrier in the environment, adding strength and corrosion resistance. CNC-milled aluminum is suited for usage in automotive, aerospace, healthcare, and consumer electronics—aircraft fittings, electronic housings, medical devices, gears, shafts, etc.
Steel
Most CNC milling steel alloys are designed for superior machinability. Steel is generally utilized for pieces that require better formability and stronger welds. Depending on the alloy, commercial items, parts requiring strong welds, gears, and shafts, and other high-stress applications are best for this material.
Stainless Steel
Heat-treatable stainless steel alloys provide corrosion resistance. CNC machining with stainless steel can be utilized for surgical equipment, electronics hardware, and other formable and weldable items. Automotive and aerospace use stainless steel alloys
Titanium
Titanium’s high melting point makes it useful in numerous sectors and applications. It’s corrosion-resistant, ductile, salt- and water-proof. Titanium is biocompatible, lightweight, and strong, making it ideal for medical implants, aviation components, and jewelry.
Brass
Brass, one of the easiest and most cost-effective CNC milling materials, gives stability but not strength. Medical equipment, consumer items, and electrical contacts are common uses. Brass is used in engineering, plumbing, steam work, and even musical instruments because of its low friction coefficient and great corrosion resistance.
Copper
Copper is a highly conductive CNC milling material. High corrosion resistance prevents rust, and thermal conductivity eases CNC machining. Cooling systems, heat exchangers, valves, and radiators are common automobile uses. Copper is weak against acids, halogen sulfides, and ammonia.
Other material includes zinc, bronze, magnesium, etc.
In addition to this wide range of metals, CNC milling technology can also be used with plastics, wood, and even fiberglass and foam.
