What is a CNC machine? CNC stands for Computer Numerical Control. When a computer is employed to control a Numerical Control (NC) machine tool, in this case, the machine is referred to as a CNC machine. Simply put, CNC machines use computer-aided design (CAD) and computer-aided manufacturing (CAM) programs to control the movement of cutting tools and workpieces to create nearly any custom shape imaginable. These machines play an important role in the manufacturing industry because they provide efficiency, accuracy, and consistency that would be impossible to achieve through manual machining.
This article mainly explores types of CNC machines. Besides, further reading the article and getting the information you want, such as its definition, how it works, pros and cons, and some tips for selecting the best CNC machine type, etc. Let us start!
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What is a CNC Machine?
CNC machines are automated tools that utilize computer programming to control their movements and operations. They are widely used in manufacturing processes to produce precise, intricate parts with high accuracy and efficiency. In general, CNC machines can create many products by using actuators, drives, and software programs.
By utilizing computer-aided design (CAD) software, operators can create detailed designs and convert them into a language that CNC machines can understand, such as G-code. This code serves as a set of instructions for the machine, guiding it through manufacturing. CNC machines offer numerous advantages, including increased productivity, improved accuracy, and reduced human error.
How Does a CNC Machine Work?
The CNC machine automatically cuts raw material depending on digital instructions from CAM (Computer-Aided Manufacturing) or CAD (Computer-Aided Design) software. Firstly, the CAD software creates a 3D model of the desired part. The 3D model is then loaded into CAM software, which generates a set of computer instructions (G-code) that governs the sequence of movements of the cutting tools on the workpiece.
This G-code comprises the coordinates of the particular part features, the needed tool, the appropriate speeds and feeds, and commands for turning on and off the coolant. The MCU (machine control unit) transforms the G-code into instructions for servo motors and spindles. According to the digital instructions, the CNC machine moves the cutting tool or workpiece on multiple axes to cut the raw material into the desired shape.
Main Parts or Elements of CNC Machine Systems
A CNC machine system comprises several basic parts or elements that work together to carry out precise and automated machining operations. These elements include:
A CNC machine’s “input device” is the device through which CNC programs are loaded into the machine. This input device might be a keyboard (for directly inputting G-code commands), a USB flash drive (for transporting the completed program from another computer), or wireless communication (if the program is to be downloaded from another computer over the local network).
The machine tool is the physical equipment that performs the actual machining operations. It can be a lathe, milling machine, router, or machine capable of cutting and shaping materials.
The CNC machine tool often has a sliding table and a spindle for position and speed control. The machine table is generally controlled in the X and Y-axis direction, while the spindle is controlled in the Z-axis direction.
Machine Control Unit (MCU)
The MCU (machine control unit) is the system’s brain. It receives instructions, typically in a G-code program, and translates them into precise movements and actions for the machine tool. MCU manages the motion control, spindle speed, tool changes, and other parameters necessary for machining operations.
Servo motors are used to drive the axes of the machine tool. They receive signals from the MCU and provide precise and controlled movements along the X, Y, and Z axes or any additional axes the machine may have. Servo motors ensure accurate positioning and motion control.
Feedback devices, such as encoders or linear scales, are used with servo motors to provide positional feedback to the MCU. These devices enable the MCU to monitor and adjust the actual position of the machine tool during machining operations, ensuring accuracy and precision.
Tooling refers to the various cutting tools and accessories used in machining. It includes drills, end mills, inserts, collets, and other tool holders. Tooling selection depends on the specific machining operation and material being processed.
Workholding devices secure the workpiece in place during machining. They can include vises, clamps, chucks, fixtures, and other specialized devices. Workholding is crucial for maintaining the stability and accuracy of the workpiece throughout the machining process.
The operator interface allows the machine operator to interact with the CNC system. It can be a control panel, a computer screen, or a combination of both. The operator interface allows the operator to input commands, monitor machining progress, and adjust the machining parameters as needed.
What are the Different Types of CNC Machines?
There are numerous methods to categorize CNC machines. The most fundamental type is based on the design and function of the CNC machine. This classification divides CNC machines into the following types:
Milling CNC Machine
CNC milling machines employ cutting tools to remove material from a workpiece and precisely shape it according to specifications. The workpiece is typically held in place as the high-speed rotating cutting tool removes material.
CNC mills can have various cutting tools, each with a specific purpose. End mills, reamers, face mills, taps, and drills are common cutting tools. These machines are available in both vertical and horizontal configurations.
Vertical milling machines feature a vertically oriented spindle that holds and rotates the cutting tool. Horizontal milling machines have a horizontally oriented spindle, allowing for more aggressive material removal and better chip evacuation. Horizontal milling machines can also accommodate larger workpieces than vertical milling machines.
Some typical applications of mill CNC machines include cabinets, furniture, prototype models, signage, and musical instruments. CNC milling machines offer high precision and versatility and can produce complex shapes that would be nearly impossible to achieve with manual machining. However, the size of these machines can process depends on the maximum travel distance of the tools and the size of the enclosure.
Router CNC Machine
A CNC router machine is similar to a CNC mill. However, it is normally used for softer materials and is typically less accurate than CNC mills. CNC routers cut a variety of forms and designs on flat surfaces made of any material. In carpentry and metalworking workshops, these machines replace manual tools, such as boring machine tools, panel saws, and spindle molders.
CNC Router machines can cut complex shapes, and their applications involve carved wood furniture, moldings, interior and exterior decorations, door carvings, signage, musical instruments, and so on. They decrease waste, improve productivity and accuracy, and speed up production. But the machine’s high noise is a point that should be considered.
Lathe CNC Machine
CNC lathes operate by rotating the workpiece material around a central axis. The workpiece is then cut with cutting tools to remove material and shape it as needed. CNC lathes include turret lathes, engine lathes, and special-purpose lathes.
CNC lathe machines are perfect for various processes such as cutting, sanding, facing, drilling, turning, knurling, etc. A non-rotary tool travels linearly on a rotating workpiece to provide a helical/spiral cutting path in CNC turning.
Generally, CNC lathes can only create symmetrical components. It can make products like camshafts, automobile parts, gun barrels, crankshafts, baseball bats, musical instruments, dining tables, and furniture legs.
Plasma Cutting CNC Machine
A CNC plasma cutting machine employs an electrical discharge arc (such as a plasma torch) to ionize the air and melt the material where the arc impacts. The method is limited to conductive materials because it operates via an electrical arc. Brass, copper, aluminum, steel, and stainless steel are common materials used in plasma cutting.
The applications of CNC plasma cutters can often be found in automobile manufacturing, automotive repairs, fabrication shops, salvage, and scrapping. CNC plasma cutting machines offer high speed and precision. They can cut through any conductive material. However, plasma cutting works by melting the material; its produced heat would leave visible heat-affected zones on the cut area.
Laser Cutting CNC Machine
CNC laser cutters cut sheets of any material with a highly concentrated laser beam. A CNC laser cutting machine creates even more precise cuts than plasma cutting. The two most common varieties of lasers are CO2 and solid-state. Solid-state lasers can cut any material. Hence CNC laser cutters are not restricted to conductive materials.
CNC Laser Cutters can find applications in aerospace parts, automobile frames, medical equipment, engraving materials, etc. Because there is no mechanical contact or force exerted on the material, high-quality clean edges can be achieved without secondary finishing. One of the limitations of CNC laser cutting machines is that they are limited to the maximum thickness of the material you can cut with them.
Electric Discharge CNC Machine
CNC Electrical Discharge Machines (EDM) use electric sparks to remove material from conductive workpieces to reshape materials. The sparks vaporize minute bits of material, removing thin layers of metal. CNC electrical discharge machines work only for conductive materials and have a slow cutting rate. They can be used for manufacturing injection molds, die casting, blanking punches, and prototyping.
Two main types of CNC EDM machines are wire EDM and sinker EDM. Wire EDM machines use a continuously moving, electrically charged wire to cut through conductive materials. These machines are ideal for cutting intricate shapes, narrow slots, and small holes and producing tight tolerances and smooth surface finishes.
Sinker EDM machines use a shaped, electrically charged electrode to remove material from a workpiece by creating a series of electrical discharges. These machines are suitable for creating complex cavities, molds, and dies with high precision and accuracy.
Waterjet Cutting CNC Machine
CNC waterjet cutters use an extremely high-pressure jet of water mixed with abrasives to cut various materials precisely. The high-velocity water jet easily cuts through metals, stones, glass, composites, etc. A waterjet CNC machine cuts all types of materials with no heat damage. It can be used for cutting parts for aerospace, automotive, electronics, arts, etc. But the speed of this machine is slower, especially around corners and curved cuts. In addition, the thickness of the material suitable for waterjet cutting is high.
Grinding CNC Machine
CNC grinding machines are employed to achieve high precision and surface finish in the grinding process. These machines utilize rotating grinding wheels to remove material from the workpiece and create the desired shape. CNC grinding machines are commonly used for camshafts, ball bearings, transmission shafts, and other parts that require a precise and correct finish. They are extensively used in the automotive, aerospace, and tool manufacturing industries.
CNC grinding machines can remove material at a slow rate, and they are often not used to shape materials. Hence, they only work for finishing and smoothing out the surfaces.
Drilling CNC Machine
CNC drilling machines use rotating drill bits to drill holes in materials. They can drill holes in exact locations quickly and accurately to meet screws, secondary assembly, or aesthetic requirements. Typical drill bits available include spotting drills, peck drills, screw machine drills, and chucking reamers.
CNC drilling machines are highly efficient and can produce a large number of parts in a short amount of time. But they cannot create deep holes or large holes. Moreover, different diameters of drill holes need specific-sized drill bits. CNC drilling machine is suitable for automobile, shipbuilding, astronautics, engineering machinery, mold making, woodworking, and furniture making.
A 3D printer, also known as an additive manufacturing machine, is a CNC machine that prints objects layer by layer. The design and a drawing for the product are created using the CAD and CAM processes. The 3D printer is then utilized to replicate that design. The CNC 3D printer is frequently used for prototyping.
Multi-Axis CNC Machine
A multi-axis CNC machine can generally move in four or more directions or axes. Multi-axis machine is more sophisticated and generates more precise parts than a two or three-axis machine. It gives machinists more machining options.
Automatic Tool Changer CNC Machine
An Automatic Tool Changer (ATC) is a variant of all typical types of CNC machines. It enables the machine’s cutting tool to be changed automatically, resulting in quicker production and less downtime. ATC is utilized to change the cutting tool type in a CNC machine or to substitute a damaged or worn-out cutting tool. It enhances the manufacturing process’s degree of automation.
Types of CNC Machines According to the Number of Axes
The types of CNC machines can be further segmented according to the number of axes. Here are some common types:
2-Axis CNC Machine
2-axis CNC machines are the most fundamental CNC systems available. They have two movement axes: the X-axis (vertical axis) and the Y-axis (horizontal axis).
These machines often make basic straight-line cuts or drill holes in boards or process only one workpiece surface without relocating it. These machines operate on a fixed workpiece.
3-Axis CNC Machine
The most prevalent form of CNC machine is a 3-axis CNC machine. They can manufacture parts in 2.5 dimensions and have three axes of movement: the X, Y, and Z-axis (depth axis).
This machine may operate on all six surfaces of a conventional square or rectangular material block, but the block must be repositioned. These machines, too, operate on a fixed workpiece.
4-Axis CNC Machine
In addition to the X, Y, and Z axes, a 4-axis machine includes a rotational axis. This axis of rotation is called A-axis. A-axis permits the rotating cutting tool to move along the X-axis. This machine is perfect for creating cutouts and cutting in an arc.
5-Axis CNC Machine
The 5-axis machine has a pivoting motion of the cutting tool (or the work table) along the Y-axis. The axis of pivoting is known as C-axis. Because of its capacity to operate on five surfaces of a workpiece concurrently without relocating the work surface, these machines can produce complex and accurate parts.
6-axis CNC Machine
The B-axis of a 6-axis CNC machine adds a third rotating direction to the cutting tool (or workpiece). These machines can manufacture forms with every imaginable surface finish by involving all conceivable movement directions of the cutting tool and workpiece.
7-Axis CNC Machine
7-axis CNC machines feature three typical axes for moving the cutting tool, three axes for revolving the workpiece, and a seventh axis for rotating the arm that holds the cutting tool. The E-axis is the name given to this seventh axis. A 7-axis CNC machine can make complex parts.
9-Axis CNC Machine
A 9-axis CNC machine combines a 5-axis milling machine with a 4-axis lathe machine. The milling machine works on the surface to achieve the desired surface finish, while the lathe does the workpiece’s interior features. Therefore, a 9-axis machine may produce the part’s internal and external features.
12-Axis CNC Machine
The most complex device in the manufacturing industry is a 12-axis CNC machine. It has two cutting heads that can move along all six axes (X, Y, Z, A, B, C). 12-axis CNC machine improves precision and production rates.
Types of CNC Machines Based on the Control System
The following are types of CNC machines based on the control system. Let’s take a closer look at them:
Point-to-Point Positioning Control
In a point-to-point (PTP) CNC controller, the cutting tool moves to a predetermined point, following which machining begins around the predetermined cutting point. PTP is frequently used for drilling, spot welding, tapping, and reverting where simultaneous positioning and machining are not demanded.
Straight Cut Positioning Control
A straight-cut positioning control system can relocate the cutting tool while processing the workpiece at the same time. Both relocation and machining occur at a regulated rate. In this control system, the machining is done in a straight line; curved cuts are impossible.
Contouring Path CNC System
The continuous path CNC system is another contouring path CNC system name. It is capable of producing the most sophisticated pieces. These systems can do both PTP and straight-cut positioning. They can also regulate the cutting tool location on several axes simultaneously. This flexibility allows for making curved surfaces (contours) on the workpiece. CNC machines, such as milling and turning, use the continuous path CNC system.
Types of CNC Machines by Servo Control Mode
Servo control mode can classify CNC machine tools. Here are some typical types:
Open Loop Control CNC Machine
An open-loop control machine lacks a detecting and feedback device. The driving circuit boosts the power before the CNC device’s single-direction instruction signal drives the stepping motor that moves the machine table.
One advantage of the open-loop control machine is its low cost, which makes it accessible. On the negative side, it has poor precision and stability, lowering job quality.
Closed-Loop Control CNC Machine
A closed-loop control machine employs a linear displacement-detecting device. This device is installed on the moving parts or tabletop of the machine tool. Often, the comparator on the CNC device would receive the actual displacement. And then, the actual displacement discovered is compared to the value of the program instruction.
It isn’t easy to regulate the stability of a closed-loop control CNC machine. This equipment, on the other hand, ensures excellent accuracy.
Semi-Closed Loop Control CNC Machine
The actual displacement of the worktable is calculated by an angular displacement detecting device of a semi-closed loop control machine. This angular displacement detection device is often mounted immediately at the end of the servo motor shaft or ball screw.
This device compares the estimated value to the original instruction displacement value from the worktable and then regulates based on the difference. The cost of this CNC machine is reasonable, but its accuracy and stability are exceptional.
The Advantages and Disadvantages of Using a CNC Machine
Advantages of Using a CNC Machine:
- Can work without constant operator interaction.
- They have high production rates.
- CNC machines have a repeatable and high level of accuracy.
- Can produce parts with minimal dimensional deviation.
- Can produce parts with complex features that would not be possible with manual machines.
- CNC programs can be modified easily to accommodate design changes.
- Reduces the risk of human error and increases safety.
Disadvantages of Using a CNC Machine:
- CNC machines cost significantly more than manual machines.
- Operating CNC machines needs expensive skilled labor.
- CNC machines require regular maintenance to ensure their optimal performance.
- Downtime for repairs or maintenance can disrupt production schedules and incur additional costs.
Tips for Selecting the Best CNC Machine Type
Here are some tips for selecting the best CNC machine type:
- Clearly define the intended application and required manufacturing processes. Determine if you need milling, turning, grinding, or other capabilities. This will guide the basic machine type selection.
- Carefully consider the size of the parts that will need to be machined. Measure maximum dimensions and weight to ensure the machine’s work envelope, and travels can accommodate them.
- Determine the level of accuracy and precision required for the parts. Tighter tolerances demand machines with high rigidity, precision components, and vibration dampening.
- Ensure the machine can cut, drill, or grind the materials you plan to use. Harder materials like steel require more rigid, powerful machine tools.
- Evaluate your production volume needs. Higher volume may necessitate faster rapid traverses, automatic tool changers, larger tool magazines, and pallet changers.
- Assess whether 4 or 5-axis machining is needed for complex 3D shaping. The 5-axis offers maximum positioning flexibility.
- Carefully select a brand known for proven reliability and mechanical precision.
- Prioritize an easy-to-use machine control interface and software compatible with your CAM system.
- Look for suppliers that provide comprehensive operator training and responsive ongoing technical support.
- Ensure that your technicians can easily repair the brand that you purchase and that the spare parts are available.
- Check the power requirements of your machine and make the necessary adjustments at the workplace.
A CNC machine is a computer-controlled machining system. They allow manufacturers to automate many manufacturing operations that would be done manually. As a result, CNC machines boost production, reduce waste, and even remove the possibility of human error.
If you feel it is challenging to choose the right type of CNC machines for your needs and don’t want to afford their high initial investments, in this case, outsourcing your CNC services to an industry-leading expert like LEADRP is a good alternative. LEADRP has 3-axis machines to multi-axis machines to meet your project needs. Do not hesitate and contact us today!
Steel, aluminum, titanium, brass, copper, stainless steel, and plastic are common metals for CNC machining. Softer materials perform well with CNC routing or CNC carving operations. Brass, aluminum, acrylic, plexiglass, and wood are among the CNC routable materials.
CNC lathes, usually referred to as turning machines, are the most popular form of CNC machine. They make cylindrical products on a rotating lathe by cutting and shaping materials such as metals, plastics, and composites.
A computer numerical control (CNC) system has three fundamental components: CNC software which is a program of instruction; a machine control unit; and processing equipment, often known as a machine tool.