CNC machining has revolutionized the manufacturing industry by providing high precision, repeatability, and efficiency in the production of complex parts. This article explores the fundamentals of CNC machining, including the systems and machines that make it possible, as well as its applications and advantages.
What is CNC Machining?
CNC machining is a method of using computer numerical control (CNC) technology to control machine tools for precision machining. The cutting path and instructions are programmed into software and transmitted to tools and machinery, which complete machining tasks according to the instructions, just like robots.
In CNC programming, the code generator assumes that mechanical operations are flawless, although errors may occur during simultaneous multi-directional cutting. The position of the tool is determined by input data called the part program.
Early CNC machine tools used punch cards to input programs, while modern CNC machine tools input programs into computers through keyboards and store them in memory. Programmers can write and edit these codes, giving CNC systems stronger computing power and flexibility. New instructions can be added to existing programs by modifying the code to continuously optimize and update the CNC system.
History of Computer Numerical Control
The development of computer numerical control (CNC) technology can be traced back to the mid-20th century, when John Parsons invented the first CNC machine in 1949. The initial design used punched cards to guide the machine’s movement, marking the inception of CNC manufacturing technology.
With technological advancements, in 1952, a research team at MIT introduced the first commercially viable CNC machine. This marked the formal application of CNC technology in industrial manufacturing, evolving from simple punch tape control devices to modern equipment capable of accepting CNC programming inputs and producing highly precise 3D machine parts.
Today, CNC technology has become an indispensable part of the manufacturing industry, enhancing production efficiency and product quality through automation and precise control. From the early punched cards to modern CAD/CAM systems, the evolution of CNC has not only transformed the landscape of manufacturing but also propelled industrial technology forward.
Most Common Cutting Tools in CNC Machining
To create various geometric shapes, CNC machine tools employ a variety of cutting tools. Here are some of the most commonly used milling tools:
- Flat, bullnose, and ball nose cutters: Used for machining slots, recesses, cavities, and other vertical walls. Each has distinct geometric features suitable for machining a wide range of characteristics. Ball nose cutters are also common in 5-axis CNC machining to create surfaces with curvature and freeform geometries.
- Face mills: Used to remove material from large and flat surfaces. Their larger diameter reduces the number of passes needed when machining large areas, thereby reducing the total machining time for producing flat parts.
- Drill bits: The most commonly used tools for rapid and efficient drilling operations. Standard drill bit sizes are extensive, catering to various hole diameter requirements. For non-standard diameters, insert-type flat head tools can be used along a spiral path.
- Thread taps: Used for machining threaded holes, requiring precise control of rotation and linear speed. While mechanical workshops often still rely on manual tapping, thread taps play a vital role in CNC machining.
- Slot milling cutters: With a shaft diameter smaller than the cutting edge diameter, these cutters are capable of cutting T-slots and other bottom cuts by removing material from the side of vertical walls.
These cutting tools provide CNC machining with flexibility and versatility, suitable for manufacturing and machining a wide range of complex parts and meeting diverse production needs.
What is CNC Machine Programming?
Plastic or metal CNC machine tool programming is a process of controlling a machine through a specified software program. CNC programming uses a language called G code to manage machine behavior, such as speed, feed rate, and coordination.
The programming process includes the following steps:
- Design drawings: Create 2D or 3D CAD drawings.
- Conversion code: Convert CAD drawings into executable computer code for CNC systems.
- Trial run: The operator conducts a trial run to ensure that the coding is correct.
In CNC manufacturing, the motion of the machine is usually carried out along the X and Y axes, and the tool is positioned and guided by a stepper motor or servo motor. According to the different control systems, they can be divided into open-loop systems and closed-loop systems. The closed-loop system can receive feedback and perform error correction to ensure the accuracy of speed and position.
Modern CNC machining is mostly automated, transforming designs into finished products through computer-aided design (CAD) and computer-aided manufacturing (CAM) software. CNC machine tools can combine multiple functions and even use robotic arms to move parts between multiple applications, ensuring efficient and consistent part production.
Different Types of CNC Machines
CNC machine tools control the movement of tools through CNC operations, and common types include:
| Machine Type | Description |
|---|---|
| CNC Milling Machine | Operates on programs composed of numbers and letters. Basic mills have a three-axis system (X, Y, and Z), while newer models can accommodate three additional axes. |
| CNC Lathe Machine | Uses a rotating tool to cut the workpiece in a circular direction. High precision and speed<br>- Mainly operates on two axes – X and Z. |
| Plasma Cutter | Uses a plasma torch to cut materials, primarily metals. Plasma generated by a combination of compressed air and an electric arc. |
| Electrical Discharge Machine (EDM) | Uses electrical sparks to shape the workpiece. Includes wire EDM and sinker EDM. |
| Water Jet Cutter | Uses high-pressure water to cut hard materials like granite and metal. Suitable for materials that cannot withstand high heat. |
| Laser Cutter | Uses a high-power laser beam for cutting. Precisely cuts metal, plastic, and other materials. Efficient for complex shapes. |
| CNC Router | Similar to milling machines, used for cutting wood, composites, aluminum, plastics, etc. Ideal for producing signage, furniture, and molds. |
Common Materials for CNC Machining
The commonly used materials for CNC machining include various metals and plastics, as follows:
| Material | Properties and Applications |
|---|---|
| Aluminum Alloy | Lightweight, good machinability, used in aerospace, automotive, and mechanical engineering. |
| Stainless Steel | Corrosion resistance, high strength, used for parts requiring durability (e.g., 304 Stainless Steel). |
| Titanium Alloy | High strength-to-weight ratio, aerospace, medical devices, and high-performance applications. |
| Brass and Copper | Good conductivity, corrosion resistance, used in electronic components and decorative parts. |
| Magnesium Alloy | Lightweight, high strength, used in automotive components and lightweight structures. |
| ABS (Acrylonitrile Butadiene Styrene) | Impact resistance, toughness, widely used in prototyping and functional parts. |
| PVC (Polyvinyl Chloride) | Chemical resistance, used for cable insulation and building materials. |
| PP (Polypropylene) | Chemical resistance, thermal stability, used for containers and pipes. |
| PS (Polystyrene) | High transparency, used for optical parts and packaging. |
| PA (Nylon) | High strength, abrasion resistance, used for mechanical and engineering components. |
CNC Machining Material Cost
CNC machining involves multiple material choices, and the cost of each material varies significantly. The physical properties of different materials directly affect the overall processing cost. For example, the bulk cost of producing metal components with dimensions of 150 x 150 x 25 millimeters for 6061 aluminum is approximately $25, while ABS blanks of the same size only cost about $17.
The difficulty of material processing can also affect costs, such as stainless steel, which is difficult to process due to its high hardness, resulting in a higher total cost. For more guidelines on CNC machining costs, please read this article: CNC Machining Cost
Why is CNC System Important?
The CNC system (Computer Numerical Control) enables machines to quickly produce products with better surface finish without the need for manual processing or extensive human involvement. The importance of these systems is reflected in the following aspects:
- Cost reduction: CNC machine tools can reduce manufacturing costs due to their efficient production and precision machining capabilities. They improve production efficiency, reduce material waste and energy consumption, thereby lowering operating costs.
- Reduce waste: Through simulation and optimization, CNC systems generate almost no waste during the manufacturing process, improving resource utilization.
- Improving worker safety: CNC machine tools reduce human-machine interaction, reduce accident risks, and can be operated remotely for preventive maintenance and software upgrades, ensuring worker safety.
- Reducing human errors: Automated CNC systems eliminate human errors, provide higher machining accuracy, complexity, and repeatability, and reduce product defects.
- Improving accuracy and complexity: CNC machine tools can achieve high-precision machining tasks, including complex contours and 3D shapes, ensuring product quality and design accuracy requirements.
- Intelligence and Integration: Some CNC systems integrate CAD and CAM software, accelerating program design and production preparation processes, while also integrating with enterprise resource planning software and other applications, improving operational intelligence and efficiency.
Although CNC machine tools have many advantages and require higher initial investment and technical support, as well as the need for skilled CNC programmers, their high efficiency and accuracy make them indispensable in modern manufacturing.
The Widespread Application of CNC Machining
CNC technology plays an indispensable role in multiple key industries and fields, and its accuracy and reliability make it the preferred method for manufacturing high-precision parts.
| Industry | Applications | Typical Products |
|---|---|---|
| Medical Devices | The products produced by CNC machinery have professional, precise, and high-quality characteristics to meet the needs of patients. | MRI machines, implants, orthopedic devices. |
| Aerospace | Aviation parts usually have extremely high requirements for dimensional accuracy, flatness, and roundness, and CNC technology can complete machining with micrometer level accuracy | Landing gear components, titanium alloy casings, wings, stator components. |
| Electronics | CNC machining is widely used in the production of various electronic components, such as conductive and non-conductive metals, as well as various polymers, due to its high precision and production speed. | Printed circuit boards, heat sinks, electronic housings. |
| Marine Industry | CNC machining for manufacturing propellers, ship engine components, insulated casings, ensuring performance and durability of marine equipment. | Propellers, ship engine components, insulated casings. |
| Automotive | From prototype design to mass production, CNC machining is relied upon, and CNC machine tools are used to manufacture various components | Engine parts, transmissions, axles, valves. |
| Oil and Gas | CNC machining used for manufacturing precision parts such as drill bits, valves, hydraulic components, ensuring equipment reliability and safety. | Drill bits, valves, hydraulic components. |
Through CNC technology, these industries are able to achieve efficient, precise, and repeatable production, meeting their complex technical and safety requirements, and driving the development and innovation of modern manufacturing.
Roles and Responsibilities of a CNC Machinist
CNC machinists play a critical role across various industries, operating and managing computer numerical control (CNC) machines to manufacture high-precision parts and products. Their primary responsibilities include:
- Reading Blueprints and Programming: Able to read and understand engineering drawings and CAD files. They perform CAM programming as needed to convert designs into specific machining paths and operational instructions.
- Setting Up and Operating CNC Machines: Responsible for setting up CNC machines, including fixtures, tools, and workpieces, ensuring the machines are ready for production.
- Quality Control: Measuring and testing machined parts using precision instruments and tools to ensure products meet specifications and quality standards.
- Troubleshooting and Adjustments: Monitoring machine operations during production, identifying and resolving mechanical or programming issues, and adjusting machining processes to optimize production efficiency and product quality.
- Maintenance and Upkeep: Conducting daily maintenance of machines, ensuring equipment is in optimal working condition, and performing preventive maintenance to reduce downtime.
Salary and Career Outlook
According to the U.S. Bureau of Labor Statistics, the average annual salary for CNC machinists in 2023 was approximately $48,550. The wages for CNC machinists vary based on skill level, experience, and industry background. This career field is full of opportunities and is well-suited for individuals with a mechanical mindset, problem-solving skills, attention to detail, and a strong interest in technology.
Ideal Candidates for CNC Machining
Successful CNC machinists typically have an aptitude for mechanics and mathematics, can work independently, and possess strong computer skills. Good communication skills and critical thinking are essential to handle challenges and changes in the production process.
Career Development and Training
To become a proficient CNC machinist, one usually needs to acquire practical experience and skills training through vocational education (such as technical colleges or vocational training schools). Additionally, continuous learning and keeping up with technological advancements are key factors in enhancing career development.
Guidelines for CNC Machining Parameters of BOYI
Most machining parameters are determined by CNC machine operators when generating G codes. The following are the key construction dimensions and accuracy parameters of CNC machines:
- Construction dimensions: Our CNC milling can process parts with dimensions up to 4000 mm x 1500 mm x 600 mm (158 in. x 590 in. x 24 in.), while CNC turning can process parts with diameters up to 200 mm x 500 mm (8 in. x 20 in.).
- Machining accuracy: CNC machining can manufacture parts with high precision and small tolerances. Typically, it can achieve a tolerance of less than half the average diameter of human hair, approximately ± 0.01 millimeters or ± 0.0004 inches.
- Default tolerance: If the technical drawing does not specify a tolerance, the operator usually processes the part with an accuracy of 0.1mm. In this case, the operator follows the ISO2768 standard.
CNC machining provides an important solution for manufacturing complex parts and high demand applications through its large-scale machining capability and high-precision machining.
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FAQ
CNC milling is a precise material processing method performed using a computer numerical control (CNC) system, suitable for complex geometries and multi-axis machining.
1.CAD to G-code Conversion: Convert the designed CAD model into G-code that the CNC machine can interpret.
2.Workpiece Preparation: Cut the raw material (blank) to the appropriate size and mount it on the machine bed.
3.Alignment and Setup: Use special tools to precisely position and align the workpiece.
4.Material Removal: Rotating cutting tools rapidly remove material from the workpiece, including roughing and finishing stages.
5.Workpiece Flipping: If machining the other side or specific features requires it, flip the workpiece and repeat the process.
6.Deburring and Inspection: Remove sharp edges after machining and inspect dimensions to ensure they meet specifications.
CNC turning is a machining process where fixed cutting tools remove material from a rotating workpiece, ideal for producing symmetrical cylindrical parts.
1.Workpiece Preparation and G-code Generation: Generate G-code based on CAD models and mount cylindrical blanks on the lathe.
2.Material Removal: The workpiece rotates at high speed while fixed cutting tools follow preset contours to progressively remove material, shaping the desired geometry.
3.Internal Hole Cutting: Utilize specialized tools to cut internal holes along the workpiece’s central axis, ensuring precision and completeness.
4.Workpiece Flipping or Movement: Depending on the requirements, flipping or moving the workpiece may be necessary to complete machining on other parts.
CNC machining provides design freedom, but cannot manufacture all complex geometric shapes. The shape of cutting tools and the number of machine axes limit the complexity of part design. Thin walls and sharp internal corners are also challenges that require special attention to stability during design and processing.
The main advantage of CNC machining is its ability to continuously produce sturdy and durable parts, suitable for a variety of engineering materials. Compared with 3D printing, parts manufactured through CNC machining have completely isotropic physical properties, which are the same as the raw materials. Although plastic processing is more challenging, CNC machining of plastics has a wide range of applications in prototype design, and later typically involves large-scale production using injection molding.
CNC machining offers high precision, versatility across materials, and efficient production capabilities, making it ideal for complex and repetitive tasks. However, it requires significant upfront investment, skilled operators, and careful maintenance to maximize its benefits while managing potential limitations in material handling and programming complexity.
Catalog: CNC Machining Guide
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
