Turning and milling belongs to multifunctional machine tools, which can complete rotary and milling operations at the same time. Turning and milling machine tools usually have two main components: spindle and turret. The spindle provides rotary power, which clamps the workpiece and enables turning operations. The turret holds tools, including milling cutters, drills, and others, for milling, boring, and drilling operations. This ensures machining efficiency and flexibility in tooling adjustments, making it primarily used in the modern manufacturing industry.
CNC milling technology, a key automation technology in manufacturing, improves product quality and ensures effective production. However, it is susceptible to external factors, requiring continuous improvement and better site management in the future.
CNC turning and milling classification
Different processing methods divide CNC milling machines into a variety of types, including common axial milling and orthogonal milling. Different milling types have unique characteristics and applications. Choosing the right method improves efficiency and quality.
1. Axial milling
Axial turning and milling can process both external and internal surfaces, offering a broader range of applications. The tool is parallel to the axis of rotation of the workpiece, which can efficiently carry out turning operations. The diameter of the milling cutter and the radial size of the spindle box limit the axial milling tool’s stroke. When the tool is too large or the spindle box too small, it reduces machining quality and may damage equipment. In such cases, adjusting process parameters is necessary to ensure part quality and meet production requirements.
2 . Orthogonal milling
Orthogonal milling characterizes the tool axis of rotation as being perpendicular to the axis of rotation of the workpiece. The cutting trajectory is a spatial curve with a more complex shape. In orthogonal turning and milling, the depth of cut and cutting thickness change with the tool axis and rotation direction. For some parts with complex machining processes, orthogonal turning and milling can provide higher machining accuracy and surface quality. In production, combining process parameters and optimizing their relationships is key to ensuring machining quality. By fully utilizing the advantages of orthogonal turning and milling, we can significantly improve the surface machining quality.
The difference between axial milling and orthogonal milling
Application analysis of CNC turning and milling center milling machining process
1. Analysis of the elements of CNC milling center milling processing
Before CNC turning and milling, it’s essential to analyze various factors due to the complexity and technical flexibility of CNC programming. Key considerations include machine tool, workpiece, tool, and fixture factors.
Machine factor analysis
The power of the machine tool, coolant selection, and maintenance conditions are key factors affecting the machining quality. The hardness and power of the milling machine must reach the standard to ensure the machining accuracy. Select coolant based on demand and ensure good fluidity to prevent overheating and tool jamming. If you don’t use coolant, you need to strengthen the daily maintenance of the milling cutter.
Workpiece factor analysis
In CNC programming, the assembly condition, positioning accuracy, and dimensional control of the workpiece are critical. The workpiece must ensure accurate positioning, otherwise, the machining process is prone to errors, affecting product quality. Proper allocation of tools and materials is essential to meet the workpiece’s size and surface quality requirements for successful machining.
Tool and fixture factor analysis
The selection of cutting tools directly affects the machining effect. Select the appropriate tool shape, material, and size according to the machining requirements. Front angle inserts help to reduce power consumption and improve the smoothness of the machining surface. Choosing the right fixture and maintaining its stability is crucial to prevent accuracy issues from debris or iron chips.
2. Preparation for CNC Milling Machining
In China’s machine tool industry, CNC milling standards are strict, focusing on both part quality and machine operation. To ensure smooth processing and minimize human intervention, operators must prepare thoroughly in advance.
Cleaning the table and fixtures
Although CNC milling relies heavily on the operation of mechanical equipment, on-site operators are still responsible for aiding production. To ensure operator safety and minimize equipment failure, it’s crucial to keep the machining site clean. Sharp metal fragments from milling can injure operators and affect machining accuracy. The longer they stay on the table, the greater the impact, so regular cleaning is essential.
Especially the fixture parts such as jaws, base clamp, etc., are easy to adhere to the fine iron chips. If not cleaned in time, the fixture will lose its precision and may even bulge, further affecting the machining precision. Unstable fixture conditions can cause product scrap, rework, economic losses, and delays in the production schedule. Therefore, before each machining, we must carefully check and clean the fixture.
Check the rough parts.
The quality of rough parts directly affects the machining accuracy of the machine tool. When inspecting rough parts, the main job is to check for any damage or defects. Replace broken or defective parts immediately to prevent affecting the machining process and causing substandard products or machine damage.
3. CNC Milling Process Analysis
CNC milling uses computer programming for automation, while manual milling relies on manual operation. Proper process programming is critical to the success of CNC milling technology. During CNC milling process analysis, keep the following key aspects in mind:
Labeling Dimensions
In CNC programming, accurately labeling dimensions, points, lines, and surfaces is crucial for machining precision and product quality. Ensure that all design data is clear, precise, and in line with machining requirements.
Analyze the influencing factors.
Programmers must understand the factors affecting CNC milling, such as cutting speeds, feeds, and tool types, and their interrelationships. Designers should review drawings carefully to identify issues and provide timely feedback to ensure process feasibility. Any problems should be addressed quickly to maintain programming accuracy and avoid production errors.
Precise positioning
In CNC milling, accurate positioning is especially important because the machining process is more concentrated. The positioning of all workpieces should use a uniform datum and ensure the accuracy of positioning. Inaccurate positioning can lead to error accumulation, affecting processing quality and product accuracy. Therefore, positioning accuracy is critical to ensure product quality.
Uniform type and size
To maximize productivity, keep CNC milling machine operations as continuous as possible and avoid frequent interruptions. Ensure the quality and suitability of the tool during selection. After installing the tool, perform routine maintenance to reduce the number of tool changes. Standardizing workpiece form and size boosts mass production, and productivity, and reduces machining errors. For geometrically symmetrical parts, the CNC mirror function can simplify programming.
4 .CNC milling machining parts clamping and positioning analysis
Proper clamping and positioning of the workpiece on the CNC milling machine are essential for accuracy, preventing displacement, and ensuring quality. The following are a few key points to focus on during the clamping and positioning process:
Accuracy of clamping and positioning
CNC milling machine should fix the workpiece on the corresponding fixture or machine tool before machining. During the clamping process, you must ensure that the workpiece does not shift due to vibration during machining. Accurately position the workpiece and ensure a proper fit between the fixture and the machine tool. By applying reasonable clamping, you can effectively prevent the workpiece from displacement or deformation during machining, thereby ensuring machining accuracy.
Requirements for one-time clamping
The operator should have the ability to operate the equipment flexibly and try to realize a successful clamping. If the clamping fails, the operator needs to make manual adjustments. Manual adjustments can affect machining efficiency and accuracy, so repeated adjustments should be avoided to minimize uncertainty from human error.
The need to reduce manual adjustment
Manual operation is time-consuming and risky, especially in high-precision processing where achieving desired accuracy is difficult. Therefore, in actual production, try to reduce manual intervention by optimizing fixture design and enhancing positioning accuracy. Increasing automation speeds up clamping improves accuracy, and reduces operator risk.
5. Determine the CNC milling machine tool selection and cutting volume
In CNC milling, the reasonable determination of tool selection and cutting volume is crucial to the machining effect. The following is a brief analysis of tool selection and cutting volume:
Tool selection
When selecting a tool, consider its impact on machining accuracy and efficiency.
Tool material and performance: Choose precise, strong, rigid, and durable tools for stable machining and longer service life.
Installation and adjustment: The tool should be easy to install and adjust, reducing the time needed for replacement and adjustment.
Workpiece Geometry: You should select tools that match the geometry of the workpiece. For example, use a specialized keyway milling cutter for a closed keyway, and choose a four-sided insert for fine machining.
Determination of cutting volume
Cutting volume is a key factor affecting machining efficiency and tool life. When determining the cutting volume, you should consider the following factors:
Depth of cut, cutting width, feed rate, and cutting speed: These parameters affect material removal and machining precision.
Spindle speed: Both excessively high and low speeds can impact machining quality and efficiency, as well as tool life.
Machine performance: The machine’s rigidity and power should match the cutting volume; excessive cutting can cause vibration or reduce accuracy.
Service life considerations
There are two ways to consider tool and machine life:
Minimum economic life: Economic efficiency is the main concern, tool life is short but replacement is frequent.
Maximum working life: The tool lasts longer and suits urgent or precision-demanding tasks.
The tool’s economic and working life should be balanced based on production needs and task urgency to ensure efficient and accurate machining.
6. Selection of CNC milling tool and feed mode
In CNC milling, tool trajectory, and feed mode have an important impact on the machining quality. A reasonable selection of tools and feed methods can effectively improve machining accuracy, extend tool life, and reduce production costs. The following are some key analyses and recommendations:
Tool path selection
The tool path is a key factor in CNC milling, which directly affects the machining effect. Reasonable tool path design can ensure machining quality and reduce unnecessary machining time. The following points need to be noted:
Optimize the tool path: Shorten the tool path to avoid long uncut paths, improving efficiency and reducing tool wear.
Adjacent toolpaths connected to ramps: Increase the arc radius to prevent direct intersection of adjacent toolpaths connected to a ramp. This ensures that the tool automatically follows the next machining path and reduces tool vibration and wear.
Arc Transitions: Arc transitions in toolpaths smooth tool movement and reduce drag, especially for tangential work, improving CNC milling quality and efficiency.
Tool feed method selection
The feed method affects cutting force and tool wear, so it must be chosen based on machining requirements. Common feed methods include longitudinal feed and spiral feed:
Longitudinal feed: The longitudinal feed method is simple, but its damage to the tool is greater. Because the tool and mold cutting force is larger, easy to cause tool wear. Therefore, the longitudinal feed is usually used for less demanding machining tasks.
Spiral feed: Compared with the longitudinal feed, the cutting force is more evenly distributed and less damaging to the tool. In practice, spiral feed is widely used. Spiral feed can reduce cutting force fluctuations, improve machining stability, and reduce tool wear.
In the use of spiral feed, the following points need to be noted:
Scientific setting of cutting amount: When using a spiral feed tool, the cutting amount should be set properly to avoid affecting machining and tool life.
Reasonable selection of screw diameter: The screw diameter must be selected to withstand the cutting load without affecting machining accuracy.
Standardize the operation process: Follow procedures to prevent tool damage from improper operation.
7. Optimize the programming process of CNC milling
Optimizing CNC milling programming is key to improving productivity, machining accuracy, and tool life. The goal of optimizing the programming process is to simplify operations, reduce human error, and maximize machine performance. Here are a few key steps to optimizing the CNC milling programming process:
Adopt standardized programming methods and specifications.s
To ensure consistent and efficient CNC milling programming, you first need to use standardized programming methods. These specifications can help programmers increase efficiency, reduce error, rs, and maintain maintainability. Standardized programming includes:
Uniform Naming Rules: Set consistent naming rules for all program parts (e.g., tools, paths, variables) to avoid confusion.
Commenting and Documentation Requirements: Include adequate comments in the code to ensure the readability and maintainability of the program. Documented programming specifications, including code structure, logic, and explanation of key parameters, to facilitate subsequent modification and optimization.
Follow programming styles: Improve programming quality and reduce errors by following certain programming styles and processes based on industry best practices.
Utilize computer-aided manufacturing (CAM) software
Utilizing advanced CAM software or other programming tools can dramatically improve the speed and accuracy of programming. CAM software automatically generates machining code and plans toolpaths based on the geometry of the part and machining requirements. Benefits of CAM software include:
Automated Programming: Using the software to automatically generate tool paths reduces manual intervention and saves programming time.
Accurate path planning: CAM software can calculate tool path, depth of cut, and feed rate for machining accuracy.
Reduced Human Error: Automated program generation reduces the risk of human programming error and improves the stability of the machining process.
Adjusts tool path and trajectory planning
Tool path and trajectory planning is an important part of CNC milling programming, and reasonable path planning can improve machining efficiency and reduce tool wear. Optimizing the tool path includes:
Optimize the cutting path: The cutting path should try to avoid empty edges and unnecessary stops to reduce cutting time and improve efficiency.
Increase feed rate: Adjust feed rate according to material properties, tool performance,ce, and machining requirements. Too slow a feed rate may lead to low productivity, and too fast may cause tool wear or workpiece deformation.
Avoid collision: In the process of programming, the relative positions of tools, fixtures, and workpieces should be taken into account to avoid collision and interference to ensure safe machining.
Use path optimization algorithms: Advanced path optimization algorithms and simulation tools can predict and avoid machining problems, ensuring a reasonable path and optimized machining sequence.
Optimize cutting parameters
Cutting parameters (such as cutting speed, feed rate, depth of cut, etc.) directly affect machining efficiency and workpiece quality. In CNC milling, optimizing cutting parameters is a key step in achieving the best machining results. The optimization process includes:
Experimental verification: According to the workpiece material, tool material,l, and machining requirements, experiments and tests are conducted to verify the effects of different cutting parameters. Adjust the cutting parameters through the test data to ensure the best machining results.
Dynamic adjustment: In the actual machining process, with the tool wear or material changes, cutting parameters may need to be adjusted dynamically. Programming should take this into account to ensure the flexibility and stability of the machining process.
Comprehensive consideration: the selection of cutting parameters needs to consider cutting force, tool life, machining accuracy productivity, and other factors, to avoid over-optimization of a single factor.
Checking the rough parts can ensure that the starting point of machining is correct, further guaranteeing the machining accuracy and the quality of the final product.
Measures to improve the quality of CNC milling processing
1. Standardize CNC milling processing and operation process
To improve the quality and efficiency of CNC milling processing, it is necessary to standardize the processing and operation process and optimize the operation process by combining advanced process technology. The following are specific optimization measures:
Operator training and process optimization
Training of operators: Improving the technical level of operators is the key to improving machining quality. We regularly conduct training not only to improve operating skills but also to strengthen the training of operating procedures, ensuring that employees operate in strict accordance with the standards.
Process sorting and standardization: Operators did not follow the procedures, so we should address this per the management system to ensure compliance with operating standards.
Formulate the use of CNC milling machine specifications
Formulate the CNC milling machine operation specification, focusing on processing precautions, and issue it to all departments.
On-site management system: according to the operation specification, formulate a detailed on-site management system. Each department head or team leader should regularly supervise the implementation to ensure strict adherence to the operation specifications and prevent any deviation.
Upgrading programming program rationalization
Rational allocation of resources: In the actual application of the CNC milling process, machine performance, programming, and machining requirements will vary. To minimize the negative impact of these differences, enterprises should rationally allocate resources to avoid waste of resources.
Regularly check equipment for quantity, purchase year, performance, and any failures. Eliminate outdated equipment based on its condition and layout needs to avoid cluttering storage or infrastructure.
Improve the machine software and hardware system
In CNC milling, both software and hardware systems define the machine’s function and reflect the digital management level of the manufacturing enterprise. To improve efficiency, companies must enhance these systems and optimize programming for stable, efficient machine operation. Specifically, this can be improved from the following aspects:
Optimize control system
The control system is the core of a CNC milling machine, and its performance directly impacts machining accuracy and stability. Regularly updating its firmware and software is essential to support complex operations. Optimizing the system improves functionality, stability, and overall performance, ensuring high precision under various conditions.
Strengthen cutting parameter management.t
The optimized management of cutting parameters has a direct impact on processing efficiency and accuracy. Optimizing cutting speed, feed rate, depth of cut, and other parameters ensures alignment with material properties and workpiece requirements. Companies should manage and regularly adjust these parameters for more efficient and accurate machining. Optimization of cutting parameters not only improves machining efficiency but also extends tool life and reduces energy consumption during machining.
Enhanced Simulation and Emulation Functions
The simulation and emulation function of the machine tool software is the key tensuringre smooth machining process. By enhancing software simulation and emulation, operators can virtually test machining paths, identify errors early, and prevent machine stoppages. This simulation helps companies reduce human error and machine downtime, resulting in increased productivity and product quality.
Improves machine tool software user interface
The ease of use of the operator interface is an important factor in improving the efficiency of a machine tool. Improving machine tool software with an intuitive graphical interface simplifies operations, making functions easier to use and boosting efficiency.
Equips itself with high-precision sensors
High-precision sensors enable real-time monitoring of the machine’s status, workpiece position, and cutting process, helping operators quickly detect abnormalities and adjust for accuracy and stability. Through real-time monitoring, it can not only improve machining accuracy but also effectively prevent equipment failure or production accidents.
3. An application of a three-dimensional surface machining process
Stereo surface machining uses 3D cutting to process curved surfaces, commonly for parts with complex shapes. The process involves several key steps to ensure efficiency and accuracy, producing complex surface parts that meet the requirements. The specific steps of the process are as follows:
3D cutting process
Designs the surface model
Engineers create or import surface models using CAD software, derived from point cloud data or designed with curve and surface tools. Accurate design is crucial for effective machining and guiding tool movements.
Planning machining paths
After designing the surface model, use CAM software to generate machining paths for 3D surface machining. This process automatically generates appropriate cutting paths based on the geometry of the design model and the machining requirements. Machining path planning involves selecting the right tools, and process parameters, and cutting paths based on the part’s characteristics and complexity to ensure efficiency and accuracy.
Tool selection
Tool selection is a key factor in three-dimensional surface machining. According to the machining path and the shape characteristics of the surface, select the appropriate tool for milling. Commonly used tools include ball-end tools, helical tools, and specialized shaped tools. We commonly use ball-ended tools for milling complex surfaces, ensuring precise contact with the surface and maintaining a stable cutting force. For specially shaped surfaces, we may need to customize tools to meet specific machining needs.
Setting Cutting Parameters
Setting cutting parameters is critical to ensuring quality and efficiency in machining. The main cutting parameters include cutting speed, feed rate, depth of cut, and direction of cut. The selection of parameters should consider the workpiece material hardness, tool performance, surface shape, and machining requirements. Proper cutting parameters improve efficiency, extend tool life, reduce vibration and heat, and enhance surface quality.
Surface Treatment and Inspection
After completing three-dimensional surface machining, the surface of the part may require further treatment to meet cosmetic and functional requirements. Common surface treatments include polishing, painting, and plating to enhance the part’s appearance, wear resistance, and corrosion protection. After the surface treatment, the parts need to undergo precision inspection to ensure that the surface shape, dimensional accuracy, and surface finish meet the design requirements. Commonly used inspection methods include three-coordinate measurement and visual inspection.
Conclusion
Since the advent of CNC milling and turning technology, China’s machinery manufacturing industry has developed rapidly, especially in recent years. Advanced processing technologies and equipment have been continuously introduced, improving the speed and quality of parts production. China has increasingly focused on the industry, investing heavily in innovation. However, there is still a gap between China’s development and that of developed countries. In the future, China should not only focus on technical research but also introduce advanced technology and equipment to address its manufacturing shortcomings.
