Introduction
In modern machinery manufacturing, controlling part machining accuracy is a key factor in maintaining product quality and improving production efficiency. Machining accuracy not only directly determines the functionality and lifespan of a product, but also profoundly impacts production cost calculations and cycle planning.
To achieve high-precision machining goals, it is necessary to systematically coordinate multiple factors such as equipment configuration, process design, tool selection, parameter adjustment and personnel skills.
This article will analyze the effective control path of part accuracy during machining from seven key dimensions.
1, Accurate selection of processing equipment
The precision performance of machining equipment is the cornerstone of ensuring part accuracy. When selecting equipment, the primary consideration is whether its accuracy level matches the part processing requirements. For example, high-precision CNC machine tools , with their automated control systems, precisely control position and motion during machining, eliminating human error at the source. Furthermore, long-term equipment stability is essential—only a machine tool operating in a stable state can consistently produce consistent machining results.
Furthermore, the rigidity, thermal stability, and motion accuracy of the machine tool are also key factors: vibration, thermal deformation, or motion trajectory deviation during machining can easily lead to machining errors. Therefore, establishing a regular maintenance and calibration mechanism (such as regularly testing spindle accuracy, adjusting guideway clearances, and calibrating feed systems) is essential for maintaining equipment accuracy.
2, Scientifically optimize the processing technology plan
The rationality of the machining process directly impacts the potential for precision improvement. Different machining methods (turning, milling, grinding, etc.) have significantly different error characteristics and applicable scenarios, requiring targeted selection based on the part’s shape, structure, dimensional tolerances, and material properties. For example, grinding is preferred for flat precision parts, while five-axis milling is more suitable for parts with complex curved surfaces.
There are three key aspects to focus on in process design:
Processing sequence planning:
Follow the principle of “roughing first, finishing later, primary work first, secondary work later” to remove most of the allowance through roughing to avoid the stress deformation caused by roughing affecting the finishing accuracy;
Processing method selection:
For thin-walled and easily deformed parts, use micro-feeding and low-temperature cutting to reduce cutting force and thermal deformation;
Fixture adaptability
Ensure that the process plan and the fixture positioning method are coordinated to avoid accuracy deviation due to clamping interference.
3, Reasonable selection of cutting tools
The quality and adaptability of cutting tools are the “key variables” in precision control. Tool wear and deformation will directly translate into part processing errors, so tool management must be done from three aspects:
Material matching:
Select tools based on the characteristics of the workpiece material. For example, CBN (cubic boron nitride) tools are used for processing high-hardness alloys, and carbide-coated tools are used for processing aluminum alloys.
Parameter design:
Optimize tool geometry (cutting edge rake angle, clearance angle, cutting edge radius) and cutting parameters (cutting speed, feed rate). For example, use a small rake angle and small feed rate during finishing to improve surface accuracy.
Dynamic maintenance:
Establish a tool wear monitoring mechanism (such as judging the degree of wear by changes in machine tool load), and regularly replace excessively worn tools to avoid dimensional deviations due to edge blunting.
4, Fine-tune process parameters
Accurately setting cutting parameters is the key to balancing precision and efficiency. Key parameters need to be dynamically optimized based on the matching relationship between machine tools, cutting tools, and workpieces:
Cutting speed:
Too high will easily lead to overheating and wear of the tool, while too low will lead to low efficiency. It needs to be adjusted in combination with the thermal conductivity of the material (for example, low-speed cutting is used to reduce heat accumulation when processing titanium alloy);
Feed rate
Too much feed can easily cause tool vibration and rough workpiece surface, while too little feed will increase processing time. Usually the finishing feed is controlled at 0.05-0.2mm/r;
Cutting depth
Rough machining can use large depth to quickly remove the allowance, and fine machining requires strict control of the depth (generally ≤0.5mm) to avoid deformation of the machine tool and workpiece due to excessive cutting force.
Some high-precision processing scenarios (such as mold mirror processing) can use an adaptive parameter adjustment system to dynamically correct parameters by real-time monitoring of cutting force, vibration and other data.
5, Optimize fixture positioning and structural design
As the “fixed reference” of the workpiece, the rationality of the fixture design directly affects the positioning accuracy and clamping stability. Optimization directions include:
Positioning method：
Use classic positioning structures such as “one side, two pins” to ensure precise alignment of the workpiece reference and the machine tool coordinate system; for complex and special-shaped parts, design special combination fixtures or modular fixtures to improve positioning consistency;
Rigidity and stability.
Use high-strength alloy materials to make fixtures to reduce fixture deformation caused by processing vibration; by increasing support points and optimizing clamping force distribution, avoid plastic deformation of the workpiece due to excessive clamping force;
Quick change adaptation.
For mass production scenarios, a quick-change fixture system is designed to shorten the changeover time while ensuring repeat positioning accuracy (usually required to be ≤0.005mm).
6, Strictly control the processing environment
The impact of environmental factors on precision machining is often overlooked, and two key variables need to be controlled:
Temperature stability:
Temperature fluctuations can cause thermal expansion and contraction of machine tool guide rails, spindles, and workpieces. For example, for every 1°C increase in steel temperature, steel will expand by 0.011mm per meter. Precision machining workshops must be equipped with a constant temperature system to maintain a temperature of 20±0.5°C and a humidity of 40%-60%.
Environmental cleanliness.
Airborne dust and oil mist can adhere to tool edges and workpiece surfaces, affecting cutting accuracy and surface quality. Negative pressure dust removal and oil mist separators are required to ensure a cleanroom environment that meets ISO Class 8 or higher.
7, Improve the professional quality of operators
Although automated machine tools have become popular, the skill level of operators is still the “last line of defense” for precision control. The ability of operators needs to be strengthened in three aspects:
Skills training: Systematic training on machine tool operation specifications, parameter debugging methods and precision testing techniques (such as the use of micrometers and three-coordinate measuring machines);
Problem prediction and handling:
Cultivate operators’ sensitivity to abnormal working conditions, such as judging tool wear or loose fixtures through cutting sound and vibration feedback, and stop the machine in time for adjustment;
Daily inspection responsibilities:
Clarify the operator’s daily inspection responsibilities for machine tools, including lubricating oil level, guide rail cleanliness, tool clamping tightness, etc., to ensure that the equipment is in the best operating condition.
Conclusion
Precision control in modern machining is a systematic undertaking, requiring a coordinated effort across seven dimensions: equipment, processes, tools, parameters, fixtures, environment, and personnel. Only by establishing a comprehensive precision control system throughout the entire process can we achieve improved production efficiency and cost optimization while ensuring product quality. For manufacturing companies, continuously honing their precision control capabilities is both a necessary requirement for meeting high-end market demands and crucial for establishing a core advantage in industry competition.
