不锈钢激光切割服务 | 生产原型

Stainless steel laser cutting represents a transformative advancement in modern fabrication, 将不锈钢的固有耐用性和耐腐蚀性统一使用高级激光技术的精确性和效率.

Since its industrial adoption in the 1970s, laser cutting has progressed from simple sheet processing to a highly refined method capable of producing intricate, high-tolerance components across a wide range of stainless steel grades and thicknesses.

Driven by demands for accuracy, 速度, 和最小的材料废物, this technique has become indispensable in industries such as aerospace, 汽车, 医疗器械, 食品加工, 和建筑设计.

Beyond its mechanical benefits, stainless steel laser cutting supports digital manufacturing trends, offering seamless integration with CAD/CAM systems, 自动生产线, and real-time quality control systems.

1. What Is Laser Cutting Technology？

激光切割 是一种非接触式, high-precision thermal cutting process that uses a focused, high-powered laser beam to melt, burn, or vaporize material along a defined path.

It is widely used in industries ranging from aerospace and automotive to electronics and medical devices due to its speed, 准确性, 和灵活性.

Principle of Operation

以其核心, laser cutting involves directing a coherent, high-intensity laser beam onto the surface of the workpiece.

The laser beam is generated within a laser resonator, where light amplification occurs through stimulated emission.

The beam is then guided through a series of mirrors or fiber optics to a cutting head, where it is focused into a tiny, high-energy spot, often less than 0.3 毫米直径.

When this focused beam contacts the material surface, it rapidly heats the targeted area to its melting or vaporization point.

The intense localized energy causes the material to melt, burn, or sublimate, allowing the laser to sever the workpiece with minimal thermal distortion.

关键组件

• 激光源: Common laser sources include fiber lasers, CO₂ lasers, and Nd:YAG lasers, each with different wavelengths and power outputs tailored for specific materials and thicknesses.
• Focusing Optics: Precision lenses or mirrors concentrate the laser beam to achieve extremely high power density (up to 10⁶ W/cm²), essential for efficient cutting.
• Assist Gas: A coaxial gas jet (such as oxygen, 氮, or compressed air) is directed alongside the laser beam to remove molten or vaporized material from the kerf, ensuring a clean cut.
  The type of assist gas also influences the cutting mechanism and edge quality.
• Motion Control System: CNC-controlled motors move the laser head or the workpiece along programmed paths, enabling complex shapes and intricate designs with repeatability and speed.

Laser Cutting Mechanisms

Laser cutting operates via three primary mechanisms, depending on the material and gas used:

1. 熔融切割 (Melt and Blow):
   The laser melts the material, and an inert assist gas (commonly nitrogen) blows the molten material away from the kerf.
   This method produces clean, oxide-free edges, ideal for stainless steel and aluminum.
2. Reactive Cutting (火焰切割):
   Using oxygen as the assist gas, the laser beam initiates an exothermic reaction with the material, adding energy to the cutting process and increasing cutting speed, especially in carbon steels.
   然而, it can result in oxidized edges.
3. 热升华切割:
   The material vaporizes directly from solid to gas without melting. This method is typical for non-metallic materials like plastics, 木头, 和复合材料, offering minimal heat affected zones.

2. Laser Sources Commonly Used

The choice of laser source is a critical factor in the efficiency, 质量, and cost-effectiveness of stainless steel laser cutting.

Different laser types vary in wavelength, power output, beam quality, and operational characteristics, making them suitable for specific applications and material thicknesses.

The three most common laser sources used in stainless steel cutting are CO₂ lasers, 光纤激光器, 和 钕: YAG lasers.

二氧化碳激光器

• Wavelength: 大约 10.6 微米 (μm)
• 操作原则: CO₂ lasers are gas lasers where a mixture of carbon dioxide, 氮, and helium gases is electrically excited to produce laser light.
• 优势:

• • Well-established technology with decades of industrial use.
  • High power outputs ranging from a few hundred watts to tens of kilowatts, suitable for thick stainless steel cutting.
  • Excellent beam quality enables precise cuts with good edge finish.

• 限制:

• • Relatively large and complex setups due to gas handling and laser cavity design.
  • Requires mirrors to guide the laser beam, resulting in maintenance needs and potential alignment issues.
  • Longer wavelength results in less absorption by metals, which can reduce cutting efficiency on reflective materials like stainless steel.

• 应用领域: Widely used for cutting medium to thick stainless steel sheets, especially where high power is required.

光纤激光器

• Wavelength: 大约 1.07 微米 (μm)
• 操作原则: Fiber lasers generate laser light via doped optical fibers pumped by diode lasers, producing a coherent beam transmitted through the fiber itself.
• 优势:

• • Higher absorption in metals due to shorter wavelength, making fiber lasers more efficient at cutting stainless steel.
  • 袖珍的, 强壮的, and low maintenance since there are no mirrors—beam delivery is via fiber optics.
  • Excellent beam quality with high focusability, enabling very fine cuts and higher speeds.
  • Typically more energy-efficient with lower operational costs.
  • Longer operational lifetimes with less downtime.

• 限制:

• • Power is generally limited to several kilowatts, though high-power fiber lasers are increasingly available.
  • May require different setups or assist gas configurations for very thick materials compared to CO₂ lasers.

• 应用领域: Ideal for thin to medium thickness stainless steel cutting, micro-machining, and applications requiring high precision.

钕: YAG (Neodymium-doped Yttrium Aluminum Garnet) Lasers

• Wavelength: 大约 1.06 微米 (μm)
• 操作原则: Solid-state lasers where a Nd:YAG crystal is optically pumped by flash lamps or diodes to emit pulsed or continuous laser beams.
• 优势:

• • Capable of very high peak powers in pulsed mode, suitable for precision cutting and micro-machining.
  • Good beam quality and ability to cut reflective materials like stainless steel.

• 限制:

• • Generally less efficient and higher maintenance compared to fiber lasers.
  • Smaller spot sizes and lower average power restrict their use in high-volume cutting.
  • More complex cooling and maintenance requirements.

• 应用领域: Often used in specialty applications, such as micro-cutting, 焊接, or marking stainless steel parts where precision is critical.

3. Why Stainless Steel Requires Specialized Cutting

不锈钢, known for its excellent corrosion resistance, 机械强度, 和审美吸引力, is widely used across industries such as aerospace, 医疗的, 汽车, 食品加工, 和建筑.

然而, these very properties that make stainless steel desirable also present unique challenges in machining and cutting.

Material Properties of Stainless Steel

Stainless steel is not a single alloy but a family of iron-based alloys with a minimum of 10.5% 铬含量. Its unique properties include:

• High Reflectivity: Especially at the infrared wavelengths used by many laser systems, stainless steel reflects a significant portion of laser energy,
  making initial beam coupling more difficult and requiring higher power or specialized lasers (例如。, fiber lasers with shorter wavelengths).
• 低导热率: Compared to carbon steel or aluminum, stainless steel does not dissipate heat as quickly.
  This can lead to localized overheating if the process is not optimized, increasing the risk of thermal distortion or poor edge quality.
• 高熔点: With a melting range of approximately 1,400–1,530°C, stainless steel demands higher energy density to initiate and sustain cutting.
• 氧化物形成: Stainless steels are prone to forming chromium-rich oxide layers at high temperatures.
  Without proper gas shielding, this can affect weldability and surface finish post-cutting.

Limitations of Traditional Cutting Methods

Conventional cutting techniques such as shearing, 锯, or mechanical punching face several limitations when applied to stainless steel:

• 工具穿: The hardness and toughness of stainless steel can cause rapid tool degradation.
• Burr Formation: Mechanical methods often leave burrs and rough edges, requiring additional deburring operations.
• 受热的区域 (热影响区): Techniques like plasma or oxy-fuel cutting generate wide HAZs, potentially altering the metallurgical properties near the cut edge.
• 有限的设计灵活性: Mechanical processes are less suitable for cutting complex geometries or tight radii without expensive tooling.

Precision and Cleanliness Requirements

Many industries that utilize stainless steel have stringent tolerances and aesthetic standards:

• 医疗设备: Require burr-free, contamination-free cuts with minimal thermal alteration to preserve biocompatibility.
• 食品加工设备: Demands hygienic, smooth surfaces that prevent bacterial buildup.
• 建筑面板: Often involve decorative finishes or mirror-polished surfaces that must not be damaged or oxidized during cutting.

激光切割, when properly configured, excels in meeting these requirements by providing:

• 高维精度
• Minimal mechanical deformation
• 干净的, oxide-free edges (especially when using nitrogen assist gas)

Surface Sensitivity and Finish Quality

Many stainless steel grades are used in polished, 刷, or patterned finishes that must be preserved during processing.

Mechanical methods risk scratching or distorting these surfaces. 激光切割, especially with fiber lasers and contactless cutting heads, avoids mechanical contact and preserves surface integrity.

4. Stainless Steel Grade-Specific Considerations

奥氏体等级 (304, 316)

• Cutting Challenges: High ductility leads to burr formation; optimized nitrogen pressure (2 MPA) 和 1.5 kW fiber laser power minimize burr height to <0.05毫米.
• Food Industry Applications: 316L cut with nitrogen meets FDA standards, with surface roughness Ra < 0.8μm for pharmaceutical equipment.

Martensitic Grades (410, 420)

• Hardness Impact: 420 不锈钢 (40 HRC) 需要 20% higher laser power than 304 due to increased thermal conductivity.
• Tooling Applications: 410 cut with oxygen at 1.2 m/min produces edges suitable for knife blades, with edge angles of 8-12° achievable.

Precipitation-Hardening Grades (17-4 ph)

• 热处理敏感性: Cutting in the solution-annealed state (条件) prevents hardening in the HAZ. Post-cut aging (H900) restores tensile strength to 1,310 MPA.
• Aerospace Use: 17-4 PH fuel tank components cut with 5kW fiber lasers show <0.1mm dimensional deviation, meeting AS9100D standards.

5. Key Process Parameters in Stainless Steel Laser Cutting

Achieving high-quality cuts in stainless steel using laser technology depends on carefully controlling several critical process parameters.

These parameters influence cut quality, 速度, edge finish, 热影响区 (热影响区), and overall efficiency.

激光功率

• 定义: The output power of the laser beam, typically measured in watts (w) or kilowatts (kW).
• 影响: Higher laser power enables cutting thicker materials and faster cutting speeds.
  然而, excessive power can cause excessive melting, 翘曲, or a wider heat-affected zone.
• 典型范围: For stainless steel, laser power ranges from a few hundred watts (for thin sheets) 到 10 kW or more (for thick plates).

切割速度

• 定义: The rate at which the laser head or workpiece moves relative to each other, usually in millimeters per second (mm/s) or meters per minute (M/我).
• 影响: Increasing speed improves productivity but can reduce cut quality if the laser energy is insufficient to fully penetrate the material.
  Too slow a speed leads to excessive heat input and poor edge quality.
• 优化: Must be balanced with laser power and material thickness for clean cuts without dross or slag.

Assist Gas Type and Pressure

• 类型:

• • 氧 (O₂): Commonly used for reactive cutting of stainless steel, promoting oxidation and enhancing cutting efficiency.
  • 氮 (n₂): Used for inert cutting to prevent oxidation, producing cleaner edges without discoloration.
  • Compressed Air: Sometimes used as a cost-effective alternative but may cause oxidation.

• 压力: Typically ranges from 0.5 到 20 bar depending on gas type and material thickness.
• 影响: Gas pressure helps blow molten metal out of the kerf, influencing cut quality, edge finish, and heat input.

Focus Position

• 定义: The relative position of the laser beam focus point concerning the material surface.
• 影响: Correct focus positioning is vital for optimal energy density at the cutting zone. Focus can be set:

• • At the material surface,
  • Slightly above (defocused),
  • Slightly below the surface.

• 影响: Improper focus causes poor penetration, wide kerf, or excessive melting.

Pulse Frequency and Duration (for Pulsed Lasers)

• Pulse Frequency: Number of laser pulses per second (赫兹).
• Pulse Duration: Length of each laser pulse (microseconds or nanoseconds).
• 影响: Controls the energy delivered per pulse. High frequency with short pulses can reduce heat input, beneficial for thin stainless steel or precision cuts.

Stand-Off Distance

• 定义: The distance between the laser cutting head nozzle and the material surface.
• 影响: Too close can damage the nozzle or cause spatter buildup; too far reduces gas jet effectiveness and cut quality.
• 典型范围: 0.5 到 2 mm for stainless steel cutting.

Kerf Width

• 定义: The width of the material removed by the laser beam.
• 影响: Affects dimensional accuracy and material utilization.
• Influencing Factors: Laser spot size, 力量, and cutting speed.

6. Advantages of Stainless Steel Laser Cutting

Laser cutting has become one of the preferred methods for processing stainless steel due to its numerous advantages over traditional cutting techniques.

Precision and High-Quality Cuts

• Minimal Kerf Width: Laser cutting produces an extremely narrow kerf (切割宽度), often less than 0.2 毫米, which results in minimal material waste and tighter tolerances.
• Clean Edges: The heat-affected zone (热影响区) is very small, reducing warping and distortion.
  Edges are typically smooth and free from burrs, often eliminating the need for secondary finishing.
• 复杂的几何形状: Laser beams can be precisely controlled with CNC systems, enabling the cutting of intricate shapes, 细节, and sharp corners that are difficult to achieve with mechanical methods.

速度和效率

• Fast Processing: Laser cutting can operate at high speeds, especially on thin to medium thickness stainless steel sheets (up to ~15 mm), significantly reducing production times.
• 自动化兼容性: Integration with CNC and robotic systems allows for continuous, unattended operation, improving throughput and reducing labor costs.
• 减少设置时间: The non-contact nature means there is no tool wear or mechanical setup changes, allowing rapid switching between different cutting jobs.

Versatility and Flexibility

• Wide Thickness Range: Laser cutting systems can handle stainless steel sheets ranging from very thin foils to several centimeters thick with appropriate power settings and assist gases.
• Multiple Gas Options: Use of different assist gases (氮, 氧, 空气) allows tailoring of cutting processes to optimize for speed, edge quality, and oxidation control.
• 物质兼容性: Apart from stainless steel, lasers can cut a variety of metals and non-metals with minor adjustments, providing versatility for mixed production lines.

成本效益

• 减少材料废物: Narrow kerf and high accuracy reduce scrap rates.
• Lower Labor Costs: Automation reduces the need for manual handling and intervention.
• 最小的工具磨损: Since cutting is done with a laser beam, there is no physical tool contact or wear, lowering maintenance expenses.
• 能源效率: Modern fiber lasers consume less power compared to traditional mechanical cutting, contributing to overall operational cost savings.

Environmental and Safety Benefits

• Non-Contact Process: Minimizes mechanical stresses on the material and reduces workplace hazards related to sharp tools or cutting debris.
• 清洁过程: Generates less dust and noise compared to plasma or mechanical cutting.
• Reduced Use of Consumables: Unlike abrasive cutting methods, laser cutting does not require consumable blades or discs, 减少浪费.

Enhanced Design and Innovation Opportunities

• 快速原型制作: The ability to quickly and accurately cut complex shapes accelerates design iterations and product development.
• 定制: Small batch or custom orders are feasible and cost-effective due to minimal tooling changes.
• Micro and Fine Feature Fabrication: Laser cutting can produce extremely fine cuts suitable for high-precision applications in electronics, 医疗器械, and decorative stainless steel parts.

7. Limitations and Challenges of Stainless Steel Laser Cutting

While laser cutting offers numerous benefits for processing stainless steel, it also presents certain limitations and challenges that must be carefully managed to ensure optimal results.

厚度限制

• Reduced Efficiency on Thick Materials: Laser cutting is most efficient for thin to medium thickness stainless steel sheets, typically up to 15–20 mm.
  Cutting thicker sections requires higher laser power and slower speeds, which can increase costs and processing times.
• 热影响区 (热影响区) Growth: As thickness increases, the heat input needed to melt through the material rises, causing a larger HAZ.
  This can lead to thermal distortion, metallurgical changes, and degraded edge quality.

Surface Reflectivity and Material Quality

• High Reflectivity: Stainless steel’s reflective surface can cause laser beam reflection, leading to inefficiencies, unstable cutting, or even damage to laser optics.
  Fiber lasers mitigate this more effectively than CO₂ lasers but still require careful parameter tuning.
• Material Variability: Variations in stainless steel composition, 表面饰面, or coatings can affect laser absorption and cutting quality, requiring process adjustments.

Edge Quality and Dross Formation

• Dross on Cut Edges: Improper gas selection or insufficient assist gas pressure can cause molten material to adhere to the cut edge (浮渣), necessitating secondary cleaning or grinding.
• Striations and Roughness: At higher cutting speeds or thicker materials, striations or rough edge textures may develop, impacting aesthetics or mechanical fit.

Assist Gas Selection and Costs

• Gas Dependency: The choice of assist gas (氮, 氧, 或空气) significantly influences cut quality, 速度, 和氧化:

• • 氧: Promotes faster cutting with oxidation but can cause rougher, 氧化边缘.
  • 氮: 生产清洁, oxide-free edges but is more expensive and may reduce cutting speed.
  • 空气: A cost-effective option but less consistent in quality.

• 运营成本: High-purity gases, especially nitrogen, contribute to increased operating expenses.

Equipment and Maintenance

• 高初始投资: Advanced laser cutting machines, especially high-power fiber lasers, require substantial capital investment.
• Optics Sensitivity: Laser optics are sensitive to contamination and damage from reflected beams or dust, necessitating regular maintenance and alignment.
• 熟练操作: Optimal laser cutting demands trained operators and engineers to manage parameters, troubleshoot issues, and perform preventive maintenance.

Thermal Effects and Distortion

• Thermal Stresses: Concentrated laser heat can induce thermal stresses causing warping, especially in thin or intricately cut stainless steel parts.
• Microstructural Changes: Prolonged exposure to heat may alter stainless steel’s microstructure near the cut edge, affecting corrosion resistance and mechanical properties.

Limitations in Cutting Complex 3D Shapes

• Primarily 2D Cutting: Most laser cutting systems are optimized for flat sheets or simple 3D contours.
  Complex 3D shapes or thick sections often require alternative methods such as laser welding or 5-axis laser machining.
• Limited Penetration Depth: The laser’s focal length and power constrain cutting depth and angle, limiting versatility for some applications.

8. Applications of Stainless Steel Laser Cutting

Laser cutting stainless steel has become an essential technology across diverse industries due to its precision, 速度, 和多功能性.

Its ability to produce intricate designs with high-quality edges makes it ideal for many manufacturing and fabrication applications.

汽车行业

• Component Manufacturing: Laser cutting is widely used to produce precise parts for automotive engines, 排气系统, and chassis components from stainless steel sheets and plates.
• Prototyping and Customization: The technology enables rapid prototyping and customized parts with complex geometries, helping automotive engineers test designs quickly and efficiently.
• 装饰元素: Laser cutting allows the creation of intricate trims, badges, and grills with clean edges and detailed patterns.

航空航天和航空

• 结构成分: Stainless steel parts for aircraft frames, 引擎, and landing gear often require high strength and corrosion resistance, achieved through precision laser cutting.
• 减轻体重: Laser cutting’s ability to produce lightweight, complex shapes helps aerospace manufacturers optimize structural integrity while minimizing weight.
• 紧张的公差: Aerospace components require stringent tolerances and smooth finishes, which laser cutting can consistently deliver.

Medical Device Manufacturing

• 手术器械: Stainless steel laser cutting is critical in fabricating sharp, sterile, and precise surgical tools such as scalpels, 钳子, and scissors.
• 植入物和假肢: 激光切割可以生产复杂的产品, biocompatible implants and prosthetic components with exacting specifications.
• 医疗设备: Laser cutting is used to manufacture housings and parts for diagnostic and treatment devices, where accuracy and cleanliness are paramount.

建筑和建筑

• Decorative Panels: Laser cutting allows architects to create complex, artistic stainless steel panels, screens, and facades that combine aesthetics with durability.
• Structural Elements: Precision cutting of stainless steel components for support structures, 括号, and fixtures improves build quality and safety.
• Custom Fixtures and Fittings: Tailor-made stainless steel elements like stair railings, 栏杆, and signage benefit from laser cutting’s flexibility.

食品和饮料行业

• Sanitary Equipment: Stainless steel’s corrosion resistance makes it ideal for hygienic environments. Laser cutting is used to manufacture tanks, 管道, and processing equipment that meet stringent cleanliness standards.
• Packaging Machinery: Precision-cut stainless steel parts improve the reliability and efficiency of food packaging and bottling machinery.
• Decorative and Functional Components: Custom laser-cut stainless steel elements are used in kitchen appliances and commercial food service equipment.

电子和电气行业

• Enclosures and Casings: Laser cutting produces precise stainless steel housings for electronic devices, offering protection and heat resistance.
• Microfabrication: 小的, detailed components such as connectors, 联系人, and shielding parts benefit from the accuracy and repeatability of laser cutting.
• Heat Sinks and Cooling Systems: Custom laser-cut stainless steel parts help manage heat dissipation in electronic assemblies.

Art and Custom Fabrication

• Sculpture and Art Installations: Artists leverage laser cutting for intricate stainless steel designs and patterns that would be difficult or impossible to achieve with traditional methods.
• Custom Jewelry and Accessories: Laser cutting enables detailed and delicate stainless steel pieces with smooth edges and complex shapes.
• Signage and Branding: Businesses utilize laser-cut stainless steel signs and logos for durability and a professional finish.

9. Quality Control and Standards

Ensuring the highest quality in stainless steel laser cutting involves rigorous control of dimensional accuracy, edge quality, 和物质完整性.

Adherence to international standards and the use of advanced testing methods are critical for reliable and consistent results.

维度的准确性

• Tolerance Ranges:
  Laser cutting stainless steel achieves tight tolerances depending on material thickness. For thin sheets (1–3毫米), typical dimensional tolerances are ±0.1 mm.
  For thicker plates ranging from 10 到 20 毫米, tolerances widen to ±0.3 mm, in accordance with ISO 2768-m (medium tolerance grade).
  These standards ensure parts meet design specifications for precise assembly and function.
• Edge Quality Classes:
  根据 在ISO中 9013, edge quality is classified by surface roughness (RA):

• • 班级 1: RA < 2.5 μm, suitable for high-precision applications such as medical devices and aerospace components.
  • 班级 2: RA < 5 μm, typically used in general industrial applications where moderate surface finish is acceptable.

非破坏性测试 (NDT)

• 视觉检查:
  Using magnification ranging from 10x to 50x, operators examine cut edges for burrs, dross deposits, 氧化, and other surface defects.
  This step ensures the surface integrity meets aesthetic and functional requirements before further processing or assembly.
• 超声测试:
  For thicker stainless steel grades such as 316L at 10 毫米厚度, ultrasonic inspection with 5 MHz probes is employed to detect subsurface defects within the Heat Affected Zone (热影响区).
  This method can identify flaws as small as 0.2 毫米, providing a critical quality assurance step in safety-critical applications.
• 腐蚀测试:
  Corrosion resistance is essential for stainless steel components, 特别是在恶劣的环境中.

• • ASTM B117 Salt Spray Tests show that parts laser cut with nitrogen assist gas exhibit superior corrosion resistance, withstanding over 500 hours without significant degradation in 304 不锈钢.
  • 相比之下, oxygen-assisted cuts typically endure around 300 hours before corrosion signs appear. This highlights the importance of cutting gas selection for durability and lifespan.

10. Comparison with Other Cutting Methods

When choosing a cutting technique for stainless steel, it’s crucial to evaluate various methods based on precision, 速度, 成本, 质量, and suitability for specific applications.

Below is a comprehensive comparison of laser cutting with other common cutting technologies: plasma cutting, waterjet cutting, and mechanical cutting.

11. 结论

Stainless steel laser cutting stands at the intersection of precision engineering and modern manufacturing innovation.

With the ability to deliver fast, 干净的, and highly accurate results, it has become indispensable across multiple industries.

As technology evolves, the adoption of smart laser systems and sustainable practices will continue to push the boundaries of what’s possible in metal fabrication.

常见问题解答

What thickness of stainless steel can be cut using a laser?

It depends on the laser power:

• 到 6 毫米: 1–2 kW fiber lasers handle thin sheets with high precision.
• 6–12毫米: 3–6 kW lasers are typically used.
• 12–25 mm: Requires 6–10 kW+ fiber lasers with proper assist gas and optics.
  笔记: Edge quality and speed may decline as thickness increases.

Does laser cutting cause edge oxidation on stainless steel?

Only if 氧 is used as an assist gas. To avoid oxidation and discoloration:

• 使用 氮 as an inert gas.
• This produces bright, 干净的边缘, ideal for aesthetic or corrosion-sensitive applications (例如。, 医疗的, 食品级设备).

What are typical tolerances for laser-cut stainless steel parts?

Tolerances vary by thickness:

• ±0.1 mm for 1–3 mm thick sheets.
• ±0.2–0.3 mm for 10–20 mm plates.
  标准如 ISO 2768-m 和 在ISO中 9013 define general and fine tolerance classes.