Piezas mecanizadas de CNC

  Tipo de material Los fabricantes e ingenieros deben considerar cuidadosamente varios factores al seleccionar los métodos de procesamiento de superficie más adecuados para Piezas mecanizadas de CNC. En este artículo, profundizaremos en los factores clave que deben tenerse en cuenta para garantizar resultados óptimos en el procesamiento de la superficie. La elección del material es un factor fundamental en las decisiones de procesamiento de superficie. El mecanizado CNC se puede aplicar a una amplia gama de materiales, incluidos metales (como aluminio, acero y titanio), plásticos, compuestos, y más. Cada material tiene propiedades únicas que influyen en la selección de técnicas de procesamiento de superficie. Por ejemplo, los metales pueden requerir diferentes procesos en comparación con los plásticos o compuestos debido a las diferencias en la dureza, la conductividad y la reactividad química. Ciertos materiales, como acero inoxidable o herramienta de acero endurecido, puede ser más difícil de procesar debido a su dureza. En tales casos, métodos abrasivos como molienda o perfeccionar puede ser necesario para lograr el acabado superficial deseado. Por otro lado, los materiales más suaves pueden ser más adecuados para tratamientos químicos o electroplacas. Diseño de piezas y geometría La geometría y el diseño de la parte mecanizada son consideraciones cruciales al elegir métodos de procesamiento de superficie. Las piezas con formas complejas, tolerancias estrechas o características intrincadas pueden requerir enfoques especializados. Por ejemplo, las piezas con canales internos profundos o patrones intrincados pueden ser difíciles de acceder con ciertas herramientas de procesamiento. Además, el tamaño y la forma de la pieza pueden influir en la viabilidad de las diferentes técnicas de procesamiento. Las superficies grandes y planas pueden beneficiarse de procesos abrasivos como lijado o fresado, mientras que las características pequeñas y detalladas podrían requerir métodos más precisos como Grabado químico o grabado láser. Requisitos de acabado superficial El acabado superficial es un factor crítico que afecta directamente la apariencia, el rendimiento y la funcionalidad de las piezas mecanizadas CNC. El acabado superficial requerido puede variar significativamente según la aplicación prevista. Los parámetros comunes de acabado superficial incluyen rugosidad (AR), textura de la superficie y brillo. Para las piezas que requieren un acabado liso y de espejo, pueden ser necesarios procesos de pulido o pulido de pulido. Alternativamente, si se desea una textura o patrón específico, se pueden emplear técnicas como grabado, explosión de cuentas o caída de medios abrasivos. La elección del acabado superficial debe alinearse con el propósito previsto de la pieza, ya sea para atractivo estético o requisitos funcionales como fricción reducida o adhesión mejorada.                    

  Surface quality is a key indicator for measuring the precision of CNC machined parts. It involves three aspects: roughness (microscopic unevenness), waviness (macroscopic periodic unevenness), and texture (machining tool path direction).   I. Surface Processing Types (How to Achieve)   Different processing operations and strategies can achieve different surface finishes. The following is arranged in order from coarse to fine. Typical achievable roughness (Ra) description of processing types and applicable scenarios Rough machining of 12.5 μm - 3.2 μm uses a large cutting depth and high feed rate to quickly remove the material, leaving obvious tool marks and a poor surface. When the parts are initially formed, machining allowances are reserved for non-critical surfaces. Semi-finishing is 3.2 μm - 1.6 μm to prepare for finishing, remove the marks of rough machining, and ensure an appropriate allowance for finishing. The final processing of most non-mating surfaces, installation surfaces, etc. Conventional finishing of 1.6 μm - 0.8 μm adopts small cutting depth, small feed rate and high rotational speed. The knife marks are visible to the naked eye but smooth to the touch. The most common precision requirements are used for static mating surfaces, sealing surfaces, bearing housings, etc. High-precision finishing of 0.8 μm - 0.4 μm requires optimized parameters, sharp cutting tools, high-rigidity machine tools and effective cooling. The surface is extremely smooth. Dynamic mating surfaces, hydraulic cylinder walls, and high-load bearing surfaces. Superfinishing of 0.4 μm - 0.1 μm requires the use of single crystal diamond tools, extremely high machine tool accuracy and a stable environment (constant temperature). Optical components, precision instrument surfaces, silicon wafer processing. Manual polishing/grinding < 0.1 μm: Remove the knife marks by hand or mechanical means such as sandpaper or oilstone to achieve a mirror-like effect. Appearance parts, mold cavities, surfaces of food and medical equipment. Ii. Symbols, Charts and Annotations (How to Specify)   Engineers clearly specify the requirements on the drawing through surface roughness symbols.   1. Basic symbols   Explanation of symbol meanings √ Basic symbols indicate that the surface can be obtained through any process and are meaningless to use alone. Youdaoplaceholder0 is the most commonly used to remove materials. It indicates that the surface is obtained by removing the material through processing methods such as milling, turning and drilling. "Non-removal of material refers to surfaces formed through casting, forging, rolling, etc., which do not require processing."   2. Complete annotation (taking the removal of material symbols as an example) :   ` ` ` [a] - Roughness parameters and values (such as Ra 0.8) [b] - Processing methods (such as "milling ") [c] - Texture direction symbols (such as "=") [d] - Machining allowance (e.g. 0.3mm) [e] - Sampling length (e.g. 0.8mm)     3. Common Annotation examples:   · ⌝ Ra 1.6: the most common form. It indicates that the maximum surface roughness Ra value is 1.6 μm by the method of removing the material. · ⌝ Ra max 3.2: the Ra value shall not exceed 3.2 μm. · ⌝ Ra 0.8 / Rz 3.2: both Ra and Rz values are specified. · ⌝ Rz 10 N8: marked with "N grade", N8 corresponds to Rz 10μm.   4. Surface texture direction symbol: The texture direction is crucial for sealing and motion coordination. The symbol is marked on the extension line.   Schematic diagram of symbol meaning The tool path direction of the projection plane parallel to the view is parallel to the boundary of the plane it is on Perpendicular to the projection plane of the view, the direction of the tool path is perpendicular to the boundary of the plane where it is located The X-cross texture tool path is in a cross shape (such as milling back and forth) M multi-directional without a dominant direction (such as point milling) The C approximate concentric circles are produced by turning R-approximate radiation is produced by end face turning or end face milling. Iii. Surface Roughness Testing (How to Verify)   After processing is completed, professional instruments should be used for objective measurement to verify whether it meets the requirements of the drawings.   1. Contact profilometer (needle tracing method)   · Principle: This is the most classic and authoritative method. An extremely sharp diamond probe (with a tip radius of approximately 2μm) gently slides across the surface of the workpiece. The vertical displacement is converted into an electrical signal, which is then amplified and calculated to obtain parameters such as Ra and Rz. · Equipment: Surface roughness measuring instrument. · Advantages: Precise measurement, compliance with national standards, and capable of measuring various complex shapes. · Disadvantages: It is a contact measurement, which may scratch extremely soft materials and has a relatively slow measurement speed.   2. Non-contact optical profiler   · Principle: By using techniques such as light interference, confocal microscopy or white light scattering, a 3D surface topography is constructed by analyzing the reflection of light on the surface, thereby calculating the roughness. · Advantages: Fast speed, no scratching of workpieces, and capable of measuring extremely soft materials. · Disadvantages: Sensitive to surface reflective characteristics (difficult to measure transparent and highly reflective materials), and the equipment is usually more expensive.   3. Compare Sample Blocks (Quick and Practical Method)   · Principle: A set of standard sample blocks with known Ra values are used. Through fingernail touch perception and visual comparison, the surface to be measured is compared with the sample blocks to estimate the approximate roughness range. · Advantages: Extremely low cost, fast and convenient, suitable for workshop sites. · Disadvantages: It is highly subjective and has poor accuracy. It can only be used for rough estimation and preliminary judgment and cannot be used as the basis for final acceptance.   Suggested measurement process   1. Drawing analysis: Clearly identify the parameters to be measured (such as Ra) and their theoretical values. 2. Clean the surface: Ensure that the tested area is free of oil stains, dust and burrs. 3. Selection method: · Quick online check → Use comparison blocks. · Final quality inspection → Use a contact profilometer. For soft or mirror-finished workpieces, consider non-contact optical measurement. 4. Conduct measurements: Take the average of multiple measurements at different positions on the surface to ensure the representativeness of the results. 5. Recording and Judgment: Record the measured values and compare them with the requirements of the drawings to make a judgment of qualified or unqualified.   Only by combining the correct processing technology, clear drawing marking and scientific measurement verification can the surface quality of CNC parts be fully controlled.