{
    "slug": "surface-finish-ra",
    "title": "机加工零件表面粗糙度 (Ra) 快速参考",
    "description": "表面粗糙度 Ra 对照表（µm 与 µin 双单位）：每个数值的外观与手感、相对机加工状态的加工成本倍数、可达到该粗糙度的工艺，以及各表面处理去除的材料量，便于选工艺与估成本。",
    "lang": "zh",
    "tables": [
        {
            "caption": "表面粗糙度 (Ra) 数值、外观、成本及典型应用",
            "columns": [
                "Ra (µm)",
                "Ra (µin)",
                "视觉描述",
                "手感",
                "成本倍数（相对于机加工状态）",
                "典型应用",
                "可通过以下方式实现"
            ],
            "rows": [
                {
                    "Ra (µm)": "0.05",
                    "Ra (µin)": "2",
                    "视觉描述": "真正的镜面——清晰、无畸变的物体反射",
                    "手感": "完全光滑，玻璃般的手感",
                    "成本倍数（相对于机加工状态）": "4–6x",
                    "典型应用": "光学镜面、精密光学元件",
                    "可通过以下方式实现": "多级抛光和研磨"
                },
                {
                    "Ra (µm)": "0.1",
                    "Ra (µin)": "4",
                    "视觉描述": "非常光滑，反射呈雾状——物体可见但模糊",
                    "手感": "非常光滑，纹理几乎难以察觉",
                    "成本倍数（相对于机加工状态）": "3–4x",
                    "典型应用": "医疗器械、液压部件、模具型面",
                    "可通过以下方式实现": "精密抛光"
                },
                {
                    "Ra (µm)": "0.2",
                    "Ra (µin)": "8",
                    "视觉描述": "半反射，近距离检查时可见细微纹路",
                    "手感": "光滑，用指甲可察觉极轻微的纹理",
                    "成本倍数（相对于机加工状态）": "2–3x",
                    "典型应用": "轴承、密封面、精密配合面",
                    "可通过以下方式实现": "精抛、滚抛"
                },
                {
                    "Ra (µm)": "0.4",
                    "Ra (µin)": "16",
                    "视觉描述": "光滑，可见细密的定向纹路。反射率低。",
                    "手感": "光滑，指尖可感到轻微纹理",
                    "成本倍数（相对于机加工状态）": "1.5–2x",
                    "典型应用": "通用精密零件、装饰用不锈钢",
                    "可通过以下方式实现": "发纹处理、精抛"
                },
                {
                    "Ra (µm)": "0.8",
                    "Ra (µin)": "32",
                    "视觉描述": "光滑，但近距离检查时可见加工痕迹",
                    "手感": "纹理均匀，略微粗糙",
                    "成本倍数（相对于机加工状态）": "1.2–1.5x",
                    "典型应用": "CNC精加工道次、轻载密封面",
                    "可通过以下方式实现": "CNC精加工道次、轻度珠粒喷砂"
                },
                {
                    "Ra (µm)": "1.6",
                    "Ra (µin)": "63",
                    "视觉描述": "可见刀具痕迹。标准机加工外观。",
                    "手感": "明显粗糙，可感觉到加工痕迹",
                    "成本倍数（相对于机加工状态）": "1x",
                    "典型应用": "非关键加工面、标准表面处理",
                    "可通过以下方式实现": "机加工原态"
                },
                {
                    "Ra (µm)": "3.2",
                    "Ra (µin)": "125",
                    "视觉描述": "更粗糙，加工纹路明显。粗加工道次常见。",
                    "手感": "粗糙，触感明显",
                    "成本倍数（相对于机加工状态）": "Included",
                    "典型应用": "非关键表面、隐藏特征、涂装前",
                    "可通过以下方式实现": "机加工原态（粗加工）"
                },
                {
                    "Ra (µm)": "6.3",
                    "Ra (µin)": "250",
                    "视觉描述": "明显粗糙，加工痕迹深，呈锯切割外观",
                    "手感": "非常粗糙，指甲划过会卡住",
                    "成本倍数（相对于机加工状态）": "Included",
                    "典型应用": "隐蔽表面、涂装前准备、焊前准备",
                    "可通过以下方式实现": "锯切、粗铣"
                }
            ]
        },
        {
            "caption": "哪种表面处理能达到哪个 Ra",
            "columns": [
                "如果你的零件需要……",
                "表面处理",
                "典型 Ra 目标 (µm)",
                "成本系数"
            ],
            "rows": [
                {
                    "如果你的零件需要……": "无外观要求，隐蔽或内部表面",
                    "表面处理": "As-machined",
                    "典型 Ra 目标 (µm)": "0.8–3.2 µm",
                    "成本系数": "Included"
                },
                {
                    "如果你的零件需要……": "均匀的哑光外观，遮盖加工痕迹",
                    "表面处理": "Bead blast",
                    "典型 Ra 目标 (µm)": "1.6–6.3 µm",
                    "成本系数": "1x (baseline)"
                },
                {
                    "如果你的零件需要……": "均匀的哑光外观，且在阳极氧化或涂装前具有一致的色泽",
                    "表面处理": "Bead blast + anodize/coat",
                    "典型 Ra 目标 (µm)": "1.6–3.2 µm",
                    "成本系数": "1x + coating cost"
                },
                {
                    "如果你的零件需要……": "方向性纹理外观（不锈钢面板、装饰饰条）",
                    "表面处理": "Hairline / brush finish",
                    "典型 Ra 目标 (µm)": "0.4–1.6 µm",
                    "成本系数": "1.2–1.5x"
                },
                {
                    "如果你的零件需要……": "同时对许多小零件进行去毛刺和轻度平滑处理",
                    "表面处理": "Vibratory tumbling",
                    "典型 Ra 目标 (µm)": "0.8–3.2 µm",
                    "成本系数": "0.5–1x (batch)"
                }
            ]
        },
        {
            "caption": "各种表面处理会去除多少材料",
            "columns": [
                "工艺",
                "单面材料去除量",
                "直径方向去除量（两侧）",
                "能否控制？",
                "建议"
            ],
            "rows": [
                {
                    "工艺": "As-machined",
                    "单面材料去除量": "0 mm",
                    "直径方向去除量（两侧）": "0 mm",
                    "能否控制？": "N/A",
                    "建议": "无需预留加工余量。"
                },
                {
                    "工艺": "Bead blasting",
                    "单面材料去除量": "0.002–0.005 mm",
                    "直径方向去除量（两侧）": "0.004–0.01 mm",
                    "能否控制？": "有限——取决于介质、压力、时间",
                    "建议": "对大多数公差可忽略。遮蔽螺纹和孔。"
                },
                {
                    "工艺": "Hairline / brush",
                    "单面材料去除量": "0.005–0.02 mm",
                    "直径方向去除量（两侧）": "0.01–0.04 mm",
                    "能否控制？": "中等——由磨料粒度和道次控制",
                    "建议": "在拉丝表面上预留 0.02 mm。"
                },
                {
                    "工艺": "Vibratory tumbling",
                    "单面材料去除量": "0.01–0.05 mm",
                    "直径方向去除量（两侧）": "0.02–0.1 mm",
                    "能否控制？": "低——批次工艺，难以精确控制",
                    "建议": "在整个批次范围内预留 0.02–0.05 mm。"
                },
                {
                    "工艺": "Sanding / grinding",
                    "单面材料去除量": "0.01–0.1 mm",
                    "直径方向去除量（两侧）": "0.02–0.2 mm",
                    "能否控制？": "良好——由磨料粒度递进控制",
                    "建议": "精磨时预留 0.02–0.05 mm。"
                },
                {
                    "工艺": "Polishing",
                    "单面材料去除量": "0.01–0.1 mm",
                    "直径方向去除量（两侧）": "0.02–0.2 mm",
                    "能否控制？": "中等——取决于起始表面",
                    "建议": "从机加工状态抛光时，预留 0.02–0.05 mm。"
                },
                {
                    "工艺": "Mirror polishing",
                    "单面材料去除量": "0.02–0.1 mm",
                    "直径方向去除量（两侧）": "0.04–0.2 mm",
                    "能否控制？": "中等——多阶段，累计",
                    "建议": "镜面抛光表面上至少预留 0.05 mm。"
                },
                {
                    "工艺": "Lapping",
                    "单面材料去除量": "0.005–0.05 mm",
                    "直径方向去除量（两侧）": "0.01–0.1 mm",
                    "能否控制？": "很好——由时间和磨料控制",
                    "建议": "研磨常用于达到最终尺寸精度。"
                }
            ]
        },
        {
            "caption": "精加工前应遮蔽的特征",
            "columns": [
                "特征类型",
                "风险等级",
                "建议"
            ],
            "rows": [
                {
                    "特征类型": "Press-fit bores (H7/p6)",
                    "风险等级": "High",
                    "建议": "遮蔽这些表面或不对其进行精加工。即使去除 0.01 mm 也会改变过盈配合。"
                },
                {
                    "特征类型": "Threaded holes",
                    "风险等级": "Medium",
                    "建议": "喷珠通常可以接受（去除量极小）。抛光会去除螺纹牙顶，可能导致配合松动。遮蔽或避免。"
                },
                {
                    "特征类型": "Shaft diameters in bearings",
                    "风险等级": "High",
                    "建议": "除非在公差链中计入材料去除量，否则不要抛光或喷砂轴承轴颈。"
                },
                {
                    "特征类型": "Sealing surfaces (O-ring grooves)",
                    "风险等级": "Medium",
                    "建议": "如果过程受控，打磨或研磨密封面是可以接受的。应避免喷砂（介质嵌入）。"
                },
                {
                    "特征类型": "Flatness-critical faces",
                    "风险等级": "High",
                    "建议": "手工抛光会使大型平面产生波纹。有平面度要求时，应采用机械磨削或研磨。"
                },
                {
                    "特征类型": "External cosmetic surfaces",
                    "风险等级": "Low",
                    "建议": "只要尺寸去除量在轮廓度公差范围内，外观面的尺寸去除量是可以接受的。"
                }
            ]
        }
    ]
}