尺寸公差和表面光洁度：终极指南
了解精度如何影响密封环、喷嘴、模具等的性能。
精度基础知识：公差、表面光洁度及其重要性
了解影响零件配合和功能的关键概念：尺寸公差、表面光洁度以及精度在实际应用中的作用。
什么是尺寸公差？
尺寸公差告诉我们尺寸与图纸可以有多少偏差。这就好比说：“这个零件应该是10毫米，但稍微多一点或少一点都没问题——可能是±0.01毫米。”
什么是表面光洁度？
表面光洁度告诉我们表面的光滑程度。它以 Ra（平均粗糙度）来衡量。Ra 值越低，表面越光滑。Ra 值越高，表面越粗糙。
为什么精度在实际使用中很重要
精度不仅仅关乎数字——它决定了密封件是否泄漏，喷嘴喷射是否笔直，或者模具能否生产出完美的零件。公差或表面光洁度不佳会导致早期故障或性能下降。
如何在图纸上指定公差和表面光洁度
清晰标注尺寸公差，例如“Ø10.00 ±0.01mm”。并添加表面光洁度符号，例如 Ra 0.4µm。如不确定，请咨询供应商。
明确标记公差
务必清晰地写出允许的尺寸范围。例如：Ø10.00 ±0.01mm。这能告诉工厂零件的精度要求。
添加表面粗糙度符号
不知道该写什么？问问你的供应商。好的供应商会帮你选择合适的公差和表面光洁度。
有疑问时，请询问
精度不仅仅关乎数字——它决定了密封件是否泄漏，喷嘴喷射是否笔直，或者模具能否生产出完美的零件。公差或表面光洁度不佳会导致早期故障或性能下降。
Surface Finish Levels and Common Applications
Different Ra values define how smooth a surface is. This chart shows typical finishes and where they are used.
| Ra (µm) | 描述 | Common Use |
|---|---|---|
| 3.2 | Rough | Castings, rough milling |
| 1.6 | Normal machined finish | General turning/milling |
| 0.8 | Fine machined | Precision shafts |
| 0.4 | Very smooth | Molds, sealing faces |
| 0.2 | Mirror-like | Sealing rings, optics |
Frequently Asked Questions About Tolerance & Surface Finish
These are the most common questions customers ask when preparing drawings or placing precision part orders. Clear answers help you avoid costly mistakes.
Q1: What if I don’t specify the tolerance?
Standard machining tolerances will be used, which may not meet your exact needs.
Q2: How do I know what Ra I need?
It depends on the part’s function. Contact us if unsure—we’ll recommend the best level.
Q3: Can Retop achieve Ra 0.2µm?
Yes, we offer precision polishing for ultra-smooth finishes.
Q4: Can I request different tolerances for different parts of the same drawing?
Yes, you can specify different tolerances for different features. Just make sure they are clearly labeled on the drawing.
Q5: What happens if my drawing only shows dimensions but no Ra or tolerance?
We will follow standard machining and finishing practices, but results may not match your performance expectations. Always specify if it’s critical.
Q6: How does surface finish affect tool performance or lifespan?
Smoother surfaces reduce friction and wear, which improves sealing, flow, and overall lifespan—especially for high-precision components.
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