尽管增材制造（AM）为设计师提供了更大的设计几何复杂物体的自由，但仍存在一些局限性。其中之一是成本。虽然设计师可以从自己的想象中创建任何东西，但可能无法制造。或者，该零件可能需要其他处理步骤以确保特定的机械特征。
The laser powder-bed fusion additive process, for example, can bring residual stresses to parts made with this technology. Residual stress occurs because of the rapid heating and cooling of the laser as it sinters each layer in the build process. Remember, powder bed fusion is a layer-by-layer build process. Thus, as the laser moves over a fresh sweep of powder, it melts that layer fusing it to the layer it melted previously. The laser in effect creates weld pools which adhere the layers together. This process happens in microseconds. But, just as quickly as the laser heats up the top layer, the hot metal begins to cool and solidify. As that top layer cools, it contracts. Because this layer is constrained by the already built solid layers below it, the contraction sets up shear forces between the solidified layers, which introduces residual stresses.
Residual stress occurs because of the rapid heating and cooling of the laser as it sinters layers on top of one another in the build process. Just as quickly as the laser heats the top layer, the hot metal begins to cool and solidify. As that top layer cools, it contracts. Because this layer is constrained by the already built solid layers below it, the contraction sets up shear forces between the solidified layers, which introduces residual stresses.
每一层都有残留的应力，最终可以构建到扭曲零件的点。这种失真可以采取层的形式，在从支撑支架上拉开的边缘或层上卷曲。在极端情况下，压力可能会超过材料和零件设计的强度，导致破裂，或者零件可以脆弱，崩溃并容易折断。在其他情况下，残余应力可能会扭曲构建板。
Parts with large cross-sections tend to experience these effects the most because the long weld tracks give shear forces more distance to act.
Tips to reduce residual stress
One way to reduce residual stress is to include a hatching pattern within the part. In hatching, the laser is moved back and forth in a pattern that varies the length of the scan vectors. The following are hatch patterns recommended by Renishaw.
One way to reduce residual stress is to include a hatching pattern within the part.
蜿蜒的孵化彭定康creates a 67° rotation after each layer. It offers a high build rate and is suitable for small and thin features.
The Stripe Hatching Pattern creates a homogenous distribution of residual stresses. This pattern suits large parts.
棋盘孵化的棋盘将每一层划分为5 x 5 mm岛，并在每一层之后使用整个图案和每个岛的67°旋转。它也产生了残余应力的同质分布。它也适用于大零件。
The orientation of scan vectors can be rotated from one layer to the next so that stresses are not all aligned in the same plane. A rotation of 67 degrees is typically used between each layer to ensure that it is many layers before the scanning direction is exactly repeated.
另一种技术是加热构建板以减少残余应力。通常，供应商会建议将零件放置在炉子或热处理中，以减少残留应力的影响。这种治疗将倾向于缩小零件的最终维度，因此，如果公差很重要。
Thus, in summary:
–Design out residual stresses where possible
- 不间断熔体的大面积
- 谨慎横截面的变化
- 使用较厚的建筑板，在压力可能很高的情况下
- 选择适当的扫描策略
soutece：Renishaw,www.enishaw.com
Filed Under:3D打印•添加剂制造•立体光刻
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