Implementation of Sacrificial Support Structures for Hybrid Manufacturing of Thin Walls

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Vaughan, Derek M.
Saldaña, Christopher J.
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Hybrid manufacturing enables a single machine to achieve the benefits of additive and subtractive manufacturing methods, allowing complex parts to be produced with less waste material and tight tolerances. One example of parts that have the potential to benefit from the use of hybrid manufacturing are those with thin walled features. Cutting forces can induce deflection in thin walls, which results in geometric error on the final part. Traditional thin wall machining uses the stiffer stock material to limit deflection by only machining at the current base of the wall. With hybrid manufacturing the feature is already near net shape prior to machining. This makes the production of thin walls more difficult as there is very little “stock” material to provide stiffness during machining. This work attempts to solve this problem by integrating sacrificial support structures to additively produced thin walls to increase their stiffness during machining. The supports are machined away while machining the thin wall itself. The angle, spacing, and height of these supports are varied in several experiments to observe the resulting geometric error and surface finish of these thin walls after machining. A comparison of time versus quality is then produced to determine the efficiency of changing the parameters of these support structures. The addition of these supports relative to the unsupported case provided a deflection reduction of around 0.2mm. Surface roughness is improved by approximately 1.5µm. Increasing values of support height correspond to reduced wall deflection. Similarly, decreasing values of support angle and support spacing improved geometric accuracy. Efficiency comparisons show that increases in print time correspond to rapidly diminishing gains in geometric accuracy but can continue to improve surface roughness.
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