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The links, guide arm and carriage were additively manufactured (with Fused Deposition Modelling - FDM). This greatly simplified the task of fabricating the complex geometry of the guide arms in addition to reducing machining time required. PLA was the fabrication material of choice as it is less susceptible to warping compared to other materials available for fabricating with FDM (e.g. ABS - see failed build with ABS in Fig. 2). Also, it provided enough strength and smoothness for the sliding of the rollers on the guide arms. To ensure holes were dimensionally accurate and properly-aligned, they were undersized in the CAD models and then drilled to the right sizes on a milling machine after printing.
Fig. 2: Failed build of guide arm caused by excessive warping of ABS
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