Design of a Custom CNC Milling Machine
Objective: Complete conceptual design of a hobby-level CNC milling machine
The requirement of my second year design course (MIE243) term project was to conceptually design a simple CNC milling machine using part selection knowledge acquired from the course. As well as the lead designer, I worked as the project manager in my team of five, leading my team through the process of creating engineering specifications, generating candidate designs, and making justified design decisions. I was able to directly apply lessons learned from my Moonbuggy and Eta Speedbike experiences.
Engineering Specifications
I pressed my team to frame this open-ended project by applying the requirements of the Human Powered Vehicle Design Team (HPVDT) for a CNC mill as our own. Like Aerovelo, the team works heavily with carbon fibre and required a CNC mill to create precise moulds from soft epoxy based tooling boards like Renshape. The machine was specified to be under $2000 in parts, with a cutting area of up to 9" x 6" x 3", and a repeatability of 2-3 thou. This decision proved to be a good one because it gave us a very specific set of use cases and allowed easy quantification of capabilities.
Design
I completed the conceptual design of the selected configuration. It is a three-axis design with the stage translating along the Y direction and the spindle translating in the X and Z directions atop the gantry. I advocated for this configuration because it limits the number of axial dependencies; reducing inaccuracies due to amplification of imprecisions.
I also guided my teammates through component selection of rotational to linear motion conversion mechanisms, linear supports, spindle design, stage, workpiece clamping mechanisms, and structural elements. For every decision, various options that completed the component's function were considered, and were evaluated for optimized machining accuracy, cost, ease of maintenance, and complexity.
I completed the majority of CAD modelling in Solidworks, and also created professional engineering drawings, further demonstrating my competence as a mechanical engineering designer.