ME 321 Kinematics and Dynamics of Machines Design

ME 321 – Kinematics and Dynamics of Machines Design Process Notes (Continued) Steve Lambert Mechanical Engineering, U of Waterloo 3/4/2021

Design Process · Preliminary Design – Product planning and clarifying the task (needs analysis), · Conceptual design, · Embodiment (layout) design, and · Detail (systems) design. 3/4/2021

Conceptual Design l l Identify a number, usually 3, of conceptually different, viable solutions to satisfy the need In order to be conceptually different, proposed solutions should be based on different physical principles Each concept is refined to a sufficient level of detail to allow a fair evaluation of each concept so that the best one may be chosen This is often difficult 3/4/2021

Creating Alternative Solutions l l 3/4/2021 Copy other products – this is also useful to establish a baseline Refine existing products – change scale, place in parallel or serial, etc. Combine various existing elements Inversion – ex. , piezoelectric crystal

Stimulating Creativity l l l 3/4/2021 Trial and error Brainstorming Analogy Empathy Morphological approach (parallel) – consider many solutions simultaneously Systematic approach (serial) – subdivide the problem and solve separately

Morphological Box 3/4/2021

Design Selection l l 3/4/2021 Designs are selected based on their fit with design criteria Selection process can be either quantitative or qualitative The advantage of a quantitative scheme is that it can accommodate different priorities in your criteria through different weighting factors The advantage of a qualitative scheme (+, -, or same as a reference solution) is that it does not accommodate different priorities numerically so that the designer is forced to argue each case as a whole

Quantitative Design Selection 3/4/2021

Qualitative Design Selection 3/4/2021

Embodiment (Layout) Design l l l 3/4/2021 Takes design from the concept stage (sketch) to a layout drawing, which includes material specifications and geometry Physical sizing and selection of specific components is done at this stage This stage involves more detailed design calculations, required to select materials and geometry

Embodiment Design Principles l l l l 3/4/2021 Separate functions Provide a direct and short transmission path Do not over-constrain a component, but provide sufficient constraint Match impedance or eliminate gradients Provide functional symmetry Design for self-help Design for fail-safe

Detail Design l l l 3/4/2021 Involves the individual design or specification of components such as beams, trusses, connections, shafts, bearings, etc Often requires detailed analysis of your component and/or assembly using FEM or CFD, for example Often involves the production and testing of physical or software (solid model) prototypes Testing is intended to identify possible problems before production Changes to the basic configuration should not occur at this stage, only a refinement