Product development processes and methodologies

Concurrent engineering workflow

This is a workflow that instead of working sequentially through the stages a number of tasks is carried out in parallel. For example starting tool design before the detailed design of the product is finished; or the engineer started on detail design solid models before the concept design surfaces models are complete. Although this does not necessarily reduce the amount of manpower required for a project it does drastically reduce lead times and thus time to market. Feature based CAD systems have for many years allowed the simultaneous work on 3D solid model and the 2D drawing by means of 2 separate files with the drawing looking at the data in the model, when the model changes the drawing will associatively update. Some CAD packages also allow associative copying of geometry between files. This allows, for example, the copying of a part design into the files used by the tooling designer. The manufacturing engineer can then start work on tools before the final design freeze, when a design changes size or shape the tool geometry will then update. Concurrent engineering also has the added benefit of providing better and more immediate communication between departments, reducing the chance of costly, late design changes. It adopts a problem prevention method as compared to the problem solving and re-designing method of traditional sequential engineering.

Bottom-up design

Bottom-up design is where the definition of 3D models of a product starts with the construction of individual components. These are then virtually brought together in sub-assemblies of more than one level until the full product is digitally defined. This is sometime known as the review structure showing how the product will look like. The BOM contains all of the physical (solid) components; it may (but not also) contain other items required for the final product BOM such as paint, glue, oil and other materials.

Top-down design

Top-down design follows closer the true design process This starts with a layout model, often a simple 2D sketch define basic size and some major defining parameters. Geometry from this is associatively copied down to the next level which represents different sub-systems of the product. The geometry in the sub-systems is then used to define more detail in levels below. Depending on the complexity of the product a number of levels of this assembly are created until the basic definition of components can be identified, such as position and principle dimensions. This information is then associatively copied to component files. In these files the components are detailed; this is where the classic bottom-up assembly starts. The top down assembly is sometime known as a control structure. If a single file is used to define the layout and parameters for the review structure it is often known as a skeleton file.

Front loading design and workflow

Front loading is taking Top down design to the next stage. The complete control structure and review structure as well as downstream data such as drawings, tooling development and CAM models is constructed before the product has been defined or a project kick-off has been authorised. These assemblies of files are a template from which a family of products can be constructed. When the decision has been made to go with a new product the parameters of the product are input into the template model and all the associated data is updated. Obviously predefined associative models will not be able to predict all possibilities and will require additional work. The main principle is that a lot of the experimental/investigative work has already been completed. A lot of knowledge is built into these templates to be reused on new products. This does require additional resources “upfront� but can drastically reduce the time between project kick-off and launch. Such methods do however require organisational changes as a large amount engineering skills are moved into “offline� development departments. It can be seen as an analogy to creating concept car to test out new technology for future products, but in this case the work is directly used for the next product generation.

Design in context

Individual components cannot be constructed in isolation. CAD models of components are designed within the context of part or all of the product being developed. This is achieved using assembly modelling techniques. Other components’ geometry can be seen and referenced within the CAD tool being used. The other components within the sub-assembly, may or may not have been constructed in the same system, their geometry being translated from other CPD formats. Some assembly checking such as DMU is also carried out using Product visualization software.

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