Design for Assembly – looking downstream before pulling the trigger

As engineers are tasked with more responsibility and fewer resources, they are finding themselves challenged to not only meet the performance criterion of the product in application, but also the efficiency of the part as it relates to production assembly. Introducing a new design or material for a component without a plan for assembly is like buying the latest high tech running shoes in the wrong size – one does not work without the other.Design for assembly must include several basic considerations, along with ancillary tenets related to the goals of the finished product.

The first consideration for assembly is whether the unit will be mechanically assembled or hand assembled.Mechanical assembly offers economy and precision, but is expensive to set up… normally there must be volume (000,000’s or more) to offset the set up costs. Depending on the number of components that must be assembled together, this could entail a simple process, or an extended assembly line with both mechanized and manual aspects to assembly. The design of the component must allow for any condition related to the way assembly is set up – for example, does the component need to be symmetrical so it can be assembled in either direction, or must it follow a specific line/pattern to fit into the assembly? The geometry and surface of the component must cater to these realities, and provide as much room for dimensional and assembly variance as possible.

The next consideration is how the component will be located and ultimately affixed in the assembly. Ideally, all components should complement each other so that location can be lead, aligned, and affixed with as little variance as possible. Ancillary consideration must be given to operations such as sonic welding of plastics, fasteners, or adhesives. Does the geometry promote location and alignment with mating parts? Can any fastening mechanism necessary to complete assembly be used without being impeded, and is the fastening material compatible with the component? Does the geometry allow for a repeatable process to be employed when affixing the assembly together? These kinds of “downstream” questions should be asked and validated with process engineers responsible for putting the unit together before finalizing a design. A minor investment in this kind of planning can pay substantial dividends in the long run.

Other ancillary considerations should include surface texture, color identification, part number stamping, and aesthetics. The surface texture must not create undue friction which might impede the flow of the assembly. It should, however, have a texture that will allow for optimum gripping or interface. Component coloration is used in many applications in order to enforce warranty claims or to identify lots or batches of product for traceability. A plan should be coordinated with process engineering to detail the coloration plan, and ensure that production can easily synchronize with assembly to meet plan objectives. Many times specific product identification is necessary with a serial number and/or barcode, so the component must offer a surface area to accommodate this requirement. Throughout this process, aesthetics will have to be considered at every step – virtual 3D CAD models work nicely to get the approval of marketing/sales.

There is an extensive array of material choices to meet engineering objectives, Real Seal has the experience to assist in choosing or developing a material that will meet not only the engineering specifications, but also to meet process and marketing management objectives. The Real Seal Design Support Team has highly qualified and experienced engineering and chemical based personnel who can assist in bringing plastic and rubber products full circle from design to full production and create satisfied end customers.