The previous part of our Introduction to Enclosure Design summarised the key design considerations relating to the detailed design. With the goal of producing a functional, marketable and manufacturable product, the Lead Engineer discusses Design for Manufacture and Design for Assembly
Manufacturing method and materials
While the initial aim for any product developer is realising a concept quickly to enable testing and demonstrations with project stakeholders, a compromise must be made for investing sufficient time to ensure that the proposed design solutions are easily manufacturable – something commonly referred to as Design for Manufacture (DFM). DFM has a heavy influence on the details in any design, however it can also impact external aesthetics, including: surface finish, whether it’s possible to manufacture the desired external forms and curves, or the number and location of visible “shut lines” on the exterior of a product. It’s interesting to think how these two phenomena in the evolution of product aesthetics, with modern manufacturing technologies and expertise enabling significant improvements in both
The major milestone in DFM is choosing which manufacturing methods to use. Considerations for enclosure component manufacturing methods (and also materials) will include:
- Size, loads and stresses
- Methods of internal component mounting (external panels and frame vs monocoque, for example)
- Adaptability or ease of modification (if a prototype)
- Speed of design or manufacture
- Material availability
- Dirt and dust traps – ease of cleaning
- Corrosive properties and fluid compatibility
- Available finishes (e.g., paint)
In cases where parts are highly stressed, it can be important to assess mechanical performance of components during the prototype stage by using (or closely replicating) the production manufacturing processes. An example of this is cast parts – under high stress, the mechanical performance of a cast part vs a CNC-machined equivalent can be the difference between a part failing or not. While investing in casting tools is expensive, lost-wax sand casting can be used to cost effectively create a cast component that will perform similar to a mass-produced part. In the case of plastic components, rapid prototyping is an excellent choice for manufacturing products that will be injection moulded or vacuum formed in production.
Design for Assembly (DFA) is a process often reduced to the aim of minimising the number of parts to ease assemble and reduce overall cost, but this is not always true (and just the tip of the iceberg). DFA involves the careful planning and selection of assembly methods to minimise both labour time and part cost. It includes not only the initial build but any subsequent maintenance and rebuild requirements.
Alternative fastenings including snap-fit fittings or adhesive bonding should be considered – this up-front investment in innovation can make a significant difference to the product cost and business overheads. All fastenings are load bearing and therefore to choose the right fasteners we consider: load, aesthetics, corrosion resistance (e.g., galvanic corrosion in salt water environments), as well as the use of special fastener types (e.g., torx or bespoke fasteners) which can be used to denote maintenance-only access points.
It is often pertinent to use the skills and perspectives of assembly technicians during DFA to identify potential issues and help determine efficient solutions. At 3DC, we often do this via a Virtual Build review which involves running through the assembly process using 3D CAD models with our in-house and customer build teams. This serves to review access during assembly but is also a quality control exercise where clashes between components are checked.
The final component of DFA must also include a review of part tolerances to ensure that under all manufacturing error margins the parts can still be assembled. Here, skilled designers will apply Geometric Dimensioning and Tolerancing (a standardised system for defining engineering tolerances) in order to ensure that, not only will the parts fit, but that tight manufacturing tolerances that incur higher costs are avoided wherever possible.
The 3D Consultancy is an engineering led design and manufacturing consultancy providing technical solutions utilising advanced 3D scanning, 3D printing/additive manufacturing and CAD digital processes using the latest materials and processes, with industry leading expertise in composite materials technologies.
If you have a technical challenge with very tight deadlines that require exacting specifications and an agile working approach to achieve results, then please contact us.