- Design Guidelines for Manual Assembly
- Design Guidelines for Part Handling
- Design Guidelines for Insertion and Fastening
- Assembly Efficiency
- Estimating Handling & Assembly Time Based on Part Attributes
- Provides a tool for the design team to assure considerations of product complexity and assembly happen at the earliest design stage. This eliminates the danger of focusing on function without regarding cost or competitiveness.
- Guides the design team to simplify the product to save in both assembly and part costs.
- Gathers information normally held by the experienced design engineer and arranges it conveniently for use by less-experienced designers.
- Establishes a database of assembly times and cost factors for various design situations and product conditions.
Design Guidelines for Manual Assembly
Design Guidelines for Part Handling
- Design parts that have end-to-end symmetry and rotational symmetry about the axis of insertion. If this can't be done, try to design as much symmetry as possible.
- Design parts to be obviously asymmetric if they cannot be symmetric.
- Provide features that prevent jamming when parts are nested or stacked.
- Avoid features that allow tangling of parts when stored in bulk.
- Avoid parts that stick together or are slippery, delicate, flexible, very small or very large, or are hazardous to the handler (sharp, splinters, etc).
Design Guidelines for Insertion and Fastening
- Design so there is minimal resistance to insertion and provide chamfers to guide the insertion of two mating parts. Generous clearance should be provided, but avoid clearances that cause parts to jam.
- Standardize by using common parts, processes, and methods across models and even product lines to use cheaper higher volume processes.
- Use pyramid assembly - provide for progressive assembly about one axis, generally best from above.
- Avoid needing to hold down parts to maintain orientation while handling during assembly. Try to design for fastening right after insertion.
- Design locating features so that the part can be released before being fastened.
- When using common mechanical fasteners, the following chart plots them based on cost.
- snap fitting
- plastic bending
- Avoid needing to reposition a partially completed assembly.
2 main factors are
- number of parts in the product
- ease of handling, insertion, and fastening
The DFA index is a way to evaluate how efficiently your product is assembled
- is theoretical minimum number of parts
- is the basic assembly time for one part
- is the estimated time to assemble the whole product
Theoretical minimum parts is achieved when parts are combined until all satisfy at least one of the below.
- During normal operation, the part moves relative to all other parts already assembled (unless by living hinge).
- Part must be a different material or isolated from all other parts assembled (for insulation, electrical insulation, vibration damping, etc).
- Part must be separate from all other assembled parts for some other reason.
Do this analysis without taking general or service design requirements so more things can be simplified.
Estimating Handling & Assembly Time Based on Part Attributes
See the book chapter 3 for charts and details.