Design for Manufacture and Assembly

The public domain proliferates with acronyms, such as DFM and DFA. These do not comprise a standalone concept; there is a relationship between design for man­ufacturing (DFM) and design for assembly (DFA) to meet the objective of lower production costs. In this book, fabrication and assembly are two components of the manufacturing process and are combined as DFM/A. Chart 17.1 shows the typical steps in DFM/A application.

DFM/A is concerned with the design synthesis of parts fabrication and assembly as an integral part of manufacturability. DFM/A analyses involve competition and risk – that is, balancing the trade-off between cost and performance. This eventually

ensures affordability for operators as the best buy. This multidisciplinary study searches for aerodynamic mould lines with surface-smoothness requirements (i. e., tolerance specification) to minimize performance penalties without imposing dif­ficulties in manufacturability. The associated structural-design concepts facilitate parts fabrication and assembly (i. e., low manhours and low parts count, as well as enhanced interchangeability). Bought-out items are selected for efficient and cost- effective system integration leading to better reliability and maintainability during the aircraft’s operational lifespan. Based on an awareness of customer affordability and requirements, designing and manufacturing target costs are established, which measure the objectives of lower production costs, improved quality, and reduced manufacturing cycle times, while increasing the product value without sacrificing design integrity, safety, and established specifications.

As a complex product, an aircraft is constructed of myriad parts. Assembleabil – ity, as a measure of the relative ease of product assembly, plays a prominent role for produceability. Following are the main goals of DFM/A considerations, which reduce parts count and assembly time:

• improvement of the efficiency of individual parts fabrication

• improvement of the efficiency of assembly

• improvement of product quality

• improvement of the assembly-system profitability

• improvement of the working environment within the assembly system

• product’s usefulness in satisfying customer’s needs

• relative importance of the needs being satisfied

• availability of the product relative to when it is needed

• best cost of ownership to the customer