First in a series of blogs on design and manufacturability.
Designing a product so that it can be manufactured and simultaneously meet the cost, performance, quality, and reliability goals requires a set of skills, experience, and knowledge across a variety of areas beyond design engineering. Fortunately, strategies and methods have evolved that are effective both in determining the manufacturability of a product and providing potential areas for cost reduction.
There are a number of acronyms for these methods – in this blog we’ll review several of the more widely used terms.
In his book, “Design for Manufacturability: How to use Concurrent Engineering to Rapidly Develop Low-Cost, High Quality Products for Lean Production”, Dr. David Anderson defines DFM as “the process of proactively designing products to (1) optimize all the manufacturing functions: fabrication, assembly, test, procurement, shipping, delivery, service, repair and (2) assure the best cost, quality, reliability, compliance, safety, time-to-market, and customer satisfaction.
Before DFM was a focus, engineering teams designed products and “threw it over the wall” to the manufacturing team to figure out how to get the design into production – this often resulted in significant delays and increased costs as the manufacturing team pleading to the engineers for changes to the design (which was often met with “it’s too late”) in order to meet the manufacturing objectives.
Today, product development teams are often multi-functional with early and consistent participation from the operations side (procurement, manufacturing, quality finance, etc), as well as marketing/sales, service, and so on. The team works together to optimize the design for ease of manufacturing, cost, quality, reliability, testability, servicing, safety, regulatory compliance, etc. from the beginning and throughout the design process.
Design for assembly is a process where products are designed with ease of assembly as the goal. In addition, if the parts are designed with features making it easier to handle and insert, assembly time and costs will also be reduced. The primary theory is that by reducing the number of parts in a design, you’ll lower the assembly time and therefore reduce the assembly costs. In the 1970’s, numerical evaluation methods were developed to facilitate studies on both existing and designs in process to assess ease of assembly. In the late 1970’s Geoff Boothroyd developed the DFA method, which could be used to estimate time for manual assembly of a product along with automatic assembly machine cost. As the most important factor to reduce assembly cost was to minimize the number of parts in a product, he developed three criteria to theoretically determine whether any of the parts in the product could be eliminated or combined with other parts. These criteria, along with tables that relate assembly time to design factors that influence part grasping, orientation and insertion, could be used to estimate total assembly time and to rate the quality of a product design from an assembly viewpoint. For automatic assembly, tables of factors could be used to estimate the cost of automatic feeding and orienting and automatic insertion of the parts on an assembly machine. Since that time there have been many other methods developed based on the original DFA work done, and are all referred to as DFA methods. Commercially available software (Boothroyd-Dewhurst, Inc,) is now available to assist companies in the process of DFA.
It's worth noting that this methodology is most successful when utilized at the earliest phases of the product development cycle (ie, DESIGN for Manufacturability, DESIGN for Assembly). DFM/DFA was one of the founding principles for Acorn – it’s in our DNA and in all the work we do, starting at the conceptual design phase.
We’ll talk more about the DFM/DFA process in subsequent blogs.
Ken Haven has been CEO of Acorn Product Development since the company’s founding in 1993. Ken has more than 25 years of product development experience including technical leadership roles with NeXT Computer, Attain, Inc., and Hewlett-Packard. He holds MS and BS degrees in mechanical engineering from Cornell University.