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What is DFMA?

What is DFMA?

DFMA stands for Design for Manufacturability and Assembly.  I learned this technique during my first year of my engineering design career, back in 2000, and I have used it ever since.  When applied properly, the techniques taught during DFMA can elevate the skillset of even the most skilled designers and engineers.

DFMA was created in the 70’s by these two guys Boothroyd and Dewhurst.  They created a foundation that is still in existence, and has worked to perfect these methods.  Pretty awesome (if you’re a nerd like me).

One of the best examples that I have seen is the front console panel for the Longbow Apache Helicopter designed a built by Bell Helicopter Textron Inc.  When they built the first front console, it was done quickly, probably Skunkworks style (sorry Lockheed), and it was made from a whole crapload of parts.  Was it awesome?  Of course – it’s Bell and it’s the Apache helicopter.

But…. They took a look at the cost and actually counted all the parts.  Parts that had to be bent, painted, held together, riveted, and assembled.  There were around 250 parts and it took them 691 manhours to build the unit!   They decided to do something about it.

They applied a new technique, Design for Manufacturability and Assembly (DFMA), and likely spent days or weeks with several iterations of the design.  They were able to get it down to something that was worth the engineering and design time spent.

You can probably guess, they reduced the console panel, which has 35 flat surfaces, down to 9 major parts.  Yeah, they are extremely complicated sheet metal parts, but the big payout was in the assembly time.  The reduced the assembly time by 73%, down to 181hrs, and cost also went down by a whopping 74% !

What’s even more amazing is that another subsequent project reduced the panel to a single component panel, with a further cost reduction to 10% of the original cost.  In addition, the variability or tolerance stackup was reduced because this design was from one CNC setup made from billet aluminum.  Awesome, right?

Moral of the story is, it took a ton of engineering hours to figure it out, and lots of at the CNC shop to the part prototypes.  In the end the cost savings was a recurring savings that more than paid for the engineering time.  I used to think this cost was only saved every time they built a helicopter, but research has shown that when DFMA is applied, the product actually gets more reliable.  Let’s think on this for a second.  You are applying a technique that focuses on reducing the quantity of parts and fasteners, and it happens to make it more reliable.  Wow!

The above fact might not seem like a big deal, but when someone asks me to make a part more reliable, my thought pattern isn’t to automatically reduce the number of parts.  My mind starts considering all the factors that make something reliable, and it seems like a very complex problem all of a sudden.

All that to say, one of the best tools in the toolbelt of DFMA is to reduce the part count of the device or product you are making.  There are programs and spreadsheets that I’ve used.  These are methodical tools to count the parts, and evaluate each one of them individually, based on the required function.    However, once the DFMA methods are taught, engineers and designers are able to “bake”  this technique into their method.

I teach a class on this at our local university which, due to COVID, I have a recording of it.  In addition I have a more thorough Power Point for a 3 day course.  I plan to make both of these available on the website.  Before that point, if you are interested, email me and I’ll send you a copy.

Overall DFMA is one of the most applicable tools for engineers and designers to use. I highly recommend you take a class or get some training in this area.  You won’t regret it.

About the Author: Willem Mast is the owner and operator of WMD Squared.  He loves mechanical design of all types, optimizing engineering systems, and bicycles.