What is Design for Manufacturability (DFM) and How Does It Affect Lean Manufacturing?

DFM is typically seen as reducing the complexity of a part to make it easier to manufacture. While this is largely true, it isn’t the whole story. From an engineer’s perspective, a part may be simple yet from a machinist’s it may be complicated and vice versa.

The more complicated the part, from the machinist’s perspective, the more difficult it is to make which is likely to translate into more scrap and rework – which are costs that get passed back onto the OEM. It can also increase the amount of cycle time on the part, which means extra waiting for the next step, plus it can increase your lead time overall. While two manufacturers can have very different lead times, scrap rates and overall costs for the exact same part, engineering still plays a part in all that. The goal of good DFM is to manage complexity so that that the part’s effectiveness is maintained while reducing the machinist’s complexity, thereby reducing costs.

Lean manufacturing waste from engineering design isn’t just about complexity. It comes down to understanding the process that manufacturers your part. For example, machining a flat bottom hole is more expensive than one with a point. Sometimes a flat bottom hole is necessary, but do you really want to pay an extra $0.50 per hole? At Hastreiter Industries we’ll double check with the engineer to make sure that’s what he/she really wants and often they’ll revise. Another example is having a pocket or slot with a very small radius that is very deep. With that design, it takes a very small diameter tool that is very long, such tooling is more liable to break which means the machine must be slowed down. While a machinist may be able to find something else to work on for the extra unnecessary time while the machine is running (thus reducing the waste of waiting), you’re still being quoted on based on the total estimated run time.

Extra-Processing is the final category that engineering affects lean manufacturing. Engineering and manufacturing is all about delivering the right quality at the right time at a fair price every time. When parts are designed with higher requirements than necessary it increases manufacturing costs. A prime example are a part’s tolerances for an assembly (this is now getting into DFA, design for assembly). Typically, it would be more dangerous to implement too loose of tolerances than too tight of tolerances. However, too tight of tolerances can drastically increase extra-processing by requiring more work to be put into the parts than is necessary for the reality of the application. Finding the balance in tolerances is not always easy which is where DFM expertise comes in, to help find the right balance because sometimes loosening up a 0.001 tolerance isn’t going to impact performance though it would save you money. In other circumstances loosening up the tolerance might not save you anything so how would you know?

There are a lot more nuances to manufacturing than flat bottom holes and radius to depth ratios and the implementation of DFM can range from eliminating entire features to simply redesigning a feature that was very thin and could affect the defect rate. New technologies like generative helps, especially for applications like 3D printing, though there is no replacement yet for good ol’ human ingenuity. While engineers may not have the time to get on the floor and make some parts themselves to learn the process, they can lean on their in-house manufacturing experts or on their supplier for DFM collaboration. Such collaboration and effort on behalf of the supplier can even be free, as they simply have your back on small recommendations while on more involved projects involving their engineering & manufacturing team with FEA (finite element analysis) the savings could be split. A good supplier has a wealth of knowledge that you can tap in to, especially if they already have a knowledgeable engineering & manufacturing team.

Here at Hastreiter Industries, we’re a machine shop that offers engineering services including DFM, FEA, reverse engineering and industrial design for human ergonomics, CNC milling such as advanced 5 axis milling services, CNC turning and advanced metrology. Every one of our engineers is also a machinist, creating a wealth of DFM knowledge and interdisciplinary skills. Our purpose is to make sure our customers have a worry-free supply chain while using our resources to positively impact our community.