Design for Component Fabrication
In this section we explain all about designing for how your parts will be made. But before we begin, let's do a quick recap of the steps we've covered thus far.
DFM Recap
Design for Minimalism: First, we started by taking a close look at our design to weed out as many unnecessary parts as possible.
Design for Standardization: Next, we looked at the remaining parts to see if we can creatively optimize or add features that allow them to be re-used elsewhere in the assembly, thus reducing the number of unique parts.
Design for Assembly: After that, we took a closer look at the assembly and asked what features we can add to our parts to make them easier to assemble.
Now its time to take a closer look at how each individual part is designed, in conjunction with how that part is manufactured, in order to optimize the design to lend itself to manufacturability as much as possible.
What is design for component fabrication?
Designing for component fabrication is at the heart of all things DFM. Here we look at each part with respect to how it is manufactured. We ask what we can do with part features and geometries to make the part easier to fabricate. This topic is where the subject matter of DFM can go very deep. There are infinite ways that a part can be manufactured, which includes existing manufacturing methods and methods that have yet to be invented. Below are just a few:
- Machining
- Injection Molding
- Stamping
- Extruding
- Metal Forming
- Die Casting
- Additive Manufacturing
This article could not possibly cover all subject matter that is designing for component manufacturing, nor can the human brain. Various subject matter experts can dedicate their lives to becoming knowledgeable in just one of these areas of manufacturing, and they do so only through years of raw hands on experience. One could certainly never gain this kind of knowledge from a textbook nor a blog post. And hence, we will not attempt to explain the technical aspects of these manufacturing methods in detail. Instead, we provide a practical path for how to approach this when taking on a new product design.
1. The fundamental design inputs & outputs
Knowing these three universal inputs and outputs of DFM can really help drive to a better and more manufacturable design. You can use them to shed light on what areas of a component's design are in need of attention, for you to then dive deeper into technical brainstorming and innovative thinking.
DFM Inputs:
Most mechanical designs have the same three key inputs in common, regardless of what you are designing:
- The form factor: How are your part physically designed? Do the geometries lend themselves to manufacturability?
- The material: What material is the part to be made from? Does it give you just the right properties required at the lowest possible cost?
- The manufacturing process: What process have you chosen to manufacture your design? Does this method adequately meet the design intent at best possible cost?
For virtually any design, you can focus your team's creativity and brainpower on these key 3 areas to dramatically optimize manufacturability.
DFM Outputs:
Next, we need to know what we want to achieve by modifying these inputs. There are generally 3 main DFM outputs that are common to all parts:
- Cost: This is perhaps the most definitive of manufacturability metrics. How much does it cost to make this part? When manufacturing in-house, this can be a clear cut equation of materials, labor, and yield. When purchasing from vendors, the costs are in the quotes you receive. A high cost implies difficulty to manufacture, hence designers should understand what is driving the cost and seek alternative designs if possible.
- Throughput: Manufacturing throughput measures the time to make a product from start to finish. Throughput red flags typically show up as long lead times for components. This metric directly contributes to cost, but also gives you a sense of what is driving your cost. Long lead times may imply a labor issue or aspect of the design that is difficult to manufacture. It may also imply a material that is rare or difficult to procure. Knowing these drivers can help drive brainstorming for alternative solutions that are more ideal for your design.
- Yield: Yield also directly contributes to cost, but gives you yet another avenue to focus your attention on. Knowing where these quality issues are occurring and what is the root cause of them can help you focus on creative design alternatives that eliminate the yield problems.
These three design outputs are relatively universal. Having a good understanding of them when optimizing design inputs, provides measurable metrics to definitively know that your design work is improving manufacturability.
2. Where to start in our DFM efforts
Often, it's not practical for product teams to perform a full DFM analysis on every part in a given assembly. We're all understaffed in our efforts to tackle impossible timelines. Let's be honest, attempting to iterate and prototype on every part in an assembly may not be possible. This will likely not give you much bang for your buck either.
So, where do we start? This is where prioritization is key and we can utilize a cornerstone manufacturing prioritization tool: the Pareto chart. More specifically the cost Pareto. You may already be familiar with a Pareto chart, or at least Pareto's 80/20 rule, which in short means about 80% of your problem comes from about 20% of all sources.
How it works? We simply plot a bar graph with each part on the X-axis, and their measured cost on the Y-axis. The graph is sorted from left to right in order of most expensive part to least expensive. The pareto graph also superimposes a line graph at each part, summing the running % of part cost. Hence as you move from left to right, you typically find that ~20% of parts (2 parts in the example graph below) account for ~80% of product cost.
What this boils down to? Instead of focusing your efforts on all parts, you can focus efforts on a few parts only (say 20% of parts in the assembly) and really make an impact (80%) on the overall cost of components.
3. How to experiment while minimizing project risk
There are typically 2 risk areas that DFM naysayers like to bring up when shutting down DFM efforts. First is intense project timelines and second is limited project budget. Let's tackle these one by one.
Naysay #1: We have no time
We've all fallen under the pressure of timelines, forcing us onto one simplified and unrealistic project path: design, validate, implement by year end. Any complication or deviation results in a meltdown for most project managers. The best approach to intense timelines is to parallel path!
This usually starts by taking a safe design as the main path, completing all design work done for this, and placing parts on order as soon as possible. This is the main path that you publicize to the greater project team, assuring everyone that all is on track.
Next, you hack together Design B, which has the potential to be dramatically better but may be an untested or wild idea. Tell only the people that need to know about Design B. Tell them its a pet project or an insurance plan if Design A doesn't work. Order as many alternative designs deemed needed. These should not impact timelines as they are parallel paths, and only stand to give you more options to ensure the project stays on schedule, say if Design A should not work out as intended.
Naysay #2: We have no money
Yes, we need money to test and iterate designs. When working with a limited budget to test alternative designs, its best to start by simplifying your prototypes as much as possible. Maybe you don't need to make an entire part to test out the specific feature you are trying to optimize. Can this be proven out on a coupon instead? By coupon, we mean a test sample that isolates only the features in question. This may take the form of half a machined part instead of the full one. Or, a sample piece of that alternative material instead of a fully formed part of the same alternative material. How crafty can you get with your coupons to test the features in question?
We can also look to cut out non-recurring engineering cost as much as possible. A common example: 3D printing all or some of a molded part design before cutting molds. Another common example, visiting the manufacturer of an equipment you are considering to use as a better manufacturing method. Often manufacturers have an applications lab or an option to rent equipment for a trial period to test on your application, thus avoiding a capital expenditure.
Final Note: Manufacturing for Design
Often us manufacturing engineers will joke when a complicated design is thrown our way. We may say this was not designed for manufacturability and are now stuck manufacturing for design. Jokes aside, manufacturing for design indeed serves a crucial purpose in the lifecycle that is DFM! After all, Ford could not have DFM'd the Model T without someone first pioneering the manufacturing methods for steel. Likewise, before design for injection molding existed, someone needed to first invent the injection molder. We could not design for any process without the process being invented first through raw engineering ingenuity.
There will always be a need for manufacturing innovation and this indeed is a crucial element for DFM. Design and innovation always pushes us to new frontiers, and we eventually hit a point where we can no longer find great ways to optimize for existing manufacturing platforms. We must then turn to creating new manufacturing platforms for future products to be designed from. Innovative Manufacturing for Design is one of the ultimate DFM challenges, where DFM legends are born! 🤓
Next Up:
Andrew Akagawa
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