Many companies turn to standard sheet metal enclosures because they think a custom enclosure will not meet their tight timelines. Unfortunately, standard or “one size fits all” enclosures can hurt quality, create unnecessary costs and make it difficult to scale for production. Applying design for manufacturing/design for manufacturability (DFM) principles to create custom enclosures can reverse this trend.

Bob Kuenzi, one of Maysteel’s Senior Program Engineers, has 47 years of experience in sheet metal fabrication. He says DFM isn’t meant to be obscure. “DFM is really about innovating by simplifying. It all comes down to designing an enclosure that can successfully respond to varying demands and revs.”

To see what he means, we’ll describe seven DFM principles below, with valuable insights from Kuenzi to help. We’ll also give an example of DFM integrated into an actual sheet metal enclosure project.

Whether you’re an engineer or a buyer, the following will help you better understand how DFM can:

• Expedite lead times
• Reduce spending
• Improve product performance

But before we dive into those principles, let’s be clear on what we mean by DFM.

What is design for manufacturing (DFM)?

Design for manufacturing also referred to as design for manufacturability, (DFM) optimizes a product’s design for efficiency, repeated production at the lowest cost while also meeting the product needs of the end-user. In real-world scenarios, DFM enables a manufacturer to scale up production with minimal challenges and without costly redesign.

Manufacturing made easier: 7 DFM principles for sheet metal enclosures.

Don’t overload your enclosure with fastener hardware.

Fastener hardware in sheet metal fabrication can include nuts, studs, screws, pins and rivets. Although there are many options, Kuenzi says, “Limiting overall hardware is crucial for DFM.”

For example, take insert hardware that includes threads for fastening a joint. Kuenzi says there are other ways of creating threaded features without hardware, such as formed features in the part. By forming the threads right into the part, you are cutting down on the amount of hardware required to fasten the components together.

“You need to remember that loading up an enclosure design with hardware typically means putting those things in manually,” said Kuenzi, “If a company were to invest in an automated press, that would be a significant investment.” The hardware burden becomes even more problematic when inserts vary. “Let’s say you have 25 total inserts that require five slightly different through-holes.

The hardware will be difficult to keep track of. Plus, you just made it really challenging to manufacture an enclosure repetitively in an efficient way.” Kuenzi said.

Go easy on the number of bend radii

An internal bend radius is a minimum radius you can form a part without damaging it or compromising its integrity.

“When you’re designing an enclosure, don’t use all kinds of different internal bend radii,” Kuenzi shared. “Why not? Because you’re going to need specialized tooling to form each of them.” Specialized tooling may mean going back and forth between a manual press and a pneumatic press, which increases labor time and cost.

It can also mean additional tooling investments. It comes down to the more tooling needed, the more complicated the process, the longer the lead time and the more challenging it will be to meet scaled-up production expectations.

Be sparing when it comes to rivets

When it comes to rivets, there is more manual labor required than with typical fasteners. That’s because rivets:

• Are shot manually and can create a more expensive and time-consuming process.
• Must be counted and can be challenging to keep track of as their amount goes up.
• Need to be checked to make sure they’re properly seated.
• Can be easily missed, which creates a quality issue.

“Five or six rivets isn’t a problem. But an enclosure with 50 rivets? That’s a lot of work to do efficiently and consistently,” Kuenzi said.

Don’t include impractical material requests

DFM involves using simple, easily accessible raw material. That’s why a design that requires some impractical requests can create considerable delays and expenses.

“Let’s say you have a sheet metal fabricator who holds 18- and 20-gauge material thicknesses, but you design for 19 gauge. If you want to wait for 19 gauge, it could be something like a 40,000-pound minimum buy and take four months. That makes no sense,” Kuenzi said.

If possible, it is also beneficial to consider communizing sheet thicknesses in your design. “Common thicknesses allow our team to better nest them in the sheets. This allows us to use less material and keep costs down,” Kuenzi shared.

Opt for powder coating (not wet paint)

At the manufacturing stage, powder coating has essential advantages over wet paint. Kuenzi explains that powder coating is generally a superior option because:

• It’s incredibly durable. Powder coating is usually applied in thicker layers and undergoes a thermal bonding process for curing. Among other benefits, this creates a finish that’s more resistant to fading, chipping and scratching.
• It’s environmentally friendly. The solvents in liquid paint often contain pollutants like VOCs (volatile organic compounds). Because powder coating doesn’t contain solvents, it reduces the health risk on operators and eliminates the need for expensive pollution control measures.
• It’s cost-effective. Powder coating is made up of tiny pigment particles and resin that are electrostatically sprayed, and therefore stick to the sheet metal enclosure. This drastically reduces waste in the manufacturing process. Processing times for powder coating are also shorter, which helps facilitate the lead time.

Minimize masking points

Enclosures need to be grounded for electrical continuity in case of lightning strikes and other electrical hazards. Since paint can interrupt that continuity, masking can keep certain areas covered during the powder coating/painting process.

However, masking has its problems. “I’ve seen designers want to put a hundred masking points on a part,” said Kuenzi, “But masking is a manual process. And if you miss a mask point, the enclosure becomes a quality reject. Requiring lots of areas to be masked makes the manufacturing process complicated in a hurry.”

You can eliminate or significantly reduce the number of masking points---and the labor that comes with them---by using a grounding strap or grounding pad instead. “That’s a much cheaper option,” Kuenzi said.

See the big picture when it comes to packaging costs

Once the fabrication process is completed, the packaging step can be integral to the success of your product. One specific suggestion Kuenzi has is to consider returnable packaging.

For example, it can work great for high-volume projects. “You can ship products back and forth in the same crates, have no damage to the parts, and life is good. Yes, the crates cost money, but you’re going to be better off in the long term.”

Don’t forget that corrugated boxes and the wooden pallets they come on create recycling costs. “Those can really add up,” Kuenzi said.

“If you do use corrugated boxes and wooden pallets, try to maximize use to get the most for your dollar.”

Next, let’s look at what DFM looks like when applied to some actual manufacturing scenarios.

One real-world example of DFM integration

Flexibility for the Future: Designing a mid-range server A customer needed a mid-range server design that was both flexible and highly manufacturable. Here are highlights of our engineering team’s DFM solution:

• Focus on fastener reduction. The need for problem-prone rivets was virtually eliminated thanks to self-clinching joints. For example, 32 such joints and five components can be secured in a single press cycle.
  
• Flatten buttons for tight clearance. A technique was developed to flatten buttons in tight clearance spaces, allowing mating components to be slid in and out without obstruction.

• Use a pivoting interlock feature. An innovative pivoting interlock feature for air baffles was incorporated into the regular press tooling. This eliminated a secondary operation to align and insert a separate hinge pin through three air baffles.

Four models have since been produced, incorporating modifications as the electronics have evolved. And throughout, the same basic tooling has been used, creating significant cost-savings.

Next steps: What you can do to incorporate DFM principles

The DFM scenario covered above is just one example of how to incorporate DFM principles. Still, you should now have a better sense of how critical DFM can be in the success of manufacturing sheet metal enclosures.

If you’d like to see DFM principles incorporated into your sheet metal enclosures, make sure you make DFM top of mind on your upcoming projects.

Then, let your fabricator know DFM is important to you and that you’re looking for a partner who can help you gain the many advantages that come with it.

Ready to speed up your production timelines using DFM principles? Let’s talk!

©2020 Maysteel Industries, LLC