Even the simplest of electronic products need to be enclosed somehow. Additionally, having a basic understanding of how electronics enclosures are fabricated can go a long way to a more successful overall design and positive end-user experience. While there are electronic products that are more suitable for plastic enclosures, sheet metal electronic enclosures have the added benefit of electrical conductivity, which is important for EMI (electromagnetic interference) applications, emission reductions, protection from external noise, and the ability to withstand a harsh industrial environment. Sheet metal’s lightweight, non-corrosive, conductive, and strength properties make it particularly popular in electronics applications.
Sheet metal enclosures for electronics housings range from RU server chassis, cabinets, rack components, PCB, DIN rail, to NEMA-style electrical boxes made of aluminum construction with weather-rated powder coating and more.
Before you speak in detail with a sheet metal fabricator, it would be wise to get to arm yourself with basic sheet metal design concepts and an understanding of the common design parameters to consider when determining the appropriate sheet metal selection for your enclosure.
“Sheet metal tends to be considered either this mysterious dark art to some engineers,” says Matt Garrett, an applications engineer for Rapid, a Protolabs Company, “or something that is overlooked until the last minute, or to others with a notion that ‘it’s just sheet metal.’ A safe mindset would be somewhere right in the middle of these two concepts as sheet metal can be quite finicky.”
Garret suggests familiarizing yourself with the following basic sheet metal design concepts that should fulfill most of your general sheet metal needs.
- Maintain uniform wall thickness. Sheet metal parts are manufactured from a single sheet. You cannot have a 14ga (gauge) base with a 16ga flange with formed parts. This would require welding two components of differing thicknesses together.
- The 4 x Rule (4 x material thickness).
- Flange length must be a minimum of 4x material thickness. This is due to the need to maintain three points of contact with the form tooling — two points (one on either side of the bottom die and with a center point of the punch).
- Holes, slots, and other cut features must be 4x material thickness in distance away from the bend line of a flange to prevent distortion when forming. All sheet metal features are cut in the flat prior to forming so if a feature that is close to the bend is critical, post-machining and added cost is required.
- Do not use 3D software default values for bend Radii. Most sheet metal design software defaults to using material thickness value for bend radii size. This is not realistic in the context of available press brake tooling. Rapid’s standard radius tooling is as follows: .010”,.030” (preferred and most common), 0.060”, 0.090”, 0.120”, 0.188”, 0.250”, 0.375”, 0.500”, 0.750”, and 1.000”
Smart designers keep it simple
Keeping a design and design requirements simple is nearly always a challenge but it’s a sure-fire way to attack shrinking time-to-market expectations. The holy grail is a fabrication process that is cost effective, consumes minimal time, generates minimum waste and rework, and meshes with the final design.
“I have experienced many situations where our customers have designed themselves into corners,” says Garrett. “By the time they come to us with a tight deadline they have very little wiggle room in their design.”
For example, when specifying punch features without design flexibility such as embosses, ribs, bridge lances, and louvers, you run into the need for custom tooling which is not conducive to a low cost, quick turn sheet –metal solution.
“I always ask our customers to reach out to us with any questions they may have prior to finalizing their design,” says Garrett. “We are here to help.”
Rapid’s expanding list of sheet metal capabilities include: laser cutting, punching, press brake forming, TIG, MIG and Spot welding, PEM hardware, hardware insertion, rolling, riveting, secondary/post machining, assembly, plating, power coating, silk screen, and part marking.