Sheet Metal Enclosures: Engineering of Designs & Art of Designing

Sheet metal designing is a complex process and requires several skills related to metal works, and compromises in design intent, machine capability and working knowledge. Most importantly it needs patience from sheet metal designer in fast paced development of metal designs and drafts in ideal CAD environment. All in all, a sheet metal component designer has to have all around working knowledge from sheet metal designing to sheet metal fabrication. If the designer fails to incorporate the allowances, the fabricator faces production downtimes originating form non-compliance of designs with the fabrication environment.

Fabricators involved in works of sheet metal enclosure fabrication, usually find bending as the most commonly used operation. With a variety of materials like stainless steel, cold steel, GI sheets, aluminum etc. used for sheet metal fabrication there are a numerous options available to fabricate the desired shape and form of the enclosure. Besides, working with any fabrication process of bending, forming, welding etc. is easy with sheet metal. Importing all the geometries and details in CAD models in the initial stage will essentially allow the designer and fabricator to tune up at the same frequency for understanding design intents.

Design Driven Sheet Metal Enclosure Fabrication

With the right technology, materials, and design minds; it is possible to fabricate any desired shape of sheet metal enclosures. The challenge is arriving at a fabrication process that is cost effective, consumes minimal time, generates minimum waste and rework, and is synchronized with the finalized designs. An expert CAD designer can work with several tricks of bend, form, slotting, punching holes and other fabrication processes that satisfy all the design constraints and deliver appropriate solution for a sheet metal fabricator.

As a simpler solution for fabricators, 3D CAD designs are more substantial, quicker and accurate instead of 2D   designs. Most of the CAD tools and software will do all the math work for bends and other fabrication process. But a designer needs to understand the shop floor conditions and provide sufficient allowances and tolerances of components, depending on the bend angle, radius and material properties in the bend region. Any sheet metal enclosure will at the least need one bend in the entire forming process. Bending, thus, forms the most common kind of operation in the fabrication of sheet metal enclosures and designer needs special allowances while designing to match the shop floor conditions within CAD environment.

Bend Allowances & CAD Software – The Duo

When working with sheet metal, it needs to be folded, bent and flattened several times, to have the desired shape of enclosure. Usually, with CAD software, there are several methods for bend allowance calculations such as bend allowance, bend deduction, k factor, bend tables etc.

However, a designer usually focuses on three main methods to select one from:

  • Bend allowance: Simply put, bend allowance is the length of the arc along with the sheet metal piece is bending. The specialty of CAD software is it allows the designer engineer to calculate the developed size of sheet metal.
  • Bend deduction: Bent deduction in CAD software allows the designer to calculate the bend deduction while flattening the sheet metal plate. CAD software gives the designer liberty by automatically calculating the bend deductions based in sheet thickness, bend angle, inside radius of the bend, etc.
  • K factor: CAD software calculates the exact value of bending allowance by understating the bending phenomena about the neutral line of the sheet. [Center line of compression and tension of the metal] Essentially used for flat patterns, k factor allows the user to determine and anticipate bend deductions without being dependent on charts.

Does the fabricator have a say to which allowance should be used?

That’s the beauty of it! Sheet metal fabricators are the ones who take a call of bend allowance for sheet metal enclosures. It is so because the fabricator is the one who knows the metal pieces in real conditions. Sometimes, the fabricator provides the relevant data for bend allowance from the handbook or by calculations. In either case, CAD software will calculate the value as per the need, set standard rules and formulae for designs that are based on various design parameters like thickness, bend angle, radius, material type etc.


This makes it a complete beauty with engineered facts of sheet metal bending for fabricating enclosures. Enhanced technology in CAD systems has eased the sheet metal fabrication business by tuning the fabricators and design engineers at the same frequency. Along with bending, there are several other processes involved in designing sheet metal enclosures, however; one at a time approach makes more sense.

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