What is Sheet Metal Prototype Fabrication?
The whole point of creating a prototype product is to verify the design intent for production and this is no different in sheet metal prototype fabrication. In a lot of cases, rapid prototype methods are used such as 3D printing, CNC machining, or even casting, however, when it comes to sheet metal fabricated parts, these methods are often impossible to use or impractical due to the limitations of the processes. The use of 3-D printing to start can save costs, however, they are typically not suitable for heat and stress tests, as the materials (typically polymers) will warp and respond far more differently than components that will later be made from sheet metals. The same goes for corrosion or other environmental factors, this testing must be carried out using the production intent material.
A sheet metal fabricated part can often be larger and may have complex compound curved surfaces, such as a car body panel or some internal automotive component with complex shapes and geometry. These prototypes can only be made using sheet metal fabrication which allows for fit, form, and functional testing as well as verifying production ability to cut, form, punch, and weld the part design.
Another important point when selecting a sheet metal prototype is the functionality of an electronics shielding point of view. Take the requirements for the Federal Communication Commission (FCC) and electromagnetic interference (EMI), these cannot be tested using plastic prototypes as plastic offers no shielding protection. These tests can only be performed using the final metal intended for production.
Methods Used in Sheet Metal Prototypes
There are multiple sheet metal processing options available to create prototype parts and it is beneficial to select the preferred production method during the prototype stage as a verification step. This step may identify issues with the design and the production process, therefore, highlighting where you may have to implement change to achieve product specifications.
Some of the key processes to check at the prototype stage are:
- Creating the pre-formed shape that will be used to create the final part. This can be achieved with many processes such as laser cutting, water jet cutting, blanking, or punching.
- Adding additional features such as slots, holes, notches, and indentations.
- Forming or bending the preform into shape.
- Adding fixings such as clinch nuts or screw studs that provide assembly features to the part.
- Welding the fully formed part if this is a requirement.
Advantages of sheet metal prototypes
- Physical product – having the ability to hold a tangible product as early as possible in the product development stage allows for design reviews and provides feedback on production processes and methodology selection.
- Fit, Form, & Function – a physical product that allows for fit, form, & functional testing.
- Fit – The initial fit test of sheet metal formed parts within an assembly at the prototype stage can often show errors such as gaps, overlaps, misalignments, and other assembly issues. These errors need to be reviewed and analyzed to establish if they are design or process-related so they can be corrected in the next prototype iteration.
- Form – The form of the part is all about aesthetics and how the part looks and feels. It also takes account of the size, weight, finish, color, and other visual aspects.
- Function – Testing the functionality of the part to ensure it performs as intended is the most important of the three elements. Here the prototype should be tested against all the design calculations and parameters such as strength, stress, impact, performance, reliability, and anything else that is critical to the design.
Limitations of sheet metal prototypes
- Cost – The cost of producing one-off or very low quantities of sheet metal prototypes can be high due to machine setup times and the need for any specialized tooling required for forming.
- Fabrication processes – To produce a final fabrication sheet metal part, there are many steps involved, including post-processing such as deburring, finishing, welding, painting. All this takes time and effort to achieve the prototype part.
Typical Applications for sheet metal prototype fabrication
Some of the typical industries that utilize sheet metal prototypes are:
- Automotive parts including panels, chassis, internal components, engine bay parts.
- The robotic industry for unit fabrication
- Commercial equipment such as point of sale, dispensers, ovens, ducting, storage, etc.
- Industrial equipment such as machines, transportation, furniture, construction, and medical devices
Here you can see a closer shot of a sheet metal part being formed in a brake press:
