Sheet Metal Process
The Sheet Metal Process
The most intimidating factor for many designers of sheet metal products is the engineering. Often, you can visualize the desired outcome, but without an engineering degree, it can be frustrating trying to describe your vision to an engineer.
Don’t worry; we’re not going to fry your noodle with all the specifics in this article.
But if you want your product to be developed correctly, you need to know enough about it to be able talk to those engineers and ask the right questions.
What is the Sheet Metal Process?
For any development project, engineers need to know three things first: 1) The functions (and limits of) the part, 2) Where it will be used, and 3) Its general form.
The industrial designers use this knowledge to form an abstract concept. With manufacturing limitations in mind, they work it into a sketch.
“What limitations?”, you ask (okay, I’m pretending you did)?
The engineers must be able to: 1) Start from a flat sheet 2) Cut the shape with real, three-dimensional tools and 3) Form the shape with those tools.
Sounds simple enough. But simple isn’t always easy.
There are several potholes you can fall into with this process:
Here is where our design engineers come in.
They develop that sketch created by the industrial designers into a CAD (Computer Animated Design) model. Their main function is to ensure the concept is actually possible considering both manufacturing and functionality while they turn the concept into a 3D image.
This is usually the point where they may have to tell you that, unfortunately, your bejeweled-aluminum-elephant-flashlight can’t have solar panels riveted into its tusks.
Many specifications (specs) have to be considered here. A few would be: 1.) Alloy thickness 2.) Manufacturing methods and 3.) Surface finish. All of these have to be optimized for cost and function. Waste is the mortal enemy of the engineer. High costs = low profits for everyone.
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Hover over each picture for more information on the sheet metal part.
To form sheet metal is to induce stress and strain. Most of this force causes the material to yield and bend or flex, but some of that stress spreads out into the part and remains within the unbent areas of the metal. This can cause the material to actually tear either during the forming process or far afterward while the product is in use under other loads and vibration. Ouch! Proper engineering design allows the part stretch in the right ways without breaking.
The material close to a bend line will stretch during the forming operation. Kind of like pulling comic images from the newspaper with silly putty, nearby features will stretch into odd shapes. In this example, the formerly round hole is no longer suitable for a round peg.
Don’t send a design like this to your manufacturer or you’ll end up with your picture on the wall of shame! Remember, sheet metal starts as a flat sheet so any material in a bent tab or flange feature needs to be able to flatten out without overlapping. The example above would only make sense to M.C. Escher – not to the real world.
Sheet metal parts are not typically the final product, but are one of many components making up a larger assembly. Forward-thinking design practices can include features that make the downstream assembly processes more economical. For instance, assembly tabs can be designed into the part so that the components self-locate for a welding operation instead of requiring a costly precision welding jig.
How is it built?
Prototypes are actually created using the exact same process as mass produced sheet metal parts. Of course, there is always a substantial cost difference when a part is mass produced.
Cutting: The part’s general profile has to be cut according to the specified material and thickness. There are a few different ways this can be done: 1). Shears 2). Punches 3). Lasers and even 4). Waterjets
Forming: The flat profile is turned three dimensional by bending, forming or drawing it with massive amounts of force to get the precisely desired shape. Press brakes are common and use more-or-less standard sets of tools.
Welding/Machining: So it turns out your elephant-flashlight ended up requiring a little more nuance in its creation. Maybe it requires press-kit fasteners (self-clinching permanent fasteners) cutting threads (to make screw openings) or it just needs multiple parts to be welded together.
Finishing: Here’s where your product gets a sleek coat of paint and a shiny wax job. Surface treatment makes your product shine and protects it from the slings and arrows of life. As cost is always a consideration, cost efficient options tend to vary by manufacturer.
Assembly: It’s a definite possibility that the sheet metal part you want created isn’t the whole product and in fact is just one of its components. The sheet metal part at this point has gone through the entire process and has interacted with tools, fasteners, and other components and at some point has to be manipulated to fit properly by human or machine.
WHAT’S THE BOTTOM LINE?
Our goal was to give you a brief understanding of the sheet metal process. For more information on the exact art and subtle science of sheet metal production, please download our free PDF below.