Though sheet metal may not seem like the most fascinating subject on the surface, it has an interesting and diverse history that spans across millennia. Think medieval knights, ancient Egyptian artifacts, and even Leonardo da Vinci.
Aside from all the fun stuff associated with it, the act of metal fabrication, and forming sheet metal in general, plays a fundamental role in the creation and growth of technology and human expansion.
But it can be a daunting process, looking at a piece of raw metal. How do you transform it into something functional and safe, all while aiming for style and aesthetic appeal? We’ve put together a handy guide packed with some helpful tips.
Keep reading to learn more!
What Is Sheet Metal?
Basically, sheet metal is a kind of metal formed through an industrial process to create thin slabs. It’s one of the most common metalworking materials since it can be bent and cut into a wide range of shapes. You’d be surprised to find that we make countless everyday items from sheet metal in some way.
Within the realm of sheet metal, you’ll see extremely thin pieces, called foil or “sheets,” and thicker pieces that we consider structural or plate steel. You can also get sheet metal in flat sheets or in coiled strips, each with its own uses.
Brass, steel, aluminum, copper, nickel, tin, and titanium are just a few of the metals we can make into sheets, though gold, platinum, and silver are widely used as ornamental sheets.
You can use sheet metal in a wide variety of applications, from:
- Vehicle and truck hulls
- Aviation fuselages
- Hospital tables
- Building roofs
- Transformers
- Electrical machinery
The list could go on, truly. All of these parts will be formed in different ways, so let’s take a look at what that means.
What Does Forming Sheet Metal Mean?
Sheet metal forming refers to manufacturing procedures that shape metal without affecting the mass, volume, or composition of the material. Forming does, however, alter the surface and characteristics of the metal. For example, with the right forming, you could develop a lattice structure.
There are a few ways to form metal, but they will all largely use the same principle, and that is targeted force. This is where we use force to shape cut metal into its final form. The components we make with these processes can end up weighing anywhere from a few hundred grams to several tons.
The Tools and Requirements
We’ll typically use special, electronically controlled machinery like bending machines, presses, and steam hammers, which makes what the first metal workers did even more impressive. Remember, they were working by hand.
Most sheet metal forming tools are suitable for many manufacturing processes, as long as they’re using the right integrated tool. On top of that, there are a few things to consider when forming sheet metal. These are the requirements, or rather, what you need to pay attention to when you’re working.
They are:
- The temperatures
- The type of workpiece
- The kind of mechanical stress
There are also a few different ways to form metal, and all require a good deal of understanding and expertise to get right. They are:
- Tensile forming
- Pressure forming
- Tensile compression
- Heat forming
- Bending
But understanding this and knowing how to actually form sheet metal are two very different things, and it’s helpful to have some extra tips under your belt when you get started with designing your sheet metal for fabrication or welding.
Standardize Your Dimensions
The first tip, and arguably the one that’s going to save you the most time, is to standardize the dimensions of your work. This will apply to anything from your holes to your bends, but will also apply to the stock gauge you choose. Using a standard option could save you a lot of money in the long run, though we understand this isn’t always possible.
While every sheet metal fabrication service will offer slightly different options, there is a standard sheet metal gauge in the USA that all machines are equipped to handle.
Remember that thicker metals can limit the angles of your bends, which can be difficult to work with on a press brake. Basically, if you’re looking for complicated fabrication, stick to the thinner and more pliable materials. On that note, choosing the right material could make or break your project.
Choosing the Right Material
Usually, your most significant spending cost in sheet metal will be your materials and your labor. Let’s consider the materials.
So we know that the thickness of sheet metal (or the gauge) is based on the weight of the metal per square foot per inch of thickness. This means that the interpolated thickness of the material may seem strange to a beginner. Also, keep in mind that these gauges are based on a weight of 41.82 pounds per square foot per inch, but the gauges of metals like aluminum and steel are different.
What does this mean? It means you need to select your metals with care.
Carbon steel is by far the least expensive in terms of raw material cost, followed by aluminum, then stainless steel (assuming the size and gauge are equivalent). Brass and copper will easily be more expensive.
But it’s not always about cost. You also need to consider some other important factors.
Hardness
Hardness refers to the sheet metal’s capability to withstand hard pressing. A basic hardness test should easily be able to distinguish between the following levels:
- Full hard
- 1/2 hard
- 1/4 hard
- fully annealed sheet steel
The higher your number, the harder your material will be, which is important, but it’s also not the same as tensile strength.
Tensile Strength
When choosing your material, consider the total tensile strength of your metal. This will determine the maximum load it can hold without fracturing or breaking entirely. Certain projects will demand the highest tensile strengths, so factor this into your designs.
Maximum Temperature
The temperature will ultimately affect the innate properties of your sheet metal, so if you need to tweak some things, or apply your sheet metal to a specific project, pick a material that suits your needs.
For example, some temperatures can change the electrical resistance of a metal.
Malleability
Of course, your project will have specific requirements, especially if there’s a lot of pressing and pushing involved, so choose a material that has the right amount of malleability. Remember, malleability is a material’s ability to form and mold around other shapes. It also dictates how easy it is to form.
Softer metals are obviously more malleable, but they may not have the same hardness and tensile strengths.
Elongation Ratio
This is important since it directly impacts how much your metal can stretch before breaking. Some metals have unique ratios, while others are fairly standard. Nickel, for example, does not have a particularly high elongation ratio, while gold does.
Limiting Tight Tolerances
It’s unlikely that more than a handful of your surfaces will be critical to your product’s function. However, plenty of inexperienced engineers and designers create their prototypes with needless strict tolerance call-outs on every possible dimension. For example, it is not always necessary to be strict with some:
- Hole diameters
- Distances
- Radii
- Etc.
Unfortunately, the tighter your call-outs, the more expensive your final product will be. Rather than falling into this trap, limit yourself to only including surfaces and features that are essential to the project’s functionality.
Consider this: if you want to create a piece of sheet metal, your most inexpensive option will always be a flat, unadorned piece. For every countersink, hole, hem, and bend you put in, your price will increase. This is largely because you’re increasing the amount of labor for your manufacturer.
Uniform Bends
Fabrication machines, press brakes, and basic sheet metal punch presses are all limited in their capabilities. One of them is their inability to bend an object in a new direction without first reorienting it. It will cost you money every time your sheet metal needs to be physically adjusted by your manufacturer.
Rather, make sure that all of your bends on the same plane are pointing in the same direction. It will save you much more money if you maintain the bends at the same radius. You may actually be surprised by how much this could save you.
Simplify Your Folding
In general, the more sophisticated your design is, the more expensive it will be. Simplify the angles you employ in your bends to save money. For the best sheet metal folds, choose a radius equal to or higher than the thickness of the material you’re using.
Additionally, if you’re trying to use thick parts, avoid small bends unless they’re absolutely necessary, since these can be far less accurate than on thinner materials. If they aren’t necessary, you can always go back to the drawing board!
Always see if you can simplify your sheet metal fabrication. This not only saves you time and money, but helps your manufacturer deliver a great product.
Some Other Helpful Design Rules
Even experienced designers may encounter troublesome parts, but that’s why it’s so helpful to go back to the basics of sheet metal design. We’ve put together a final list of helpful design rules to follow, which will ultimately save you money and hassle, and that’s what we like to see.
Hole Size
When designing your product, make sure that any holes have a diameter that is at least equivalent to the thickness of your material. This significantly reduces the chance that a tool or the metal will break. As a result, you’ll find your production time and cost decreases.
Similarly, having consistent hole diameters throughout can help speed up the production process because it minimizes the number of tool changes your manufacturer will need to do. Finally, locate your holes away from curves. The basic guide for this is that holes should be no closer than six times the thickness of the material.
Bend Radius
When you’re designing a sheet metal part, remember that the narrower the bend radius, the greater the strain your workpiece will encounter. The inside radius of any bend should, in general, be equal to the thickness of your sheet metal.
This is especially true for stainless steel and other ductile metals. Sometimes it’s even more helpful to have a higher bend radius for more fragile and brittle metals.
Hems
Hems are invaluable for handling the metal’s edges and creating safe edges. When you’re incorporating a hem into a section, try to avoid flat hems as much as possible. A tear-dropped or open hem is preferable since it reduces the risk of fractures.
When you’re designing your hems, it’s best to have the inside diameter of the curve be at least equal to the metal’s thickness. The length of your hem should be around four times the thickness, with an opening of about 1/4 on an inch, this measurement for tear-dropped hems.
Tabs and Notches
We’re all about optimized design, and we’re sure you are too. So knowing that precise measurements and ratios mean optimum design, means that you need to consider your tabs and notches carefully. For example, tabs should not be longer than 5x their width. They should also be at least twice the thickness of the base material.
Notches, on the other hand, should have a width at least as thick as your metal, and you should space them apart by at least 1/8 of an inch. If you need to put your notches or tabs near a curve, they should be at least 3x the thickness of your material away from the bend.
If not, they may get bent or even distorted.
Laser Focus Means Ultra Precision
While sheet metal fabrication can seem like a daunting task, it doesn’t have to be. We’re all about precision and quality, and we want that to show in your work. If you follow some of these helpful tips and tricks, you’ll not only save time and money, but you’ll end up with a better, finished product for your efforts.
For all your custom sheet metal forming needs, contact us today. We won’t bend you out of shape, but we will get your metals looking their best.
