Aluminum Extrusion Process
Aluminum Extrusion Process
What is the Extrusion Process?
Creating extrusions is a process where soft(ish) materials are confined within a space, then that space is shrunk while leaving only a small opening for the material to escape. The material retains the shape of the opening it passes through and can be referred to as an extrusion.
Think of it as toothpaste that turns hard after it leaves the tube. Yes, that’s a ridiculously simple-minded analogy. And no, my wife didn’t buy my “I was learning about manufacturing” excuse when she found fossilized toothpaste in the cabinet. You’ve been warned.
Extrusion is a great method for converting materials into shapes with complex, useful features. Especially concerning aluminum, extrusions give a blend of strength, low weight, and geometric features that are both functional and attractive to the eye. Aluminum extrusions are commonly used in assemblies where portions are exposed on the outside of a product for aesthetics and other sides of the same part are strictly functional hidden within. Naturally corrosion resistant and with some versatile surface treatment options available, aluminum extrusions are used in more places than you likely realize.
Designing an extrusion is all about determining its two-dimensional shape, its cross-section. A typical approach is to start by laying out an array of anchor dimensions or reference points and then essentially play a game of “connect-the-dots” to join the features together while following general guidelines for manufacturability. Stretching that shape into three dimensions using perspective and shading techniques then show what the physical part might look like once extruded.
Engineers will refine the product with precision and optimization in mind. A key starting point is making sure the profile is balanced. An unbalanced profile is difficult to turn into a product. Manufacturers like working with unbalanced profiles about as much as Indiana Jones likes working with snakes. They may even just flat out refuse to work it if they feel the risk is too great.
By “balanced” we’re talking about having consistent wall thickness throughout a profile, and ideally having symmetry in multiple directions. During production, balanced profiles allow the material to flow evenly and straight through the die and stay relatively straight as they exit. The evenness applies to the life of tooling as well, so good design practices protect your investment.
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Here are some features you might see engineers working into extrusion designs. They go a long way in saving time and money down the road when done well.
"Christmas Tree" Anchor
It’s not only the shape of the extrusion that determines its properties. To explain, let’s talk about your favorite kind of chocolate chip cookies (because carbs = life). The ingredients in the batter all help to determine the flavor and texture. Want chewy, soft cookies? Keep the time and temperature low.
Want hockey pucks good for dunking in a cold glass of milk? Moderate temperature, long time.
Want the chewy centers with just barely crisp edges? High temperature and short baking time (These are the best cookies. Don’t bother with the others). Each of these types is preferred by someone. There isn’t just ONE right way to bake cookies (cough, chewy), but they’re all chocolate chip cookies. They just have different properties.
In the same way, aluminum extrusions have different properties depending on its specific alloy composition and temper which help to determine the part’s strength, corrosion resistance, machinability, and workability (how well it bends without cracking). The temper or heat treatment can somewhat be viewed like the baking process, in that it’s a specifically prescribed set of time and temperature conditions that transform the dough into cookies. In the case of aluminum; however, we’re transforming the metallurgical structure for strength and hardness.
Do you want to hear the good news or bad news first?
You’ve got a fantastic design for a lightweight heat-dissipating illuminated billboard frame extrusion. It’s got all the bells and whistles you could hope for in one part and doesn’t require any fasteners or assembly to put it together. The only problem is, how do you get a 50ft long prototype? Well, that’s not going to happen without an extrusion tool.
The cost of aluminum extrusion tooling is very reasonable for the value it provides. For small extrusion sizes, it doesn’t pay to even spend time thinking about other options – just make a tool. They’re inexpensive and can be produced relatively quickly. Larger, more expensive extrusions can still be validated using other methods.
For another option, short sections of profile shapes can be cut by waterjet, laser, wire EDM (uses electrical discharges to shape it), 3D printed or pounded into shape by Chuck Norris. Haha, just kidding… Chuck Norris only looks at the profile and it becomes what he wants out of fear. The sections produced by these methods can be used to test-fit profiles to other parts or fasteners and show the usability of hinges, snap fits and other interlocks.
Gaining an understanding of the aluminum extrusion production process at a high-level helps to pick a manufacturer who is the right fit for your project and company. Download the full article for a more complete view of this. At a high level though, these are the 6 steps they’ll be taking care of: