Prototyping is a broad term. When a graphic designer builds a website mockup in a graphics design program it’s a prototype. An automotive engineer spreading clay over a frame of steel and foam is also working on a prototype. However, for most a prototype is a limited production run of a part or product that can be tested, and used to detect any serious flaws or shortcomings before the full production run is started. It is an important task and finding the best prototyping materials to build these initial prototypes is an ongoing task.

Aluminum though, is one of the best prototyping materials there is. Its strength, although less than that of steel, is close to it. Another point in aluminum’s favor is that for that strength it is very easy to work with. The same common tools and carbide blades, bits, and mills used to work with wood can be effectively used on aluminum. This means that near industry ready components and machinery can be turned out of small shops with hand tools and know-how. Aluminum is versatile, and one of the best prototyping materials available at any level of production. Even when it isn’t the material the prototype is to be made from aluminum still plays a critical role in many prototype manufacturing techniques.

Prototype Manufacturing Processes

If asked to identify how digital technology has changed manufacturing the average person might identify social media or media streaming. While these are transformative technologies, new manufacturing techniques like CNC machining and 3D printing are even more transformative. Together these two methods allow small shops, and even home hobbyists to produce components and products that would have taken a major industrial concern in previous decades.

Alongside traditional manufacturing processes these new processes open a whole new range of manufacturing and prototyping options. An overview of some of the most common prototype manufacturing processes along with their advantages and disadvantages can be seen in the table below.

3D Printing/Additive Manufacturing
Additive manufacturing in simplest terms is building up a component layer by layer, or by the addition of material a little at a time. It is a very versatile technique that has found use in everything from modeling figurines for hobbyists to printing replacement organs for transplantation. In prototyping it is most often used for producing mockups or three dimensional elements that will be used in producing the final component.
Pros: Unsurpassed versatility Rapid speed from concept to product Available on demand Little waste	Cons: Limited materials Limited print size Limited production runs Post processing Required
Computer Numerical Control (CNC) Machining
A CNC machine is an evolution of traditional subtractive manufacturing where material is removed in order to create components. The tool is turned over to the control of a computer that moves it through a range of positions on numeric coordinates in anywhere from two to 12 axis of control.
Pros: High volume continuous production Extremely repeatable production Allows for extremely tight tolerances Little post processing required Can use a wide array of materials	Cons: Geometries can be limited. High end machines are expensive Potentially wasteful of materials Can have a steep programming curve Initial setup can be time consuming
Casting
Casting describes any process where a liquid material is poured into a mold and allowed to solidify. In industry it mostly describes metal casting. This is one of humanity’s oldest methods for producing tools and actually predates recorded history. As befits a technique with such a long history there are an array of ways metal casting can work with their own unique benefits. In general though the pros and cons are:
Pros: Can produce complex shapes Large parts can be cast singularly Hollows of any shape can be cast Complex geometries can be cast	Cons: Required skill level is incredibly high Very time consuming Potentially very dangerous Results can be unpredictable
Injection Molding
Similar to casting this process is putting a liquid material into a mold and then allowing it to solidify. The major difference is that this material is injected using pressure to help ensure that all parts of a mold are filled. Although in principle the process could use metals in practice injection is used for plastics, resins, and epoxies.
Pros: Allow for complex geometries Can meet exacting tolerances Wide range of materials Efficient and cost effective	Cons: Expensive time consuming start up Design changes are time consuming
Vacuum Forming
Vacuum forming is heating plastic sheeting until they become malleable over a mold. Once they reach a ductile state a vacuum will pull them into the mold. The sucking of the vacuum helps to ensure they fit tightly within the mold and fill every available crease and crevice of the mold. It is a popular way to form thin sheet materials into complex shapes and geometries.
Pros: Suitable for making complex shapes Simple and reliable process Fast completion times Low cost	Cons: Molds can have long lead times Geometries available are limited Limited volume productions Post processing work is needed

The prototype manufacturing process can be complex, and multipart. Even a device as simple as a bracket can be a multistage process depending on the geometries that are involved. Something as simple as a hole with a compound angle may necessitate the use of an entirely different manufacturing process like casting rather than CNC machining. The mold for casting the bracket may be made of wax, and it may be produced by a 3D printer. Modern prototyping leverages multiple techniques that can make a prototype that is nearly on par with a finished product.

Prototyping is in many ways starting to become something of a misnomer. Companies that specialize in rapid prototyping possess the skill and tools needed to make a final product with a high degree of finish. Often the difference between a limited production run and a prototype, is that the prototype is followed by a larger production run. Provided the prototyping materials chosen are durable and long lasting enough a prototype might be considered simply a production run with a singular product example. One of the reasons that aluminum is among the best prototyping materials is that it is durable to be put into direct use if the prototype is found to be

Types of Prototyping Materials

While aluminum is among the best prototyping materials available there are a range of others. While we are partial to aluminum these other materials do play a role in the prototyping process. Either in the form of the actual prototype structure, or as a mold to cast or form that structure. There is a dizzying array of materials that can be used. For example if you’ve ever cut a piece of cardboard to the dimensions of an item on Amazon to see how it would fit in your home. You’ve used a cardboard prototype. However, for these purposes we will simply focus on discussion of the most common prototyping materials.

• Wood: The original prototyping material and still widely used to this day. It has advantages in that it is inexpensive, lightweight, easy to work with, and relatively strong. It has disadvantages in that it is not very durable, and dimensional stability can vary wildly with environmental conditions.
• Resins: For these purposes any organic material that is a fluid at room temperature that can be placed into a mold and solidify over time is considered a resin. This includes epoxies, latex, and urethanes. The advantages of these materials is that they can be cast into any shape easily, at room temperature. The disadvantages of these materials is that they tend to be soft, can have rough or porous surfaces, and have poor strength.
• Composites: Combine resins with a structurally strong material like glass or carbon fiber. These combine the easy moldability of resins with high tensile and structural strength. The disadvantage is that it takes a high level of expertise to produce a consistent uniform product, and any discontinuities in the composite can lead to catastrophic failure of the prototype.
• Thermoplastics: This includes a range of castable, machineable, and moldable materials that are soft when heated, but solid at room temperature. They have the advantage of being able to take on any shape. A clean smooth surface, and a high strength to weight ratio.
• Metals: The two most common metals for prototyping are steel and aluminum. Copper alloys like bronze or brass may also be used. The advantage of using metal is that the resulting prototype can be used in the same manner intended for the finished product. The disadvantage is that the work to produce the prototype is often the same as producing a final product. In the case of hard metals like steel this is a significant amount of effort.

Choosing the best prototyping material depends on what the prototype will be for. Metals are some of the most durable materials that are widely available. They are not, however, generally a good choice for prototyping dental prosthetics or implants. Unless perhaps your organization is plotting against the United Kingdom’s secret service.  Similarly, wood is an easy material to work with for mocking up dummy objects that can be held in hand to give an idea of weight and dimension of the final product. However, these dummy objects are unlikely to be suitable for bolting into place on equipment, running through operational cycles, and identifying stress points that need to be engineered out. Verified aluminum remnants available at bargain prices, but a contents you can trust are one of the best prototyping materials from a cost benefit standpoint.

The reason that aluminum alloys are objectively the best all around prototyping materials are because of the workability combined with sheer versatility. It is a metal that can be precisely cut to size with an ease that is comparable to wood. This is far better than steel which can take days of work to tool into complex shapes. At the same time aluminum can perform some of the same work as steel serving as a mold for injection or vacuum forming process using thermoplastics or resins. Whatever, you’re prototyping and what industry it will serve in aluminum is likely to play a critical role in the prototyping process even if it is not part of the final prototype itself. This makes aluminum alloys the best prototyping materials to have on hand. A savvy prototyper will have a couple of different aluminum alloy types, and other metal sample packs on hand to test out different prototyping materials to get a feel for what works best.