What is a rapid prototype model?

3D printers can be used to create models or products directly from digital designs.

A rapid prototype model is typically a plastic or metal part created from a computer drawing, which allows the customer to review a product in development. Beginning in the late 20th century, computer software was developed that allowed designers to create three-dimensional (3D) drawings. The parallel development of equipment that could create physical structures from these drawings led to the rapid modeling business.

Designing a part using 3D software starts with a conceptual drawing of the desired part. A designer can take that drawing and create a software-based 3D model that allows a part to be viewed from different angles or orientations. This software can also virtually disassemble the part to show the customer how assembly can take place in an industrial plant. Software design often includes the ability to “test” the part under different stress or impact conditions to estimate part failures or design flaws.

Rapid prototype model development became a reality with the introduction of 3D printers. Several different technologies evolved in the late 20th century, but all were tied to computer-aided design (CAD) programs that created software models. All 3D printers use a technique of building successive layers of plastics or metals in sequence to create a physical sample of the part.

One type of printer used a fine powder inside a printer cabinet. The computer software transformed the drawing into thousands of extremely thin layers, like cutting the extremely thin image. The printer sprayed a chemical binder onto the powder in the form of the lower layer. The powder was then mixed into this layer and the flat tray lowered a little. The next layer of binder and powder was added, and so on, until a 3D part was made. Depending on the complexity of the part, the printer may need to run for days to complete a sample.

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Another type of rapid prototype model printer used a meltable plastic. A nozzle placed tiny dots of the molten material in the printer tray in successive layers to form a part. These parts were often used directly from the machine, because the plastic layers formed a solid plastic prototype. This was an improvement over some powder printers, which created parts that could be handled but weren’t strong enough for testing or actual use.

A process called metal sintering can also create a rapid prototype model. A metal such as aluminum or copper with a relatively low melting point can be used in a 3D printer in a similar way to molten plastic. The finished metal part usually did not require further processing and could be used directly from the machine for further testing or development.

Many products in the 21st century were designed entirely in CAD software, making the virtual image a quick prototype model, without the need to make a physical sample. This has become common for large industrial machines, aircraft and large vehicles such as ships. Many parts were too big to create separate prototypes or they would have delayed development of the final product.

Engineers developed software tests that could simulate real test conditions, which eliminated the need for prototype testing. The first commercial aircraft were designed this way at the end of the 20th century. A commercial jet aircraft was built entirely on a computer, going from a design directly to an aircraft capable of flying without intermediate prototypes.

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