A rapid prototype model is typically a plastic or metal part created from a computer drawing, which permits a customer to review a product under development. Starting in the late twentieth century, computer software was developed that permitted designers to create three-dimensional (3D) drawings. Parallel development of equipment that could create physical structures from these drawings led to the business of rapid modeling.
The design of a part using 3D software starts with a conceptual drawing of a desired part. A designer can take this drawing and create a software-based 3D model, which allows a part to be viewed from different angles or orientations. This software can also virtually disassemble the part to show a customer how assembly can occur in an industrial plant. Software design often includes the capability to "test" the part under different conditions of stress or impact 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 twentieth century, but all were linked to the 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. Computer software turned the drawing into thousands of extremely fine layers, like slicing the image extremely thin. The printer sprayed a chemical binder over the powder in the shape of the lowest layer. Powder was then mixed onto this layer, and the flat tray lowered a tiny amount. The next layer of binder and powder were added, and so on, until a 3D part was made. Depending on the complexity of the part, the printer might need to run for days to complete one sample.
Another type of rapid prototype model printer used a meltable plastic. A nozzle placed tiny dots of the melted material onto the printer tray in successive layers to build up a part. These parts were often usable directly from the machine, because the layers of plastic formed a solid plastic prototype. This was an improvement over some powder printers, which created parts that could be handled, but might not be strong enough for testing or actual use.
A process called metal sintering could also create a rapid prototype model. A metal such as aluminum or copper with a relatively low melting point could be used in a 3D printer in a similar way to a melted plastic. The finished metal part often required no further processing, and could be used directly from the machine for testing or further development.
Many products in the 21st century were totally designed in CAD software, making the virtual image a rapid prototype model, without the need for a physical sample to be made. This became common for large industrial machinery, aircraft and large vehicles such as ships. Many parts were too large to create separate prototypes, or would have delayed final product development.
Engineers developed software testing that could simulate real testing conditions, which eliminated the need for prototype tests. The first commercial aircraft was designed this way in the late 20th century. A commercial jet aircraft was built entirely in a computer, going from a design directly to a flight-capable aircraft with no intermediate prototypes.