Cómo crear prototipos rápidos para trabajos en metal
Introducing a new product to market involves a complex process of design, market research, and manufacturing. Rapid prototyping is one part of this process where component parts are made in order to develop a working model of the product—testing its functionality and limitations. These prototypes can be made from the same material as that of the final product, or an alternative material can be used for the purposes of the test case.
Some methods of metal prototyping include:
Investment casting
Fabricating the part directly from metal stock
Machining the part directly from metal stock
Rapid prototyping methods and applications
Each prototyping method has its advantages and disadvantages, as well as factors that make it best suited for certain projects.
3D printing is a relatively new process also known as additive manufacturing—the process of printing one layer of product at a time until a 3D component is built up by the many layers. Each layer can be about 100 microns thick. The printer is controlled by a computerized system, which takes a 3D design as input and creates the 3D product as output.
Technology has evolved over time, and a wide variety of materials have become available for printing. Plastics, nylons, resins, silver, titanium, steel, wax, photopolymers, and polycarbonates can all be used as 3D printing material.
A young woman looks at a 3D printer creating a ball-shaped prototype
3D printing is an innovative form of additive manufacturing—printing one layer of a product at a time until a 3D component is created
There are three main types of 3D printing machines:
Selective laser sintering (SLS) uses printing material supplied in powder form. Each layer of the part is created by melting the powder using a laser. Fresh powder is rolled over the top of the partially completed part and the process is started again until the entire part is built.
Fused deposition modeling (FDM) uses thermoplastic filament and melts it for extrusion. The extrusion is precisely controlled by the computer in accordance with the 3D design, printing each layer in succession.
XTJ es un fabricante OEM líder dedicado a ofrecer soluciones de fabricación integral desde prototipos hasta producción. Nos enorgullece ser una empresa certificada con ISO 9001 en gestión de calidad y estamos decididos a crear valor en cada relación con el cliente. Lo logramos mediante colaboración, innovación, mejoras en los procesos y una mano de obra excepcional.
Stereolithography also uses a laser, but in this case, a liquid product is solidified one layer at a time by the laser action—it is controlled to match the design.
3D printing is popular for rapid prototyping because the process is very resource efficient. No tooling of production lines is required, labor requirements are minimal, and very little waste is generated. The disadvantage of 3D printing is that it can be time consuming—taking hours, and sometimes days, to build complex parts. The part size is limited by the printing area of the machine. In addition, it may not be possible to produce the part in the desired material due to the very high melting point of some metals.
Sand casting
In metal foundries, patterns are used to make the mold that will be used to cast the metal part. A prototype pattern is made in the simplest and most cost-effective way, so that the part can be tested and adjusted if necessary. For this reason, the pattern is often used to make a sand mold as this is the cheapest and quickest mold to produce. From start to finish, a prototype can be made in 2 to 4 weeks using a loose wooden pattern.
A loose wooden pattern is made from wood by a pattern maker using techniques such as turning, tool, die making, and fine wood working. The pattern is manufactured in accordance with the prototype design with some tolerances built in for shrinkage, which occurs as the metal cools. Where the prototype design requires parts with backdraft, these parts are made as loose pieces of the pattern held in place by pins.
Molding sand is specially constituted with the right blend of components so that it has the characteristics needed for metal casting. It must hold its shape, not release too much moisture, and give a good quality finish. Sand is packed around the loose wooden pattern to form a cast, which can then be used to make the metal prototype.
Casting a metal prototype is a standard foundry process where metal is melted, composition is controlled and molten metal is poured into the mold. Once cooled, the mold is broken off and the metal prototype is ready for finishing.
Metal casting of a rapid prototype with a loose wooden pattern is popular due to the low cost of production, and the relative ease of adjusting the pattern and recasting if necessary. It is also possible to make the prototype out of the same material as the final product, thus cutting out further steps of development down the line. Manufacturers often find that the process to develop a prototype often becomes the method for final production with minor modifications.
Investment castingInvestment casting is also a metal foundry process, but uses a different technique to make the pattern for creating the mold. The first step is the creation of a wax pattern that matches the design for the prototype. Historically, wax patterns have been made with injection molding machines or wax presses, but new materials and the development of 3D printing have created an opportunity for investment casting patterns to be made more easily and quickly.
Once the pattern has been made, it is cased in ceramic material which takes on the shape of the pattern as it sets. The mold is then heated until the wax melts and flows out of the casting mold—hence its alternative name, lost wax casting. Standard foundry casting processes follow, where molten metal is poured into the cast. When the metal has cooled and solidified, the ceramic cast is broken off, leaving the metal prototype ready for finishing.
The advantages of this method of rapid prototyping are similar to those of the loose wooden pattern—with the added benefit of finer tolerances and finishes.
Fabricating metal prototypes
Stock metal materials include sheets, rods, tubing, bars, and wire. Any of these can be used as the raw materials to fabricate a metal prototype as a downstream secondary step, rather than through primary manufacturing such as casting or 3D printing.
For sheet metal prototype manufacturing, many different processes can be employed to fabricate a prototype. For example, the physical model could be flattened and laid out on metal sheet to use it as a template, then lasers or torches could be used to cut outlines and openings, and to mark bends. Presses could be used to bend the metal at the marked boundaries, and specialized welding equipment can be used to join parts together.
Workers weld prototype automotive fabrications
Rapid prototyping by welding fabrications allows for minor adjustments to be made to samples without significant time and cost
Tubing can be used for prototyping by processing it through a number of diverse operations to create a prototype part that matches the design:
Flaring – widening the opening at the end of a tube into a funnel shape
Swaging – reducing or increasing the diameter of the tubing
Dimpling – small deformations on the metal surface
Bending – creating shapes through inserting bends at defined points in the tubing
Flattening – using a press to compress the tubing
Piercing – creating holes in the material
Expanding – using heat and tools to open the diameter of the tubing
The main advantage of fabricating a metal prototype from stock materials is the time efficiency. Patterns or molds are not needed, and the raw materials are available off the shelf. The disadvantage is that some prototype designs will be too complex for standard manufacturing processes and therefore cannot be made with this technique.
XTJ es un fabricante OEM líder dedicado a ofrecer soluciones de fabricación integral desde prototipos hasta producción. Nos enorgullece ser una empresa certificada con ISO 9001 en gestión de calidad y estamos decididos a crear valor en cada relación con el cliente. Lo logramos mediante colaboración, innovación, mejoras en los procesos y una mano de obra excepcional.
Machining metal prototypes
End-mill machining tool is used to finish a metal prototype
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XTJ es un fabricante OEM líder dedicado a ofrecer soluciones de fabricación integral desde prototipos hasta producción. Nos enorgullece ser una empresa certificada con ISO 9001 en gestión de calidad y estamos decididos a crear valor en cada relación con el cliente. Lo logramos mediante colaboración, innovación, mejoras en los procesos y una mano de obra excepcional.
