烧结普通砖Lesson33 Just in Time Design
A dizzying array of choices is available to designers needing to output their CAD designs as physical prototypes. The question of which is best requires some careful consideration. Much depends on what the designer is trying to achieve with the prototype,whether it is a study of form--requiring some degree of high finish and detail-or function, requiring a more robust technique or a particular type of material.
The accuracy of many of the techniques listed below is within a margin of around 0.1 to 0.2 mm, but this tends to vary relative to 渔港之夜the direction of the slicing and size of models. (Designers should check with the vendor first if this is a major concern.) All rapid prototyping techniques are limited by the size of parts they can produce in one piece, but vendors can be asked to divide and conquer. They are very savvy at splitting a CAD model and rejoining the pieces to create very large parts.
The Web is a uful resource for keeping an eye on all of the continually changing techniques. Rapid prototyping is such a互联网创业平台 competitive industry that vendors are always impro
ving materials and process. Models now take a third of the cost and time that they did five years ago. As a conquence, design teams can now, in theory, make three times as many models, creating a more sophisticated and mature end product.
It is worth remembering that while it is easy to be romanced by all of this computer-aided design and virtual prototyping, the tried and tested foam model, generated in an afternoon from simple 2-D drawings, will often beat out its hi-tech sister in both schedule and cost Here' s an overview of the latest modeling techniques.
Rapid prototyping: the choices.
Selective Lar Sintering(SLS) DTM Corp. Austin, TX; 512-339-2922
Method: Us lar energy to melt layers of powdered nylon, polycarbonate or elastomer 5,000th of an inch (mils) thick to build up parts with 75 percent the properties of the normal polymer.
Us: The parts have a slightly granular look making them best suited to models needing
strength rather than looks. Good for金文和 medical applications.
Laminated Object Modeling(LOM)Helisys Inc., Torrance, CA; 310-891-0600
Method: Build up low-cost sheet materials, such as paper and plastic, into models.
Us: The main advantage is model size(up to 22'' x32 " x20" )and slightly lower cost. Parts are less accurate and have a thicker,stepped look.
Fud Deposition Modeling(FDM)Stratasys Inc., Eden Prairie, MN; 612-937-3000
Method: Weaves models from a thermoplastic thread ofABS or elastomer.
Us: Atechnique still in its infancy, FDM produces a coar 3-D fabric look unsuitable for anything aesthetic.
Ballistic Particle Manufacturing(BPM)BPM Technology, Greenville, SC; 803-297-7700
Method: us a nozzle to spray tiny molten particles of thermoplastic into 3-D models. The nozzle can deliver the material from any angle, which reduces the stepping effect.
Us: Holds promi for curvy shapes.
Lar Cutting Lasrcam, Menlo Park, CA, 650-324-2525
Method: Ud extensively for architectural models of plastic, paper and wood (not always considered a rapid prototyping technique)
Us: Any design that can be built up, kitlike, from 2-D CAD profiles can be larcut. A wide variety of thickness (up to 0.5 " )浅川一中 are possible. Highly cost-and speed-effective. Excellent for mocking up the sheet metal of a design, complete with intricate vent patterns, as well as for testing hinge and other complex dynamic mechanism ideas.
CNC Machining Checking your normal modelmaking or machinist vendors.公交车文
Method: Familiar to all as the best way of showing off organic surfaces, it has kept improving in schedule and cost to compete with the emerging rapid prototype industry.
Us: If you can afford a little more cost and time, CNC is still the best way to reprent s
mooth surfaces. As an added bonus,better plastics are ud in the process, so models will not warp in the car trunk, nor fall apart during ur tests.
Stereolithography(SLA) 3D systems, Valencia, CA; 805-295-5600
Method: The ever-handy and most popular modeling technique. Us light to photopolymerize and build up thin layers of special resins direct from digital data.
Us: Great for form and surface studies that check out CAD model progress, as well as for limited functional testing of detailed parts(injection molding, die casting, etc.). The direct transfer of data eliminates the chances of human error. Can produce parts in掠组词语 steps of between 3 and 5 mm, but the resins are brittle and thermally unstable.
