Summary

Rapid prototyping quickly verifies designs and reduces development time and cost. In today's rapidly changing marketplace, product development cycles have been compressed into weeks for what may have taken months or years in the past. Computer-Aided Design, or CAD, has revolutionized the way products are developed, and offers the designer a wide range of options to physically build parts and assemblies to validate form, fit and function. This article will discuss the use of CAD models in rapid prototyping to verify designs as it pertains to injection molding and die casting.

SLS, or "Selective Laser Sintering," is one of many additive fabrication techniques used in rapid prototyping today. SLS shows a lot of promise as it provides us with an opportunity to, not only, exceed in rapid prototyping, but also make advances in technology toward rapid manufacturing. The process uses a laser to fuse small particles into parts ideal for functional applications directly from 3D CAD data. The parts are created layer by layer using a wide scope of nylon, metal, and polymer powders. SLS shares many similarities with other additive technologies such as SLA, FDM and DMLS. The machine first reads the provided 3D CAD and then scans each cross-section before creating the first layer. After the first layer has been created, the tray, on which the parts are sintered, is lowered by one layer. The next layer of material is then added and the process is repeated layer by layer until the part is created.

Stereolithography, or STL, is an additive technology which uses a UV laser to create parts from a UV curable liquid within an SLA, or Stereolithography Apparatus, system.

For a part to be created using STL, a 3D model of the desired part must first be created, after which the 3D data is seperated into a group of 2d layers of the entire part. These layers typically range from 0.10mm to 0.050mm in thickness (although a resolution of 0.050mm in thickness is usually used) and this group layers is called called "slice data." The slice data is then fed into the SLA system and the actual fabrication process begins. The platform is first lowered into the vat of clear, liquid plastic photopolymer. The polymer used is sensitive to ultraviolet light, allowing the polymer to solidify when it is exposed to the light provided by the UV laser and the materials used in this process range from soft durable plastic to hard plastics. The ultraviolet laser traces and selectively solidifies the first layer within the resin onto the platform, which is currently submerged one layer under the resin.

After the first layer has been created, the following layers are added to the first layer while adhering to the previous layer. A resin-filled "re-coater" blade is swept across the top the previous layer removing the uncured polymer while re-coating it with fresh material. The platform is then lowered gradually submerging the platform along with the base of the part (and the part itself, or rather the section of the part, which has been already created layer by layer) deeper under the resin. This process repeats itself until the last layer has been created and the part is completed. This is a relatively quick process. Up to about two minutes is needed for each layer to be created whereas an entire run might take six to 12 hours.

As with all modern scientific and technological endeavors, computers, software and internet tools play an increasingly important role. As well as the typical business application software there are a number of computer aided applications specifically for engineering. Computers can be used to generate models of fundamental physical processes, which can be solved using numerical methods.

A number of decisions have to be made which directly affect the product's overall and total cost. One of the first decisions that has to be made deals with the initial design. At one time, engineers had to convert from manual design and drafting on a drawing board to 2D CAD. Now we are starting to see a new shift in the field cad design. Within the past decade, the engineering, design and drafting world has been experiencing a shift from 2d to 3d cad. Many inventors and companies still use 2d drawings and are starting to realize the benefit of skipping the 2d step and starting off with a 3d design because 3d modeling can save time and money as well as improve customer relations. This article will explain why inventors should take 3d cad into strong consideration.

These types of transitions occur from time to time and are completely normal. Many engineers will argue with these facts because only about 50% of the engineers out there use 3d modeling software, but the fact still remains that 3d cad models can save time and money in the long run and there are many facts that prove that the assumption that the use of 2d cad drawings is inexpensive is simply a myth.

The truth is that making 2d drawings is fast and easy, but the output is still a 2D drawing, which does not readily work with downstream systems like purchasing and manufacturing. In some cases 2d drawings are sufficient but 90% of the time they are not. In prototyping, for example, a 3d model has to be made because most of the prototyping machines require 3d data. In fact, the majority of the machines used to manufacture parts need 3d cad files and do not read 2d cad drawings because 2d drawings do not contain all information needed to develop a three-dimensional product. http://cadmodels.info/