Optical Fabrication, a brief description

Stereolithography is an additive manufacturing process which employs a vat of liquid ultraviolet curable photopolymer "resin" and an ultraviolet laser to build parts' layers one at a time. For each layer, the laser beam traces a cross-section of the part pattern on the surface of the liquid resin. Exposure to the ultraviolet laser light cures and solidifies the pattern traced on the resin and joins it to the layer below. After the pattern has been traced, the SLA's elevator platform descends by a distance equal to the thickness of a single layer, typically 0.05 mm to 0.15 mm (0.002" to 0.006").
Then, a resin-filled blade sweeps across the cross section of the part, re-coating it with fresh material. On this new liquid surface, the subsequent layer pattern is traced, joining the previous layer. A complete 3-D part is formed by this process. After being built, parts are immersed in a chemical bath in order to be cleaned of excess resin and are subsequently cured in an ultraviolet oven. Stereolithography requires the use of supporting structures which serve to attach the part to the elevator platform, prevent deflection due to gravity and hold the cross sections in place so that they resist lateral pressure from the re-coater blade. Supports are generated automatically during the preparation of 3D Computer Aided Design models for use on the stereolithography machine, although they may be manipulated manually. Supports must be removed from the finished product manually, unlike in other, less costly, rapid prototyping technologies.

One of the advantages of stereolithography is its speed; functional parts can be manufactured as shortly as within a day. The length of time it takes to produce one particular part depends on the size and complexity of the project and can last from a few hours to more than a day. Most stereolithography machines can produce parts with a maximum size of approximately 50×50×60 cm (20"×20"×24") and some, such as the Mammoth stereolithography machine (which has a build platform of 210×70×80 cm),[8] are capable of producing single parts of more than 2 m in length. Prototypes made by stereolithography are strong enough to be machined and can be used as master patterns for injection molding, thermoforming, blow molding, and various metal casting processes. Although stereolithography can produce a wide variety of shapes, it is often expensive; the cost of photo-curable resin ranges from $80 to $210 per liter, and the cost of stereolithography machines ranges from $100,000 to more than $500,000. However, recent interest and technological advances are bringing the cost of stereolithography machines down in price exponentially.

The term “stereolithography” was coined in 1986 by Charles (Chuck) W. Hull,who patented it as a method and apparatus for making solid objects by successively "printing" thin layers of the ultraviolet curable material one on top of the other. Hull's patent described a concentrated beam of ultraviolet light focused onto the surface of a vat filled with liquid photopolymer. The light beam draws the object onto the surface of the liquid layer by layer, and using polymerization or cross-linking to create a solid, a complex process which requires automation. In 1986, Hull founded the first company to generalize and commercialize this procedure, 3D Systems Inc, which is currently based in Rock Hill, SC. More recently, attempts have been made to construct mathematical models of the stereolithography process and design algorithms to determine whether a proposed object may be constructed by the process.

On September 26, 2012, Formlabs (a company formed by former members of the MIT media lab) released the Form 1 3D printer, which is currently the cheapest 3D printer using the stereolithography process on the market. The printer includes a build envelope of 125 x 125 x 165 mm and a resolution of 300 microns. Formlabs also developed software that takes STL models and allows users to generate "smart" support structures that allow for overhangs and more complex geometries. The kit is currently being sold through Kickstarter for $2299. Depending on the success of the kick-start venture the Form 1 3D printer will be in competition with Fused deposition modelling (FDM), reprap and Makerbot printers.

In comparison with FDM, optical fabrication offers smoother surfaces and finer printing resolution within its print layers. The main disadvantage is that the print material is not interchangeable. While reprap uses a ABS, Polylactic acid with high stiffness properties, the Form 1 printer has a liquid based ultraviolet curable photopolymer "resin". Also the cost of photo-curable resin ranges from $80 to $210 per liter, the main question will be cost over quality. In future there might be two systems leading the manufacturing revolution of 3D printing, but for now the well established fused deposit model is winning, because its simply cheaper.

     

3D Printing file share your illegal weapon downloads

In a ever changing world the use of 3D printers may increase in numbers, Rep rap machines have been around since 2007, their ugly designs of miniature scaffolds without the buildings have been exclusive to Boffins, engineering students and nerds. Though intentionally open sourced the complex range of components and software has been exclusive, for people who can under stand this level of mechanical, electronic and software engineering.

At the heart of the of RepRap is a thermoplastic extruder, early attempts at controlling the plastic flow to the extruder was to us a Dc motor which proved inaccurate. The stepper motor allowed precision timing for the drive assembly to give the right amount of plastic to the area for printing. The whole complex operation requires full knowledge of X,Y and Z axis. RepRap's electronics based on the popular Arduino mini micro processor board platform. with additional boards to control the stepper motors. The current version uses an Arduino derived Sanguino motherboard, this architecture allows expansion to additional controls.

There are many different versions 3D printer Cubify came to light at CES 2012. Also Makerbot, which is similar to the Darwin or Mendal models of RepRap designs. Though Makerbot uses laser cut milled parts  that encases the printer into a more acceptable appearance. Makerbot's website, sells small accessories and electronic kits as well as replacement parts and printers fully assembled. This seems limited as the number of makerbot projects listed are 5 in total. Compared to Cubify's website which has a small library of files to download similar to itunes store, where each item has a small fee. the website encourages a small community to design their own products to add to the library.

Despite the online community of RepRap and Cubify's efforts of its 3D printing library, there seems to little in the way of obtaining 3D designs to download and print. Until recently Pirate bay has been a file sharing company that allows the simple sharing of mp3 and movie files, which have been controversial due to the copyright restrictions of music and film studios. Pirate bay has now added a new torrent category Physibles, which is the 3D printer plans or possibly the STL files of any virtual model to be made real by a printer. 

This will open up a new area of file sharing physical items such as toys machine parts or other peoples designs. Hopefully the use of 3D printing will eliminate the need to buy most toys from the shops, or cheap items from china. In a ideal world this will be the end of expensive packaging for toys and simple gadget products too.

There is a danger to this type of illegal downloads as it will be very easy to manufacture 3D prints of gun parts to be made as a untraceable weapon. "Haveblue" documented in a blog post that using a Stratasys 3D printer to craft the parts to a .22 pistol and fired 200 rounds with it. He also tried to assemble parts for a .223 AR-15 rile which didn't work, though it was down to the compatibility of actual gun parts and the lower receiver 3D print.

3D printing has yet to be popular.  Sales have increased and will eventually lower in price, which will probably turn the manufacturing industry on its head. Though 3D prints are not easily available, people will be turning to the internet, Pirate bay in particular for free designs. Examples in 3D print designs include clothing, shoes, toys, musical instruments and now lethal Guns. Considering that the possibilities of 3D printing can be limitless. There is a slight possibility that this new technology will be used for evil purposes.