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FEATURE STORY
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Once limited to large-scale production, CAD/CAM is now within the reach of individual studio artists and offers new possibilities in setting one-of-a-kind stones.
The Attaways designed this pendant around an original shield-cut aquamarine. They scanned the stone, then traced the image using SolidWorks software. They then sent the design to an associate who "printed" and cast the 14K gold part for the finished piece. (Left - computer generated rendering; Right - finished piece). |
Imagine a system where a few mouse clicks generate views of stones with exact dimensions and price. More mouse clicks will reveal a menu of ring designs from different suppliers that will allow the customer to select from a long list of preworked designs. By dragging and dropping different settings and stones, a customer builds a ring using a computer. As the design unfolds, the jewelry piece can be rotated and viewed from any angle, using 3D glasses, with real-time ray-tracing that simulates the flash of the stones. At the end of this process, a machine simply prints out a finished wax model ready for burnout. Maybe a machine will "print" the finished gold jewelry with the stones already in the setting. You don't think such a thing could happen in our lifetimes? Think again. Much of this is happening now! In the past two years, we've learned a great deal about the use of computers in jewelry manufacturing. It started in October of 1999, when we visited Steve's friend Mark Isbell, owner of Mark's Jewelry, located in Homewood, Alabama. Mark and his brother, Anthony, introduced us to a new jewelry manufacturing technique that uses a design generated with a computer to create wax patterns. The Isbell brothers use a computer-controlled, three-axis, wax-milling machine that allows them to rapidly create wax patterns. In the past, we have shown Mark and his brothers our oddly shaped stones, only to have them tell us how difficult and costly it would be to manufacture custom jewelry settings for them. Like most jewelers, they looked for stones cut in calibrated sizes to allow economy in manufacturing. To our surprise, they were now more interested in our uniquely shaped stones because they had an economical way of making the settings for them. Mark and his brother showed us a system that uses sharp wax bits to mill designs from a block of wax. The accuracy of the milling was stunning. They could trace the outline of a stone by laying their stones on a flatbed scanner. They then used this image to build a computer model that can be used to cut a custom wax with prongs and seats tailor-made for stones. The wax patterns generated using this method fit their stones like a glove. After seeing what the Isbell brothers could do, we were determined to find a way to send them designs for which they could create wax patterns for our one-of-a-kind gemstones. We used the Internet to search for information on this type of manufacturing process. The results of our search and experiments are described below. JEWELRY FROM RAPID PROTOTYPING.
Computer-aided manufacturing is divided into two camps. One camp uses milling machines that remove material to create parts, and the other camp creates parts in processes that add material layer by layer. The milling process is called computer numeric control (CNC) milling; the building of parts layer by layer is called rapid prototyping (RP). A rapid prototyping machine can automatically construct physical models from computer-aided design data. These machines are "three dimensional printers" that allow designers to quickly create three-dimensional designs, rather than just two-dimensional pictures. In this section, we will review the different types of rapid prototyping processes in use today. Numerically Controlled Milling Machines. Computer numerically controlled (CNC) milling machines have been around for a long time. Industry has used CNC milling machines for complex manufacturing of items like jet engines and car parts. From the jewelry perspective, the engraving industry has been the leader in CNC milling. Engravers have focused on developing software for making dies and stamps. By concentrating on coins, metals, and cameos, they mastered the use of very accurate milling in both wax and metals. The drawback for milling machines is that they are not fully three-dimensional, and the method doesn't produce a true 3D product. Instead, it produces what is called "2-1/2D" parts. Parts are cut using a high-speed drill that moves up and down, while the part moves in the plane below. Without rotating the part, undercuts are not possible, meaning that each part must be projected from a 2D surface. The design process is complex because of the limitations of bit size and cutting reach. Even though CNC manufacturing is limited, there are a lot of cool things that can be made from this process. Anthony Isbell's milling machine had an attachment for a ring that allowed some undercuts. Even though most parts he made did not have undercuts, he showed us some very complex parts that looked almost 3D. Over the last few years, several new methods have been patented that bypass many of the problems with CNC. These methods directly print or form a pattern using innovative high-tech methods. Stereolithography. The first method of rapid prototyping, patented in 1986, was called stereolithography. Stereolithography forms a model from a liquid, photosensitive polymer that solidifies when exposed to ultraviolet light. The model is built just below the surface of a vat of liquid resin, using a laser that traces out a layer in the resin. The laser solidifies a thin section of the resin, while leaving unexposed areas liquid. After a layer has cured, the model is lowered to have a new layer of liquid exposed and added to the last layer. Layer by layer, a part is printed. This method of manufacturing works great for larger parts; however, the viscosity of the resin limits the feature size and can cause a rough surface finish. In addition, free-standing parts must be supported with areas that need to be cut away after the resin is drained from the tank. The manufacturing industry has used this technique to make plastic models that are then used to cast complex items, like automobile engine blocks and railroad wheels. Laminated Object Manufacturing. Imagine building a model by cutting out paper cross sections and gluing them together. Laminated object manufacturing does this by cutting layers of adhesive-coated sheet material and bonding them together to form a part. The technique uses a paper laminated with heat-activated glue and rolled up on spools. A focused laser cuts the outline of the first layer into the paper. This process adds layer after layer of paper as needed to build the part. The advantage of rapid prototyping using laminated paper is that it is cheap. Unfortunately, the models are made of paper, which limits their size. While this technique helped to revolutionize the industry by providing a cheap manufacturing process, it does not work well for making small jewelry parts. Selective Laser Sintering. The selective laser sintering technique uses a laser beam to selectively fuse powdered materials into a solid part. It works the same way as stereolithography with one exception: instead of using a liquid, a powder is used to build up the part layer by layer. Parts are built upon a platform that sits just below the surface in a bin of the heat-fusible powder. A laser traces the first layer and sinters a thin layer of powder together. The next layer of powder is added, and the process is repeated until the part is complete. Unbound powder remains to support the part. The parts that we have seen manufactured from this technique show a smooth surface, and the parts can then be burnt out for casting. This technique works great for very large casts. The feature size for this process is limited by the melting of the powder. While this method could be used for some jewelry parts, more resolution is needed. Fused Deposition Modeling. The technique of fused deposition modeling uses what we call "glue gun" manufacturing. Some wax carvers may have seen or have used the Matt wax gun. We purchased one of these years ago and have used it to squeeze a bead of wax onto a ring mandrel. Free-form rings with swirls may be made this way. In the fused deposition rapid prototype technique, filaments of heated thermoplastic are extruded from a tip that moves in an x-y plane. Basically, it is a Matt wax gun on steroids. Under computer control, the extrusion head deposits very thin beads of material onto the building platform to form layers. While we haven't seen any actual parts built with this technique, the photos of parts we have seen indicate that the resolution is not high enough for jewelry parts. The technique also has a drawback in that it requires supports for freestanding parts. Ink-Jet Printing. The best technique that we have found for making small jewelry parts is based on ink-jet 3D printing. Ink-jet 3D printing refers to an entire class of manufacturing that employs the same technology found in ink-jet printers. If you've shopped for color computer printers, then you have seen this amazing technology in action. It works by using a small nozzle that sprays a small drop of ink onto a sheet of paper. It is called an ink jet because a fluid jet is formed as the ink is sprayed out of the print head. The first "ink-jet" rapid prototyping method was developed at the Massachusetts Institute of Technology, where models were built for parts by spraying a binding agent on powdered material. The "ink" is actually a starch that binds to the powder. An ink-jet printing head selectively "prints" binder to fuse the powder together in the desired areas. Unbound powder remains to support the part. As the platform is lowered, more powder is added and leveled, and the process is repeated. When finished, the part can be removed from the unbound powder and then sintered. This technique has been used to produce ceramic molds for investment casting. Many companies are currently testing ways of extending this method to bind powder metal that can then be sintered to produce metal tools and other products. The big advantage of using ink-jet technology is that it is an extension of an existing technology. By simply modifying a printer, a new manufacturing technique is born. The existing software for driving a printer could be modified to drive the new process. Ink-jet printing is also very accurate. As you know, most printers print at 600 dots per inch. That means that a period, ".", is made up of about 10 to 40 dots of ink. Even so, capillary action on the binder means that it will be drawn into the powder and limit the accuracy of this method.
Solidscape's ModelMaker II. The latest advance in ink-jet manufacturing is the Solidscape's ModelMaker II machine (www.solid-scape.com). This new high-tech tool allows a design to be created in a solid model (CAD) and printed in 3D with wax (CAM). Sanders Prototype of Merrimack, New Hampshire, developed a rapid prototype method that uses heated wax in an ink-jet printer head. The machine uses the ink-jet printer head to deposit thin layers of molten wax. By slowly repeating and depositing these layers, it can build up a wax pattern, even one with complicated undulations and undercuts. The machine actually uses two different types of wax. One jet dispenses a green wax to make the model, while the other jet prints a red wax for supports. The waxes are different in that the red wax can be dissolved. The lost-wax casting process is then used to convert this wax pattern into an item of jewelry. Even though a very fine layer of wax is sprayed onto each layer, the layers, as they build up, can become uneven. After each layer, a cutting tool mills the top surface to a uniform height. The method is extremely accurate, allowing the machines to be used in the jewelry industry. Remarkably enough, feature sizes of 0.2 mm with an accuracy of 0.01 mm are possible. Jewelry designers are not limited by ink-jet technology. In fact, the ModelMaker II resolution is often finer than what the typical jewelry casting technology can reproduce. The drawback for the "wax-jet" method is speed. By using very thin layers, the ModelMaker II can produce smooth wax surfaces, but each layer takes time to print and dry. While each layer prints fast, the number of layers needed to build a complex part can require a long time to print. If thicker layers are used, then the process is faster, but the parts are not as smooth. The ModelMaker II jewelry users typically produce between four and six rings in a 24-hour period at a 0.0015-inch layer thickness (medium resolution mode).
The ModelMaker II machine is currently too expensive for us to buy one for the garage (they now cost about $70,000 each), but we found a jeweler/machinist in Florida who will print and even cast the parts for us. Depending upon the resolution, parts can be "printed" in wax for about $10-15 per millimeter of height. This new tool is being used by several of the big name jewelry manufacturers, but they are being very secretive about their use of this technology. We were fortunate to meet the western regional sales manager for Sanders Prototype at this February's Tucson gem shows. He told us that over 200 machines are currently in use in the U.S. We feel that the Solidscape machine is currently one of the best for making 3D wax parts. Unlike the milling approach, where the designer has to constantly think about the manufacturing process during the design, the Solidscape machine gives the designer the freedom to design about anything that can be imagined without regard for the manufacturing process. It is more accurate than the powder binding approach, and the wax that is produced can be added to other wax parts or be modified as needed. The main drawback of the Solidscape machine is that its cost remains very high. Also, it is not easy to maintain. As you can imagine, mixing hot wax with electronic parts with small nozzles can be a finicky operation. The law of high-tech competition will eventually drive down the cost and drive up the ease of use. Multi-Jet Modeling. The multi-jet modeling process is similar to ink-jet printing. A reservoir of molten wax is siphon-fed to a multi-jet head. The ThermoJet made by 3D Systems in Valencia, California (www.3dsystems.com) uses over 300 jets. Parts are built by printing consecutive layers of wax in the shape of the part's cross-section. A multi-jet head traverses the print area with the jets turned on and off where needed. The print head has a resolution of 300 dots per inch. Although the ThermoJet and Solidscape machines sound very similar, the ThermoJet builds its parts in a very different way from the Solidscape machine. The Solidscape machine uses only two wax jets, moving each jet to trace out a line and lay down wax much like an ink plotter moves a pen as it plots. The ThermoJet uses lots of jets in an array and moves the print head back and forth with the jets' heads producing a matrix of wax dots. The second big difference between the ThermoJet and Solidscape process is that the while the Solidscape machine uses a support wax that is dissolved, the ThermoJet uses only one wax. This means that the supporting wax must be removed before the part is cast. The support structure consists of fine columns of the build material that reach from the bottom and rise to any overhanging surface. For most parts, removal of the support columns is easy, but support removal is the biggest drawback of this system. The advantage of the ThermoJet process is its speed. While the Solidscape machine may take as much as a day to print a ring, the ThermoJet machine boasts printing 30 rings in four hours. The nice thing about the Internet is that you do not have to own a Solidscape or a ThermoJet machine to make jewelry. We have found several service bureaus that will print parts. We simply e-mail the design for the part, and they ship the part to us. We found one excellent service that will cast our parts in addition to printing them. COMPUTER-AIDED DESIGN SOFTWARE. Different sources of software currently exist for creating models for three-dimensional designs. The broad classes of software include engineering design software, animation software, and jewelry design software. Engineering Design Software. The field of engineering software is well established, but is currently undergoing rapid change. Software packages like Pro/E and AutoCad have been around for more than 10 years and are used by many large industrial plants. Pro/E and AutoCad are very powerful, but some find that they are very hard to use. The big drawback for these large packages is their cost.
One advantage of engineering software is that it typically allows for accurate dimensioning, an essential feature for designing with faceted gemstones. A drawback is that complex surface designs are not easy to do. Some of the most popular software for engineering type applications are listed below: • Pro/E (www.ptc.com) Animation Software. Recent trends in animation for movies have created a variety of software that can be used for three-dimensional designs. The need for creating realistic three-dimensional Web pages is also driving the development of three-dimensional software. While truly unique shapes can be created from this type of software, they often do not lend themselves to manufacturing, nor to the exact dimensioning needed for jewelry design. The advantage of these software packages is that they are usually very economical. The market for animation software is much larger than the market for engineering software; as a result, animation software costs a lot less than engineering software. Some examples of "animation" software that have been transformed into CAD packages are: • Rhinoceros (www.rhino3d.com) Jewelry Design Software. There are several CAD products designed specifically for the jewelry market, most of which were developed for the engraving industry. Usually, these products are not truly three-dimensional packages, instead working by projecting a two-dimensional image into the third direction. This limits their ability to represent undercuts. Before the revolution in 3D printing, the nature of the machining process limited the parts that could be machined to those that could be constructed with three-axis milling machines. The 2-1/2D design was not that much of a limiting factor. One advantage of 2-1/2D is that very complex surfaces can be created without much computer power. For example, a complex Celtic weave or a raised texture can be easily mapped onto a 2-1/2D surface. Rendering the same pattern in a true 3D software package often requires enormous computer power and computer memory. Some of the big markets for engraving are corporate logos, stamps for punching designs into leather, cookie cutters, candy molds, embossing plates, special coins, commemorative medals, and cameos. You may have seen engraving software marketed at the Tucson gem and mineral shows. For example, Graphitech's product was displayed and demonstrated during Rio Grande's "Catalog in Motion" show, and the Model Master's product, ArtCAM, was on display at the AGTA/MJSA show. Both ArtCAM and Cimagrafi are targeted toward the engraving industry, as they can generate complicated raised images. If not done well or with enough detail in the rendering, the parts produced by these packages can look like Jell-O(TM) molds. If done well, they have the advantage of being able to create a more detailed surface than can be typically created using SolidWorks or IronCad. Some examples of 2-1/2D or engraving software are: • Type3 (www.type3.com) Most engraving software is designed to drive only specific types of milling machines. Most of these can create files that can be used by the Sanders Prototype machine. JewelCAD is a 3D, free-form, surface-based modeler that is designed specifically for jewelry. See:
A trend that we are seeing is the wrapping of a jewelry design interface around CAD software. For example, Digital Goldsmith Matrix from GemVision (www.gemvision.com) uses Rhinoceros as the modeling engine. Their product includes a parts library and has a jewelry-friendly interface that makes the software more compatible. Creating a good image. An important part of the design process is creating a realistic-looking picture of finished jewelry. A realistic image is important, because it enhances the communication for custom designs between the jewelry designer and the customer. Be careful not to confuse imaging software with 3D design software. Several software packages allow the user to design by working with photos. These packages are fast at overlaying and merging photos to help communicate a design. They do not, however, provide a design that can be manufactured using rapid prototyping processes. Rendering is the process of creating a photo-realistic image from the solid model. Because this is a computer-intensive process, creating a realistic image from a solid model is usually a separate step. Rendering an image from a solid model is an art in itself. One has to select the lighting, view the angle, and check the background. Some programs provide simple shading, while others will trace the rays of light from their source through the stone to give a very real image. For the better packages, it can be hard to tell if the image is from a real part or just a computer part. Most customers will be delighted with a good photo of their prospective designs. Modern computers allow us to go a step further. Imagine the possibilities when you can show a movie of a prospective design. SolidWorks has Web-based tools that allow designs to be e-mailed and viewed in three dimensions. This tool allows the fully 3D design to be reviewed. These tools also permit cross-country collaborations. Selecting a Software Tool. We have tried several different software packages for computer-aided design. Advantages and disadvantages accompany each software package. Often, the most general software will be the most difficult to use. The challenge is to find software that is capable, yet easy to use. Most of the time, the most capable and easy-to-use software is the most expensive. However, some of the more expensive software packages are all but impossible to use. There are very inexpensive 3D software options that can be used to gain experience. Older versions of Truespace, for example, are available for under $100. Out of the box, these tools may seem useless for jewelry design. However, in a presentation at the AGTA show in Tucson, Randy Hays of Jewelscapes Imaging showed how this simple package can be used very effectively if you have a parts library. For the most part, software packages are not very interchangeable. We tried to create surfaces using the engraving software and import them into the engineering software. While this was possible, it was not practical. Often the mathematical methods used to construct the model differ greatly from program to program. While we would like to have one software package that does it all, we have found that each software package excels in one or two areas. For example, one feature that is well done in SolidWorks is the ability to parametize designs. Designing a ring so that the ring size can be input as a parameter is easy in SolidWorks. Other programs require you to totally redo the design for each size ring. While SolidWorks allows engineering precision, it does not allow for easy creation of swirls and loops. While these can be created in SolidWorks, it may take 10 to 20 steps. The same process may take only a few steps for a program like JewelCAD, which was designed to do this type of thing from the start. Trying to create a cameo design in either SolidWorks or JewelCAD is next to impossible. However, ARTCAM and Semigraphi specialize in software for cameos. For most cases, learning to drive the software can take some time. CAD-CAM is quickly becoming a part of the jeweler's formal education. For example, the Gemological Institute of America is currently offering CAD-CAM training. General CAD-CAM training is also taught at community colleges across the country. In addition, many of the more expensive CAD packages offer their own training options. Most software companies offer demo versions that can be downloaded or ordered from the Web for free. Is it art? Most software packages are very powerful tools that allow you to create designs more quickly and with more precision than by hand carving the wax. However, even the most powerful manufacturing tool allows you to create a design that only you will like. Creating a design with an artistic intent that is liked by all still remains a labor of love. Remember that the invention of the camera did not replace oil paintings, and the invention of the video camera did not create millions of great movies. CAD/CAM programs that allow the manufacture of jewelry designs will not replace the artist. As we have learned more, our designs have increased in complexity. With these new tools, we can render jewelry images and make the seats for the stone that correctly correspond to the dimensions of the gemstone that we want to set. Length, width, and depth are all taken into account, as well as the pavilion angles that were used in faceting the stone. This information allows us to make such an accurate seat for the stone that it can reduce the setting time by a factor of ten. Also, tapered settings for small diamond accents or other melee allow these stones to slip in and be set without adjusting the metal very much. Designing unique gallery work in the settings for large stones is now fun. The real problem is that it is now too easy to change a design again and again because the possibilities of design exploration seem endless. If you would like to learn more about rapid prototyping, then see the Web sites listed above. You can also find more information on the Web sites: www.Sculptor.Org/Technology/rapidpro.htm; www.cc.utah.edu/~asn8200/rapid.html; and home.att.net/~castleisland. Scanning 3D Images. 3D Web pages are creating a demand for 3D images. We are already starting to see libraries of 3D images on the Web; in the near future, almost anything imaginable will be available on the Web as 3D clip art. The geometry of animals, cars, plants, and people are already available on the Internet and can be purchased on CDS. There are also tools that help create lifelike 3D images. Several companies are currently making 3D scanners. With these tools, a part can be sculpted in clay and then scanned or probed to create a surface with the computer. The idea of scanning a person's face or an object will mean that customers will be able to create very personal designs that include grandchildren and pets or that celebrate special life events. THE RAMIFICATIONS of rapid prototyping in the jewelry industry are many. Rapid prototyping allows the creation of specialty designs for those uniquely faceted gemstones that have become a trademark of the American faceter. For faceters, it means that there will be a higher demand for their uniquely cut gemstones. The expense of designing jewelry for non-calibrated, unusually shaped gemstones could drop in price, and rendering those designed pieces may become much easier to accomplish. Many gem cutters are not jewelers. With the advent of design software, gem cutters and gem carvers will now be able to design jewelry and better communicate those designs to goldsmiths. Will this new manufacturing technique be the end of the craftsman? We do not think so. Even though mass marketing of wax-injected and cast parts have already created catalogs of pre-made "easy settings," there are design limitations with these. We know that many parts cannot be cast, because pieces are too thin or fine details cannot be incorporated in the wax. Designing and manufacturing jewelry with rapid-prototyping are new and powerful tools for the jeweler's tool box. Nevertheless, jewelry design still needs an artist's touch to make it special. | ||||||||||||||
Stephen and Nancy Attaway have been running High Country Gems, a custom jewelry shop, since 1989. Stephen holds a Ph.D. in computational mechanics and is a Distinguished Member of Sandia National Laboratories' technical staff; Nancy is the editor of The New Mexico Facetor, the publication of the New Mexico Faceters Guild. Visit their Web site at www.attawaygems.com, or you can e-mail them: Steve@attawaygems.com; Nancy@attawaygems.com.
For a more step-by-step analysis of the creation of a piece of jewelry, click here to read "Technology In Practice" | Click here to read more notes about the programs from the Attaways
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