This technical information has been contributed by
3Axis Development Inc.
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Rapid Prototyping and Rapid Manufacturing Provide More Options for Precision Parts

A Variety of Processes and Materials Are Available for Specific Application Requirements

Prototyping was once not very rapid, but indeed, a very time-consuming process to produce a handful of parts. With the advent of rapid prototyping (RP) in the early '90s, demonstration parts could be made via stereolithography in a matter of days, instead of weeks or months. One clearing house for a large group of RP companies is helping define the relatively new industry in the 21st century. The company, 3 Axis Development Co., headquartered in Boynton Beach, Florida, offers all five of the most-used RP processes, as well as a large array of rapid manufacturing (RM) processes.

"Many of the companies that are jumping into rapid prototyping and rapid manufacturing are seeing quantum advances in their ability to get into the marketplace very quickly," states Charles Koch, the president of 3 Axis Development Co. "This is especially true in the medical industry, where it's important to use actual material, high-precision metal prototypes. It's letting test labs and doctors do cadaver studies in days instead of weeks. High-precision, smooth finish medical tools are possible with these RP processes. For instance, a lot of companies that produce medical implants don't even know that processes like direct metal laser sintering are even available."

3 Axis is actually a consortium of many RP and RM companies grouped together to assist OEMs and inventors and parts manufacturers with all manner of prototypes. The company's president says that the company offers one-stop-shop resourcing for clients that need anywhere from one to 100 parts very quickly.

"People come to us for their low-volume part needs, because it's hard to find someone that will do one, 10, 50, or 100 parts," says Koch. "This is really our niche, and our strength is the fact that we have so many RP and RM services under one roof. For instance, we've been able to put together all the molded plastics and metal casting-to-sheet metal processes, but for low volumes. The only thing we don't offer are metal stampings."

Several Options for Rapid Prototyping

The five basic RP processes that 3 Axis provides are stereolithography (SLA®), Selective Laser Sintering (SLS®), Fused Deposition Modeling (FD^TM), PolyJet Matri^TM printing (PMP), and Direct Metal Laser Sintering (DMLS). It is with these five processes that the companies in the group are able to make prototypes and bridge tooling for almost every manufacturing process available. This inexpensive plastic and metal tooling initiates rapid manufacturing that could eventually lead into high-volume production for castings, injection molded parts, vacuum formed parts, and even machined and fabricated parts.

"In the castings process, for example, we produce rapid investment casting patterns utilizing the CastFor^TM material from the selective laser sintering process," Koch explains. "What we are actually doing is producing simulated wax patterns. At one company, they run six machines, 24 hours per day doing these prototype wax patterns. In the same facility, we also have a full wax tooling setup. In the investment casting area, they have machines that do the pattern work, and then they do the wax tools. We can do a prototype investment casting in almost any metal, including stainless steel, aluminum, carbon steel, and even Monel and Hastalloy, in seven to 10 days." In addition, 3 Axis offers the plaster mold simulated die casting process utilizing SLA models to create tools that are used to produce aluminum and zinc castings.

The master pattern for some of these tooling applications, says Koch, is usually made from the SLA or FDM process. He says that companies are even using SLA cores and cavities for injection molding using nano-tool SLA resins. "They are able to grow the pattern with a high-resolution SLA master build," Koch continues. "In doing so, they have a core and cavity that is almost as accurate as if it were machined. And if it's a low-volume tool with a straight pull, they can make injection mold parts right out of that tool."

3 Axis has reportedly been successful in finding the right process and the right manufacturer for its clients because of its knowledge of the materials and processes involved in RP and RM. Quite often, people will merely go to the Internet to order prototype parts. In some cases, they end up with no definitive information about the materials and processes for a particular application.

"We ask them questions, like 'What are you trying to make with these prototypes?' Koch says. "In doing so, they'll tell us they want to produce it with SLA, and we find out that with the quality they want, they need to do it with SLS. And they don't know they can get a fast-turnaround investment casting. So part of our added value is we analyze the project in relation to prototyping and short run production, and we point them in the right direction on options that they might not even be aware of."

Most clients, especially new ones, are astounded at the high quality obtainable these days with rapid prototyping. The clearing house has one particular client that manufactures gun prototypes. "He used our DMLS process and said he couldn't believe we were able to give him precision threading on the parts," Koch insisted. "He said they were like machined parts without the machining. In another example with SLS, one of our companies made some non-structural replacement parts for the aviation industry. The cost to make the replacement tooling would be prohibitive with traditional metal tooling. So they've been able to prove that our parts work well in a non-load environment."

The rapid prototyping and rapid manufacturing processes are intertwined and keep changing, and the choices that are available for clients keep growing. "The Direct Metal Laser Sintering process is a full melt, powdered metal process, where a laser cures a high grain material into a solid model," according to Koch. "We have three materials that we use, including direct metal 20, 17-4 stainless steel, and cobalt-chrome. In the DMLS process, we are very accurate with small parts to +/- 0.002, and, with larger parts, tolerances can be greater. This process basically gives you a production-quality metal part."

The PolyJet Matrix^TM process from Objet Geometries is a 3D printing process, similar to using an inkjet printer but spraying resins and other materials--about eight types--instead of ink in multiple layers. With the Objet Connex 500, the process uses two materials and mixes them on the fly to create up to eight new "Digital Materials" on a single part. The process, which allows for a total of 29 different material options, can print in a rubber type of material, as well as a flexible silicone-like material. And large parts are possible with this process. "The tray size is 19 inches x 15 inches x 8 inches, and it can make layers down to 16 microns thick," says Koch. "With the Connex machine, we can print very smooth, durable surfaces, good details, and can blend two different materials, a hard and a soft material. In SLA, the Viper^TM Pro machines (from 3D Systems) can produce very small articulated medical parts up to very large 29-inch x 25-inch x 20-inch units. We also have this large format capability in the SLS machines, where we can make nylon-based materials."

Rapid Prototyping Processes Offer Multitude of Benefits

Koch explains that SLA is a very good process for making form, fit, and function models, and also for creating certain tool patterns. Selective laser sintering uses nylon-based materials, and is a more accurate, real world material, where you can make prototypes, or in some applications, real parts in a variety of materials, like glass-filled nylon. Fused Deposition Modeling (FDM^TM), developed by Stratasys, Inc., is used for everything from working prototypes to working production models because of its robust ABS base material. And many small companies are using FDM for fast-turnaround prototypes in-house, since they are buying small format machines for actual production.

PolyJet Matrix^TM is mostly a form, fit, and function design modeler, says Koch, as opposed to a production manufacturing system. But it still has very fast turnarounds and accurate processing with both material and color flexibility. Direct Metal Laser Sintering, he continues, is a prototype process for manufacturing actual, dimensionally accurate metal parts in a variety of materials that can be used for production. In many cases, it is used for field trials and for low-volume manufacturing applications.

Parts with critical performance requirements are no impediment for RP processing. One particular part with critical performance requirements was a shell extractor for a 45-caliber handgun, the part that helps pull the shell out when the gun fires. An engineer was designing a brand new part, and needed the precision and material that one of 3 Axis's processes offered. It was decided to use direct metal laser sintering. "He had us manufacture six of the precision extractor parts," Koch remembers. "After getting the parts, he took three of them apart to inspect them. He found that they could be filed and ground, much like conventional castings, and had high quality and no internal voids. So by using these 17-4 stainless steel parts, he was able to get the parts made very quickly, fit them into his application, and do his testing, all in a matter of ten days."

Other more traditional manufacturing processes are also taking advantage of both RP for pattern development and 3D software for accelerated manufacturing options, Koch says.  Some molding applications utilize SLA models to create cavity patterns for larger-part tooling, including composite injection molds, to produce both thermoplastic parts and injection-molded polyurethane foam. The application of 3D software has escalated turnaround speeds for unfolding parts, allowing rapid-turn sheet metal prototypes for short runs, he says.

For more on 3 Axis Development, visit www.3 Axis.us.

SolidWorks is a registered trademark of SolidWorks Corporation.

Pro/E is a registered trademark of Parametric Technology Corporation.

PolyJet Matrix is a trademark of Objet Geometries.

FDM is a trademark of Stratasys Inc.

SLS and SLA are registered trademarks, and Viper and CastForm are trademarks, of 3D Systems, Inc.