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Beyond Rapid Prototyping: Additive Manufacturing

New materials and machines keep pushing what’s been known as “rapid prototyping” into the realm of additive manufacturing, which is becoming more of an “essential” design and production technology.

“All the additive fabrication technologies have limitations,” admits Fred Fisher, product marketing manager for Stratasys Inc. (Eden Prairie, MN; www.stratasys.com). “We will never replace injection molding, for instance. But the faster we get our machines, the better their resolution, the better their accuracy, the closer the gap between additive fabrication technologies and other manufacturing processes. We’re working on closing that gap.” Here are examples of how two major rapid prototype (RP) and direct digital manufacturing (DDM) suppliers are closing that gap.

 

From Stratasys

ABSplus and ABS-M30 are two new thermoplastics from Stratasys for the company’s fused deposition modeling (FDM) systems. ABSplus is up to 40% stronger than standard ABS material; ABS-M30, available only for the Stratasys FDM 400mc and currently available in natural (off-white) color, is 30% to 67% stronger than ABS parts built on Stratasys’s Titan or Vantage FDM systems. The bonding strength between layers of ABS-M30 parts is more than double that of conventional ABS.

In addition, part production using ABS-M30 is 29% faster, on average, than when using conventional ABS, depending on the tip and FDM system. This is particularly true on Stratasys’s new FDM 400mc where “significant improvements” in flow control have been made, says Fisher. Flow control is “how we start and stop, push plastic out of the nozzle, and move the head around.” These improvements help reduce part porosity, yielding denser and stronger parts, and they help smooth head movement, improve the precision of head positioning, and make material-bead width more consistent. Add more precisely aligned and stiffer mechanical components, specifically the X-Y gantry, and the result is an overall improvement in the accuracy and repeatability of the system. (ABS-M30 is not the only material affected. PC-ABS parts are up to 17% stronger when built on the FDM 400mc; PC parts, up to 29% stronger.)

The 400mc footprint measures 50.5 x 35.3 x 77.3 in. The 400mc offers four layer thicknesses ranging from 0.005 in. to 0.013 in. (That 0.013-in. slice was recently added as a build option to Stratasys FDM T-Class systems. This option is best for fast builds or for larger geometries where high resolution is not required.) Besides ABS-M30, the 400mc can also run ABS, ABSi, polycarbonate (PC), PC-ABS, PC-ISO, and polyphenolsulfone. The system itself was made to be “kind of a la carte,” explains Fisher. People can buy the machine for one material and later add more canister bays to add different materials. The base system comes with a build envelope measuring 14 x 10 x 10 in., which can be enlarged to 16 x 14 x 16 in. (This upgrade includes adding dual material bays for longer build runs.) 

The FDM 200mc, introduced in May, is not quite the part-production system that the FDM 400mc is, but neither is it merely a design-shop RP machine. The 200mc is a smaller machine (27-in. wide by 34-in. deep by 41-in. high) with a smaller build envelope (8 x 8 x 12 in.); it builds parts in either 0.007-in. and 0.010-in. slices using ABSplus.

 

From 3D Systems

3D Systems Corporation (Rock Hill, SC; www.3dsystems.com) has “pretty much completely turned over [its] materials portfolio” in the last two years, says Stephen Hanna, the company’s director of stereolithography (SLA) materials. The change in materials is to get product designers and manufacturing engineers to equate a stereolithographic resin to a production material, even if it doesn’t provide the exact same properties of the final production material.

Among its new resins is Accura Xtreme, which has the look, feel, and durability of injection-molded plastic. The resin is colored gray and has an impact strength of nearly 1 ft-lb/in., an elongation at break up to 22%, and low viscosity. Because of the material’s modest thermal and moisture resistance, parts made of Xtreme last longer (do not deteriorate) than parts made of competitive materials.

DuraForm EX Black is the third commer-cially available material for the company’s Sinterstation Pro SLS systems (other colors are natural and white). This polyamide-based material has the toughness of injection-molded polypropylene and ABS. Parts of this material are tough in all three axes, even at -65° F.

Accura 25 is basically 3D Systems’s all-purpose ABS-like material. It has a similar look and feel to polypropylene, that is, it’s a fairly flexible, durable material, though it doesn’t have all of the properties of injection molded polypropylene. It builds fast, is easy to finish, and mimics many of the characteristics that an engineer would look for in an ABS plastic.

Accura 55 is an improvement on 3D Systems’s Accura 50. Both resins emulate run-of-the-mill ABS, though finished parts are significantly stiffer than polypropylene and feature much better thinner-wall construction, fine detail, and smooth surface finish. Accura 55 is a white resin and has ultra-low viscosity, which helps improve SLA-machine uptime and reduces post-processing. The material is well suited for end-use automotive interior components and similar parts, as well as master patterns for urethane casting.

Accura 60 is significantly more rigid than the other Accura resins and it’s transparent to simulate polycarbonate. This resin is geared toward automotive applications, such as headlight lenses, but it’s also suitable for quick casting applications.

Insofar as machines, the biggest splash from 3D Systems is its V-Flash Desktop Modeler (www.modelin3d.com). Costing $9,900, this unit, as befits its name, is a small 3D printer, measuring 24-in. wide, 27-in. deep, and 30-in. tall, weighing about 100 lb., and having a build volume of 7 x 9 x 8-in.. Abe Reichental, president and chief executive officer of 3D Systems, expects V-Flash to “open doors into companies that had previously looked into more traditional RP solutions and concluded that they were not affordable.”

V-Flash is based on 3D Systems’s fourth technology platform, after SLA, laser sintering, and multijet modeling: film transfer imaging (FTI). FTI is similar to photoflashing technology; it uses a photo-curable material, but the light source for curing is not compatible with other resins. The “magic” in this modeler comes from the V-Flash Cartridge, which essentially mimics the print cartridges for laser printers. (In fact, the modeler and cartridge are made by Canon Inc.) The cartridge contains all the parts that typically face wear and tear, such as pumps, dispensers, recoaters, transporters, and routine main-tenance elements. This leaves few moving parts in the modeler itself. The cartridge, says Reichental, “removes complexity and cost from the V-Flash modeler, rendering traditional maintenance elements disposable within each V-Flash Cartridge.”

V-Flash was first announced in January. It officially debuted at the 3D Systems World Conference in late September. Even by that date, no information was publicly available regarding the cost of cartridges. Typically, ink cartridges for conventional laser printers, as well as ink jets, provide a hefty income for the vendor. Be forewarned.

 

The Untold Story About Additive Manufacturing

Two words: jigs, fixtures. Though not as sexy as building finished parts, using additive manufacturing technology to make jigs and fixtures is both popular and rarely mentioned in print. This application, says Stratasys Inc.’s Fred Fisher, “is the first leap that people make in DDM [direct digital manufacturing].” Jigs and fixtures, and some hand tools, are a natural fit for DDM. The volumes are typically low. Aesthetics aren’t critical. The end-use items are relatively complex. (More complexity means more expense and time to produce using traditional manufacturing methods, such as 7-axis CNC machining. Even in injection molding, the more complex the part, the more complex and expensive the mold and the extrusion process. The cost of DDM is fixed, regardless of part complexity.)

The BMW AG plant in Regensburg, Germany, uses Stratasys FDM for vehicle design prototyping and for building some of the hand tools and fixtures used in automobile assembly and testing. These items include hand-held assembly devices for attaching car badges, gauges for positioning and assembling strikers on driver and front-seat passenger sides of the E46 Coupe/Convertible, and wire guides. In one instance, BMW used sparse-fill FDM to build a hand-held tool, replacing a solid core tool with one having internal ribs. This cut the tool’s weight by 2.9 lb.—a 72% weight reduction that quickly matters in a tool used hundreds of times per shift.

Compared to conventional metal cutting, such as milling, turning, and boring, DDM brings cost reductions in engineering documentation, warehousing, and manufacturing. DDM also frees part designs from conventional metal cutting constraints, resulting in better ergonomically designed parts for manual production. The ergonomic benefits include improved worker comfort, ease-of-use, and safety (fewer repetitive-syndrome problems), as well as improved process repeatability.

 

Don’t Forget Software

RP and DDM are nothing without software to import .stl files from CAD, automatically slice those files, generate support structures, generate extrusion paths and work platform movements, and more. Often overlooked is software to better manage production. Both Stratasys and 3D Systems have recently announced new software that makes 3D printing and the management of multiple machines easy, ultimately increasing total system throughput and utilization.

Stratasys Insight (version 6) pre-processing software for the company’s FDM systems can combine multiple machine job queues into a single Gantt chart that lets users drag-and-drop jobs for machine load balancing. The Gantt chart “can indicate blackout (non-working) times to show real production capacity. This feature omits new-job start times that couldn’t realistically occur because an operator isn’t available to remove a part and start a new job when the production floor is closed. This lets users optimize scheduling to ensure all machines are running at full capacity,” says Stratasys’s FDM product manager Patrick Robb.

From 3D Systems, there’s the 3DPro Software Suite for the company’s Viper Pro SLA Systems. (Future releases will work on other machines from 3D Systems.) The suite integrates into one package job submission, tracking, and reporting, CAD viewing and verification, and .stl file manipulation tools. The software also features drag-and-drop part placement and build preparation. The software tracks system and build data for an entire operation, which can then be used for production scheduling, forecasting, and statistical process control.