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New modeling system makes parts in minutes instead of hours.

New Modeling System Makes Parts In Minutes Instead of Hours

An addition to the fast-growing family of so-called "desktop manufacturing" technologies is said to offer even faster prototyping capability than other such systems. Stratasys, Inc., Minneapolis, says its new 3D-Modeler constructs plastic models from 3D wireframe, surface or solid CAD models in minutes, rather than the hours required by the recently introduced stereolithography systems, which create models by solidifying liquid photopolymers with a scanning laser beam.

Scott Crump, president of Stratasys and inventor of the system, attributes the quicker modeling time to his single one-step process, which doesn't require cure or post-processing. Called Fused Deposition Modeling (FDM), the process uses a spool of 50-mil-diam. thermoplastic filament, resembling wire, which feeds into a heated extruding head similar to the way wire is fed to an automated wire-feed welder. The thermoplastic filament melts at a temperature just above its solidification state prior to deposition. The material then quickly solidifies as it is directed into place with an x-y controlled extruding nozzle that creates a precisely dimensioned laminate. Successive laminations, 1 to 50 mils thick, adhere to one another to form the model. The lightweight FDM head operates at up to 900 in./min (15 in./sec).

The system uses a wax-filled plastic filament or a tough nylon-like material. The wax-filled material is a proprietary compound similar to the machinable wax used for checking out NC programs. It's said to be excellent for use as a core in lost-wax casting, since it has low ash content and leaves no residue in the cavity.

No material reportedly is wasted in model making and no cleanup is required. No fixtures are needed. One spool of material can be removed and a new spool of different material type or color can be loaded in about 1 min, says Crump.

The raw-material cost of producing an average model with the system is estimated at $5, which Crump compares with a rough average of $20 or more per part for stereolithography. Another advantage is that the system is designed to fit into a normal engineering environment, with no need for special electrical air, or venting provisions. The unit is said to be easy to operate and reportedly runs unattended. It also runs at a low temperature--about 180 F, close to the temperature of a cup of coffee. Crump adds that FDM also doesn't use potentially dangerous and expensive replacement parts such as lasers.

The FDM system accepts 3D CAD data from CAD systems supporting IGES, or STL files for 3D Systems' stereolithography apparatus, making the system compatible with most CAD systems, says Crump. The system, based on NURBS (Non-Uniform Rational B-Splines), displays real-time object slicing on a Unix computer, 3D Modeler connects to standard RS-232 ports and is driven by standard NC code.

Complete system price is $178,000, with a seven-week delivery. No systems have yet been sold.

PHOTO : The 3D-Modeler (right) from Stratasys, Inc., is said to be capable of making prototype

PHOTO : parts in minutes, rather than the hours required by most three-dimensional modeling

PHOTO : systems. For example, this prototype perfume bottle was made in 50 min.
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Title Annotation:fused deposition modeling
Author:Fallon, Michael
Publication:Plastics Technology
Date:Aug 1, 1990
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