Solid Groung Curing

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SOLID GROUND CURING

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HISTORICAL PERSPECTIVE The Cubital site in Bad Kreuznach is dedicated to marketing, sales, and service to all

of Europe. Cubital is a spin-off company from Scitex Corporation and began operation in 1987.Commercial sales began in the fourth quarter of 1991. It currently has facilities in Raanana, Israel (company headquarters and R&Dactivities), in Germany, and in the United States. To date, Cubital has sold a total of 26 machines. Its customers are from automotive, aerospace, consumer products, and medicalindustries, as well as engineering firms, academic institutions, and other researchinstitutions. Seventy percent of users of the solid ground curing (SGC) machines are rapidprototyping service bureaus. This photopolymer-based technology (SGC concept) was provided by Cubital. Thecompany has been dissolved, but the process may still available from a very feworganizations.

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INTRODUCTION TO SOLID GROUND CURING Solid Ground Curing, also known as the Solider Process, is a process that was inventedand developed by Cubital Inc. of Israel. The SGC process uses photosensitive resin hardened in layers as with theStereolithography(SLA) process. However, in contrast to SLA, the SGC process isconsidered a high-throughput production process, more expensive and not as accurate. The high throughput is achieved by hardening each layer of photosensitive resin at once.

Using layer data created by specialized software, the photomask is created on anelectrostatically charged glass plate. The electrostatic toner becomes attracted to theplate while a thin layer of liquid photopolymer resin is spread on a work platform. The early versions of the Cubital system weighed several tons and required a sealedroom. Size was made more manageable and the system sealed to prevent exposure tophotopolymers, but it was still very large.

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SOLID GROUND CURING IN BRIEF Another method of rapid prototyping is Solid Ground Curing . Using layer data createdby specialized software, the photomask is created on an electrostatically chargedglass plate. The electrostatic toner becomes attracted to the plate while a thin layer ofliquid photopolymer resin is spread on a work platform. Then, the photomask and the resin-coated work platform are aligned. Several

seconds of UV light flash through the clear area of the photomask and the exposedresin is hardened. Unexposed resin is vacuumed away from the work platform,which leaves behind a layer of hardened resin in the shape of the photomask. At the same time, the layer image is erased from the glass plate to prepare for thenext photomask. The cavities created by the removal of the unexposed, liquid resinare filled with melted wax. A cooled plate hardens the wax, which will support and

protect the run's remaining layers. The hardened, resin/wax layer is milled to achieve a precise, predetermined thicknessand a smooth, even surface. Finally, the work platform passes under a secondpowerful UV lamp for final curing and complete solidification of the resin.

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HIGHLIGHTS OF SGC Large parts, 500 500 350 mm (20 20 14 in), can be fabricated quickly. High speed allows production-like fabrication of many parts or large parts. Masks are created with laser printing-like process, then full layer exposed at once. No post-cure required. It suffered from high acquisition and operating costs due to system complexity. This ledto poor market acceptance. Milling step ensures flatness for subsequent layer. Wax replaces liquid resin in non-part areas with each layer so that model support isensured. Creates a lot of waste.

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SOLIDER 4600 Work volume : 14 X 14" X 14"

Accuracy : 0.1% up to 0.020max.

Flatness : typical 0.006

Resolution : x-y 0.004, z 0.004 0.006

Smallest feature : x-y 0.024, z 0.006

Times : preprocess 0.20 3 hours, postprocess 0.30 3 hours

Production rate : 120 seconds/layer

Input format : solid formats automatically, 2D with user interaction, CT/MRI voxelsetc.,

Cost : $275,000US

Used to produce investment casting

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SOLIDER 5600 Work volume : 20 X 14" X 20"

Accuracy : 0.1% up to 0.020max.

Flatness : typical 0.006

Resolution : x-y 0.004, z 0.004 0.006

Smallest feature : x-y 0.024, z 0.006

Times : preprocess 0.20 3 hours, postprocess 0.30 3 hours

Production rate : 65 seconds/layer

Input format : solid formats automatically, 2D with user interaction, CT/MRI voxelsetc.,

Cost : $400,000US

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CAD STANDARDS INFRASTRUCTURE ANDPART SHAPE ACQUISITIONS

Cubital has developed a proprietary software package called the Solider

Data Front End (DFE).

This software has editing and file manipulation capabilities that prepare

adequate STL files for processing on any RP system.

Features include cutting, patching, facet trimming, scaling, and file preview.

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MATERIALS Cubital currently offers two types of materials for use in its Solider machines (Solider

4600 & 5600)

The primary material is photopolymer resin, and the secondary material is wax.

The photopolymer materials are G5601 and XA7501. These are conventional

materials used to make plastic models.

Research efforts are focused on developing an epoxy resin to compete with 3D

Systems' epoxy resin and on developing a new methodology for making wax patterns

for investment casting.

This includes developing a new wax material that is suitable for use in the lost wax

process of investment casting.

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ADVANTAGES

No need for time consuming post-curing.

Part complexity does not effect speed, however volume does.

Elimination of post curing reduces internal stresses, and warping.

Jobs can be stopped, other jobs run, then the first job restarted at a later time.

Weights may be inserted at any time to alter the centre of gravity.

Supports are not required.

Models with moving parts can be produced because of the firm holding of work inthe process.

Layers can be milled off if they are found to be in error.

Many parts can be run at the same time.

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DISADVANTAGES Overexposure of the polymer may increase the viscosity, and make it

unusable, thus greatly increasing the volume of expensive polymers used.

The resins require that light sealed chambers and toxic material handlingprocedures be used.

The machine is very large.

Machining is noisy.

Maintenance is high, requires supervision.

Very few materials available.

Removal of wax after production is required.

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APPLICATIONSSome of areas are using Solid Ground Curing. They are

Automotive

Aerospace

Consumer products

Medical industries

Engineering firms

Academic institutions

Other research institutions.

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The Cubital SGC process fabricates complex plastic models used for design validationand as functional models. New applications are in various stages of development.

CastingCubital is currently working to develop a method for fabricating wax patterns forinvestment casting. This includes capturing the wax pattern in a thin polymer coating,then removing the polymer coating from around the wax pattern. This process is in theearly stages of development. Small, simple patterns were shown to the team.

ToolingTooling was mentioned as a focus of R&D at Cubital. Development of epoxy resin isevidence of this effort.

MedicalThere were no examples of medical applications cited, although the systems can readand build parts from data received from various CT and MRI equipment.

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PHOTOSModel of mechanism made using solid ground curing

Processes SGC

Model Category : Technical, Mechanics

Materials Epoxy

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Model of pump wheel made using solid ground curing

Processes : SGC

Model Category : Technical, Mechanics

Materials : Epoxy

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COMMERCIAL RAPID PROTOTYPING SYSTEMS

Stereolithography and Selective Laser Sintering by 3D Systems, Inc.of Valencia, California.Solid Imager Stereolithography byAaroflex, Inc.of Fairfax, Virginia.Solid Ground Curing by Cubitalof Raanana, Israel.Paper Lamination Technology by KIRA Corporationof Aichi, Japan.Laminated Object Manufacturing by Cubic Technologies Inc.of Carson, California.Fused Deposition Modeling byStratasys, Inc.of Eden Prairie, Minnesota.Three dimensional plotting by Solidscape Inc.(formerly Sanders Prototype Inc.) of Merrimack,

New Hampshire.Direct Shell Production Casting by Soligen Inc.of Northridge, California.Laser Sintering of metals and plastics by EOS GmbHof Munich, Germany.DeskPrototurns CAD models into parts using an automatic desktop NC milling machine (no

CNC knowledge required). Produced by Delft Spline Systemsof Utrecht, The Netherlands.Laser Engineered Net Shaping (LENS) by Optomec Design Companyof Albuquerque, New

Mexico. The process builds up metal parts by injecting metal powder into the focus spot of ahigh power laser beam.

Digital Light Processing (DLP) by Envision Technologies GmbHof Marl, Germany.Polyjet, a photopolymer-jetting technology by Objet Geometries Ltd.of Rehovot, Israel.Z810Ink Jet Printer by Z Corporationof Burlington, Massachusetts. Z Corporation is a

subsidiary of Contex of Denmark.