UNIT -3 1. SOLID GROUND CURING 2 Highlights: 1. Large parts of 500x500x350mm can be fabricated quickly. 2. High speed allows production of many parts.

UNIT -3UNIT -3

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SOLID GROUND SOLID GROUND CURINGCURING

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Highlights:Highlights:

1. Large parts of 500x500x350mm can 1. Large parts of 500x500x350mm can be fabricated quickly.be fabricated quickly.

2. High speed allows production of many 2. High speed allows production of many parts.parts.

3. Masks are created.3. Masks are created. 4. No post curing required.4. No post curing required.

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5. Milling step ensures flatness of 5. Milling step ensures flatness of subsequent layers.subsequent layers.

6. Wax supports model, hence no extra 6. Wax supports model, hence no extra support is required.support is required.

7. Create a lot of wastes.7. Create a lot of wastes. 8. Not as prevalent as SLA and SLS but 8. Not as prevalent as SLA and SLS but

gaining ground because of high throughput gaining ground because of high throughput and large parts.and large parts.

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Process:Process: The steps in process are as follows The steps in process are as follows First a CAD model of the part is created First a CAD model of the part is created

and it is sliced in to layers using and it is sliced in to layers using cubitos cubitos data front end softwaredata front end software..

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1. Spray photosensitive resin:At the beginning of a layer creation step the flat work surface is sprayed with photosensitive resin.

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2. Development of photomaskFor each layer a photomask is produced using cubitals proprietary ionographic printing technique.

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3. Expose photomaskThe photomask is positioned over the work surface a powerful UV lamp hardens the exposed photosensitive resin.

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4. Vacuum uncured resin and solidify the remnantsAfter the layer is cured all the uncured resin is vacuumed for recycling leaving the hardened area intact the cured layer is passed beneath a strong linear UV lamp to fully cure in and solidify any remnants particles as shown in figure.

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5. Wax is applied to replace uncured resin areaWax replaces the cavities left by vacuuming the liquid resin. The wax is hardened by cooling to provide continuous solid support for the model as it is fabricated extra supports are not needed.

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6. The top surface is milled flatIn the final step before the next layer, the wax resin surface is milled flat to an accurate reliable finish for next layer.

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Once all layers are completed the wax is removed and any finishing operations such as sanding etc can be performed no post curing is necessary.

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AdvantagesAdvantages The entire layer is solidified at once.The entire layer is solidified at once. Reduction in the part build time for Reduction in the part build time for

multipart builds.multipart builds. Larger prototypes can be nested to utilize Larger prototypes can be nested to utilize

the build volume fully.the build volume fully. No postcuring is required.No postcuring is required.

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DisadvantagesDisadvantages The system is large, noisy and heavy.The system is large, noisy and heavy. It wastes a large amount of wax which It wastes a large amount of wax which

cannot be recycled.cannot be recycled. SGC systems are prone to breakdowns.SGC systems are prone to breakdowns. The resin models of SGC are not suitable The resin models of SGC are not suitable

for investment casting because coefficient for investment casting because coefficient of thermal expansion is more than ceramics of thermal expansion is more than ceramics in resin which may lead to cracks in casting.in resin which may lead to cracks in casting.

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Laminated object Laminated object ManufacturingManufacturing

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IntroductionIntroduction

Laminated Object Manufacturing is a Laminated Object Manufacturing is a rapid prototyping technique that produces rapid prototyping technique that produces 3D models with paper, plastics or 3D models with paper, plastics or composites. composites.

LOM was developed by Helices LOM was developed by Helices Corporation, Torrance, California. LOM is Corporation, Torrance, California. LOM is actually more of a hybrid between actually more of a hybrid between subtractive and additive process.subtractive and additive process.

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In this technique models are built up with In this technique models are built up with layers of cross section of the part. Hence as layers of cross section of the part. Hence as layers are been added, the excess material layers are been added, the excess material is not required for that cross section is being is not required for that cross section is being cut away.cut away.

LOM is one of the fastest RP processes for LOM is one of the fastest RP processes for parts with longer cross sectional areas which parts with longer cross sectional areas which make it ideal for producing large parts.make it ideal for producing large parts.

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System Hardware:System Hardware: LOM system is available in two sizes. LOM system is available in two sizes. LOM 1015 produces parts up to 10x15x14 inches.LOM 1015 produces parts up to 10x15x14 inches. LOM 2030 produces parts upto20x30x24 inches.LOM 2030 produces parts upto20x30x24 inches. Common build material is paper.Common build material is paper. Build material has pressure and heat sensitive Build material has pressure and heat sensitive

additive on the banking.additive on the banking. Material thickness ranges from 0.0038-0.005 Material thickness ranges from 0.0038-0.005

inches.inches.

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