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65.5 SOLID GROUND CURING (SGC)

•Basic Process,

1.A computer program preprocesses a part so that it is in sliced layers.

2.A plate (glass?) is charged selectively and coated with a back powder. This process is much like photocopying.The result is a photographic mask of clear and opaque areas for a single slice of the part.

3.A thin layer of photopolymer is spread in a part vat.

4.The mask is placed over the photopolymer and a UV lamp is used to expose the layer and selectively harden the polymer.

5.The photographic plate with the mask is cleaned.

6.The unhardened polymer is removed from the surface.

7.A find layer of wax is deposited and hardened.

8.The surface is milled flat for uniform thickness.

9.The process begins again at step 2 and continues until all of the layers have been added. Note: Some steps can be done concurrently for the mask and the vat (i.e., 2,5 AND 3,6,7,8) to decrease build times.

•Developed by Cubital Inc. in Israel, started in 1987.

•two commercial machines - Solider 4600 and 5600

•Uses photosensitive polymers, but these are developed using a UV light and a photopolymer

1.photopolymer is developed and hardened by a UV mask that has the pattern for one slice of the part.

2.Unhardened polymer is cleaned away and replaced with wax, that is solidified with a cooling plate.

3.the polymer/wax layer is machined to exact thickness, and coated with a new layer of polymer. (a vacuum is used to remove cut chips)

4.The process continues until done

•The masks are made using a glass plate with electrostatic powder distribution (similar to photocopiers). A slice is used to electrostatically charge a glass plate, electrostatic sensitive powder coats the charged areas, and the mask is complete. After use the glass is cleaned and reused.

•After completion the wax is melted, and the complete part remains. (the wax was used to support work and eliminate supports.)

************ Include SGC figures from pg 60 and 64

•the UV lamp is 4KW and is exposed to the polymer for a few seconds

•a resin applicator spreads the photopolymer across in thin layers

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•material changeover requires a few minutes of “flushing-out’

•Advantages,

-a good variety of materials available

-easy material change

-low maintenance costs

-thin parts produced fast

-tolerance of +/- 0.005” overall

-no supervision required

-no toxic materials

-very compact size

-low temperature operation.

•Disadvantages,

-seam line between layers

-the extrusion head must continue moving, or else material bumps up

-supports may be required

-part strength is weak perpendicular to build axis.

-more area in slices requires longer build times

-temperature fluctuations during production could lead to delamination

•selected specifications for the FDM1000 are,

• Approximate costs are,