Özgür METİN, 030040004, 4th Week

Photopolymer Fabrication

Specially formulated liquid polymers have been developed that can be cross-linked to a controlled depth under the influence of UV (or, sometimes, visible) light. The polymer is in a vat that has a vertically movable platform. To begin with, the platform is below the surface of the liquid by one slice thickness and the first slice is solidified by controlled exposure to light. Processes differ in the way a light is applied.

a. The light is generated by a laser and the beam is scanned across the surface. The platform is then dropped and the process is repeated until all slices are made. Overhanging parts need support.

b. The polymer layer is exposed to UV light through a glass mask on which the pattern is made by copier-like techniques. The nonexposed liquid is vacuumed off and replaced with wax, the layer is milled flat, and the platform is lowered for the repetition of the sequence. The wax provides support and, upon completion of the part, is removed by melting or dissolution.

(Schey John A., Introduction to Manufacturing Processes 3rd Edition, p.800)

Liquid-state Deposition

The material is heated into the melt regime and deposited in a pattern by various techniques.

a. A filament of thermoplastic polymer or wax is heated and extruded through a nozzle, the movement of which is controlled in x-y coordinates. The table drops when a layer is completed. Rapid solidification gives sufficient strength to obviate the need for outside support.

b. By spraying through masks cut out by laser, a shaped part can be built up in layers. In a variant, a laser beam is directed through the center of a powder-delivery nozzle; thus, the part is built directly from fused layers.

c. When the platform (or the nozzle) is given a programme a z-axis movement, 3-D shapes can be built up directly by the coil-building method. The part may also be built as a continuous weld bead. Surface quality will have to improve before these processes can be used for functional parts.

(Schey John A., Introduction to Manufacturing Processes 3rd Edition, p.801)