Development of a LCD Photomask Based Desktop Manufacturing System

Desktop manufacturing refers to various rapid prototyping (RP) techniques where threedimensional components are directly built, layer-by-layer, from a computer data description or computer aided design (CAD) file. Due to their ability and relative ease in transforming a conceptual design into a physical model, desktop manufacturing technologies have met escalating demand in the industry for shortening new product development cycle time. The layer-by-layer fabrication methodology also allows complex models to be made with ease. In the desktop manufacturing processes, the geometry of the object to be manufactured can be obtained from computer aided design (CAD) model data, an existing object (through Reverse engineering) (Puntambenker et al., 1994) (Soboh et al., 1994) (Chua Chee Kai, 1994) or mathematical data (e.g., surface equations) (Ren C Luo & Yawei Ma, 1995). Prashant et al. (Prashant Kulkarni et al., 2000) had reviewed many process planning techniques in layer manufacturing. Most desktop manufacturing systems accept model data described in an intermediate file format called the .STL format. This file format approximates the original model geometry using a series of triangular facets. After loading a .STL model, a slicing procedure is then applied to the tessellated model. In this process, the model is intersected with a set of horizontal planes to create a series of cross sections, or slices, comprised of contours that represent the material boundaries of the part to be generated. The contours are subsequently used to generate the NC tool paths for the desktop manufacturing system. There are many commercial RP systems available on the market today such as InVision (3D Systems Corporation), Objet (Objet Geometries Ltd.), Perfactory (Envisiontec Inc.), stereolithography (SLA) (3D Systems Corporation) and fused deposition modeling (FDM) (Stratasys, Inc.). The InVision 3-D printer combines 3D Systems' multi-jet modeling (MJM) printing technology with an acrylic photopolymer model material. The Objet’s Polyjet technology works by jetting photopolymer materials in ultra-thin layers (0.016 mm) onto a build tray, layer by layer, until the part is complete. The Perfactory RP system uses a photomonomer resin and a DLP projector to polymerize 3D finished parts. The stereolithography (SLA) and fused deposition modeling (FDM) are old RP processes. Both the laser beam of SLA system and the thermal extrusion head of FDM system generate 2D cross sectional areas using one-dimensional tool paths. The disadvantages of these systems