Cutting path generation of linear hotwire cutter for VLM-ST

Abstract

Most rapid prototyping (RP) processes adopt a solid CAD model, which will be sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; eventually, the stacked layers form a physical part of the model. A new thick-layered RP process, the transfer-type variable lamination manufacturing process using expandable polystyrene foam sheets (VLM-ST), has been developed to reduce building time by employing thick layers and to improve the surface finish of parts with a sloping surface. This paper describes the method to generate the unit shape layer (USL), the cutting path data of the four-axis hotwire cutter for the VLM-ST process. The USL is the basic unit of cutting and building in the VLM-ST process and it is also the basic unit of cutting path data of each layer. The USL includes data such as layer thickness, positional coordinates, side angles of each layer, and reference shape. The method to generate the USL is as follows: (1) the mid-slice of each layer is generated from the CAD model, (2) each mid-slice is converted into a simply-connected domain, (3) the rotation angle of the hotwire of the cutting system is calculated for each layer, and (4) the reference shape of each layer is generated for manual stacking. The procedure to generate the cutting path data of the linear hotwire cutter for VLM-ST was practically applied and verified for various three-dimensional shapes.