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Author

Yunyou Liu

Date of Award

2010

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

Supervisor

Tim J. Nye

Language

English

Abstract

Making large RP parts is always a challenge for common commercial RP machines or other CNC machining process. Either it is not possible to fabricate the large RP models, or can only be done at high cost.

This thesis investigates a new method to make large RP parts in a very rapid and cost-effective way, and the part size could be theoretically unlimited. A software program for slicing 3D CAD models is developed in the Autodesk Inventor VBA environment to generate DXF files, and a common 3-axis CNC router is employed for cutting the sliced layers from sheet material by importing the DXF files from the slicing software tool. The sheet material sliced layers are laminated together to form the RP models with staircases on the laminated body surface, then epoxy resin filler is applied to cover the staircases. The surface finishing process such as sanding and coating makes the RP model closely match the original designed part shape.

By directly slicing a 3D CAD model in Inventor with the slicing software tool, the cutting profiles are obtained and saved in the DXF file format. The errors usually caused by slicing STL files with most conventional RP machines are eliminated and hence the geometry data is more accurate for making sliced layers. The slicing process becomes quite simple with the help of the slicing software tool, and it only takes a few minutes to get the DXF files for CNC router cutting.

Three different slicing and CNC router cutting methods are discussed in this thesis. For different shapes of 3D CAD models, an appropriate slicing method can be applied to reach the optimal results of RP model making.

The uniform slicing method is an effective way to slice large parts and generate sliced layers with the same thickness; the adaptive slicing method is a supplement for uniform slicing and makes thinner layers to save time for post-finishing such as staircase filling and surface grinding; and the adaptive slope cutting method is developed for choosing different sloped cutters for CNC router to cut sliced layers with standard grooving router bits.

The experiment is performed to make RP models of a sailboat keel pattern with the different slicing methods. Measurement is done for the fabricated RP models for comparing the surface deviations between the original designed 3D CAD models and the fabricated RP parts. The deviation plot made by software Geomagic shows that the RP model closely matches the original 3D CAD model, the surface deviation is mostly within lmm between the RP model and CAD model in the research experiment. The fabrication cost for RP model is also analyzed based on the experiment models in this research.
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