Reverse Engineering and Rapid Tooling Applied to the Metal by jxg91389

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									            Reverse Engineering and Rapid Tooling Applied to the Metal Casting Process
                                       Bernadette G. Currie B. E Sc., M.Eng Candidate
                                                   Email: bcurrie@bcit.ca

         Reverse engineering technology enables the                       The aim of the industry project was to establish a
creation of a digital model using data collected from an         means to generate a useable 3D CAD format of the parts
existing object. In a broader sense, an object may be given      for input into an anticipated CAM process. Without
a virtual representation based on its physical form and          accurate CAD data that can exactly represent the required
possibly the design intent of the original article. With this    geometry, any downstream processes will not have
in mind, data capture need not be the starting point or          acceptable results. The primary tactic for generating the
automated modeling of surfaces the end goal, leaving the         data in the essential format was to utilize ‘knowledge-
door open for more interactive, knowledge driven                 driven’ reverse engineering. The rest of the project
approaches. Potential information sources for reverse            focused on finding novel ways to improve or even
engineering projects can be physical parts, CAD file             radically reform the manufacturing process through the
formats, milling g-code, laser scan data and CMM data.           introduction of computer assisted methods. The CAD
An article may exist in the absence of descriptive               model would be the archetype for a new process.
geometry because data was either not used for its creation
or has since been lost. Engineers can use nondestructive
probe techniques to extract the design concept and details
stored within the finished part.

         Rapid Tooling describes the process which either
uses a rapid prototyped pattern to create the mold or
directly fabricates molds, dies or tooling for a prototype       Figure 1-3 CAD model of the propeller blade pattern, a
or limited number of production parts. A key aspect is the       surface model from digitized data, propeller rendering.
time it takes to produce the final tooling compared to
conventional methods. Fabrication of tooling by additive                   Two main components required as proof of the
and subtractive approaches is a major application of direct      viability of the RE to CAD to CAM principle are model
manufacturing. These technologies show promise in                validation and an evaluation of the feasibility of the
emerging applications such as mass production of                 proposed approach for producing marine propellers.
customized devices and build-to-order manufacturing.             Models for two emerging manufacturing approaches were
The market for the technology is diversifying, spanning          prepared and included the associated metal casting
automotive, marine, aerospace and consumer industries.           components. Both methods represent a considerable cost
                                                                 and time savings as the handmade wooden pattern from
          A practical project was sought to apply concepts       which the sand mold is formed is eliminated. The
from the field of reverse engineering and rapid tooling to       advantages, disadvantages, suitability and limitations of
improve a real manufacturing process. A good fit was             each of the two distinctive approaches are demonstrated
found in the marine industry, with Osborne Propellers, a         in the production of sample machined and rapid
local company that specializes in manufacture of                 prototyped molds ready for pouring.
propellers by the metal casting process. As boat building
becomes more advanced, the propeller must also be
refined. To improve quality and be more competitive in
the market, the technological aspects of propeller
production need to advance and incorporate new
fabrication and verification methods. Vessel particulars
dictate unique specifications for each propeller, making
every job a custom run. The question posed was “Could
applying research from the field of reverse engineering
and introducing CAM technology to propeller production,
increase the ease of manufacture, improve the quality of
the final part and make the process more efficient?”
Problems facing foundries can be summarized as follows;
• Prohibitive cost of manufacturing handmade patterns
• High level of specialized skills required
• Long production lead times
                                                                 Figure 4-5 The mold flask for the sand casting process
• Impracticality of storing and verifying patterns
                                                                 and a scaled rapid prototype of a propeller pattern.
• Increasing complexity of parts
• Quality assurance of the finished product
References:
[1] Maas, D., Patternless and Digital Production of
    Molds and Cores for Sand Casting Applications,
    Advanced Materials & Processes, Sep2000, p31-33.
[2] Várady, T., Martin, R. and Cox, J., Reverse
    Engineering of geometric models-an introduction.
    Computer-Aided Design, 1997, pp 255-268

								
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