Özgür METİN, 030040004, 5th Week

Graph-Based Method

Topological relationships between geometric entities of a CAD model can be represented using a graph approach that simplifies the analysis of the geometric entities for feature recognition. Simple heuristics can be applied to the graph to identify features. In this approach, the B-rep of a part is translated into a graph whose nodes and arcs represent the information of a part. Feature recognition is achieved by finding a sub graph from the shape of a designed object where the subgraph is isomorphic to the feature graph.

(Nasr E. A. & Kamrani A. K., Computer-Based Design and Manufacturing, p. 109)

Syntax-Based Method

Syntax-based methods are deeply rooted in classical pattern recognition techniques. The only

difference is that these appropriate techniques have been extended from catering for 2D situations to 3D situations. Feature syntax can be expressed in terms of either edges or faces, and it is based on their local characteristics. In order to recognise some common types of holes, three different types of syntactic elements can be defined.

Syntactic elements for holes and their possible instances

HSS – Hole-Starting-Surface: A planar surface with an internal circular loop

HES – Hole-Element-Surface: Cylindrical/conical surface bound by two circular edges

HBS – Hole-Bottom-Surface: Planar circle, cone, HSS

(Xu X., Integrating Advanced Computer-Aided Design, Manufacturing, and Numerical Control: Principles and Implementations, p. 94)

Press Brake

The press brake is a gap frame press with a very wide bed. A model has a bed width of 9.15 m (30 ft) allows a number of separate dies (simple V-bending dies are typical) to be set up in the bed, so that small quantities of stampings can be made economically. These low quantities of part, sometimes requiring multiple bends at different angles, necessitate a manual operation. For a part requiring a series of bends, the operator moves the starting piece of sheet metal through the desired sequence of bending dies, actuating the press at each die, to complete the work needed.

(Groover M. P., Fundamentals of Modern Manufacturing: Materials, Processes and Systems 3rd Edition, p. 465)

Metal Injection Molding

Injection molding is closely associated with the plastic industry. The same basic processses can be applied to form parts of metal or ceramic powders, the difference being that the starting polymer contains high content of particulate matter, typically from %50 to %85 volume. When used in powder metallurgy, the term metal injection molding (MIM) is used. The more general process powder injection molding (PIM), which includes both metal and ceramic powders. The steps in MIM proceed as follows:

1. Metallic powders are mixed with an appropriate binder.

2. Granular pellets are formed from the mixture.

3. The pellets are heated to molding temperature, injected into a mold cavity, and the part is cooled and removed from the mold.

4. The part is processed to remove the binder using any of several thermal or solvent techniques.

5. The part is sintered.

6. Secondary operations are performed as appropriate.

(Groover M. P., Fundamentals of Modern Manufacturing: Materials, Processes and Systems 3rd Edition, p. 352)