Project ForgeManufacturing Engineering
Machining Processes
GATE 2014
Hard
For machining a rectangular island represented by coordinates P(0,0), Q(100,0), R(100,50) and S(0,50) on a casting using a CNC milling machine, an end mill with a diameter of 16 mm is used. The trajectory of the cutter centre to machine the island PQRS is
- (−8,−8), (108,−8), (108,58), (−8,58), (−8,−8)
- B(8,8), (94,8), (94,44), (8,44), (8,8)
- C(−8,8), (94,0), (94,44), (8,44), (−8,8)
- D(0,0), (100,0), (100,50), (50,0), (0,0)
Explanation
Since PQRS is an "island" (material to be left standing, with everything around it removed), the cutter must travel OUTSIDE the island boundary by one tool radius (8 mm) at every edge to avoid cutting into it. Offsetting each corner outward by 8 mm gives (−8,−8), (108,−8), (108,58), (−8,58), back to (−8,−8).
Source: GATE ME 2014 (Session 1 / Set-1) (2014)
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