ME or MEng Master of Engineering Master of Engineering Computer-Aided Manufacturing 4 — Questions and Answers
Question 1: In DMLS (Direct Metal Laser Sintering), residual stresses are primarily managed by:
- Reducing laser power below sintering threshold
- Optimizing scan strategy and applying post-build stress relief heat treatment (Correct answer)
- Increasing build plate temperature above material melting point
- Using pure nitrogen atmosphere exclusively
Correct answer: Optimizing scan strategy and applying post-build stress relief heat treatment
Alternating scan patterns and stress relief annealing after printing mitigate the thermal gradients that cause residual stresses in DMLS parts.
Question 2: What is the primary advantage of 5-axis CNC machining over 3-axis machining?
- It eliminates the need for coolant
- It allows the tool to maintain optimal cutting angle to complex curved surfaces without repositioning (Correct answer)
- It doubles the material removal rate automatically
- It requires fewer tool changes due to larger tool diameters
Correct answer: It allows the tool to maintain optimal cutting angle to complex curved surfaces without repositioning
5-axis machines tilt the tool or part continuously, maintaining ideal cutting geometry on complex surfaces in a single setup.
Question 3: In a manufacturing context, which lean tool is used to map the flow of materials and information from supplier to customer to identify waste?
- Fishbone diagram
- Value Stream Mapping (VSM) (Correct answer)
- SIPOC diagram
- Poka-yoke checklist
Correct answer: Value Stream Mapping (VSM)
Value Stream Mapping visualizes all steps in production flow, distinguishing value-added from non-value-added activities.
Question 4: Which cutting tool material offers the highest hardness and heat resistance for dry high-speed machining of hardened steels?
- High-speed steel (HSS)
- Uncoated carbide
- Cubic Boron Nitride (CBN) (Correct answer)
- Aluminum oxide ceramic
Correct answer: Cubic Boron Nitride (CBN)
CBN is second only to diamond in hardness and retains its properties at high temperatures, making it ideal for hard steel machining.
Question 5: In CAD/CAM integrated manufacturing, what is the role of a Post-Processor?
- It checks the CAD model for geometric errors before machining
- It translates generic toolpath data (CLDATA) into machine-specific G-code (Correct answer)
- It simulates material removal to detect collisions
- It generates the Bill of Materials from the design model
Correct answer: It translates generic toolpath data (CLDATA) into machine-specific G-code
A post-processor converts CL (cutter location) data from CAM software into the specific G-code dialect required by a particular CNC controller.
Question 6: What does 'Design for Manufacturability (DFM)' primarily aim to achieve?
- Maximizing part complexity to showcase manufacturing capability
- Reducing production cost and defects by designing parts that are easier to manufacture (Correct answer)
- Ensuring every design is prototyped using additive manufacturing
- Standardizing all parts to a single material
Correct answer: Reducing production cost and defects by designing parts that are easier to manufacture
DFM integrates manufacturing constraints into the design phase to minimize cost, simplify assembly, and reduce defect rates.
Question 7: In injection molding simulation, sink marks on a part surface are most directly caused by:
- Excessive injection speed
- Insufficient cooling time leading to subsurface shrinkage (Correct answer)
- Mold temperature set too low
- Gate location too close to the part edge
Correct answer: Insufficient cooling time leading to subsurface shrinkage
When thick sections cool slowly and the outer skin solidifies before the core, subsurface shrinkage pulls the surface inward, creating sink marks.
ME or MEng Master of Engineering Master of Engineering Computer-Aided Manufacturing 4
In DMLS (Direct Metal Laser Sintering), residual stresses are primarily managed by: