BME Advanced Manufacturing 3 — Questions and Answers
Question 1: In sheet metal forming, springback occurs because:
- The metal work-hardens beyond its yield point
- Elastic recovery causes the part to partially return toward its original shape after forming (Correct answer)
- The die temperature drops during the stroke
- Friction between punch and die increases
Correct answer: Elastic recovery causes the part to partially return toward its original shape after forming
After plastic deformation, the elastic component of strain recovers when the load is removed, causing the sheet to spring back toward its original geometry.
Question 2: Which surface finish process is most appropriate for achieving a mirror-like finish on hardened steel molds?
- Rough grinding
- Electropolishing
- Superfinishing (honing with fine abrasive stones) (Correct answer)
- Shot blasting
Correct answer: Superfinishing (honing with fine abrasive stones)
Superfinishing uses fine abrasive stones with oscillating motion to remove micron-level surface asperities, achieving Ra values below 0.05 µm on hardened steel.
Question 3: In a just-in-time (JIT) production system, the kanban card primarily serves as a:
- Quality inspection checklist
- Signal to authorize production or material replenishment (Correct answer)
- Worker performance tracker
- Machine maintenance schedule
Correct answer: Signal to authorize production or material replenishment
A kanban card is a visual signal that authorizes upstream production or delivery of exactly the quantity consumed, pulling material through the system.
Question 4: What is the key advantage of friction stir welding (FSW) over conventional fusion welding for aluminum alloys?
- Higher welding speed for thick sections
- Solid-state process avoids melting defects like porosity and hot cracking (Correct answer)
- No need for joint preparation
- Produces higher penetration depth per pass
Correct answer: Solid-state process avoids melting defects like porosity and hot cracking
FSW operates below the melting point, using frictional heat and plastic deformation, eliminating solidification-related defects common in fusion welding of aluminum.
Question 5: In stereolithography (SLA) 3D printing, the photopolymer resin is cured by:
- Infrared laser heating
- UV laser or projector selectively crosslinking the resin (Correct answer)
- Electron beam bombardment
- Chemical catalyst injection
Correct answer: UV laser or projector selectively crosslinking the resin
SLA uses a UV light source to photopolymerize (crosslink) liquid resin layer by layer, building up the part from a vat of photosensitive material.
Question 6: Which of the following is a primary benefit of cellular manufacturing layout?
- Maximum machine utilization through large batch sizes
- Reduced material handling distance and faster throughput for part families (Correct answer)
- Lowest capital investment in equipment
- Simplest production scheduling
Correct answer: Reduced material handling distance and faster throughput for part families
Cellular manufacturing groups machines by part family, reducing material handling, work-in-process inventory, and lead time compared to functional layouts.
Question 7: In hot forging, the workpiece is heated above its recrystallization temperature primarily to:
- Increase yield strength before forming
- Reduce flow stress and improve ductility for easier deformation (Correct answer)
- Prevent tool wear
- Achieve a finer surface finish
Correct answer: Reduce flow stress and improve ductility for easier deformation
Heating above the recrystallization temperature dramatically lowers flow stress and restores ductility, allowing large plastic deformations with lower forming forces.
BME Advanced Manufacturing 3
In sheet metal forming, springback occurs because: