1.1 Fabrication

Question 1

Why would the manufacture of structures use cut sheets of flat stock rather than machine from solid?

Answer 1

• less waste material when making a hollow structure
• Can produce accurate flat sheets

Question 2

Name 3 types of fabrication techniques

Answer 2

⚫ Laser machining
⚫ Plasma machining
⚫ Water jet machining

Question 3

What are lasers used for

Answer 3

⚫ Cutting & Drilling
⚫ Welding
⚫ Engraving
⚫ Surface treatment

Question 4

Advantages of laser machining

Answer 4

⚫ Fine cut width
⚫ Non contact
⚫ No mechanical force
⚫ No tool wear
⚫ High positional accuracy
⚫ Narrow heat effected zone
⚫ Processes metals and non metals

Question 5

Disadvantages of laser machining

Answer 5

⚫ Low metal removal rate
⚫ narrow cuts, therefore high cutting speed
⚫ High specific power consumption
⚫ inefficient conversion of input energy into light
⚫ Beam is focused to a point, causes
⚫ Roundness on holes > 0.8 mm
⚫ Tampering of holes – deeper the hole, more the taper
⚫ Long depth of focus
⚫ Charring of the holes and irregularities
⚫ stress raisers

Question 6

Common Industrial Plasma’s

Answer 6

⚫ Flames
⚫ Glow Discharges

Question 7

What is a Transfer Torch and it’s advantages

Answer 7

⚫ Used for cutting
⚫ Can achieve high power densities
⚫ Water submerged plasma
⚫ cools nozzle
⚫ muffles sound
⚫ dissociates water to form H2 and O which assists cutting when
they recombine
Advantages
⚫ 9x cutting speed of conventional torches
⚫ small heat effected zone
⚫ Edges of near machine finished quality

Question 8

what is a Non transfer torch

Answer 8

⚫ Lower power density as heat has to be
removed from nozzle
⚫ Applications
⚫ Cutting non conducting materials
⚫ e.g. leather
⚫ Plasma Spraying
⚫ plasma gas heated to 16000o C
⚫ powdered materials introduced in gas instantly melt and are
projected on the workpiece
⚫ used to recover worn components or up grade substrates
⚫ achieves high coating strength

Question 9

Advantages of water-jet cutting

Answer 9

⚫ Cuts almost all materials and substances
⚫ Precise
⚫ Smooth edges and minimal kerf
⚫ No heat load
⚫ Environmentally friendly
⚫ Water is recyclable

Question 10

Factors effecting cut quality

Answer 10

⚫ Pump pressure
⚫ Nozzle distance
⚫ Nozzle diameter
⚫ Cutting pressure
⚫ Feed speed