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Engineering Applications 3004 > Manufacturing Processes (Cutting & Forming) - Week 4 > Flashcards

Manufacturing Processes (Cutting & Forming) - Week 4 Flashcards

1
Q

What does the process hierarchy consist of?

A

Casting, Cutting, Forming and Joining

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2
Q

What is most common type of manufacturing process?

A

Cutting is probably the most common type of manufacturing process,
including machining, drilling and grinding

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3
Q

How does cutting operate?

A

All cutting processes operate by selectively removing material from a solid
to produce the required shape; thus waste is always created

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4
Q

When is cutting used in most cases?

A

Cutting is often used as a secondary or finishing process following casting,
forming or powder processing

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5
Q

What is cutting used to do as a secondary process?

A

▪ Improve dimensional tolerance (high precision work such as the
machining of crankshaft journals)
▪ Improve surface texture
▪ Produce geometrical features such as holes or slots
▪ Remove sprue from an injection moulding

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6
Q

Give some examples of mechanical cutting machines?

A
  • Lathe/drill
  • Lathe
  • Milling machine
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7
Q

What is Electrochemical Machining?

A
  • Used for (slowly) cutting hard metallic materials into complicated shapes
  • Used for mass production
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8
Q

Explain the process of ElectroChemical Machining

A
  • A cathode (tool) is advanced into an anode (workpiece)
  • The pressurized electrolyte is injected at a set temperature to the area being cut.
  • As electrons cross the gap, material from the workpiece is dissolved, as the tool forms the desired shape in the workpiece.
  • The feed rate is the same as the rate of gas turning into liquid of the material
  • The gap between the tool and the
    workpiece varies within 80-800 micrometers
  • The electrolytic fluid carries away the metal hydroxide formed in the process
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9
Q

What must the metal involved for ECM be?

A

Fundamentally, the metal involved must be electrically conducting

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10
Q

What are the Advantages of ECM?

A

▪ Can cut small or odd-shaped angles, intricate contours or cavities in hard
and exotic metals
▪ As no contact there is no need to use expensive alloys to make the tool
tougher than the workpiece.
▪ Less tool wear in ECM, and less heat and stress are produced in processing
that could damage the part.
▪ Both external and internal geometries can be machined.
▪ Fewer passes are typically needed, and the tool can be repeatedly used

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11
Q

What are the disadvantages of ECM?

A

▪ High tooling costs
▪ Up to 40,000 amps of current must be applied to the workpiece.
▪ The saline (or Acidic) electrolyte also poses the risk of corrosion to tool,
workpiece and equipment.
▪ Its use is limited to electrically conductive materials

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12
Q

Give some examples of exotic metals

A
  • Titanium aluminides and high nickel
  • Cobalt
  • Rhenium alloys
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13
Q

What is Electrical Discharge Machining?

A

A manufacturing process whereby a
desired shape is obtained using electrical discharges (sparks)

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14
Q

What is EDM referred to as?

A

Spark machining/spark eroding/burning/die sinking/wire erosion

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15
Q

Explain the process of EDM?

A

A low conductivity (dielectric) fluid is placed between the two electrodes;
metal is removed (vaporised) precisely by high voltage sparking between
the tool (anode) and the workpiece (cathode)

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16
Q

How is the material removed in EDM?

A

Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage

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17
Q

What are the names of the electrodes used?

A

One of the electrodes is called the tool-electrode, while the other is called the workpiece-electrode

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18
Q

What happens when the distance between the two electrodes is reduced?

A

The intensity of the electric field in the volume between the electrodes becomes greater than the strength of the dielectric, which breaks, allowing current to flow between the two electrodes. As a result, material is removed from both the electrodes

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19
Q

What happens when the current flow stops?

A

New liquid dielectric is usually conveyed into the inter-electrode volume enabling the solid particles (debris) to be carried away and the insulating proprieties of the dielectric to be restored

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20
Q

What are the advantages of EDM?

A

▪ Complex shapes that would otherwise be difficult to produce with conventional cutting tools
▪ Extremely hard material to very close tolerances
▪ Very small work pieces where conventional cutting tools may damage the
part from excess cutting tool pressure.
▪ There is no direct contact between tool and work piece. Therefore delicate
sections and weak materials can be machined without any distortion.
▪ A good surface finish can be obtained.
▪ Very fine holes can be easily drilled

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21
Q

What are the disadvantages of EDM?

A

▪ Slow rate of material removal.
▪ Reproducing sharp corners on the workpiece is difficult due to electrode
wear.
▪ Specific power consumption is very high.
▪ Power consumption is high.
▪ Excessive tool wear occurs during machining

22
Q

What is laser cutting used for?

A

A CO2 laser can be used for precision cutting and drilling of narrow, parallel-sided slots and holes

23
Q

What are the advantages of Laser cutting?

A
  • There is no cutting load on the work-piece and no tool wear.
  • Laser machining of non-metals is fast, efficient and clean, providing good
    edge quality
  • The cut quality in ferrous metals of thicknesses up to 10mm is usually far superior to that produced by oxy-fuel or plasma cutting
24
Q

What reactive gas is used with laser cutting?

A

Laser cutting of metals is generally carried out with a jet of reactive gas
like oxygen

25
Q

What is water jet cutting?

A

A focused jet of water at very high pressure can be used for cutting non-metals like unreinforced or reinforced plastics, or even hard materials such as ceramics

26
Q

What materials is water jet cutting favourable for?

A

Water-jet cutting is favoured for polymer composites such as aramid fibre reinforced plastic (AFRP) and carbon fibre reinforced plastic (CFRP).

27
Q

Explain the process of water jet cutting?

A
  • High-pressure water inlet (water pressurized at 50,000 psi or greater) enters the cutting head at relatively slow
    speed, in the order of a few feet per second
  • Water is then moving in excess of 2200 mph(3657 kph).
  • Abrasive (garnet) is then added which is hitting the material and causes erosion, the more garnet the faster the erosion
28
Q

Why is water jet cutting favourable for Aramid fibre reinforced plastic (AFRP)?

A

AFRP materials are extremely tough and it is very difficult to achieve good
edge quality using mechanical techniques

29
Q

Why is water jet cutting favourable for Carbon fibre reinforced plastic (CFRP)?

A

CFRP materials generate huge amounts of carbon dust when machined mechanically, giving rise to health and safety concerns, and the water deals with this problem at source

30
Q

What is forming?

A

Forming processes involve shaping material in the solid state

31
Q

Why do forming processes require a lot of energy?

A

The forces required to make solids flow are much higher than those for
liquids, so forming processes normally require a lot of energy and
strong, robust, tooling

32
Q

What reasons may make forming favourable?

A
  • Geometrical requirements
  • Microstructural reasons
  • Processing reasons
33
Q

What is deep drawing used for?

A

Deep drawing is used to generate cup shapes from sheet material, such as
the main component of metallic cans used for food and drink

34
Q

What processes do Bulk deformation include?

A

Bulk deformation processes include rolling, forging and extrusion

35
Q

What are the bulk deformation processes used for?

A

These processes are used to reduce the cross-sectional area of a starting
billet

36
Q

Explain the process of powder processing?

A

The powdered material is held in a mould and then heated to a temperature below the melting point. The atoms in the powder particles diffuse across the boundaries of the particles, fusing the particles together and creating one solid piece

37
Q

Why is powder processing used for materials with extremely high melting points?

A
  • The sintering temperature does not have to reach the melting point of the material
  • examples of materials with extremely high melting points are tungsten and molybdenum
38
Q

What is 3D printing?

A

3D printing or additive manufacturing is a process of making three
dimensional solid objects from a digital file

39
Q

Do all 3D printers use the same technology?

A

No, there are several ways to
print differing mainly in the way layers are build to create the final object

40
Q

How do the methods differ?

A
  • Some methods use melting or softening material to produce the layers
  • Another method is achieved curing a photo-reactive resin with a UV laser or similar power source one layer at a time.
41
Q

What common technologies are used for melting or softening material for 3D printing?

A

Selective Laser Sintering (SLS) and Fused Deposition Modelling (FDM) are the most common technologies using this way of 3D printing

42
Q

What common technologies are used for using a photo-reactive resin with a UV laser?

A

The most common technology using this
method is called Stereolithography (SLA)

43
Q

What are the 7 Additive Manufacturing processes categories?

A
  1. Vat Photopolymerization
  2. Material Jetting
  3. Binder Jetting
  4. Material Extrusion
  5. Powder Bed Fusion
  6. Sheet Lamination
    7.Directed Energy Deposition
44
Q

Who developed the 7 Additive Manufacturing processes categories?

A

The American Society for Testing and Materials (ASTM) group

45
Q

What is the advantage and disadvantage to Rapid prototyping for 3D printing?

A

Advantage - single items can be produced inexpensively without incurring the mould and tooling costs of traditional manufacturing
Disadvantage - Entry-level 3D printers produce goods that are often inferior to those produced using traditional methods

46
Q

What is the advantage and disadvantage to Reduced Lead times for 3D printing?

A

Advantage - lead times can be reduced as a result of being able to produce goods relatively quickly
No disadvantages

47
Q

What is the advantage and disadvantage to Rapid Innovation for 3D printing?

A

Advantage - new innovations can be created and revised quickly since 3D printing is an iterative process
No disadvantages

48
Q

What is the advantage and disadvantage to Rapid manufacturing for 3D printing?

A

Advantage - Just-in-time inventory can be easily managed and created
Disadvantage - Depending on the type of printer, it can be slow to produce large volumes of products

49
Q

What is the advantage and disadvantage to Recued overhead for 3D printing?

A

Advantage - overhead required to invest in inventory, and warehouse, is reduced since items can be printed as needed
No disadvantages

50
Q

What is the advantage and disadvantage to Mass customisation for 3D printing?

A

Advantage - products can be customised for a single purpose or created in small and economical production runs
Disadvantage - Limited materials can be printed through 3D printers for commercial production

51
Q

What is the advantage and disadvantage to Mass production for 3D printing?

A

Advantage - Unique products that can’t be made using traditional manufacturing methods can be produced for mass production
Disadvantage - most 3D printers cannot produce extremely large products

Engineering Applications 3004 (11 decks)

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