Manufacturing Processes Flashcards
1
Q
In how many directions can a milling machine be used to remove material from the work part?
A
Milling allows you to move the tool up and down (z direction) while you move the work piece in the x and y directions, meaning you are able to shape the piece in 3D space.
2
Q
In how many directions can a lathe remove material?
A
Turning on a lathe removes material in 2D space for a cylinder, so in the axial and radial directions.
3
Q
In how many directions can a drill press remove material?
A
Drill presses can only remove material in the z direction.
4
Q
What is another name for face milling?
A
End milling
5
Q
What are others name for peripheral milling?
A
surface, slab, form, or plain milling
6
Q
How does peripheral milling differ from face milling?
A
Peripheral: the milling bit is oriented paralell to the work piece and rotates clockwise while the work piece is fed through. Best way to describe this is like a rolling pin.
End: The milling bit is oriented perpendicular to the work piece.
7
Q
What is Broaching?
A
The process of removing metal wth a tool that has teeth aranged in a row that get successively higher than the previous tooth. It is used to create inside “square” corners. (basically like drilling a hole but it’s square so you can’t use spinning motions)
8
Q
What are the two types of broaching? How are they different?
A
Linear: only has teeth on one side of the tool, looks kind of like a key
Rotary: Has teeth on all or multiple surfaces of the tool.
9
Q
What are the types of chips caused by material removal?
A
- discontinuous chips
- continuous chips
- continuous with built up edge (BUE)
10
Q
What indications can be taken from a discontinuous chip?
A
- brittle work material
- small rake angle
- coarse feeds and low speeds
11
Q
What indications can be taken from a continuous chip?
A
- ductile work material
- large rake angle
- fine feeds and high speeds
- use of coolant and good chip flow
12
Q
What indications can be taken from a continuous chip with BUE?
A
- high friction between the work and tool cause high temperatures that will occasionally weld the chip to the tool. This will break free, but the effect is a rough surface on the work piece.
13
Q
How are shear plane angle and shear plane relevant to the forces involved in cutting?
A
Higher shear angle means a smaller shear plane which leads to:
- lower shear force
- lower cutting forces
- lower power
- lower temperature
14
Q
Theoretically, what is the difference between a positive and negative rake angle?
A
Positive essentially means that the material is being pushed off the work piece.
Negative means the material is being pulled off, in a scraping motion.
15
Q
In terms of chip formation, what is r?
A
chip thickness ratio
16
Q
In terms of chip formation, what is to?
A
Thickness before chip
17
Q
In terms of chip formation, what is tc?
A
thickness after chip
18
Q
In terms of chip formation, what is ls?
A
????????
19
Q
In terms of chip formation, what is alpha?
A
rake angle
20
Q
In terms of chip formation, what is phi?
A
shear angle
21
Q
In terms of chip formation, what is gamma?
A
shear strain
22
Q
In terms of chip formation, what is Fc?
A
cutting force
23
Q
In terms of chip formation, what is Ft?
A
tangential force (sometimes call thrust force)
24
Q
In terms of chip formation, what is R?
A
Resultant force
25
In terms of chip formation, what is F?
Friction force ( between tool and chip)
26
In terms of chip formation, what is N?
Normal force (between tool and chip)
27
In terms of chip formation, what is Fs?
Shear force
28
In terms of chip formation, what is Fn?
Normal force to shear plane
29
What strategy can we use to calculate forces involved in cutting?
Merchant's circle diagram
30
In terms of chip formation, what is Beta?
friction angle
31
In terms of chip formation, what is As?
Area of the shear plane.
32
In terms of chip formation, what is Tau?
Shear stress which is equal to shear strength, S.
33
Since we know that increasing the shear plane angle decreases force, power, and temperature, what are some methods to increase the shear angle?
- increase the rake angle
| - reduce the friction angle and/or the coefficient of friction.
34
In terms of chip formation, what is w?
width of cutting
35
What are some properties of cutting tools?
1. Hardness
2. Toughness
3. Resistance to abrasion and wear
4. Strength to resist bulk deformation
5. adequate thermal properties
6. Correct geometry
36
What is the relation between hardness and toughness?
Materials with higher hardness have lower toughness.
37
What is toughness?
The ability of a material to absorb energy and plastically deform without fracture.
38
What is hardness?
The ability of a material surface to withstand local deformation.
39
Whats is the basic principle in regards to tool material hardness?
You need a material with a higher hardness than your stock material
40
What may cause tool failure?
- Fracture failure: forces on the tool exceed the tool strength
- Temperature failure: high temperatures lead to plastic deformation or premature wear.
- Gradual wear: normal wearing process of the tool.
41
For a Tool flank wear VS Time of cutting graph, what are the three regions?
- break in period
- Steady state wear region
- Failure region
42
What are the wear modes for a cutting tool?
- Nose radius wear
- Flank wear
- Crater wear
- Notch wear
43
What are the wear types for a cutting tool?
- Abrasion
- Adhesion
- Diffusion
- Plastic deformation
44
Abrasion is the dominant cause of what?
Flank wear
45
Explain adhesion. What types of wear are associated?
High pressure localized fusion and rupturing. Flank and notch wear.
46
Explain diffusion. What type of wear is associated?
Loss of hardening atoms at the too-chip boundary. Crater wear.
47
Plastic deformation contributes to what?
Flank wear.
48
In terms of wear, what is v?
cutting speed
49
In terms of wear, what is T?
Tool life
50
In terms of wear, what is n and C?
constants
51
What are some common machining tool materials?
1. Plain carbon steel
2. High speed steel
3. Carbides
4. Ceramics
5. Synthetic diamonds and cubic boron nitride.
52
Plain carbon steel is usually used for what in machining?
Not used much anymore because it loses hardness at low temp (150 - 300 C)
Used for: taps, dies, chisels.
53
What properties make HSS a valid option for drill bits, lathe tools, and end mills?
- withstand up to 600 C
- usually have the best toughness of most materials.
- can often be coated with titanium/cobalt to extend lifetime
54
How are carbides better than HSS?
- Cutting speed is 3-5x faster than HSS.
- withstand up to 800 C
- can be coated to increase resistance to wear
55
What are ceramics typically used for and why?
- cut 2-3x faster than carbides
- mainly used for high speed turning of cast iron and steel
- have poor thermal and shock resistance
56
What determines the geometry of a cutting tool?
- properties of the work piece material
- material of the cutting tool
- type of cutting operation
- strength of cutting edge
57
Which tools are typically used for negative rake angles?
- carbide
- diamond
- ceramics
58
What property of a material is important for small or negative rake angles?
Hard/brittle!
59
What does the nose radius affect for the work piece?
surface finish
60
What is the function of coolant as a cutting fluid?
- lubricant: reduce friction, extends tool life, reduces forces/energy consumption.
- cools the cutting zone
- protects new surfaces from corrosion
- helps to remove chips for area
61
Machined parts can be classified into two categories. What are they?
- Rotational: cylindrical or disk like
| - Nonrotational: block like or plate like
62
What factors affects the characteristic part geometry?
1. Relative Motions - generating: part geometry is determined by the feed trajectory of the cutting tool
2. Shape of the cutting tool - forming: part geometry is created by the shape of the cutting tool
63
What methods are used for generating shape?
- straight turning
- taper turning
- contour turning
- slab milling (peripheral)
- profile milling (end)
64
What methods are used for forming a shape?
- form turning
- drilling
- broaching
65
What are some methods that combine both generating and forming?
- thread cutting on a lathe
| - slot milling
66
In terms of turning, what is V?
Linear cutting speed
67
In terms of turning, what is N?
rotational speed of spindle
68
In terms of turning, what is f?
feed
69
Does cutting force increase of decrease at higher speeds?
Force slightly decreases at higher cutting speeds.
70
What variations of turning can be performed on a lathe?
- basic turning
- facing
- contour turning
- chamfering
- cutoff
- threading
71
What is facing?
Tool is fed radially inward
72
What is chamfering?
cutting edge cuts an angle on the corner of the cylinder, forming a chamfer.
73
What is parting?
Tool is fed radially inward into rotating work at some location to cut off end part.
74
What methods are used to hole the work piece in a lathe?
- holding between centers
- chuck (3 jaw or 4 jaw)
- collet
- face plate ( for offset or non cylindrical workparts)
75
What is boring?
This class haha jk
Boring is turning but performed on the inside diameter of an existing hole
76
What is the difference between drilling and boring?
Boring can only enlarge an existing hole.
77
Why is peck drilling commonplace?
improves chip evacuation
78
Drill bits have 3 common point angles; 118, 60-90, and 135. What are each used for?
118: general drilling, soft steel, most metals.
60-90: low helix angle, non-ferrous materials.
135: hard materials, shorter cutting edge means lower friction.
79
What is reaming?
Reaming slightly enlarges a hole, which provides and better tolerance on diameter and improves surface finish.
80
What is tapping?
Makes internal screw threads on an existing hole
81
What is milling?
a machining operation in which work is fed past a rotating cutter with multiple cutting edges resulting in a planar surface.
82
What is peripheral milling?
the cutter axis is parallel to the surface being machined and cutting occurs only on the outside of the cutter.
83
What is face/end milling?
the cutter axis is perpendicular to surface being machined and cutting occurs on the outside and end of the cutter.
84
What is slotting?
when the width of the cutter is less than the width of the workpiece, therefore a slot is created in the workpiece.
85
What is form milling?
the cutter has a specific form.
86
What is slot, partial, and end milling in terms of face milling?
The cutter diameter is less than work width.
87
What is profile milling?
The cutter moves along the outside of the part to create a flat surface.
88
What type of milling would be used to create shallow pockets?
End milling
89
What type of milling would be used to create a three dimensional surface?
Surface contouring
90
What is the "golden rule" in milling?
Thick to thin
91
Why is up milling occasionally preferable to down?
less shock to cutter, less vibration
92
While up milling is more conventional, why is down milling sometimes better?
- chip is thickest at the start
- surface finish is better on brittle materials
- but this results in more shock to the cutter.
93
What are some disadvantages of conventional milling?
- does not meet golden rule
- heat diffuses into the work and causes hardening
- more difficult to hold work in place
- chips are carried upward messing up the finish
94
When is conventional milling recommended over climb milling?
a) the machine is older and backlash is a concern
| b) when milling castings or forgings or when the part is case hardened.
95
What is the difference between shaping and planing?
shaping - the tool moves
| planing - the work moves
96
What tool material is typically used for shaping and planing?
HSS
97
What are some economic and product design considerations in machining?
- machinability
- tolerances and surface finish
- selection of cutting conditions
- machining economics
98
What is machinability dependent on?
- work material
- type of machining operation
- tooling
- cutting conditions
99
How do you compare machinability?
Compare the machinability rating (MR) of the best material to that of the base material (1.00)
100
Name some methods of machinability testing.
- tool life
- tool wear
- cutting force
- power required
- cutting temp
- MRR
101
How does hardness of work affect machinability?
high hardness means abrasive wear increases so tool life is reduced and so is machinability.
102
How does strength of work affect machinability?
high strength means higher cutting forces, specific energy, and cutting temperature.
103
How does ductility of work affect machinability?
high ductility means tearing of metal as chip is formed causing poor surface finish.
104
What factors relate to surface roughness in machining?
- geometric factors of the tool
- work material factors
- vibration and machine tool factors
105
What End Cutting Edge Angle (ECEA) is more favourable in regards to surface roughness? 0 or 30?
0 will provide a smoother finish.
106
In terms of surface roughness, what is Ri?
theoretical arithmetic average surface roughness
107
In terms of surface roughness, what is f?
feed
108
In terms of surface roughness, what is NR?
nose radius
109
In terms of surface roughness, what is Ra?
actual surface roughness
110
There are typically two alternatives for machining economics. What are they?
1. maximum product rate
| 2. Minimum unit cost
111
If your goal is to achieve a maximum production rate what actions should you take?
minimize cutting time per unit
112
In terms of production cycle time, what is Th, Tm, Tt, and Tc, and np, respectively?
```
Th: Part handling time per part
Tm: machining time per part
Tt: tool change time per part
Tc: production cycle time per piece
np: # of pieces cut in one tool life
```
113
What are Co and Ct?
Co: cost rate for operator and/or machining
Ct: cost per cutting edge
114
How are disposable inserts favourable over regrindable tools?
Lower tool change time
115
What are the factors on which the selection of feed in a machining operation should be based?
- type of tooling
- roughing or finished
- surface requirements
- cutting forces
116
Name 6 metal forming operations.
- machining
- casting
- rolling
- extrusion
- forging
- stamping
117
What is casting?
Taking a liquid or highly plastic work material and creating a part by solidifying the material in a mold.
118
What are the 5 steps involved in casting?
1. Make the mold
2. Melt the metal
3. Pour into mold
4. Let freeze
5. Remove the mold
119
What are the advantages of casting?
- complex part geometries (external and internal shapes)
- near net shape
- well suited to mass production
120
What are the diasadvantages of casting?
1. Limitations on mechanical properties
2. Poor dimensional accuracy and surface finish
3. safety hazards
4. environmental problems
121
What are the types of metal casting?
- expendable mold
- permanent mold
- continuous mold
122
Sand casting:
- relatively slow cooling
- course microstructure
- inferior mechanical properties
123
Die casting:
- relatively fast cooling
- refined microstructure
- improved mechanical properties
- uses force and pressure
124
Draw the cooling curve for a pure metal:
```
____
.
.
.
.________
.
.
.
.
```
125
Draw the cooling curve for an alloy:
Same as pure metal but the flat part in the middle is angle downward.
126
In terms of casting, what is Tm, Tp, H, Hf?
Tm: Melting temp
Tp: Pouring temp
H: energy required to melt
Hf: latent heat of fusion
127
In terms of casting, what is Tst?
Total solidification time
128
In terms of casting, what is V?
Volume of casting
129
In terms of casting, what is A?
Surface area of casting
130
In terms of casting, what is Cm?
mold constant
131
What does the mold constant, Cm, depend on?
- mold material
- thermal properties of casting metal
- pouring temp relative to melting point.
132
What does the volume to surface area ratio tell us about casting?
higher ratio = longer cooling time
133
Why must the riser have a high volume to surface area ratio than the casting?
The riser must solidify after the casting so that the molten metal can be fed to the main cavity.
134
What is the difference between fast and slow cooling rates
slow- results in coarse dentritic structures with large spacing between them
fast- results in fine dentritic structure
135
How do dentrites affect mechanical properties?
as the grain and structure size decreases:
- strength increases
- high temp ductility increases
- microporosity decreases
136
What is SDAS?
Secondary Dentrite Arm Spacing
137
In terms of SDAS, what is CR?
Cooling rate
138
Investment casting:
- one of the oldest
| - allow the production of components with accuracy, repeatability, versatility, and integrity
139
Permanent Mold:
- reusable mold usually made of metal
| - uses gravity to fill the mold
140
In continuous casting there are 3 cooling system, what are they?
1. primary: in mold
2. secondary: between rollers
3. Tertiary: air
141
What are some advantages to high pressure die casting (HPDC)?
The very fast filling of the mold allows for extremely thin-walled, shell-like structures.
142
How is squeeze casting different from HPDC?
mold filling is done rather slowly and in a vertical movement, therefore the die has significantly less gas defects but the minimum wall thickness is slightly higher than HPDC.
143
What are the advantages and disadvantages of expendable molds?
+ more intricate geometries are possible
+ typically lower level of automation
- higher production cost
144
What are the advantages and disadvantages of permanent molds?
- fixed basic geometries
+ lower production cost
- higher level of automation
+ more economic for mass production
145
What are the pros and cons of continuous casting?
+ highly advanced
+ effective process and quality assurance control
+ mass production of specialty Fe alloys
- economically viable in mass production only
- requires strict control over center line segregation and shrinkage porosity
146
In terms of casting, what is Cl?
Weight specific heat of the liquid metal
147
In terms of casting, what is To?
starting temp
148
In terms of casting, what is Cs?
weight specific heat for the solid metal
149
What are important factors to consider in order to achieve a successful pour of molten metal?
- pouring temp
- pouring rate
- turbulence
- surface tension
150
What is shrinkage?
volume is lost during that transition from liquid to solid (internal)
151
What is contraction?
volume reduction during cooling of the solid metal (external)
152
What are some possible casting defects?
- misrun: molten metal does not completly fill mold
- cold shut: there is an unfilled cavity at the core
- cold shots: there are smaller bubbles of air throughout the mold
- shrinkage cavity: the interior core experiences shrinkage.
- microporosity:
- hot tear: crack
153
What is metal forming?
A manufacturing process in which plastic deformation is used to change the shape of metal workpieces
154
What are desirable material properties in metal forming?
- low yield strength
| - high ductility
155
What are some examples of bulk deformation?
- rolling
- forging
- extrusion
- wire and bar drawing
156
What are some examples of sheet metalworking?
- bending
- deep drawing
- cutting
157
What is rolling?
Rolling a material between rollers to flaten, like a pasta maker
158
What is forging?
Pressing the material between a die to change the shape
159
What is extrusion?
Applying a force to the back of a material to push it through a die.
160
What is drawing?
Pulling a material through a die.
161
When sheet metalworking, what is the part called and what are the tools used?
```
Part = stampings
Tool = punch and die
```
162
What is the difference between a punch and a die?
```
punch = the tool applying force, fits into die
Die = the receiving tool that shapes the work.
```
163
What is shearing of sheet metal?
applying a force on one side of the sheet metal to essentially tear into two pieces
164
What happens to strength during deformation?
Typically strength will increase as a consequence of strain hardening
165
In terms of sheet metal working, what is Yf?
Flow stress: instantaneous value of stress required to continue deforming the material
166
How does flow stress relate to yield strength and tensile strength?
Flow stress is the intermediate value between the two.
167
In terms of sheet metal working, what is Yf bar?
average flow stress, determined by integrating the flow curve
168
What happening to the strength (K) and strain hardening exponent (n) at higher temperatures?
both are reduced
169
What are the three temperature ranges in metal forming?
- cold
- warm
- hot
170
Cold Working:
- performed at or just above room temp.
| - minimum or no machining required
171
What are the advantages of cold forming?
1. dimensional accuracy
2. surface finish
3. strain hardening
4. no heating
172
What are the disadvantages of cold forming?
1. higher forces
2. clean surfaces required
3. ductility and strain hardening limit formability
4. residual stress
173
Warm working:
- performed above room temp but below recrystallization temp
174
What are the advantages of warm forming?
1. lower forces
| 2. more intricate geometries
175
Hot working:
- performed above recrystallization temp = 0.5Tm
176
What is Recrystallization?
the process in which deformed grains of the crystal structure are replaced by a new set of stress-free grains that nucelate and grow until all the original grain have been consumed.
177
What are the advantages of hot forming?
- far more plastic deformation
- much less forces
- n is theoretically = 0
178
What phenomenon occurs during deformation, especially at elevated temperatures?
Strain rate sensitivity; as strain rate increases so does resistance to deformation
179
Why is friction undesirable in metal forming?
- metal flow is slowed
- forces are increased
- tool wears faster
180
What types of rolling?
- flat rolling: reduce thickness
| - shape rolling: makes square, round, I, T cross sections
181
What is draft?
amount of thickness reduction
182
In terms of rolling, what is F?
Rolling force
