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MEC 322 > Metrology > Flashcards

Metrology Flashcards

Midterm Review

1
Q

what is metrology

A

the study of measurement

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2
Q

What is interchangeable part

A

Every part has to be made of specific dimensions, and specific tolerance

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3
Q

what is a dimension and tolerance

A

linear or angular sizes of a component specified on a part or drawing. Tolerance is the allowable variation permitted in the manufacturing process

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4
Q

Micro x10^-6
Nano x10^-9

A
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5
Q

what 5 things impact tolerance

A
  • speed of operation
    -temp
  • Lubrication
  • Variation of Incoming Material
  • other factors
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6
Q

What is Bilateral Tolerance

A

a tolerance in both the positive and negative direction

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7
Q

What is the tolerance of/what kind of tolerance is it:
+0.005
-0.005

A

Bilateral Tolerance: 0.010
Remember: Tolerance is the a DIFFERENCE btwn the max and minimum

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8
Q

what is a balanced tolerance

A

a bilateral tolerance with the same max and min.
i.e +0.005
-0.005

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9
Q

what is a unilateral Tolerance

A

a tolerance only in 1 direction
+0.005
-0.000

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10
Q

What is a Limit Dimensions

A

A tolerance of a maximum dimension and a minimum dimension.
i.e : 2.505
2.495

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11
Q

what is a clearance fit

A

a fit where the shaft can fit easily into the whole

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12
Q

what are the 3 kinds of fits

A

clearance: slides in easily
interference: force it through as the shaft is slightly bigger than the whole
Transition fit: the hole and shaft have very close tolerance

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13
Q

what is Allowance

A

The specific difference in dimensions between mating parts

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14
Q

what is basic size?

A

the dimension from which limits of size are derived

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15
Q

what is a datum

A

theoretically exact axis, point, line or plane

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16
Q

what is interference

A

negative clearance

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17
Q

what is clearance

A

the space between mating parts

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18
Q

what is another way to say normal surface?

A

Nominal Surface:
appear as absolutely straight lines, ideal circles, round holes, and anything else deemed as “geometrically perfect”

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19
Q

what is actual surfaces

A

determined by the manufacturing process used to design a part. i.e nominal is what we want, actual is what we are going to get.

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20
Q

why are surfaces important?

A
  • aesthetics
  • safety
  • friction and wear
  • assembly
  • operation(i.e painting coating welding)
  • smooth surfaces make better electrical contacts
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21
Q

what are the 4 elements of surface texture

A
  1. roughness
  2. waviness
  3. lay
  4. flaws
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22
Q

what is roughness

A

variation of tiny specific section(zoomed in)

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23
Q

waviness

A

the shape on a larger scale (zoomed out)

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24
Q

how to calculate roughness average

A

r= (a+b+c…..)/n

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25
Q

what is lay

A

the direction in which the pattern of surface is in

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26
Q

what are flaws

A

irregularities that occur occasionally on the surface

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27
Q

what is the cutoff length

A

distinguishes between the roughness and waviness by being less than the waviness length/width

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28
Q

Surface integrity is…..

A

surface integrity is a crucial aspect of manufacturing that involves understanding and managing the properties of the surface and subsurface layers of materials to ensure the desired performance and functionality of the final product.

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29
Q

residual stress in…

A

subsurface layer i.e bending of sheet metal

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30
Q

cracks are…

A

microscopic and macroscopic breaks. i.e tearing of ductile metals in machining

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31
Q

what are hardness variations

A

work/strain hardening. happens in plastic deformation when the material becomes much harder than it originally were

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32
Q

the two main surface changes caused by mechanical energy are….

A

residual stress and hardness variations(work hardening)

33
Q

what are surface changes caused by?

A

caused by forms of energy during processing

34
Q

what are the surface changes by thermal energy

A
  1. metallurgical changes: recrystallization, grain size changes, phase changes as surface
  2. redeposited: melted metal is removed, then added back before it solidifies
  3. resolidified: same as redeposited except it is not detached
  4. heat affected zone in welding: heated but not melted area to undergo changes
  5. Hardness changes (usually heat causes things to become less hard)
35
Q

what are the surface changes by chemical energy

A
  1. intergranular attack: corrosion/oxidation
  2. chemical contamination
  3. absorption of elements(H and CI) in metal surface: leads to a property change
  4. Selective Etch : removing a material through chemical reaction: concentrate on certain components in base metal
  5. alloy depletion and resulting hardness changes
36
Q

surface changes by electrical energy

A

1.Changes in conductivity and/or magnetism:

  1. Craters: These are rough surface depressions left behind due to short circuits during certain electrical processing techniques such as arc welding, Electro Discharge Machining, and Electro Chemical Machining.
37
Q

what is the difference between accuracy and precision?

A

Accuracy: degree to which the measured value agrees to the true value
Precision: degree of repeatability

38
Q

What is repeatability of an instrument

A

variation of equipment/the ability for an instrument to provide similiar results

39
Q

what is reproducibility?

A

variation of operator on the same equipment

40
Q

what does calibration mean

A

comparing a measurement device to one having a known relationship to national standards

41
Q

what is resolution?

A

the smallest increment on a measurement device.

42
Q

why does product quality matter in manufacturing?

A
  • for interchangeable manufacturing
  • standardization and mass production
  • the product components must assemble properly and be replaceable
  • prevention of defects
43
Q

what makes a high quality product?

A

reliability in performance and a higher cost

44
Q

what makes a low quality product?

A

less reliable/fails after a short time, hard to use and low cost

45
Q

what is inspection?

A

using measurement and gaging techniques to determine whether a product, and its specific components align with a design specification

46
Q

what is inspection by variable?

A

actually measuring a product or part using necessary instruments

47
Q

what is inspection by attribute?

A

indirectly measuring something using gages to determine if they fit into the tolerance limits.

48
Q

inspection by variable or attribute?
Measuring the diameter of a cylindrical part

A

variable

49
Q

inspection by variable or attribute?
Measuring the temperature of an oven

A

variable

50
Q

inspection by variable or attribute?
Measuring the electrical resistance on electrical components

A

variable

51
Q

inspection by variable or attribute?
Gaging a cylindrical part with a GO/NO=GO gage to determine if it is within tolerance

A

attribute

52
Q

inspection by variable or attribute?
Determining the defect rate of sample of production parts

A

attribute

53
Q

inspection by variable or attribute?

Counting the number of defects in an automobile as it leaves the final assembly

A

attribute

54
Q

what is gaging and what is it good for?

A

it determines if the characteristics of the part meets the requirements. It is faster but does not tell you a lot about the feature

55
Q

what are pros and cons of Manual Inspection

A

its boring and takes a time. theres a high risk of error, but for small batches of data is is often used.

56
Q

what con does sampling inspection cause?

A

it may lead to inaccuracy because it only takes a small portion of a large data set.

57
Q

what two categories make up how automated inspection is used ?

A
  • to sort parts into quality levels. I.e acceptable and unacceptable
  • to have inspection feedback to reduce variability and improve quality
58
Q

when is the best time to do inspection?

A

the earlier the better, when the product is being made.

59
Q

what are the three testing points in inspection?

A
  • Receiving inspection
    –> sample inspection of raw materials
  • In process “
    –> inspecting any amount of quality related costs and customer requirements
  • Final “
60
Q

What is acceptance sample, give pros and cons

A

sample inspection- analyze materials and either accept or reject it.

pro: it provides risk assessement, feasible, less time and energy

Cons: does not work for stable processes,, only detects poor qualit things, it does not add any benefit/improvement/prevention (tells you whats wrong but not how to fix it)

61
Q

What is the economic model equation

A

Break even analysis: p*C2 = C1
C1= cost of inspection
C2 = Cost of repair
p= number of failing parts

p>C1/C2, use 100% inspection
P< C1/C2, do nothing

62
Q

Give examples of/ state the uses of Contact and Non-contact inspection

A

Contact: inexpensive, accurate and practical

  • Coordinate measuring machine (measures mechanical dimensions)
  • stylus type surface texture “ (measures roughness and waviness)
  • Electrical contact probe( testing circuits and circuit boards.

Non contact: fast, feasible 100% inspection, can access things some contact inspections can’s, avoiding damages.

  • optical light : machine vision, laser scanning, roughness/profile measurement etc
  • non optical : use of energy forms besides light such as radiation, electric fields X-RAY etc.
63
Q

what kind of measuring devices include a set of markings on a linear/angular scale

A

Graduated measuring devices

64
Q

what kind of measuring devices have no scale and are used to compare dimensions

A

non graduated measuring devices

65
Q

What is a GO/NOGO Gages?

A

One gage limit can be inserted whilst the other can not.

GO Limit: measures dimension at maximum material condition, i.e min size for internal and max size for external feature

NOGO: measures dimension at minimum material condition

66
Q

what is Dial Gage amplification?

A

amplifies a linear motion into a circular motion

67
Q

what are the disadvantages of optical flats

A

fragile
thin sample, could bend
if the optical flat is not flat enough, it could alter the accuracy

68
Q

what is an alternative to optical flats?

A

interferometers: uses the same principles hower provide more accuracy and does not damage the sample

69
Q
A

interfermometry does not look beneath the surface

70
Q

what is a better way to measure surface roughness instead of interferometry

A

interferometry is a great way to measure surface roughness but a stylus is cheaper

71
Q

what is a disadvantage of a stylus

A

it is a contact measurement and the radius of the stylus can impact the accuracy and resolution

72
Q

what does CMM stand for

A

coordinate measuring machine: measuring x-y-z measurements

73
Q

what are the 4 componenets of CMM

A

bridge - made out of granite
ram
probe - can move in xyz direction
reference

74
Q

styles of CMM

A

gantry style- most accurate
Horizontal arm- not stable
articulate arm- portable but the least accurate

75
Q

what are the 3 kinds of touch probes for CMM

A
  • Fixed - contact and easily breakable
  • Touch triggered - contact
  • optical -
76
Q

what 2 things impact what kind of probe you use

A

effective working length_ length of probe

diameter of probe

77
Q

what are some benefits of CMM

A
  • Versatile
  • great accuracy and precision
  • higher productivity
78
Q
A

MEC 322 (4 decks)

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