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Manufacturing Technology > Metrology > Flashcards

Metrology Flashcards

1
Q

What’s the purpose of calibration?

A

Provide confidence about a measurement instruments accuracy and repeatability

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2
Q

What is a gauge block

A

Very accurately machined steel alloy or ceramic block.

Used to calibrate callipers and other measurement instruments

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3
Q

What is a gauge bar

A

Used to calibrate measuring equipment

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4
Q

What is a CMM

A

Coordinate measuring machine

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5
Q

What does a cmm do

A

Uses discrete points on an objects surface to measure it

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6
Q

How does a non contact cmm machine work, and where might it be used

A

Uses video technology to measure discrete points.

Used in application where contact would deform object

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7
Q

What type of cmm machine is portable

A

Multi axis measurement arm cmm

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8
Q

Which part of a cmm contacts the object being measured?

A

Touch trigger probe

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9
Q

What is a key problem with cmm’s that is often overlooked

A

They need a skilled operator to be used

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10
Q

What properties would a good touch trigger probe stylus have?

A

Stylus should be as short and stiff as possible.

The stylus ball should be as large as possible

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11
Q

Why is good surface texture important?

A

Can improve:
- fatigue resistance
-bearing properties
-wear resistance

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12
Q

What properties should a bearing surface have?

A

Contact area should have valleys to hold lubrication.

Perfect surface would bond with other surface

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13
Q

Would a larger or smaller surface area suffer more wear?

A

Smaller

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14
Q

What is the definition of roughness?

A

Irregularities from cutting processes

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15
Q

What is the definition of waviness?

A

Irregularities produced by machine vibration and deflections under cutting force

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16
Q

What is the definition of errors of form

A

Departure from geometrical shape

17
Q

Out’ve waviness and roughness, which is primary and which is secondary?

A

Primary - Roughness

Secondary - Waviness

18
Q

How many measurements are taken to determine surface texture

A

5

19
Q

What is the equation for roughness?

A

Roughness = (Z1+Z2+Z3+Z4+Z5)/5

20
Q

What errors can influence calibration?

A
  • Temperature
  • Pressure
  • humidity
  • vibration
  • electrostatic fields
  • electromagnetic fields
  • human interaction
21
Q

What shaft property will increase bearing wear?

A

If the shaft is not round

22
Q

What is the first step in measuring roundness?

A

Find the centre point of the shaft using a vblock

23
Q

What are the 2 types of roundness measuring machines?

A

Rotating workpiece

Fixed workpiece

24
Q

What are the advantages and disadvantages of the fixed workpiece machine? (Roundness)

A
  • precision spindle carries light load, high accuracy with low cost
  • work table can be large, allowing for large parts
  • computer aided cantering
  • Internal and external measurements possible
25
Q

What are the advantages and disadvantages of the rotating workpiece machine? (Roundness)

A
  • concentricity and alignments easier
  • measurement head can move into constricted positions
  • straightness can be measured
  • limit to size of part being measured
  • computer aided centring available
26
Q

How are roundness results recorded?

A

On a polar chart

27
Q

What is the definition of accuracy?

A

Deviation of reading from known input

28
Q

What is the definition of precision?

A

Ability to reproduce a certain reading with a given accuracy

29
Q

What is the definition of sensitivity?

A

Ratio of instrument scale change to change in measured variable

30
Q

What is the definition of error?

A

Quantified deviation between the instrument reading and the known input

31
Q

What is the definition of uncertainty?

A

Deviation between readings when a known reference value does not exist

32
Q

What is a systematic error?

A

Remains constant, or changes in a regular fashion

33
Q

What is a random error?

A

Differences between results of separate measurements that cannot be predicted

34
Q

What are sources of random errors?

A

Human error
Environmental error
Equipment error

Manufacturing Technology (1 decks)

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