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Design and Manufacture 2 > Limits and fits > Flashcards

Limits and fits Flashcards

1
Q

What are some of the results of guilding parts

A

Minimises number of parts
Design for ease of assembly
Design to be fool proof during assembly

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2
Q

What are the benefits for DMforA

A 
Shorter time to market
Smoother transition to production
Fewer components is production
Easier Assembly
Lower production costs
Higher production quality
Greater customer satisfaction
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3
Q

What is another name for simultaneous engineering

A

Concurrent Engineering

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4
Q

What has the to be the same between to parts for interchangabilitity

A

The size and tolerance

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5
Q

Closer tolerance leads to better performance but it is….

A

More expensive

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6
Q

What Tolerance should you choose

A

The largest possible tolerance without reducing the function of the part

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7
Q

What is tolerance

A

an undesirable but permissible deviation from a desired dimension

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8
Q

What errors cause tolerance

A

Material behaviour, temperature during process, wear of tools, human error

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9
Q

What is an allowance

A

Intentional desired difference between dimensions of two meeting parts

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10
Q

What percentage of parts of lie within 3 standard deviations of the nominal size

A

99.76%

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11
Q

Describe clearance, interference and transition fit

A

Clearance- shaft is smaller than hole
Interference- hole is smaller than shaft
Transition- a fit that may provide either clearance or interference

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12
Q

What British Standard table do we use for shaft and hole sizes

A

BS4500

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13
Q

What is the fundamental deviation

A

The closest deviation to the 0 line, gives the tolerance with respect to 0

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14
Q

What is a shaft based system

A

When the fundamental deviation of the shaft is always 0, i.e shaft always lies on the dotted line.

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15
Q

What is a hole based system

A

When the fundamental deviation of the hole is always 0, i.e the hole always lies on the dotten line.

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16
Q

What are the fundamental deviations denoted by for both holes and shafts

A

Holes use Capital letters

Shafts use lower case letters

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17
Q

What letter is used for a shaft based system

A

h

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18
Q

What letter is used for a hole based system

A

H

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19
Q

What is the basic size of 25 H11-c11

A

25

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20
Q

Is 25 H11-c11 a shaft or hole based system

A

Hole

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21
Q

What is the hole tolerance grade of 25 H11-c11

A

11

22
Q

What is the shaft tolerance grade of 25 H11-c11

A

11

23
Q

When does Maximum Material condition occur

A

When hole diameter is a minimum and shaft diameter is at a maximum

24
Q

When does least material condition occur

A

when hole diameter is at a maximum and shaft diameter is at a minimum

25
Q

What is more commonly used hole based system or shaft based system and why

A

Hole based system because holes are usually only made to standard sizes

26
Q

When might a shaft based system be used

A

When fitting several parts to one shaft

27
Q

What are allowance and Tolerance functions of

A

Basic size

28
Q

How many grades do tolerances come in

A

18

29
Q

The tolerance grades are IT01, 1T0 and….

A

IT1-IT16

30
Q

Tolerances are made depending on if the part is to

A

Mate with another part and how they are to made

31
Q

What are functional and non functional parts

A

Functional parts are essential to the operation of the part so use close tolerances. Non-Functional parts are not as important and use more generous tolerances

32
Q

What is the equation for process capability index

A

PCI=T(tolerance)/6*standard deviation

33
Q

Does a hole make a difference to thermal expansion

A

No

34
Q

How is increase in allowance related to original allowance

A

Linearly

35
Q

What are shrink fits useful for

A

High torque and large axial loads

36
Q

What is the equation for allowance at maximum material condition for thermal expansion

A

Allowance at max material condition=Min hole-Max shaft+ Shaft expansion

37
Q

What is the equation for allowance at maximum material condition for thermal contraction

A

Allowance at Max material condition= Min Hole -Max shaft + Shaft contraction - Hole contraction

38
Q

What is the equation for allowance and thermal change and what are the sign convention

A

Allowance at Max material condition=Min hole-max shaft-shaft change +hole change
Expansion is positive
Contraction is negative

39
Q

What do the symbols stand for in the equation for shrink fitted parts

A

1=Length
alpha = linear coefficient pf temperature
T= temperature

40
Q

What are the symbols in the interference pressure

A 
P= interference pressure
Sigma= total diameter interference
a=outer radius of inner
b=outer radius of inner
Eo= youngs modulus of outer
Ei= youngs modulus of inner 
v= poisons ratio
41
Q

What is the equation for the torque carried by the shrink fitted

A

T=2muppia^2*l

42
Q

What do the symbols in the torque equation mean

A 
T=torque
mu= co of friction 
p= pressure
a=interference radius
L=length of inference fit
43
Q

What percentage of parts would you expect to find within + or - 1 standard deviation of nominal size

A

68.26%

44
Q

What percentage of parts would you expect to find with + or - 2 standard deviations nominal size

A

95,46%

45
Q

What percentage of parts would you expect to find within + or - 3 standard deviations of nominal size

A

99.73%

46
Q

What is the upper deviation of the shaft.

A

Distance between max diameter and the zero line (basic size)

47
Q

What is the lower deviation of the shaft

A

Distance between min diameter and zero line (basic size)

48
Q

What is the upper deviation of the hole

A

Distance between max diameter and zero line (basic size)

49
Q

What is the lower deviation of hole

A

Distance between min diameter zero line ( basic size)

50
Q

What is the Equation for PCI

A

PCI= Tolerance/ (6x standard deviation)

Design and Manufacture 2 (5 decks)

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