1. Product specification Dimensioning and tolerancing
It is impossible to make a perfect component so when we design a part we specify the acceptable range of features that make-up the part.

2. Chapter 2 Suppliment DIMENSIONS, TOLERANCES, AND SURFACES
Dimensions, Tolerances, and Related Attributes
Surfaces
ASME Y14.5 Form Geometry
Effect of Manufacturing Processes
IE 316 Manufacturing Engineering I - Processes

3. THE DESIGN PROCESS Product Engineering
How can this be accomplished?
1. Clarification of the task
2. Conceptual design
3. Embodiment design
4. Detailed design
Design Process
Off-road bicycle that ...
1. Conceptualization
2. Synthesis
3. Analysis
4. Evaluation
5. Representation
Functional requirement -> Design
Steps 1 & 2 Select material and properties, begin geometric
modeling (needs creativity, sketch is sufficient)
mathematical, engineering analysis
simulation, cost, physical model
formal drawing or modeling

4. DESIGN REPRESENTATION
Engineering
Representation
Manufac-
turing
• Verbal
• Sketch
• Multi-view orthographic drawing (drafting)
• CAD drafting
• CAD 3D & surface model
• Solid model
• Feature based design
Requirement of the representation method
• precisely convey the design concept
• easy to use

5. A FREE-HAND SKETCH Orthographic Projection

6. A FORMAL 3-VIEW DRAWING 0.9444" A 4 holes 1/4" dia
around 2" dia , first
hole at 45°
2.000
0.001 A

7. DESIGN DRAFTING Y P r o f i l e p l a n e I I H o r i z o n t a l Z IX I I V F r o n t a l p l a n e
Third angle projection
Drafting in the third angle

8. INTERPRETING A DRAWING

9. DESIGN DRAFTING Partial view A - A Cut off view and auxiliary view2 . 1
Partial view A - A
Cut off view and auxiliary view
Provide more local details

10. DIMENSIONING Requirements 1. Unambiguous 2. Completeness
3. No redundancy
Incomplete
dimensioning
0.98 '
1.22 '
1.72 '
0.83 '
3.03 '
Redundant dimensioning
0.86 '
1.22 '
0.83 '
3.03 '
Adequate dimensioning

11. TOLERANCE Dimensional tolerance - conventional
Geometric tolerance - modern
nominal dimension + -
means a range
tolerance
+ 0.10
- 0.00
+ 0.00
- 0.10
unilateral
bilateral
0.95
1.05 + -

12. TOLERANCE STACKING
1. Check that the tolerance & dimension specifications are
reasonable - for assembly.
2. Check there is no over or under specification.
"TOLERANCE IS ALWAYS ADDITIVE" why?
1.20 '
±0.01
0.80 '
±0.01
1.00 '
±0.01 ?
What is the expected dimension and tolerances?
d = = 3.00
t = ± ( ) = ± 0.03

13. TOLERANCE STACKING (ii)?
0.80 '
±0.01
1.20 '
±0.01
3.00 '
±0.01
What is the expected dimension and tolerances?
d = = 1.00
t = ± ( ) = ± 0.03

14. TOLERANCE STACKING (iii)x
1.20 '
±0.01 ?
0.80 '
±0.01
3.00 '
±0.01
Maximum x length = = 1.03
Minimum x length = = 0.97
Therefore x = ± 0.03

15. TOLERANCE GRAPH d,t d,t d,t A B C D E d,t G(N,d,t)
N: a set of reference lines, sequenced nodes
d: a set of dimensions, arcs
t: a set of tolerances, arcs
d : dimension between references i & j
t : tolerance between references i & j ij ij
Reference i is in front of reference j in the sequence.

16. EXAMPLE TOLERANCE GRAPH
d,t
d,t
d,t
A B C D E
d,t
different properties
between d & t

17. OVER SPECIFICATION
If one or more cycles can be detected in the graph, we say that the dimension and tolerance are over specified. d1 d2
A B C
d1,t1
d2,t2 d3
Redundant dimension
d3,t3 A B C t1 t2
A B C t3
Over constraining tolerance
(impossible to satisfy) why?

18. UNDER SPECIFICATION
When one or more nodes are disconnected from the graph, the
dimension or tolerance is under specified. d1 d2
A B C D E d3 A B C D E
C D
is disconnected from the
rest of the graph.
No way to find

19. PROPERLY TOLERANCED A B C D E
d,t
d,t
d,t
A B C D E
d,t

20. TOLERANCE ANALYSIS For two or three dimensional tolerance analysis:
i. Only dimensional tolerance
Do one dimension at a time.
Decompose into X,Y,Z, three one dimensional problems.
ii. with geometric tolerance
? Don't have a good solution yet. Use simulation? d i a m e t e r
& t o l e r a n c e
A circular tolerance zone, the size is influenced
by the diameter of the hole. The shape of the
hole is also defined by a geometric tolerance. t r u e p o s i t i o n

21. 3-D GEOMETRIC TOLERANCE PROBLEMS
datum surface
datum
surface
± t
Reference
frame
perpendicularity

22. TOLERANCE ASSIGNMENT Tolerance is money
• Specify as large a tolerance as possible as long as functional and assembly requirements can be satisfied.
(ref. Tuguchi, ElSayed, Hsiang, Quality Engineering in Production Systems, McGraw Hill, 1989.) Q u a l i t y
function C o s t
cost + t - t d ( n o m i n a l d i m e n s i o n )
Tolerance value
Quality cost

23. REASON OF HAVING TOLERANCE
• No manufacturing process is perfect.
• Nominal dimension (the "d" value) can not be achieved exactly.
• Without tolerance we lose the control and as a consequence cause functional or assembly failure.

24. EFFECTS OF TOLERANCE (I)
1. Functional constraints
e.g.
flow rate
d ± t
Diameter of the tube affects the flow. What is the allowed
flow rate variation (tolerance)?

25. EFFECTS OF TOLERANCE (II)
2. Assembly constraints
e.g. peg-in-a-hole dp
How to maintain the clearance? dh
Compound fitting
The dimension of each segment affects others.

26. RELATION BETWEEN PRODUCT & PROCESS TOLERANCES
Machine uses the locators as the reference. The distances from the machine coordinate system to the locators are known.
The machining tolerance is measured from the locators.
• In order to achieve the 0.01 tolerances, the process tolerance must be or better.
• When multiple setups are used, the setup error need to be taken into consideration. A . 1 t o l e r a n c e s
Design specifications S e t u p l o c a t o r s . 5 . 5 . 5
Process tolerance

27. TOLERANCE CHARTING
A method to allocate process tolerance and verify that the process sequence and machine selection can satisfy the design tolerance.
Not shown are
process tolerance
assignment and
balance
blue print
Operation
sequence
produced tolerances:
process tol of 10 + process tol of 12
process tol of 20 + process tol 22
process tol of 22 + setup tol

28. PROBLEMS WITH DIMENSIONAL TOLERANCE ALONE
As designed: 1 . . 1 6 . . 1
As manufactured: 1 . 1
Will you accept the part
at right?
Problem is the control of
straightness.
How to eliminate the
ambiguity? 1 . 1 1 . 1 6 .

29. GEOMETRIC TOLERANCES
ANSI Y14.5M-1977 GD&T (ISO 1101, geometric tolerancing;
ISO positional tolerancing; ISO 5459 datums;
and others), ASME Y
FORM
straightness
flatness
Circularity
cylindricity
ORIENTATION
perpendicularity
angularity
parallelism
Squareness
roundness
LOCATION
concentricity
true position
symmetry
RUNOUT
circular runout
total runout
PROFILE
profile
profile of a line

30. DATUM & FEATURE CONTROL FRAME
Datum: a reference plane, point, line, axis where usually a plane where you can base your measurement.
Symbol:
Even a hole pattern can be used as datum.
Feature: specific component portions of a part and may include one or more surfaces such as holes, faces, screw threads, profiles, or slots.
Feature Control Frame: A
datum
// M A
modifier
symbol
tolerance value

31. MODIFIERS Maximum material condition MMC assembly
Regardless of feature size RFS (implied unless specified)
Least material condition LMC less frequently used
Projected tolerance zone
Diametrical tolerance zone
T Tangent plane
F Free state
maintain critical wall thickness or critical location of features.
MMC, RFS, LMC
MMC, RFS
RFS

32. SOME TERMS MMC : Maximum Material Condition
Smallest hole or largest peg (more material left on the part)
LMC : Least Material Condition
Largest hole or smallest peg (less material left on the part)
Virtual condition:
Collective effect of all tolerances specified on a feature.
Datum target points:
Specify on the drawing exactly where the datum contact points should be located. Three for primary datum, two for secondary datum and one or tertiary datum.

33. DATUM REFERENCE FRAME .
Three perfect planes used to locate the imperfect part.
a. Three point contact on the primary plane
b. two point contact on the secondary plane
c. one point contact on the tertiary plane P r i m a r y T e r t i a r y S e c o n d a r y
Secondary
O M A B C
primary
Tertiary C B A

34. STRAIGHTNESS Tolerance zone between two straightness lines. . 1. 1
Value must be smaller than the size tolerance.
1.000 '
±0.002 M e a s u r e d e r r o r Š . 1 . 1
1.000 '
±0.002 . 1
Design
Meaning

35. Dimensions and Tolerances
In addition to mechanical and physical properties, other factors that determine the performance of a manufactured product include:
Dimensions - linear or angular sizes of a component specified on the part drawing
Tolerances- allowable variations from the specified part dimensions that are permitted in manufacturing
IE 316 Manufacturing Engineering I - Processes

36. Surfaces
Nominal surface - intended surface contour of part, defined by lines in the engineering drawing
The nominal surfaces appear as absolutely straight lines, ideal circles, round holes, and other edges and surfaces that are geometrically perfect
Actual surfaces of a part are determined by the manufacturing processes used to make it
The variety of manufacturing processes result in wide variations in surface characteristics
IE 316 Manufacturing Engineering I - Processes

37. Why Surfaces are Important
Aesthetic reasons
Surfaces affect safety
Friction and wear depend on surface characteristics
Surfaces affect mechanical and physical properties
Assembly of parts is affected by their surfaces
Smooth surfaces make better electrical contacts
IE 316 Manufacturing Engineering I - Processes

38. Surface Technology Concerned with:
Defining the characteristics of a surface
Surface texture
Surface integrity
Relationship between manufacturing processes and characteristics of resulting surface
IE 316 Manufacturing Engineering I - Processes

39. Figure 5.2 ‑ A magnified cross‑section of a typical metallic part surface
IE 316 Manufacturing Engineering I - Processes

40. Surface Texture The topography and geometric features of the surface
When highly magnified, the surface is anything but straight and smooth. It has roughness, waviness, and flaws
It also possesses a pattern and/or direction resulting from the mechanical process that produced it
IE 316 Manufacturing Engineering I - Processes

41. Surface Integrity
Concerned with the definition, specification, and control of the surface layers of a material (most commonly metals) in manufacturing and subsequent performance in service
Manufacturing processes involve energy which alters the part surface
The altered layer may result from work hardening (mechanical energy), or heating (thermal energy), chemical treatment, or even electrical energy
Surface integrity includes surface texture as well as the altered layer beneath
IE 316 Manufacturing Engineering I - Processes

42. Figure 5.3 ‑ Surface texture features
Repetitive and/or random deviations from the nominal surface of an object
Figure 5.3 ‑ Surface texture features
IE 316 Manufacturing Engineering I - Processes

43. Four Elements of Surface Texture
Roughness - small, finely‑spaced deviations from nominal surface determined by material characteristics and process that formed the surface
Waviness - deviations of much larger spacing; they occur due to work deflection, vibration, heat treatment, and similar factors
Roughness is superimposed on waviness
IE 316 Manufacturing Engineering I - Processes

44. Figure 5.4 ‑ Possible lays of a surface
3. Lay - predominant direction or pattern of the surface texture
Figure 5.4 ‑ Possible lays of a surface
IE 316 Manufacturing Engineering I - Processes

45. 4. Flaws - irregularities that occur occasionally on the surface
Includes cracks, scratches, inclusions, and similar defects in the surface
Although some flaws relate to surface texture, they also affect surface integrity
IE 316 Manufacturing Engineering I - Processes

46. Surface Roughness and Surface Finish
Surface roughness - a measurable characteristic based on roughness deviations
Surface finish - a more subjective term denoting smoothness and general quality of a surface
In popular usage, surface finish is often used as a synonym for surface roughness
Both terms are within the scope of surface texture
IE 316 Manufacturing Engineering I - Processes

47. Surface Roughness
Average of vertical deviations from nominal surface over a specified surface length
Figure 5.5 ‑ Deviations from nominal surface used in the two definitions of surface roughness
IE 316 Manufacturing Engineering I - Processes

48. Surface Roughness Equation
Arithmetic average (AA) is generally used, based on absolute values of deviations, and is referred to as average roughness
where Ra = average roughness; y = vertical deviation from nominal surface (absolute value); and Lm = specified distance over which the surface deviations are measured
IE 316 Manufacturing Engineering I - Processes

49. An Alternative Surface Roughness Equation
Approximation of previous equation is perhaps easier to comprehend:
where Ra has the same meaning as above; yi = vertical deviations (absolute value) identified by subscript i; and n = number of deviations included in Lm
IE 316 Manufacturing Engineering I - Processes

50. Cutoff Length
A problem with the Ra computation is that waviness may get included
To deal with this problem, a parameter called the cutoff length is used as a filter to separate waviness from roughness deviations
Cutoff length is a sampling distance along the surface. A sampling distance shorter than the waviness width eliminates waviness deviations and only includes roughness deviations
IE 316 Manufacturing Engineering I - Processes

51. Figure 5.6 ‑ Surface texture symbols in engineering drawings:
the symbol, and (b) symbol with identification labels
Values of Ra are given in microinches; units for other measures are given in inches
Designers do not always specify all of the parameters on engineering drawings
IE 316 Manufacturing Engineering I - Processes

52. TRUE POSITION T o l e r a n c e z o n e Dimensional tolerance . 2 2 1. 2 2 1 . . 1 1 . 2 . 1 O . 8 . 2
Hole center tolerance zone O . 1 M A B
True position
tolerance T o l e r a n c e z o n e . 1 d i a 1 . B A 1 . 2

53. HOLE TOLERANCE ZONE Tolerance zone for dimensional toleranced
hole is not a circle. This causes some assembly
problems.
For a hole using true position tolerance
the tolerance zone is a circular zone.

54. TOLERANCE VALUE MODIFICATION1 . . 2 O . 1 M A B
Produced True Pos tol
hole size
out of diametric tolerance
out of diametric tolerance 1 .
M L S B 1 . 2
MMC
LMC A
The default modifier for
true position is MMC.
For M the allowable tolerance = specified tolerance + (produced hole
size - MMC hole size)

55. MMC HOLE ,
Given the same peg (MMC peg), when the produced hole size is greater than the MMC hole, the hole axis true position tolerance zone can be enlarged by the amount of difference between the produced hole size and the MMC hole size.

56. PROJECTED TOLERANCE ZONE
Applied for threaded holes or press fit holes to ensure interchangeability
between parts. The height of the projected tolerance zone is the thickness
of the mating part. . 3 7 5 - 1 6 U N C - 2 B O . 1 M A B C . 2 5 p

57. Surface Integrity
Surface texture alone does not completely describe a surface
There may be metallurgical changes in the altered layer beneath the surface that can have a significant effect on a material's mechanical properties
Surface integrity is the study and control of this subsurface layer and the changes in it that occur during processing which may influence the performance of the finished part or product
IE 316 Manufacturing Engineering I - Processes

58. Surface Changes Caused by Processing
Surface changes are caused by the application of various forms of energy during processing
Example: Mechanical energy is the most common form in manufacturing. Processes include metal forming (e.g., forging, extrusion), pressworking, and machining
Although primary function is to change geometry of workpart, mechanical energy can also cause residual stresses, work hardening, and cracks in the surface layers
IE 316 Manufacturing Engineering I - Processes

59. Surface Changes Caused by Mechanical Energy
Residual stresses in subsurface layer
Cracks ‑ microscopic and macroscopic
Laps, folds, or seams
Voids or inclusions introduced mechanically
Hardness variations (e.g., work hardening)
IE 316 Manufacturing Engineering I - Processes

60. Surface Changes Caused by Thermal Energy
Metallurgical changes (recrystallization, grain size changes, phase changes at surface)
Redeposited or resolidified material (e.g., welding or casting)
Heat‑affected zone in welding (includes some of the metallurgical changes listed above)
Hardness changes
IE 316 Manufacturing Engineering I - Processes

61. Surface Changes Caused by Chemical Energy
Intergranular attack
Chemical contamination
Absorption of certain elements such as H and Cl in metal surface
Corrosion, pitting, and etching
Dissolving of microconstituents
Alloy depletion and resulting hardness changes
IE 316 Manufacturing Engineering I - Processes

62. Surface Changes Caused by Electrical Energy
Changes in conductivity and/or magnetism
Craters resulting from short circuits during certain electrical processing techniques
IE 316 Manufacturing Engineering I - Processes

63. Tolerances and Manufacturing Processes
Some manufacturing processes are inherently more accurate than others
Examples:
Most machining processes are quite accurate, capable of tolerances = 0.05 mm ( in.) or better
Sand castings are generally inaccurate, and tolerances of 10 to 20 times those used for machined parts must be specified
IE 316 Manufacturing Engineering I - Processes

64. Surfaces and Manufacturing Processes
Some processes are inherently capable of producing better surfaces than others
In general, processing cost increases with improvement in surface finish because additional operations and more time are usually required to obtain increasingly better surfaces
Processes noted for providing superior finishes include honing, lapping, polishing, and superfinishing
IE 316 Manufacturing Engineering I - Processes