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Surfaces Contaminant 1 nm 1–100 nm

1–100 nm 10–100 nm 1–100 mm

Adsorbed gas Oxide layer Beilby (amorphous) layer Work-hardened layer Metal substrate

FIGURE 4.1 Schematic illustration of the cross-section of the surface structure of metals. The thickness of the individual layers depends on processing conditions and the environment. Source: After E. Rabinowicz and B. Bhushan.

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Terminology for Surface Finish Flaw Waviness height

Lay direction

Roughness height, Rt Roughness spacing

Roughness-width cutoff Waviness width

=

Surface profile

+

+

Error of form

Maximum waviness height Maximum R a Minimum R a

Waviness

0 .0 .0 02 02 -2 -2 125 63 0.010 0.005

Roughness

M ax ax im im um um wa wa vi vi ne ne ss ss wi wi dt dt h Roughness-width cutoff Maximum roughness width

Lay (a)

Lay symbol

Interpretation

Examples

Lay parallel to the line representing the surface to which the symbol is applied

Lay perpendicular to the line representing the surface to which the symbol is applied

FIGURE 4.2 (a) Standard terminology and symbols used used to describe surface finish. The quantities are given in µin. (b) Common surface-lay symbols.


X

Lay angular in both directions to line representing the surface to which symbol is applied

X

P

Pitted, protuberant, porous, or particulate nondirectional lay

P

(b)

Surface Roughness

Digitized data y

A

x

f g hi j k l a b c de

Ra Roughness

B

Surface profile

Center (datum) line

Ra =

ya + yb + yc + · · · + yn n

1 =

n

1

! yi = l n i=1

Z

l

| y| dx

0

FIGURE 4.3 Coordinates used for measurement of surface roughness, used in Eqs. (4.1) and (4.2).

Rq Roughness



2

Rq =


2

2

2

ya + yb + yc + · · · + yn n

 1

=

n

! yi = n 2

i=1

l

1/2

Z  y2 dx

0

Stylus Profilometry Stylus Head

Stylus path

Rider

Actual surface Stylus Workpiece

(a)

(b)

0.5 µm (20 µin.)

0.6 µm (25 µin.)

0.4 mm (0.016 in.) (c) Lapping

3.8 µm (150 µin.)

(d) Finish grinding

5 µm (200 µin.)

(e) Rough grinding


(f) Turning

FIGURE 4.4 (a) Measuring surface roughness with a stylus. The rider supports the stylus and guards against damage. (b) Path of the stylus in measurements of surface roughness (broken line) compared with the actual roughness profile. Note that the profile of the stylus' path is smoother than the actual surface profile. Typical surface profiles produced by (c) lapping, (d) finish grinding, (e) rough grinding, and (f) turning processes. Note the difference between the vertical and horizontal scales.

Micro-Scale Adhesion

N

F

Microweld Plastic Projected contact patches

Elastic

FIGURE 4.5 (a) Schematic illustration of the interface of two contacting surfaces, showing the real areas of contact. (b) Sketch illustrating the proportion of the apparent area to the real area of contact. The ratio of the areas can be as high as four to five orders of magnitude.


Friction in Manufacturing A r << A F , e c r o f n o i t c i r F

A r ~ A

A r < A

Forging, extrusion F

 N

Drawing, rolling

Stretch forming Deep drawing

Coulomb Friction µ

F =

N

Ar

! =

Ar

! =

"

Metal cutting

Bending

Tresca Friction Normal force, N

FIGURE 4.6 Schematic illustration of the relation between friction force F and normal force N. Note that as the real area of contact approaches the apparent area, the friction force reaches a maximum and stabilizes. At low normal forces, the friction force is proportional to normal force; most machine components operate in this region. The friction force is not linearly related to normal force in metalworking operations, because of the high contact pressures involved. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

m

!i =

k

"

Coefficient of Friction in Metalworking

Process Rolling Forging Drawing Sheet-metal forming Machining

Coefficient of Friction (µ) Cold Hot 0.05-0.1 0.2-0.7 0.05-0.1 0.1-0.2 0.03-0.1 — 0.05-0.1 0.1-0.2 0.5-2 —

TABLE 4.1 Coefficient of friction in metalworking processes.


Effect of Lubrication Good lubrication

Poor lubrication

(a)

1

2

3

4

(b)

FIGURE 4.7 (a) The effects of lubrication on barreling in the ri ng compression test. (a) With good lubrication, both the inner and outer diameters increase as the specimen is compressed; and with poor or no lubrication, friction is high, and the inner d iameter decreases. The direction of barreling depends on the relative motion of the cylindrical surfaces with respect to the flat dies. (b) Test results: (1) original specimen, and (2-4) the specimen under increasing friction. Source: A.T. Male and M.G. Cockcroft.


Ring Compression Test Original dimensions 80 of specimen: OD = 3/4 in.= 19 mm ID = 3/8 in.= 9.5 mm Height = 1/4 in.= 0.64 mm 70

7 7 5 . 0 = µ

0.40 70 0.30

= 1.0

m

60 60

0.20

) 50 % ( r e t e 40 m a i d 30 l a n r 20 e t n i n 10 i n o i t 0 c u d e R210

0.15 0.12 0.10 0.09 0.08 0.07 0.06 0.055 0.05 0.04

220

) 50 % ( r e t e 40 m a i d l a 30 n r e t n i n 20 i n o i t c u 10 d e R

0.7

0.5

0.3

0.2

0

0.15

0.03 210

230

0.10

240 250

~0.02 0 0

10

20 30 40 50 60 Reduction in height (%)

70

(a)

220 0

10

0.05 20 30 40 50 Reduction in height (%)

60

70

(b)

FIGURE 4.8 Charts to determine friction in ring compression tests: (a) coefficient of friction, µ; (b) friction factor, m. Friction is determined from these charts from the percent reduction in height and by measuring the percent change in the internal diameter of the specimen after compression. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education

Profile Evolution Due to Wear Scale:

250 µm 25 µm

Unworn

Worn (a)

Unworn

Worn (b)

FIGURE 4.9 Changes in originally (a) wire-brushed and (b) ground-surface profiles after wear. Source: E. Wild and K.J. Mack.


Adhesive Wear Model Hard Plastic zone (microweld) (a)

(b)

Soft

Metal transfer (possible wear fragment) (c)

FIGURE 4.10 Schematic illustration of (a) asperities contacting, (b) adhesion between two asperities, and (c) the formation of a wear particle. Unlubricated k Mild steel on mild steel 10−2 to 10−3 6040 brass on hardened tool steel 10−3 Hardened tool steel on 10−4 hardened tool steel Polytetrafluoroethylene (PTFE) 10−5 on tool steel Tungsten carbide on mild steel 10−6

Lubricated 52100 steel on 52100 steel Aluminum bronze on hardened steel Hardened steel on hardened steel

k

10−7 to 10−10 10−8 10−9 10−9 10−9

TABLE 4.2 Approximate order of magnitude for the wear coefficient, k, in air.


Archard Wear Law: V

=

LW k 3 p

Abrasive and Other Wear Top die

2

Chip

5

1 5 3 4 2 1

5

1 5 3 4 1

1 Erosion 2 Pitting (lubricated dies only) 3 Thermal fatigue

Hard particle

4 Mechanical fatigue

Ejector

Bottom die

5 Plastic deformation

C L

FIGURE 4.11 Schematic illustration of abrasive wear in sliding. Longitudinal scratches on a surface usually indicate abrasive wear.


FIGURE 4.12 Types of wear observed in a single die used for hot forging. Source: After T.A. Dean.

Regimes of Lubrication Tooling Lubricant Workpiece (a) Thick film

(b) Thin film Boundary film

(c) Mixed

(d) Boundary

FIGURE 4.13 Regimes of lubrication generally occurring in metalworking operations. Source: After W.R.D. Wilson.


Roller Burnishing

Roller Roller Burnished surface

Roller

Workpiece (a)

(b)

(c)

FIGURE 4.14 Examples of roller burnishing of (a) the fillet of a stepped shaft, (b) an internal conical surface, and (c) a flat surface.


Thermal Wire Spraying Wire or rod Gas nozzle

Air cap

Workpiece

Combustion chamber Oxygen Fuel gas

High-velocity gas

Molten metal spray Deposited coating

FIGURE 4.15 Schematic illustration of thermal wire spraying.


Chemical Vapor Deposition Carrier gases

Exhaust

Exhaust scrubber TiCl4

Graphite shelves Tools to be coated

Electric furnace

Stainless steel retort

FIGURE 4.16 Schematic illustration of the chemical vapor deposition process.


Electroplating +

SO4-H+ Cu++ SO4-Cu++

-

Agitator

Cu++

SO4

--

SO4-H+

H+

Cu++ SO4-H+

Cu++

H+ SO4

--

Part to be plated (cathode)

Heating coils

Sacrificial (copper) anode

(a)

(b)

FIGURE 4.17 (a) Schematic illustration of the electroplating process. (b) Examples of electroplated parts. Source: Courtesy of BFG Electroplating.


Coordinate Measuring Machine

z

-axis spindle

Probe adapter Probe

(b)

Measuring table

Computer controller

Machine stand

(c)

FIGURE 4.18 (a) A coordinate measuring machine with part being measured; (b) a touch signal probe measuring the geometry of a gear; (c) examples of laser probes. Source: Courtesy Mitutoyo America Corp.


Dimensional Tolerancing e c n a r e l o T

n o i t a i v e d r e w o L

m r r e u t m e u t m e e i m x m i a a i n m a i i d M d M

n o i t a i v e d r e p p U

Hole

e z i s c i s a B

Shaft

e c n a r e l o T

n o i t a i v e d r e w o L

n o i t a i v e d r e p p U

r m e u t e m i n m a i i d M

Zero line or line of zero deviation m r e u t m e i x m a a i d M

e z i s c i s a B

(a)

Bilateral tolerance

40.00 + 0.05 mm - 0.05 1.575 + 0.002 in. - 0.002

(b)

Unilateral tolerance

(c)

40.05 + 0.00 mm - 0.10 1.577 + 0.000 in. - 0.004

Limit dimensions

40.05 mm 39.95 1.577 in. 1.573

(d)

FIGURE 4.19 (a) Basic size, deviation, and tolerance on a shaft, according to the ISO system. (b)-(d) Various methods of assigning tolerances on a shaft. Source: L.E. Doyle.


Tolerances by Process N1 N2 N3 N4 N5 N6 N7 N8 N9 N10 N11 N12 ISO No. 0.100

0.025 0.05 0.1 0.2 0.4 0.8 1.6 3.2 6.3 12.5 25 s t a

) . n i (

e g n a r e c n a r e l o T

c d l d n a m o t S e n e l l a n e S h r g r m e P r , f o e t e d s a P l x t r u i l l t t l l , e e h m m c a s t r o g r t e o u w d i e H o a s , r P o A l - d n t c h l a n e e l l c n e o t m r d i u n , p t u r e s d e, l l p Z n d , u i , a p e r I n v r n t i r D S h e x g l d h , C o u g o R w d r a m i l l l d e M r o h s E D b C a n k i i , o l F n M m C h t u r n n b E i r e a s o s i i c i n h, e f c , P r o a r i n d B r h g

0.010

0.001

i s F i n

1

2

4

1.0 0.5

0.1 0.05

m m

0.01

n e , h o , l a p h s i l P o

0.0001 0.5

50 µm 2.0

0.005 8

16

32

63 125 250 500 1000 2000

Surface roughness,

R a ( µin.)

FIGURE 4.20 Tolerances and surface roughness obtained in various manufacturing processes. These tolerances apply to a 25-mm (1-in.) workpiece dimension. Source: After J.A. Schey.


Frequency Distribution 10 e c n ) e s r r t f u a c h c s o f f o o r y e c b n m e u u n q ( e r F

8 6 4 2

0 12.95

99.73% 95.46

e c n e r r u c c o f o y c n e u q e r F

13.00 Diameter of shafts (mm)

13.05

68.26

4

3

- ! -

2

1

-

-

(a)

e c n e r r u c c o f o y c n e u q e r F

0

1

+

+

2

3

+

+

4!

(b)

10 8 6

n o i t a c i r f e i c w e o p L s

n o i t a c i r f e i p c p e p U s

4 2 0 12.95

13.00 Diameter of shafts (mm)

13.05

(c)


FIGURE 4.21 (a) A plot of the number of shafts measured and their respective diameters. This type of curve is called a frequency distribution . (b) A normal distribution curve indicating areas within each range of standard deviation. Note: The greater the range, the higher the percentage of parts that fall within it. (c) Frequency distribution curve, showing lower and upper specification limits.

Control Charts ) 13.04 m13.03 m ( x 13.02 , r 13.01 e t e 13.00 m a 12.99 i d e 12.98 g a r 12.97 e v 12.96 A

Average of 5 samples Average of next 5 samples Average of next 5 samples UCL x _

x (average

of

averages) LCL x

0

Time (a)

0.12

) m0.10 m (

UCLR

0.08 R , 0.06 e g 0.04 n a R0.02 0

R (average

range) LCLR Time (b)


FIGURE 4.22 Control charts used in statistical quality control. The process shown is in good statistical control, because all points fall within the lower and upper control limits. In this illustration, the sample size is five, and the number of samples is 15.

Constants for Control Charts Sample Size 2 3 4 5 6 7 8 9 10 12 15 20

A2

D4

D3

d2

1.880 1.023 0.729 0.577 0.483 0.419 0.373 0.337 0.308 0.266 0.223 0.180

3.267 2.575 2.282 2.115 2.004 1.924 1.864 1.816 1.777 1.716 1.652 1.586

0 0 0 0 0 0.078 0.136 0.184 0.223 0.284 0.348 0.414

1.128 1.693 2.059 2.326 2.534 2.704 2.847 2.970 3.078 3.258 3.472 3.735

TABLE 4.3 Constants for Control Charts.


Control Chart Trends Tool changed ) m m ( _ x , r e t e m a i d e g a r e v A

UCL x _ _

x

LCL x _ Time (a)

) m m ( _ x , r e t e m a i d e g a r e v A

UCL x _

LCL x _ Time (b)

) m m ( _ x , r e t e m a i d e g a r e v A

UCL x _

LCL x _ Time (c)


FIGURE 4.23 Control charts. (a) Process begins to become out of control, because of factors such as tool wear. The tool is changed, and the process is then in good statistical control. (b) Process parameters are not set properly; thus, all parts are around the upper control limit. (c) Process becomes out of control, because of factors such as a sudden change in the properties of the incoming material.

Micrometers

(a)

(b)

Digital gages

Display examples

CRT

Floppy disk drive

Bar-code reader

Printer

(c)

FIGURE 4.24 Schematic illustration showing integration of digital gages with a miniprocessor for real-time data acquisition and SPC/SQC capabilities. Note the examples on the CRT displays, such as frequency distribution and control charts. Source: Mitutoyo Corp.


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