1. Chapter 1 MACHINE TOOLS AND MACHINING OPERATIONS Prof. Dr. S
Chapter 1 MACHINE TOOLS AND MACHINING OPERATIONS Prof. Dr. S. Engin KILIÇ

2. MACHINING IS THE REMOVAL OF THE UNWANTED METAL FROM A WORKPIECE IN THE FORM OF CHIPS SO AS TO OBTAIN A FINISHED PRODUCT OF DESIRED SIZE, SHAPE, AND FINISH.

3. History of Machining
Before 18th century main material used was wood.
Development of metal machining starts with invention of steam engine (1776).
The production of cylinders of the engine was a problem.
Wilkinson invented horizontal boring machine to cope with this problem.

4. Fundamentals of Machining
The principle used in all machine tools is generating the surface required by providing suitable relative motions between cutting tool and the work piece.
Metal removed is called chip.
Two types of relative motion must be provided by a metal cutting machine tool: Primary and feed motion.

5. Fundamentals of Machining
The primary motion is the main motion provided by a machine tool or manually to cause relative motion between the tool and the work piece so that the face of the tool approaches to the work piece material.
Usually the primary motion absorbs most of the total power required to perform a machining operation.

6. Fundamentals of Machining
The feed motion is a motion that may be provided to the tool or work piece by a machine tool which, when added to the primary motion, leads to a repeated or continuous chip removal.
This motion may proceed by steps or continuously; in either case it usually absorbs a small proportion of the total power required.

7. Relative motion between tool and workpiece
Primary motion
Secondary motion
Cutting motion
Feed motion
Feed speed
Cutting speed

8. Classification of the chip removing
methods according to relative motions

9. Resultant cutting motion
in cylindrical turning

10. ISO Machine Tool Axis Definition

12. RIGHT HAND RULE

13. RIGHT HAND RULE
Vertical Machine
Horizontal Machine

14. Types of cutting tools CUTTING TOOL SİNGLE POİNT CUTTİNG TOOL
MULTI POİNT
CUTTİNG TOOL
ABRASIVE
TOOL

15. Typical single-point cutting tool

16. Machine tools using single-point cutting tools
Lathes
Shapers
Planers
Boring M/C’s

17. Drilling M/C’s Milling M/C’s Broaching M/C’s Hobbing M/C’s
Machine tools using multiple-point
cutting tools
Drilling M/C’s
Milling M/C’s
Broaching M/C’s
Hobbing M/C’s

18. Machine tools using abrasive tools
Grinding M/C’s
Honing M/C’s

19. Machine Tool Provides work holding tool holding
relative motion between tool and workpiece

20. LATHES

21. Bed Headstock Assembly Tailstock Assembly Carriage Assembly
Components of a Lathe
Bed
Headstock Assembly
Tailstock Assembly
Carriage Assembly
Quick-change Gear Box
Lead Screw and Feed Rod.

22. A typical turning machinez X Y

23. Engine Lathe z X Y

24. Automatic screw machines Swiss-type automatic screw machines
Types of Lathes
Engine lathe
Tool-room lathe
Turret lathe
CNC lathes
Automatic screw machines
Swiss-type automatic screw machines

25. Cutting Tools
For cutting tools used in lathes, geometry depends mainly on the properties of the tool material and the work material.

26. Tool geometry for a single point tool
Base
Face
Major flank
Corner
Major cutting edge
Minor flank
Minor cutting
edge
Tool axis
Shank
Cutting part

27. Tool geometry for a single point tool

28. Tool geometry for a single point tool

29. Operations that can be performed on a lathe
Turning
Boring
Facing
Parting (Cutoff)
Threading

30. Typical Lathe Operations

31. Typical Lathe Operations

32. Turning is the machining operation that produces axisymmetrical parts

33. Turning The process of machining external cylindrical surfaces
Usually performed on a lathe

34. Turning defined as the machining of an external surface
with the work-piece rotating,
with a single-point cutting tool
fed parallel to the axis of the work-piece
at a distance from the work axis to remove a layer from the outer surface of the work.

35. Turning process and adjustable parameters
Feed
Depth of cut
(back engagement)
Spindle speed

36. Turning process

37. Average cutting speed
nw:rotational frequency of workpiece
dw:diameter of workpiece
dm:diameter of machined surface

38. Metal removal rate
F : Feed
ap : back engagement (depth of cut)
nw : rotational frequency of workpiece
dm: diameter of machined surface

39. Boring involves the enlarging of an existing hole, which may have been made by a drill or may be the result of a core in a casting

40. Typical boring operation

41. Metal removal rate
f : feed
ap : back engagement
nw : rotational frequency of workpiece
dm: diameter of machined surface

42. Facing is the process to produce a flat surface normal to work axis in turning

43. Typical facing operation

44. Maximum cutting speed
nw: rotational frequency of workpiece
dm: diameter of machined surface

45. Metal removal rate Zw,max
f :feed
ap :back engagement
nw :rotational frequency of workpiece
dm :diameter of machined surface

46. Parting is the operation by which one section of a work-piece is severed from the remainder by means of a cutoff tool

47. Typical parting operation

48. In threading primary motion of tool is combination of –C’ and –Z’ to generate a helix on the workpiece by setting the gears that drive the lead screw to give the required pitch of the machined threads.

49. Typical threading operation

50. Vertical Boring Machine
Similar to lathes but with a vertical axis to accommodate large and heavy workpieces

51. A typical Vertical Boring Machine

52. Horizontal Boring Machine
They are very versatile and thus particularly useful in machining large parts

53. Essential features of Horizontal Boring Machine
A rotating spindle that can be fed horizontally.
A table that can be moved and fed in two directions in a horizontal plane.
A headstock that can be moved vertically

54. Horizontal Boring MachineX Y

55. Shaping and Planing
Shaping is used to produce flat surfaces only suitable for small parts in low –batch quantities

56. Among the oldest single-point machining processes
Shaping and Planing
Among the oldest single-point machining processes
Largely replaced by milling and broaching
In shaping, workpiece is fed at right angles to the cutting motion between successive strokes of the tool.

57. A shaper and a planer from 18th century
Shaping and Planing
A shaper and a planer from 18th century

58. Classification of shapers according to their general design features
Horizontal
Pull-cut
Push-cut
Vertical
Regular
Keyseater
Special

59. Horizontal Push-cut ShaperY X

60. A typical vertical shaper

61. Vertical Shaper (Slotter)X Y Z
Vertical and inclined surfaces
External and internal cylindrical surfaces
Circular feeding of table between strokes
Keyseater specially designed for mach. keyways inside wheel and gear hubs

62. Shaping and Planing
Planing is used to produce flat surfaces on workpieces that are too large to be accommodated on shapers.

63. Classification of Planers according to their general design features
Double-housing type planers
Edge planers
Open side planers
Pit planers

64. Typical Planers Z X Y

65. Machines Using Multipoint-Cutting Tools

66. Drilling Machine (Drill Press)

67. Drilling Used to produce holes.
Constitutes about 25% of all machining processes

68. Parts of a Typical Drilling Machine
Powerhead
Column
Spindle
Table
Base

69. Various types of Drilling Machines
Gun (deep hole) drilling
Gang Drilling
Turret Drilling

70. Typical operations performed on drilling machines
Center Drilling
Reaming
Spot Facing
Spot facing

71. Drilling, formulations
ac :undeformed chip thickness
f :feed
Кr :Major cutting edge angle

72. lw:lenght of specimen f:feed nt:rotational frequency of the tool
Machining time:
lw:lenght of specimen
f:feed
nt:rotational frequency of the tool

73. Metal removal rate: f:feed nt:rotational frequency of the tool
dm:diameter of the machined surface

74. Metal removal rate for hole enlargement:
f:feed
nt:rotational frequency of the tool
dm:diameter of the machined surface

75. MILLING

76. A process by which a surface is generated by progressive chip removal.
Milling
A process by which a surface is generated by progressive chip removal.
Performed on a wide variety of milling machines.
The cutting tool is used is known as milling cutter.

77. Major components of a milling machine

78. Types of milling machines
Horizontal Milling Machines
Vertical Milling Machines

79. Milling operation

80. Milling operation with coolant

81. Horizontal Milling Machines
In horizontal milling machines the milling cutter is mounted on a horizantal arbor driven by the main spindle.

82. A typical Horizontal Milling Machine

83. Used to generate a horizantal surface on the workpiece
Slab Milling Operation
Used to generate a horizantal surface on the workpiece

84. Slab milling formulations

85. Maximum undeformed chip thickness:

86. Time for machining:

87. Metal removal rate:
Zw= ae. ap.vf
ae :working Engagement
ap :width of cut
Vf :feed speed of the workpiece

88. Vertical milling machines
In vertical milling machines the milling cutter is mounted on a vertical arbor driven by the main spindle

89. Vertical milling operations
End Milling
Face Milling

90. A Vertical Milling Machine

91. Used to generate surface that is at right angle to the cutter axis
Face milling
Used to generate surface that is
at right angle to the cutter axis

92. Various face and end milling operations

93. In Face Milling feed is ;
f:feed
Vf:Feed speed of the workpiece
nt:rotational frequency of the cutter

94. Maximum undeformed chip thickness:
Vf:Feed speed of the workpiece
nt:rotational frequency of the cutter
N:Number of teeth on the cutter

95. Machining time if the path of the tool axis passes over the workpiece:
lw :Lenght of the specimen
dt :Diameter of the tool
v f :Feed speed of the workpiece

96. Milling time analysis Slab milling: Approach distance, A : A = d (D-d)
Time to mill workpiece, Tm:
Tm = (L + A)/fr
Face milling:
Allow for over-travel O where A = O:
Full face A = O = D/2
Partial face A = O = w (D – w)
Machining time:
Tm = (L + 2A)/fr

97. Machining time if the path of the tool axis does not pass over the workpiece:
lw:Length of the specimen
ae:Working engagement
dt:Diameter of the tool
Vf:Feed speed of the workpiece

98. Milling Operatios

99. BROACHING

100. Broaching is the machining of metal by means of a tool which is composed of a series of single point cutting edges each slightly larger than the previous one, made on bar.

101. Finishes an entire surface in a single pass.
Broaching
Finishes an entire surface in a single pass.
Is used in production to finish holes, splines and flat surfaces.
Is one of the most productive of the basic machining processes.

102. Vertical broaching X Z y

103. The average metal-removal rate (Zw) can be estimated by dividing the total volume of metal removed by the machining time.

104. Machining time for broaching:
lt:Lenght of the Broach
V:Cutting Speed

105. ac=af=f af:Feed engagement f:Feed
Feed is the motion which an imaginary single cutting edge would have to be given by the machine tool to produce the same result as the array of cutting edges with which the tool is actually provided. It is the height difference between the two successive teeth. Uncut chip thickness:
ac=af=f
af:Feed engagement
f:Feed

106. ABRASIVE MACHINING PROCESSES

107. Abrasive Machining
The basic process in which chips are formed by very small cutting edges that are integral parts of abrassive particles

108. Two unique characteristics:
Abrasive Machining
Two unique characteristics:
Cutting edge is very small, very fine cuts are possible.
Cutting edges are actually extremely hard abrasive particles therefore very hard materials can be machined

109. Abrasive machining: Grinding
A material removing process that involves the interaction of abrasive grits with the work piece at high speeds and shallow penetration depths.
Abrasive machining is the oldest machining operation.
Cutting edges are very small and can cut simultaneously.
Very fine and smooth surfaces can be obtained

110. Types of grinding operations
Traverse Grinding: The primary feed motion is the reciprocating traverse motion along the length (or axis) of the part with an intermittent infeed (cylindrical grinding)/cross feed (surface grinding) at the end of each stroke.
Plunge Grinding: Intermittent feed motion is normal to the work surface (infeed) at the end of each stroke of the traverse motion (surface grinding); infeed motion (normal to work surface) without traverse motion (cylindrical grinding).

111. Types of grinding machines
Horizontal-Spindle Surface-grinding Machine
Vertical-Spindle Surface-grinding Machine
Cylindrical-grinding Machine
Internal-grinding Machine

112. Horizontal-Spindle Surface-Grinding Machine
Has a horizontal spindle that provides primary motion to the wheel. The feed motion is the reciprocation of the worktable on which the work is mounted.

113. Horizontal-spindle surface-grinding machine
Traverse grinding

114. Metal removal rate for traverse grinding:
f:Feed
ap:Back Engagement
Vtrav.:Traverse Speed

115. Machining time:
bw:Witdh of the workpiece
F:Feed
nr:Frequency of reciprocation

116. Plunge grinding process with horizontal-spindle surface-grinding machine

117. Metal removal rate for plunge grinding:
f :Feed
ap :Back Engagement
Vtrav.:Traverse Speed

118. Machining time: at :tool depth of workpiece f :feed
nr :frequency of reciprocation
ts :sparking-out time

119. Vertical-Spindle Surface-Grinding Machine
Employs a cup-shaped abressive wheel and performs an operation similar to face milling operation.

120. Metal removal rate: Vertical-Spindle Surface-Grinding Machine f:Feed
ap:Back Engagement
Vtrav.:Traverse Speed

121. Machining time: Vertical-Spindle Surface-Grinding Machine
at:tool depth of workpiece
f:Feed
nw:Frequency of reciprocation worktable
ts:Sparking-out time

122. Cylindrical grinding

123. Traverse grinding on a cylindrical grinder
Max. metal removal rate:
f :feed per stroke of the machine table
dw :diameter of the work surface
Vtrav.:traverse speed

124. Machining time: Traverse grinding on a cylindrical grinder
at:tool depth of workpiece
f:Feed
nr:Frequency of reciprocation
ts:Sparking-out time

125. Plunge grinding on a cylindrical grinder
Max. metal removal rate
ap:back engagement
dw:diameter of the work surface
Vf.:feed speed

126. Machining time: Plunge grinding on a cylindrical grinder
at:tool depth of workpiece
vf:Feed speed
ts:Sparking-out time

127. Internal-grinding machine
Commonly used for producing internal cylindrical surfaces

128. Max.metal removal rate:
Traverse grinding on an internal grinder
Max.metal removal rate:
f :feed per stroke of the machine table
dm :diameter of the machined surface
Vtrav.:traverse speed

129. The machining time: Traverse grinding on an internal grinder
at:tool depth of workpiece
f:Feed
nr:Frequency of reciprocation
ts:Sparking-out time

130. Max.metal removal rate:
Plunge grinding on a internal grinder
Max.metal removal rate:
ap:back engagement
dm:diameter of the machined surface
Vf.:feed speed

131. The machining time is; at:tool depth of workpiece vf:Feed speed
ts:Sparking-out time

132. Abrasive machining: Honing
A stock removal process that uses fine abrasive stones to remove very small amounts of metal.
Cutting speed is much lower than that of grinding.
Used to size and finish bored holes.

133. Specific Cutting Energy
For a given work material machined under given conditions, the energy required to remove a unit volume of material (ρs) can be measured. This mainly depends on the work material.

134. Pm = ps Zw Machining power Ps:Specific cutting energy
Zw:Metal removal rate

135. Electrical motor power
Pm: Power required to perform machining ηm: Overall efficiency of the machine tool

136. Unit for specific cutting enegy

137. Specific Cutting Energy ps vs Uncut Chip Thickness ac

138. Selected Problems
bars 80 mm in diameter and 300 mm long must be turned down to 65 mm diameter for 150 mm of their length. The surface finish and accuracy requirements are such that a heavy roughing cut (removing most of the material) followed by a light-finishing cut are needed. Both the roughing and the light finishing cuts are to be taken at maximum power. The light finishing cut is to be taken at a feed of 0.13 mm, a cutting speed of 1.5 m/s.
Assume that the lathe has a 2 kW motor and an efficiency of 50 %, specific cutting energy for the work material is 2.73 GJ/m3, the time taken to return the tool to the beginning of the cut is 15 s, and the time taken to load and unload a workpiece is 120s.
a) Calculate the total production time in kiloseconds (ks) for the batch of work
b) Calculate the machining time of one part in the roughing cut
c) Calculate the machining time of one part in the light finishing cut

139. Selected Problems 1.1. SOLUTION Given: Nb=2000
dw=80 mm dm=65 mm lm=150 mm
Psmax= 0.5x2= 1 kW = 1000 W
ps=2.73 GJ/m3
flf= 0.3mm vlf = 1.5 m/s
tr=15 s tl = 120 s
tpr= Nb(tl + tmr + tmlf + 2 tr ) only the machining times for the roughing and the light finishing cuts are unknown
Machining time can be found by dividing the volume to be removed for a given operation to the metal removal rate for the operation. Hence we need to find the metal removal rate first.

140. Selected Problems 1.1. SOLUTION (cont.’d) Zw= Psmax /ps
Since for both the roughing and the light cutting operations maximum available power at the spindle are to be utilized; the metal removal rate for both of the operations wiil be the same.
Hence:
Zw= (1000 J/s)/(2.73 J/mm3) = 366 mm3/s
a) tmT= tmr+ tmlf = Vr/ Zw + Vlf / Zw =(Vr+ Vlf)/Zw =VT/ Zw
VT= (dw ).lw/4 = ( ). 150/4 = mm3
tmT= /366.3≈ 700 s
tpr= 2000( x ) = 1700ks

141. Selected Problems 1.1. SOLUTION (cont.’d)
b) tmr= Vr/ Zw = /366.3 ≈ 538 s
c) tmlf = Vlf /Zw = 59251/366.3 = 162 s
Machining time for light finishing operation can also be found by using the given cutting parameters, i.e. v=1.5 m/s and f= 0,13 mm
ap = Zw /(fv) = 366.3/(0.13x1500) = 1.88 mm
tmlf =  dlfave lm/vf
dlfave = dw+ ap= = mm
tmlf = ( x x 150)/(1500 x 0.13) = 162 s