IE 312 PRODUCT DESIGN AND
MANUFACTURING PROCESSES
MACHINING PROCESSES
AND ABRASIVE MACHINING PROCESSES
Course Instructor
Prof. Edward C. De Meter
Dept. of Industrial & Manufacturing Engineering
The Pennsylvania State University
READING ASSIGNMENT
Reading Assignment: Kalpakjian
Chapter 8 Material-Removal Processes
Complete within the next three lecture
periods

MACHINING PROCESSES
VALUE-ADDED
Near Net Shape/
Net Shape
Bulk Material
Refinement
Surface Coating
Surface Geometry
Refinement
Yes
No
No
Yes
internal thread cutting
end milling
sawing
gear hobbing


Machining is a class of material removal processes used to shape
mechanical parts
their bulk properties
Machining processes are capable of generating a near net shape and
surface geometry refinement
TOPIC OUTLINE
Definition
Attributes and Limitations
Process Overview
Technical Issues

MACHINING PROCESS DEFINITION
deformed and
fractured chip
cutting tool
machined
surfaces
A class of manufacturing processes that create a precise geometric surface via
the controlled
of material from a solid part
The process is enabled through the controlled relative motion between the
work-piece and a cutting tool
ATTRIBUTES OF MACHINING PROCESSES
Versatility
Accuracy

VERSATILITY
Machining is the most versatile of the
mechanical shaping processes with regard
to:


part size
 input work-piece shape


MATERIAL VERSATILITY
Machining processes are used to shape all,
engineered materials including:

metals
polymers
ceramics (green state)
composites
woods

PART SIZE DIVERSITY
Machining processes are used to make
very
parts

PART SIZE DIVERSITY
Machining processes
are used to make
very
parts

Milling of a Fluid End Valve for the Natural Gas
Industry (courtesy of Advanced Manufacturing
Inc.)
INPUT WORK-PIECE SHAPE VERSTALITY
finished part
work-piece after first
machining sequence
bulk solid work-piece


Machining processes are used to create shapes from bulk
solid work-pieces
The bulk solid work-pieces are cut from
called
INPUT WORK-PIECE SHAPE VERSTALITY
machined surfaces appear metallic
aluminum die casting
Machining processes are used to create refined surfaces
on

are derived from processes such as:

Casting processes
 Bulk deformation processes
 Sheet metal processes
 Powdered metal processes
 Plastic shaping processes

INPUT WORK-PIECE VERSATILITY
plastic parts created by
plastic injection
molding process
plastic injection molds
created by machining
processes
Machining processes are used to create the
molds used to create
parts

MANUFACTURING VOLUME VERSATILITY
Milling of an Impeller on a Stand Alone 5 Axis
Machining Center (courtesy of Haas)
Machining processes are used by
to make a great number of part types in very
small numbers (down to 1)

MANUFACTURING VOLUME VERSATILITY
Machining processes are
used by large volume
manufacturers to make a
in very large
numbers (> 5M annually)

Milling of a Diesel Engine Component on a
Horizontal Machining Center Within a Flexible
Machining Line (courtesy of Lamb Technicon)
GEOMETRIC ACCURACY ACHIEVED BY MACHINING PROCESSES
Structural
Number of Surface Designs
Number of Machining
Processes
Flow
Rolling/Sliding Contact Incidental Contact
EM transmission
Locational Contact
1 µin
.0001 in
10 µin
.1 in
Geometric
Error
Geometric
Error
(in.)
.001 in
.01 in
.05 in
SURFACE FINISH ACHIEVED BY MACHINING PROCESSES
Structural
Number of Surface Designs
Number of Machining
Processes
Flow
Rolling/Sliding Contact
Incidental Contact
EM transmission Locational Contact
.5 µin
5 µin
16 µin
urface
Finish
SSurface
Surface
Finish
(Ra: µin)
Finish
32 µin
80 µin
200 µin
300 µin
ECONOMIC IMPORTANCE
Due to their versatility and accuracy,
machining processes are used to either
directly or indirectly shape nearly all
mechanical parts in use today

Machining processes account for
of the economic output of all
manufacturing processes1

LIMITATIONS OF MACHINING PROCESSES

The
needed to machine a near net shape is substantially
greater than other processes such as:



Casting
Forging
Plastic injection molding

The
disparity grows with a growth in the number of distinct
surfaces (e.g.
)
Significant material removal applications are
limited to

It may not be possible to machine


due to issues of
It may not be possible to machine thin walled geometry due to part
distortion and chatter
MACHINING PROCESS CONCEPTS
Topics to be Covered:

Workpiece
Cutting Tool
Fixture
Machine Tool
Programming
Roughing vs Finishing

WORK-PIECE
Solid part whose shape is to be altered by
machining processes

A work-piece that has yet to experience its first
machining operation is often called a “blank”

Work-pieces and machining processes are
typically classified as:



ROTATIONAL



A
machining process is
one in which the work-piece is
rotated about an axis, and is in
rapid motion relative to a quasistationary cutting tool
Quasi-Stationary Cutting Tool
Surface types that are machined
are
Work-pieces that undergo
rotational operations are called
rotational work-pieces
Work-piece is rotated with respect to the spindle axis
Rotation Direction
PRISMATIC
Cutting tool is rotated with respect to the spindle axis
Rotation Direction



A
machining process is
one in which the cutting tool is
rotated about an axis, and is in
rapid motion relative to a quasistationary work-piece
Any surface type is capable of
being machined including a
surface of revolution
Work-pieces that undergo
prismatic operations are called
prismatic work-pieces
Quasi-Stationary Work-piece
MACHINE TOOL

The machine used to execute a machining process



Supplies the
and deform and fracture chips from the work-piece
Moves the cutting tool relative to the work-piece along a
controlled trajectory for the purpose of surface generation
Machine tools are specially built for either rotational
operations or prismatic operations
TURNING CENTER

A computer controlled (CNC)
controlled machine tool
designed for rotational
machining operations is
called a turning center
HAAS SL-20 Turning Center
MACHINING CENTER

A computer controlled
(CNC) controlled
machine tool designed
for prismatic machining
operations is called a
machining center
HAAS VF-2 Machining Center
CUTTING TOOL


A device which contacts the work-piece and deforms
and fractures the chip
A cutting tool is comprised of a body and cutting
teeth

Cutting teeth contact the work-piece

The

The cutting teeth
is used to transmit power to the cutting teeth
with the body
Non-Integral Cutting Teeth
Tool Body
Replaceable Cutting
Tooth Insert
•Designing the cutting tool as an assembly allows for:
•
for both the body and insert
•quick replacement of the primary wear component
•cheaper long term tooling costs
INTEGRAL CUTTING TEETH
(Courtesy of Kennametal)
Tool Body
Cutting
Teeth
,10mm
Designing an integral cutting tool allows for:



cheaper tool manufacture in some cases

FIXTURE

The device used to:

the work-piece relative to the machine tool axial
reference frame
unwanted work-piece motion during machining




provide power transmission in the case of rotational
machining operations
FIXTURES USED FOR ROTATIONAL PROCESSES
Work-piece
Three Jaw Chuck

Live Center
There are different types of devices used to fixture rotational parts


Two popular choices are the three jaw chuck and
FIXTURES USED FOR PRISMATIC MACHINING
Manifold Casting
Vise Holding a Single
Rectangular Work-piece for
Machining on a VMC




Hydraulically Actuated
Tombstone Fixture for Holding 8
Manifold Castings for Machining
on an HMC
There is a great variety of fixtures and fixture technologies that are
used to hold prismatic work-pieces
Most fixtures are designed specifically for the application (e.g.
)
However the vise is widely popular for holding rectangular shapes
PROGRAMMING
Geometric Model of
Cutting Tool
Geometric Model of
Work-piece
Machining Process Plan
and Process Variables
Tool Path Generation
CAM
Software
Tool Path Plan
Post Processing
Machine Specific CNC
Program in G Code Format
MACHINING DATUM REFERENCE FRAME
MDRF
z y
x
•
•
The
of the Machining Datum Reference Frame (MDRF)
is defined in the machine tool work space during machine tool set-up
During a machining cycle, the controller
Machine Tool Axial Reference Frame (MTRF)
in the MDRF to the
ROUGHING PROCESSES VERSUS FINISHING PROCESSES
Original work-piece surface
Intermediary work-piece surface after the completion of the 1st roughing process
Semi-finished work-piece surface after the completion of the last roughing process
Finished work-piece surface after the completion of the finishing process
Surface Generation Within a Machining Operation

Roughing processes are used to remove layers of material from the workpiece at


A finishing process is used to impart


Primary issue is to
material removal rate while maintaining a reasonable
rate of
and staying within the technical limits of the machine tool
Primary issue is to generate a surface that will satisfy
be completed in the least amount of time
and that can
In many applications, a cutting tool will be used for a roughing process or a
finishing process but not both
MACHINING PROCESS OVERVIEW
ROTATIONAL
MACHINING
OPERATIONS
Turning
Profiling
Facing
Cut-Off
Grooving
Threading
PRISIMATIC
MACHINING
OPERATIONS
HOLE MAKING
Drilling
Spot Drilling
Reaming
Boring
Tapping
Face Milling
End Milling
Slot Milling
Thread Milling
ALTERNATIVE
Sawing
Filing
Broaching
Shaping
Gear Shaping
ROTATIONAL PROCESSES
TURNING PROCESSES
Straight Turning

Profile Turning
Turning processes are used to machine surfaces
through tool motion that is primarily
FACING AND CUT-OFF PROCESSES
Facing


Cut Off
Facing is used to generate a profile surface predomin antly
through motion that is
to the spindle axis
Cut off is a process used to
a workpiece from stock
GROOVING PROCESSES
Courtesy of Kennametal

Grooving processes utilize
small in-feeds coupled
with specialized tools to
cut grooves for:




O-rings
Snap rings
Oil rings
Geometry clearance for
threading operations
Profile Turning
SINGLE POINT THREADING PROCESSES
Courtesy of Kennametal
internal thread cutting
Courtesy of Kennametal
external thread cutting
threading processes are used to machine

threads
PRISMATIC PROCESSES
FACE MILLING PROCESSES
Face Milling


Courtesy of Kennametal
Face milling is used to machine a flat surface with a fine surface finish
The machined surface is
to the spindle axis
END MILLING PROCESSES
End Milling

Used to create general




Courtesy of Kennametal
features including:
channels and shoulders
cavities
curvilinear surfaces
Many end mill designs have evolved for various classes of features
CHANNELS AND SHOULDERS
HSS
End Mill
Solid Carbide Indexable
End Mill
End Mill
Courtesy of Kennametal

Flat end mills with cutting edges along the
used to machine channels and shoulders
are
CAVITIES
HSS
End Mill



Carbide Center-Cutting,
End Mill Indexable Insert
End Mill
Courtesy of Kennametal
Cavity milling requires plunge capability
End mills with “center cutting capability” can be directly plunged into
solid material with simple axial motion
Center cutting is enabled by teeth that extend from the flute at the
CAVITIES
Indexable
End Mill
Ramp and
Plunge Mill (RPF)
RAMP
PLUNGE
& FEED
Z
HELICAL
INTERPOLATION
C° ramp
angle
Courtesy of Kennametal


End mills without center cutting capability must be
into solid material in order to cut a clear path
Newer CNC machining centers utilize canned cycles
for
CURVILINEAR SURFACES

Curvilinear surfaces are typically machined using
end mills

Note that the
radius must be smaller than the smallest radius of
curvature of the machined surface in order to prevent gouging
SLOT MILLING PROCESSES
Minimum
Slotting Cutter
Slot Milling
Adaptor Mounted
Courtesy of Kennametal

Slot milling is used to create a channel at

The slotting cutter is held using an arbor and standard tool holder

This type of tool is substantially
commonly used for deep, narrow slots
than an end mill and is
THREAD MILLING PROCESSES
Thread Mill Cutters
Tool Motion

Courtesy of Kennametal
Thread milling is used to create external threads and/or internal threads for:

Difficult to machine materials

Blind holes without a thread relief groove

Large bore diameters

Nonstandard thread geometries
DRILLING PROCESSES
Courtesy of Kennametal


Used to machine a hole into a solid work-piece
Typically the
hole making process used in a hole making
sequence (e.g. proceeds reaming, boring, or tapping)
DRILL TECHNOLOGY HISTORY
1820
Twist Drill
Made from
carbon steel
1900
Twist Drill
made
from
High
Speed Steel
1970
1930
Indexable
Carbide
Insert Drills
Carbide Tip
Drills
Present

Drills have been used since the middle ages

However the first documented use of twist drills
is 1820
Solid Carbide
High Performance
Courtesy of Kennametal
CHIP AND HEAT CONTROL

Critical to the success of a drilling operation is the removal of
chips and heat from the tip of the drill

Chips can
drill to break

Chips can also become compacted at the tip, spoil the cutting
action, and increase the thrust force until the drill breaks

Excess heat can cause the drill material to soften and fail and/or
the work-piece material to weld to the tip

the lands and the hole, causing the
Excess heat can also cause the drill diameter to
within the hole; causing drill breakage
CHIP AND HEAT CONTROL

To
from
the tip and out of the hole
requires a combination of:



auger action
coolant flow
Courtesy of Kennametal

Externally
Supplied
Flood
Coolant
Thru the
Nozzle
Coolant
This is done through a
combination of:






drill point geometry
flute shape
chip breakers
flood coolant via the flutes
internal coolant via the core
compressed air via the core
SPOT DRILLING

 Dc
 Dc x β
Chamfer Specification
Profile View of a 5/8 in. Spot Drill
D

Spot drilling is used to create:



Linear Path at
Controlled Feed Rate
a chamfer or countersink at the rim of
an existing hole
a pilot hole for a subsequent drilling
operation
The point angle of the spot drill must
equal the chamfer spec.
N
f
Dc
dr
reference
plane

Linear Path at
Rapid Traverse
Feed Rate
Dc
dd

Chamfer and Pilot Hole Creation Using a Spot Drill
in Combination with a Straight Drilling Cycle
D
REAMING
reference plane
dr
f
lch
N
Linear Feed
Rate
Rapid Traverse
Feed Rate
dd d b
Profile View of a 1/4 in. Reamer with
Helical Flutes
Hole Reaming Carried Out with a Reamer in
Combination with a Straight Drilling Cycle

Reaming is used to
purpose of improving the
a pre-drilled hole or pre-bored hole for the

The pre-existing hole diameter is typically .008 in to .015 in. smaller than
the reamer diameter
BORING ROTATIONAL
Boring Bar
Courtesy of Kennametal

Boring is used to enlarge a pre-drilled hole for the purpose of

It is also used to create non-standard size holes and holes with large depth to diameter
ratios

When performed as a rotational operation, the insert is held by a boring bar

The finished hole diameter and radial depth of cut are controlled through the positioning
of the X axis on the turning center
BORING PRISMATIC
Cutting Insert
Boring Head


Courtesy of Kennametal
When performed as a prismatic operation, the cutting insert(s) is
held by a rotating
The finish hole diameter and radial depth of cut are controlled
through the axial slide adjustment of the radial position of the
cutting insert(s)
RIGID TAPPING
Kalpachian

A rigid tapping process is used to cut an
into a
pre-drilled hole using either a machining center or turning
center

A tapping process requires a special tool called a tap

A rigid tapping cycle requires synchronization of the axial feed
rate and tool rotation;

Tapping is typically used for applications involving small thread
sizes (major diameter < 1” )
TECHNICAL ISSUES
Cutting Speed, Chip Load, and Material Removal Rate
 Power Consumption and Specific Cutting Power
 Gradual Tool Wear
 Tool Fracture
 Chatter
 Chip Control
 Workpiece Distortion
 Minimum Surface Layer Removal
 Workpiece Material Machinability

CUTTING SPEED
S



Cutting speed (S) is the
magnitude of the
of the cutting tool
with respect to the workpiece
surface
For rotational processes, the
cutting speed is equivalent to
the tangential velocity of the
For prismatic processes, the
cutting speed is equivalent to
the tangential velocity of the
Courtesy of Kennametal
CHIP LOAD AND MATERIAL REMOVAL RATE


The
(Achip) of the undeformed chip that is swept away by a tooth
is called the chip load
swept area
The material removal rate (MRR) associated
with a tooth passing through a workpiece is
expressed as:


The total material removal rate can be
increased by increasing the:



Cutting speed
Chip load (increasing feed and depths of cut)
Total number of teeth engaged in the
workpiece
Courtesy of Kennametal
POWER CONSUMPTION
S
Kalpachian

The power (Pc) necessary for a tooth to remove material from a
workpiece is:


Where Uc is the specific cutting power of the process
SPECIFIC CUTTING POWER

Typical units for Uc are:






The power necessary to machine a
specific class of metal (e.g. aluminum
alloy) can be controlled significantly
through metal chemistry
Metals with near equivalent strength
properties can have significantly
different specific cutting powers
One of the measures of
is specific cutting power
GRADUAL TOOL WEAR

Rake face
Rake face
Flank wear
Crater wear
Flank face
Flank face
Gradual tool wear implies a steady loss of tool material over the service life of the
tool due to a combination of:




The long term consequences of gradual tool wear are:




of tool material into the underside of the chip
of tool material from hardened inclusions in the workpiece material
between asperities at the tool-chip interface and
Greater forces and power consumption due to loss of designed tool geometry
Degradation of machined surface finish due to
Weakening of the tool structure and increasing its susceptibility to catastrophic failure
The rate at which a material gradually wears out a cutting tool is another measure
of its
GRADUAL WEAR RATE

The rate at which cutting tool material erodes due to gradual wear is a
direct function of the following three factors:





-> Cutting Zone Temperature
Proportional to: cutting speed and specific cutting power
Abrasiveness and Chemical Affinity of the Work-piece Material
 Greater abrasiveness/hardness implies greater ability to abrade
the cutting tool
 Greater affinity implies greater ability to remove tool material via
adhesive wear and diffusion
Cutting Tool Material
 Chemical affinity to work-piece material
HOT HARDNESS



Hot hardness refers to the
hardness/strength of a material at
high temperatures
Cutting tool materials in use today
have high hot hardness as an intrinsic
property
Note that cutting tool materials with
the greatest hot hardness (e.g.
ceramics, diamond, cubic boron
nitride) also exhibit the greatest:




Compressive strength
IMPACT OF TOOL MATERIAL ON GRADUAL WEAR

The
(T) of a cutting tool is
typically related to
(V)
by the following equation:
log( c) log(V )
log(T ) 

n
n

The curves illustrate the dramatic
impact that cutting tool material has
on gradual wear
TOOL FRACTURE

A downside to brittle cutting tool materials are that they are susceptible to
fracture

Consequently cutting tools made of carbides, ceramics, CBN, or diamond
are often prone to chipping and cracking

Both mechanisms result from the following:
Mechanical
 Mechanical
 Thermal
 Thermal

due to impact
to due cyclic loading (typical of milling processes)
(analogous to filling a hot glass with cold water)
due to cyclic heating and cooling (typical of milling processes)
TOOL FRACTURE & CHATTER
Kalpachian
Chatter Marks Left on a Turned Surface



Unstable vibration in the machining process (e.g. chatter) is a leading source
of tool
Chatter also destroys
Chatter is due to insufficient dynamic stiffness in the closed loop machining
system
CHIP CONTROL
segmented
chip
entangled,
unbroken
chip
Short, segmented chips are easy to wash from the cut zone
Long, stringy chips entangle around the rotating tool/workpiece, can scratch
the finished machined surface, and force the process to be shutdown in
order to be cleared out

lead to stringy chip formation
CHIP BREAKER
rake face


A chip breaker is a feature added to the
of the cutting tool for the
purpose of forcing additional
into the chip and breaking it into
segments
These features may be additive, but are typically
principal rake face of the tool
behind the
WORKPIECE DISTORTION
Face Mill
Clamped Workpiece Subject to
Face Milling Process

Machined surface free from
measureable profile error and
chatter marks
UnClamped Workpiece in the
Free State Condition
The removal of a small layer of material from a structurally
rigid workpiece typically leads to a machined surface free
from:


WORKPIECE DISTORTION
Machined surface with chatter
marks
Workpiece
Distortion
Face Mill
Clamped Workpiece Subject to
Face Milling Process

Machined surface with
measureable profile error
UnClamped Workpiece in the
Free State Condition
The removal of a small layer of material from a structurally
workpiece typically leads to:


workpiece distortion due to
which leads to measurable
unstable machining and
and
,
WORKPIECE DISTORTION
Machined surface with
measureable profile error
Face Mill
Clamped Workpiece Subject to Face
Milling Process
UnClamped Workpiece in the
Free State Condition
The removal of a small layer of material from a thin section w orkpie ce
typically creates a
 When unclamped, the machined, workpiece distorts to
the
internal stresses
 Measurable profile error appears on the machined surface

MINIMUM SURFACE LAYER REMOVAL
Semi-Finished Surface
Minimum Material Removal Layer
dmin
Finished Surface
A
(thickness dmin
≈ .0001”) must be removed in order to
impart a quality finished surface (e.g.
)

REQUIRMENT FOR COMPLETE CLEAN UP
dmi
MMRE
n
Finished Part Geometry
Finished Part Geometry
Encapsulated within the Minimum
Material Removal Envelope (MMRE)
Op #10 Work-piece Encapsulates the MMRE at a
Non-Standard Orientation and Position


OP # 10
Op #10 Work-piece Encapsulates the MMRE at
the Required Orientation and Position Relative
to the MDRF
OP # 10
Op #10 Work-piece Does Not Encapsulate the MMRE
at the Required Orientation and Position Relative to
the MDRF
In order for an N operation sequence to completely
all required
surfaces, the part
must be completely encapsulated by the work-piece
while both are
relative to the machining datum reference frame in the
Near net workpieces subject to substantial
clean up
often do not
MATERIAL MACHINABILITY
Material machinability is defined in
terms of:


Surface finish
Specific cutting power


MACHINABILITY RATINGS






Material machinability is rated relative to
(resulfurized) in terms of cutting speed to achieve an average
tool life of
is rated at 100 when machined at 100 ft/min
A material rated as 200 can be machined at 200 ft/min
A material rated as 50 can be machined at 50 ft/min
Ratings are
to a number of factors;
for
cutting speed selection
Ratings provide a good measure of the relative machining cost
of materials
READING ASSIGNMENT
Reading Assignment: Kalpakjian
Chapter 9 Material-Removal Processes:
Abrasive, … ; Sections 9.1 – 9.8
Complete by the next lecture period

ABRASIVE MACHINING PROCESSES
VALUE-ADDED
Near Net Shape/
Net Shape
Bulk Material
Refinement
Surface Coating
Surface Geometry
Refinement
Yes
No
No
Yes
Deformed Metal Chip
Magnified View of a Grinding Wheel Surface

Utilize
designed shape



as cutting tools rather than a singular
Grains are held within a media that ranges from
(grinding) to
(lapping)
Grit is typically diamond or a ceramic such as: aluminum oxide, silicon carbide, or
cubic boron nitride
Grit size determines
GRINDING PROCESSES
Surface Grinding Process






Profile Grinding Process
Cylindrical Grinding Process
Typically applied after
to further improve form error
and surface finish
Many different variations
Utilize a grinding wheel with a
Grit is held within a solid matrix of
Grinding wheel must be periodically
to maintain surface profile
Grinding typically leads to: Geo Error < .00005 in; 1 μin < Ra < 8 μin
HONING PROCESSES
Honing Machine
Honing a Bore
Honing is a super finishing process done after
to improve
the form error and surface finish of cylindrical surfaces
 The hone is assembled with
consisting of ultra
fine grit
 The hone orbits the surface with light
while
traversing in and out axially

LAPPING PROCESSES



Lapping is a super finishing process done after grinding to improve the form
error and surface finish of
The flat part surface rides on a
, and
floating on top of a lap
Abrasion is enabled by gravity pushing the part down on the film while the
lap is translated
ABRASIVE FLOW MACHINING


Abrasive flow machining is a process used to improve the
surface finish of
Paste with abrasive grit is pumped through the passage
ways
POLISHING




Polishing is a process used to improve the
of a previously
machined, ground, or super finished surface
Polishing uses a paste containing an ultra fine grit
The paste is applied to a brush, which in turn is rubbed against the
surface
Grit within the paste
to reduce their height
ABRASIVE WATER JET MACHINING



Abrasive water jet machining is a 2D cutting process that competes with
sawing, plasma arc cutting, and laser cutting
Water carrying abrasive grit is shot through a
(.002” < ID <
.04”) at the workpiece under great pressure pressure (60 ksi to 200 ksi)
Used to cut a large variety of materials ranging from cloth to ceramics