Manufacturing Processes Chapter 21 and 22
generating and forming
2 operations that create part shape
peripheral milling and face milling
2 other types of milling operations
universal milling machine and ram mill
2 types of knee-and-column milling machine
x-y tracing and x-y-z tracing
2 types of tracer mills
(a) hacksawing, (b) band sawing, and (c) circular sawing
3 types of saw cutting operations
mounting the work between centers, chuck, collet, and face plate
4 common methods used to hold the work parts in turning
reaming
used to slightly enlarge a hole, provide a better tolerance on its diameter, and improve its surface finish
triplex mills
add a third spindle mounted vertically over the bed to further increase machining capability
tracer mill
also called a profiling mill, is designed to reproduce an irregular part geometry that has been created on a template
down milling
also called climb milling, the direction of cutter motion is the same as the feed direction when the teeth cut the work; milling "with the feed"
threading die
An alternative to using a single-point tool in single-point threading is a ___
mounting the work between centers
At the headstock center, a device called a dog is attached to the outside of the work and used to drive the rotation from the spindle. The tailstock center has a cone-shaped point that is inserted into a tapered hole in the end of the work.
knurling
it is a metal forming operation used to produce a regular cross-hatched pattern in the work surface
both involving the use of a single-point cutting tool moved linearly relative to the work part. In conventional shaping and planing, a straight, flat surface is created by this action. In shaping, the speed motion is accomplished by moving the cutting tool, while in planing, the speed motion is accomplished by moving the part
Difference between shaping and planing?
single-point tools
Do most lathe operations use single or multiple point tools?
- relative motions between the tool and the work part - the shape of the cutting tool
Each machining operation produces a characteristic geometry due to what 2 factors?
horizontal
Is the conventional engine lathe a horizontal or vertical turning machine?
secondary
Machining is classified as a ___ process.
tailstock
Opposite the headstock, in which a center is mounted to support the other end of the workpiece
- single-point tools - interrupted cutting - limited to low speeds due to their start-and-stop motion
Shaping and planing features
simplex mills
Single spindle bed machines
tapping
The most common process for cutting internal threads in which a cylindrical tool with cutting teeth arranged in a spiral, whose pitch is equal to that of the desired screw threads, is simultaneously rotated and fed into a preexisting hole
single point threading
The simplest and most versatile method of cutting an external thread on a cylindrical work part, which employs a single-point cutting tool on a lathe
(1) Multiple operations in one setup (2) Automatic tool changer and tool storage unit (3) Automatic pallet changers (4) Automatic pallet storage and handling system
The typical features that distinguish a machining center from conventional machine tools and make it so productive include:
multiple-spindle bar machines
To increase cutting tool utilization and production rate, have more than one spindle, so multiple parts are machined simultaneously by multiple tools.
lathe
What machine tool is turning performed on?
facing, taper turning, contour, form turning, chamfering, cutoff, threading, boring, drilling, and knurling
What other operations can be performed on a lathe? (10)
contouring
__ on a band saw involves cutting a part profile from flat stock
profile milling
a form of end milling in which the outside periphery of a flat part is cut
vise
a general-purpose work-holding device possessing two jaws that grasp the work in position
threading (thread cutting or single-point-threading)
a pointed tool is fed linearly across the outside surface of the rotating work part in a direction parallel to the axis of rotation at a large feed rate, thus creating threads in the cylinder
gear shaping
a reciprocating tool motion is used rather than a rotational motion as in form milling and gear hobbing
boring
a single-point tool is fed linearly, parallel to the axis of rotation, on the inside diameter of an existing hole in the part
friction sawing
a steel disk is rotated against the work at very high speeds, resulting in friction heat that causes the material to soften sufficiently to permit penetration of the disk through the work.
gear shaper
a vertical shaper with a specially designed rotary feed table and synchronized tool head to generate teeth on gears
jig
a work-holding device that is also specially designed for the work part
up milling
also called conventional milling, the direction of motion of the cutter teeth is opposite the feed direction when the teeth cut into the work; milling "against the feed"
peripheral milling
also called plain milling, the axis of the tool is parallel to the surface being machined, and the operation is performed by cutting edges on the outside periphery of the cutter.
slotting
also called slot milling, in which the width of the cutter is less than the workpiece width, creating a slot in the work—when the cutter is very thin, this operation can be used to mill narrow slots or cut a work part in two
abrasive cutoff
an abrasive disk is used to perform cutoff operations on hard materials that would be difficult to saw with a conventional saw blade.
pocket milling
another form of end milling to cut shallow pockets into flat parts
bed-type milling machines
are designed for high production and are constructed with greater rigidity than knee-and-column machines, thus permitting them to achieve heavier feed rates and depths of cut needed for high material removal rates.
planar type mills
are large milling machines and have the general appearance and construction of a planer (see Figure 21.31); the difference is that milling is performed instead of planing
the ways
are like tracks along which the carriage rides, and they are made with great precision to achieve a high degree of parallelism relative to the spindle axis.
gears
are machine components used to transmit motion and power between rotating shafts.
gear broaching
as a gear-making process is noted for short production cycle times and high tooling cost. It is therefore economical only for high volumes. Good dimensional accuracy and fine surface finish are also features of gear broaching. The process can be applied for both external gears (the conventional gear) and internal gears (teeth on the inside of the gear)
gear grinding
can be based on either of two methods: (1) form grinding, in which the grinding wheel has the exact shape of the tooth spacing (similar to form milling), and a grinding pass or series of passes is made to finish form each tooth in the gear; or (2) generating the tooth profile using a conventional straight-sided grinding wheel.
screw threads
can be defined as grooves that form a spiral around the outside of a cylinder (external threads) or the inside of a round hole (internal threads).
collet
consists of a tubular bushing with longitudinal slits running over half its length and equally spaced around its circumference inside diameter is used to hold cylindrical work such as bar stock. The slits allow one end of the collet to be squeezed to reduce its diameter and provide a grasping pressure against the work.
headstock
contains the drive unit to rotate the spindle, which rotates the work
casting, forging, and bar rolling
examples of basic processes
drilling
feeding the drill into the rotating work along its axis
rotational work part
has a cylindrical or disk-like shape The characteristic operation that produces this geometry involves a cutting tool removing material from a rotating work part, such as turning and boring.
horizontal milling machine
has a horizontal spindle, and this design is well suited for performing peripheral milling (e.g., slab milling, slotting, side and straddle milling) on work parts that are roughly cube-shaped.
horizontal broaching machine
has a horizontal tool path
self-centering chuck
has a mechanism to move the jaws in or out simultaneously, thus centering the work at the spindle axis.
vertical milling machine
has a vertical spindle, and this orientation is appropriate for face milling, end milling, surface contouring, and die-sinking on relatively flat work parts
single-spindle bar machine
has one spindle that normally allows only one cutting tool to be used at a time on a single work part.
collapsible taps
have cutting teeth that automatically retract into the tool when the thread has been cut, allowing it to be quickly removed from the tapped hole without reversing spindle direction
tool post
holds the cutting tool and is fastened to the cross slide
surface contouring
in which a ball-nose cutter (rather than square-end cutter) is fed back and forth across the work along a curvilinear path at close intervals to create a three-dimensional surface form
x-y tracing
in which the contour of a flat template is profile-milled using two-axis control
end milling
in which the cutter diameter is less than the work width, so a slot is cut into the part
side milling
in which the cutter machines the side of the workpiece
upright drill
it stands on the floor and consists of a table for holding the work part, a drilling head with powered spindle for the drill bit, and a base and column for support
conventional face milling, partial face milling, end milling, profile milling, pocket milling, surface milling and surface contouring
in which the diameter of the cutter is greater than the work part width, so the cutter overhangs the work on both sides
form milling
in which the milling teeth have a special profile that determines the shape of the slot that is cut in the work
x-y-z tracing
in which the probe follows a three-dimensional pattern using three-axis control.
ram mill
in which the tool head containing the spindle is located on the end of a horizontal ram; the ram can be adjusted in and out over the worktable to locate the cutter relative to the work.
maximum distance between centers
indicates the maximum length of a workpiece that can be mounted between headstock and tailstock centers
band sawing
involves a linear continuous motion, using a band-saw blade made in the form of an endless flexible loop with teeth on one edge.
hacksawing
involves a linear reciprocating motion of the saw against the work.
thread milling
involves the use of a form-milling cutter to shape the threads of a screw.
gang drill
is a drill press consisting basically of two to six upright drills connected together in an in-line arrangement
machining center
is a highly automated machine tool capable of performing multiple machining operations under computer numerical control in one setup with minimal human attention
radial drill
is a large drill press designed to cut holes in large parts; it has a radial arm along which the drilling head can be moved and clamped.
turret lathe
is a manually operated lathe in which the tailstock is replaced by a turret that holds up to six cutting tools, which can be rapidly brought into action against the work one by one by indexing the turret.
gear burnishing
is a plastic deformation process in which one or more hardened gear-shaped dies are rolled in contact with the gear, and pressure is applied by the dies to effect cold working of the gear teeth
sawing
is a process in which a narrow slit is cut into the work by a tool consisting of a series of narrowly spaced teeth; cutoff operation
face plate
is a work-holding device that fastens to the lathe spindle and is used to grasp parts with irregular shapes that, because of their shapes, cannot be held by other work-holding methods
fixture
is a work-holding device that is usually custom-designed for the particular work part designed to achieve higher accuracy in positioning the part relative to the machining operation, faster production rates, and greater operator convenience in use than vises
internal broaching
is accomplished on the internal surface of a hole in the part. Accordingly, a starting hole must be present in the part so as to insert the broach at the beginning of the broaching stroke
gear hobbing
is also a milling operation, but the specialized cutter, called a hob, is much more complex and therefore much more expensive than a form-milling cutter
nonrotational (prismatic) work
is block-like or plate-like This geometry is achieved by linear motions of the work part, combined with either rotating or linear tool motions. Operations in this category include milling, shaping, planing, and sawing.
cross slide
is designed to feed in a direction perpendicular to the carriage movement; the tool can be fed radially into the work to perform facing, form turning, or cutoff.
vertical broaching machine
is designed to move the broach along a vertical path
carriage
is designed to slide along the ways of the lathe in order to feed the tool parallel to the axis of rotation; tool can be fed parallel to the work axis to perform straight turning
dead center
is fixed to the tailstock, so that it does not rotate; instead, the workpiece rotates about it. Because of friction and the heat buildup that results, this setup is normally used at lower rotational speeds.
multitasking machine
is often used for such machines that perform multiple processes and control up to five axes
external broaching
is performed on the outside surface of the work to create a certain cross-sectional shape on the surface
bar machine
is similar to a chucking machine except that a collet is used (instead of a chuck), which permits long bar stock to be fed through the headstock into position. At the end of each machining cycle, a cutoff operation separates the new part.
spot facing
is similar to milling and is used to provide a flat machined surface on the work part in a localized area
speed lathe
is simpler in construction than the engine lathe; it has no carriage and cross-slide assembly, and therefore no leadscrew to drive the carriage
toolroom lathe
is smaller and has a wider available range of speeds and feeds; it is also built for higher accuracy, consistent with its purpose of fabricating components for tools, fixtures, and other high-precision devices.
slotting
is the cutting of a thin slot into a part
swing
is the maximum work part diameter that can be rotated in the spindle, determined as twice the distance between the centerline of the spindle and the ways of the machine.
knee-and-column milling machine
it derives its name from the fact that its two main components are a column that supports the spindle and a knee (roughly resembling a human knee) that supports the worktable. It is available as either a horizontal or a vertical machine
turning
machining process in which a single-point tool removes material from the surface of a rotating workpiece. The tool is fed linearly in a direction parallel to the axis of rotation to generate a cylindrical geometry
high-speed machining
means using cutting speeds that are significantly greater than those used in conventional machining.
(1) toolroom lathe, (2) speed lathe, (3) turret lathe, (4) chucking machine, (5) automatic screw machine, and (6) numerically controlled lathe
other machines for turning besides an engine lathe
reaming, tapping, counterboring, countersinking, centering, and spot facing
other operation related to drilling (6)
(1) knee-and-column, (2) bed type, (3) planer type, (4) tracer mills, and (5) CNC milling machines
other type of spindle operations (5)
slab milling, slotting, side milling, straddle milling, and form milling
other types of peripheral milling (5)
tapping
performed by a tap and is used to provide internal screw threads on an existing hole
counterboring
provides a stepped hole, in which a larger diameter follows a smaller diameter partially into the hole
live center
rotates in a bearing in the tailstock, so that there is no relative rotation between the work and the live center; hence no friction between the center and the workpiece.
multiple-spindle drill
several drill spindles are connected together to drill multiple holes simultaneously into the work part
centering or center drilling
similar to counterboring, except that the step in the hole is cone-shaped for flat head screws and bolts
countersinking
similar to counterboring, except that the step in the hole is cone-shaped for flat head screws and bolts
thread grinding
similar to thread milling except the cutter is a grinding wheel with the shape of the thread groove, and the rotational speed of the grinding wheel is much greater than in milling.
bench drill
smaller and is mounted on a worktable or workbench rather than the floor
slab milling
the basic form of peripheral milling in which the cutter width extends beyond the workpiece on both sides
engine lathe
the basic lathe used for turning and related operations
chamfering
the cutting edge of the tool is used to cut an angle on the corner of the cylinder, to create a chamfer
blind holes
the drill does exits the opposite side of the work
through holes
the drill exits the opposite side of the work
generating
the geometry of the work part is determined by the feed trajectory of the cutting tool. The path followed by the tool during its feed motion is imparted to the work surface in order to create shape.
computer numerical control (CNC)
the machine tool operations are controlled by a "program of instructions" consisting of alphanumeric code.
thread cutting
the pointed shape of the cutting tool determines the form of the threads, but the feed rate generates the threads.
straddle milling
the same as side milling, only cutting takes place on both sides of the work
forming
the shape of the part is created by the geometry of the cutting tool. In effect, the cutting edge of the tool has the reverse of the shape to be produced on the part surface
contour turning
the tool follows a curved or irregular path rather than a straight path, thus creating a contoured form in the turned part
form turning (forming)
the tool has a shape that is imparted to the work by plunging the tool radially into the part
taper turning
the tool is fed at an angle instead of parallel to the axis of workpiece rotation, thus creating a tapered cylinder or conical shape
cutoff
the tool is fed radially into the rotating work at some location along its length to cut off the end of the part
facing
the tool is fed radially into the rotating work on one end to create a flat surface on the end
slotting (slot milling)
the width of the cutter determines the width of the slot, but the feed motion creates the slot.
horizontal boring operation
the work is fixtured to a rotating spindle, and the tool is attached to a cantilevered boring bar that feeds into the work. OR the cutting tool is mounted on a boring bar that is supported and rotated between centers. The work is fastened to a worktable that feeds it past the tool.
reamer
tool used in reaming; it usually has straight flutes
T/F Milling is an interrupted cut operation.
true
conventional face milling,
types of face milling (6)
duplex mills
use two spindle heads
vertical boring machine
used for large, heavy work parts with large diameters; usually, the work part diameter is greater than its length. The part is clamped to a worktable that rotates relative to the machine base.
chucking machine
uses a chuck in its spindle to hold the work part; the tailstock is absent, so parts cannot be mounted between centers. This restricts the use of a chucking machine to short, lightweight parts.
broaching
uses a multiple-tooth tool to take multiple cuts by moving the tool linearly relative to the work in the direction of the tool axis. Advantages include good surface finish, close tolerances, and variety of work shapes.
circular sawing
uses a rotating saw blade to provide a continuous motion of the tool past the work
teeth
what the milling cutting edges are called
milling cutter
what the milling cutting tool is called
partial face milling
where the cutter overhangs the work on only one side
self-opening threading dies
which are designed with an automatic device that opens the cutting teeth at the end of the cut.
universal milling machine
which has a table that can be swiveled in a horizontal plane (about a vertical axis) to any specified angle. This facilitates the cutting of angular shapes and helixes on work parts
arbor
which is basically a shaft that holds the cutter and is driven by the spindle
interrupted cut operation
which means that the teeth of the cutter enter and exit the work during each revolution
CNC mill-turn center
which usually has the general configuration of a turning center, but it can position a cylindrical work part at a specified angle so that a rotating cutting tool (e.g., milling cutter) can machine features into the outside surface of the part
chuck
with three or four jaws to grasp the cylindrical work part on its outside diameter.
