2. NEED FOR AUTOMATS
Limitation of manually operated lathes
• Movement of tool to precise location
becomes difficult
• Idle time between tool changeover,
setting of tool and setting time of
workpiece is larger
5. Automatic lathes can be
classified as follows:
(i) Single spindle automatics
(ii) Multi spindle automatics
(iii) Chucking machines
(iv) Horizontal spindle machines
(v) Vertical spindle machines.
6. In fully automatic lathes, once the
machine is set up, all the
movements related to the
manufacturing cycle and also the
loading of blanks and the
unloading of machined parts are
performed without the operator's
participation. In semiautomatic
machines, the two latter
movements are accomplished by
the operator.
7. •Single spindle automatics have
only one spindle and they
machine one component at a
time.
•Multi spindle automatics have
more then one spindles (4 to
8). Multi spindle machines
have higher production rate as
compared to single spindle
machines.
8. •Chucking machines hold castings
or forgings in the chuck or in
special fixtures for machining them.
•Horizontal spindle machines have
their spindle in the horizontal
position.
•Vertical spindle machines have
their spindle in vertical position. Less
floor space as compared to
horizontal spindle machines.
13. Turret and Capstan, both, are
production machines and are
usually of semiautomatic, type.
Both turret and capstan lathes
are provided with tool head,
usually hexagon, to carry a set
of tools and to supplement this
by an additional slide carrying
tools for cutting off and forming
operations.
14. A Capstan lathe is usually a
small or medium size machine
with the tool head carried
upon a slide mounted in a
saddle bolted to the bed of
the lathe, while a turret lathe
has the (hexagon) tool head
mounted on a saddle sliding
directly on the bed
15. Capstan lathe has the
hexagon tool head
carried upon a slide
mounted in a saddle
bolted to the bed of
the lathe
Turret lathe has the
(hexagon) tool head
mounted on a saddle
sliding directly on the
bed.
Capstan lathe, having
a relatively short stroke
of the tool head and
automatic indexing,
results in a rapid
presentation of the
tools to the work
The turret lathe, on the
other hand, is suitable
for long and heavy
work.
limited to a maximum
of 300 mm diameter
chucks.
chuck work upto 750
mm diameter
16. Size and Specification of
Turret Lathes
(i) Maximum diameter of bar that
can be passed through the
machine spindle
(ii) Swing diameter of the workpiece
(iii) Spindle speeds
(iv)Feeds
(v) Chuck size
(vi)Drive motor capacity
18. Advantages of Automatic
Lathes
•Minimized production time.
•Large scale production of
identical components.
•Part accuracy is more than that
obtained on other types of lathes.
•One worker can look after more
than one machines at a time
20. CAMS….
A cam and follower system is
system/mechanism that uses a cam
and follower to create a specific
motion. In most cases it is a merely flat
piece of metal profile machined onto
it. It is attached to a shaft. As the cam
rotates it is the profile or shape of the
cam that causes the follower to move
in a particular way. The movement of
the follower is then transmitted to
another mechanism or another part of
the mechanism.
21. GENEVA MECHANISM
•The Geneva drive is a mechanism
that translates a continuous
rotation into an intermittent rotary
motion. It is an intermittent gear
where the drive wheel has a pin
that reaches into a slot of the
driven wheel and thereby
advances it by one step.
22. •The drive wheel also has a
raised circular blocking disc
that locks the driven wheel in
position between steps.
24. • The turret 1 is mounted on the spindle 5.
• The index plate 2, the bevel gear 3 and the indexing ratchet
4 are keyed to the spindle 5.
Turret indexing mechanism
25. • The plunger 14 locks the index plate by spring pressure 15 and
prevents any rotary movement of the turret as the tool feeds into
the work.
• A pin 13 fitted on the plunger 14 projects out of the housing.
• An actuating cam 10 and indexing pawl 7 are attached to the lathe
bed 9 at the desired position.
Turret indexing mechanism
26. • Both the cam and the pawl are spring loaded.
• As the turret reaches the backward position , the actuating cam 10
lifts the plunger 14 out of the groove in the index plate due to the
riding of the pin 13 on the beveled surface of the cam 10 and thus
unlocks the index plate 2.
• The pawl 7 which by this time engages with a groove on the ratchet
plate 4 causes the turret to rotate as the turret head moves backward.
Turret indexing mechanism
27. • When the index plate or the turret rotates through one sixth of
revolution, the pin 13 and plunger 14 drops out of cam 10 and the
plunger locks the index plate at the next groove.
• The turret holding the next tool is now fed forward and the pawl is
released from the ratchet plate by the spring pressure.
Turret indexing mechanism
28.
29. • The ratio of the teeth between the pinion and gear are so chosen
that when the tool mounted on the face of the turret is indexed to
bring it to the cutting position, the particular stop rod for
controlling the longitudinal travel of the tool is aligned with stop
12.
Turret indexing mechanism
30. • The setting of the stop rods 8 for limiting the feed of each
operation may be adjusted by unscrewing the lock nuts and rotating
the stop rods on the plate.
• Thus six stop rods may be adjusted for controlling the longitudinal
travel of the tools mounted on the six faces of the turret.
Turret indexing mechanism
31.
32. Bar Feeding Mechanism
• A - Rotating sleeve B - Spindle C - Headstock
D - Guide Bar E - Pulley F - Stand
33. The rotating sleeve mounted on
the guide bar carries the rear
end of the bar stock. The other
end of the bar stock passes
through the spindle to project
outside the collet chuck.
34. Under the action of wire rope
and weight, the sleeve and
bar stock have a tendency to
move to right i.e. towards the
headstock and thus out from
the collet chuck.
After the finished piece has
been parted off, the chuck
opens and thus the bar stock
automatically moves forward
and rests against the bar stop
fitted on the turret.
35. SINGLE SPINDLE AUTOMATIC
LATHE
• preferably and essentially used for larger volume
of production i.e., large lot production and mass
production
• used always for producing jobs of rod, tubular or
ring type and of relatively smaller size.
• run fully automatically, including bar feeding and
tool indexing, and continuously over a long
duration repeating the same machining cycle for
each product
• provided with upto five radial tool slides which
are moved by cams mounted on a cam shaft of
relatively smaller size and power but have higher
spindle speeds
36.
37. Multi Spindle Bar Automatics
•Each spindle carries a bar of
material
•One machining stage is performed
at each spindle position, and each
workpiece passes consecutively
through all positions, I to IV.
•Thus, one revolution of the spindle
cylinder (carrier) is required to
machine a workpiece
38. •Each time the tools are
withdrawn and the spindle
carrier indexes one station, a
finished workpiece is, cut off
and a new piece is started.
39. Multi Spindle Automat
(Parallel Type)
Same action on each
spindle is performed
Number of workpieces
machined simultaneously
will be equal to number
of spindles
41. Progressive type…..
• In progressive type the workpiece in each
spindle are machined progressively in
each station
• It has a head stock mounted on the left
side to which the spindle carrier is fixed
• The carrier periodically indexes, bringing
each spindle to the tool
• In one revolution of the carrier, number of
components produced is equal to the
number of spindles
43. Automatic Screw Machines
Automatic screw machines were
developed for the high speed
production of large numbers of
identical precision parts. The
machine tool has been designed
to perform the maximum number
of operations, either
simultaneously, or in a very rapid
sequence.
44. Automatic Screw Machines….
• These are fully automatic with
turrets employed for tool changeover
and cams for tool movement
• There are also two front and rear
cross slide, provided with cross
feeding tools
• A vertical cross slide above the work
spindle is also provided
45. Swiss Type Screw Machines
•The swiss type screw machine was
developed for precision turning of
small parts to tolerances of 0'005
mm to 0'0125 mm.
•It does not have a turret. Instead,
the cutting tools are held and
moved in radial slides. The stock is
held and rotated by an
accurately made collet.
•Sliding head stock through which
bar passes and held by collet
47. Swiss Type Screw Machines….
•Simultaneous longitudinal
movement of headstock and
cross wise movement of cross
slide enables us to have wide
variety of formed
components.
48. Swiss Type Screw Machines..
• The headstock travels enabling axial feed of
the bar stock against the cutting tools.
• There is no tailstock or turret
• High spindle speed (2000 – 10,000 rpm)
• The cutting tools (upto five in number
including two on the rocker arm) are fed
radially
• Drilling and threading tools, if required, are
moved axially using swivelling device(s)
49. A - Micrometer Adjustment C - Cam
B - Infeed Cam Arm D - Tool Bit
