7. • Crank shaper: Shapers whose ram reciprocates
with the help of a crank mechanism
• Geared shaper: The ram reciprocates with spur
gear mechanism. this type of shaper carries a
rack under the ram for to and fro motion.
• Hydraulic shaper: the movement of the ram is
provided by hydraulic pressure
8. • Horizontal shaper: The ram reciprocates in
horizontal direction.
• Vertical shaper: The ram reciprocates in vertical
direction.
• It is also known as slotter.
• Travelling head shaper: a shaper whose
reciprocating tool head is mounted on a bed in
such a way that the head may be fed laterally on
ways provided on the bed prior to each cutting .
9.
10.
11. • Base: The base is a heavy cast iron casting which is fixed to the shop floor. It
supports the body frame and the entire load of the machine. The base
absorbs and withstands vibrations and other forces which are likely to be
induced during the shaping operations.
• Body (Pillar, Frame, Column): It is mounted on the base and houses the
drive mechanism compressing the main drives, the gear box and the quick
return mechanism for the ram movement. The top of the body provides
guide ways for the ram and its front provides the guide ways for the cross
rail.
• Cross rail: The cross rail is mounted on the front of the body frame and can
be moved up and down. The vertical movement of the cross rail permits
jobs of different heights to be accommodated below the tool.
• Saddle: Sliding along the cross rail is a saddle which carries the work table.
Crosswise movement of the saddle causes the work table to move side
ways.
• Ram: The ram is driven back and forth in its slides by the slotted link
mechanism. The back and forth movement of ram is called stroke and it can
be adjusted according to the length of the workpiece to be-machined.
12. • Tool head: The tool head in a dovetail at the front of the
ram by means of T-bolts. It can swivel from 0 to 90 in a
vertical plane.
• Tool head can be raised or lowered by hand feed for
vertical cuts on the work pieces.
• Tool head holds tool. The tool head imparts the tool,
necessery vertical and angular feed movement.
• The tool slide controls the feed in the cutting tool into
the workpieces by a lead screw.
• The clapper box allows the cutting tool to lift on the
return or idle stroke so that the tool is not dragged back
through the uncut workpice and get damaged.
• Tool post carries the cutting tool.
13.
14.
15.
16.
17.
18.
19.
20. The cutting speed depends on
Type of material
Machining condition
The return stroke allow the ram to move at a faster rate to
reduce the idle time which is known as Quick Return
Mechanism.
The reciprocating movement of ram and quick return
mechanism of the machine are obtained from
(i) Crank and Slotted link mechanism
(ii) Whitworth quick return mechanism
(III) Hydraulic Shaper Mechanism
21. Crank and Slotted link mechanism
•Slotted link mechanism is very common in mechanical
shapers.
•It is simple and compact. It converts rotary motion of the
electric motor and gearboxinto the reciprocating motion of
the ram.
•The return stroke allow the ram to move at a faster rate to
reduce the idle time which is known as Quick Return
Mechanism, reducing the time waste during return stroke.
•Bull gear is driven by a pinion which connects to the motor
shaft through gear box.
•The bull wheel has a slot. The crank pin A secured into this
slot, at the same time it can slide in the slotted crank B.
22. As the bull gear rotate cause the crankpin A also to turn and
side by side slides through the slot in the slotted crank B.
This makes the slotted crank to oscillate about its one end C.
This oscillating motion of slotted crank (through the link D)
makes the ram to reciprocate.
The intermediate link D is necessary to accomdate the rise
and fall of the crank.
23.
24.
25. The principle of Quick Return Mechanism
When the link is in position AP1, the ram will at extreme
backward position of stroke
When the link position is at AP2, the extreme forward position
Ram will have been reached
AP1 and AP2---- Tangent to the crank pin circle
Forward cutting stroke takes place when the crank rotates
through an angle C1KC2
Return stroke ---- the crank rotates through angle C1LC2
It is seen that C1KC2 > C1LC2
The angular velocity of crank pin remains constant.
26. The ratio of cutting time and return time :
It varies from 2:1 and the practical limit 3:2
Disadvantage:
The cutting speed and return speed is not constant throughout the
stroke
1 2
1 2Re
C KCCutting time
turntime C LC
27. Adjustment of the length of stroke
How the length of stroke in a crank shaper can be adjusted?
Ans:
The crank pin (11) is fastened to the sliding block (10) which
can be adjusted and the radius of its travel may be varied.
The block (10) is again mounted upon the radial slide (16)
bolted to the centre of bull gear.
The bevel gear (18) placed at the centre of the bull gear may
be rotated by a handle causing the bevel gear(17) to rotate
The bevel gear (17) is mounted upon the small lead screw
(13) which passes through sliding block (10).
The rotation between bevel gear (17) will cause the sliding
block (10) carrying the crank pin (11) to be brought inwards
or outwards with respect to the centre of bull wheel.
28.
29. Note :
The closer the pin is brought to the centre of the bull wheel, the
smaller will be the stroke.
Maximum stroke of the ram obtained when the crank pin is
shifted towards the farthest end of slide.
30. Adjustment of the position of stroke
The position of ram relative to the work can be adjusted by
Rotating the hand wheel (5) the screw shaft (3) which is
fitted in the ram may be rotated through two bevel gears
(6&7).
The ram block (8) which is mounted upon the screw shaft (3)
acts as a nut.
When the machine is in operation, the clamping lever (4) is
tightened upon the ram body (2) and the ram block, the
screw shaft and ram block becomes as one unit.
To set the position of stroke, the clamping lever (4) is
loosened and by rotating the hand wheel (5), the screw shaft
(3) will rotates within the ram block.
31.
32. The unit remaining fixed in position, rotation of screw will cause
the ram to move forward or backward respect the ram block
according to the direction of rotation of hand wheel (5).
Thus the position of ram can be adjusted with respect to the work
piece.
The clamping lever (4) must be tightened after the adjustment
has been made.
34. • Crank PC revolves at uniform speed. During cutting
stroke the point P travels from P1 to P2 through y.
• The ram is returned at high speed as the crank rotates
from P1 to P2 through x.
• The ratio of cutting time and return time :
Cutting time /return time=P1YP2/P1XP2
• The stroke length can be changed by varying the radius
OA.
35. Difference between Crank and slotted link
mechanism and whitworth quick return
• The slotted lever mechanism is used in Shaper machines
for quick return mechanism; while whitworth mechanism is
used in Slotting machine.
• The velocity of forward stroke in Crank and slotted lever
mechanism remains same for different stroke length while
the velocity of return stroke decreses for smaller stroke
lengths.Thus for smaller stroke lengths Slotted lever serves
no advantage over quick return.
36. Hydraulic Mechanism
Hydraulic shaper has the same major parts as the mechanical
one. However, the ram is driven by a hydraulic cylinder.
The sppeds of the shaper ram and feeds of the work table are
controlled by hydraulic mechanism. A lever operates Valve that
varies the quantity of oil delived to the ram cylinder and therby
governs the ram speed.
The ram moved forward and backward by a piston moving in a
cylinder placed under the ram
The machine consists of a constant discharge oil pump, a valve
chamber, a cylinder and a piston.
The piston rod is bolted to ram body.
The oil under high pressure is pumped from the reservoir and is
made to pass through the valve chamber to the right side of oil
cylinder exerting pressure on piston
40. • This mechanism are suitable increasingly popular these
days as of their bigger litheness, smooth process,
capability to slip in case of excess, capacity to withstand
obstructions with no damaging tool or machine and the
option of change speed with the feed during process.
This system can efficiently use as rapid return
mechanisms. Shaper ram is on its forward cutting
strokes with is moving as of right to left. Oil as of
reservoir is passed through a filter with pump. Pump,
drive by an electric motor, push oil in a stable amount
with at reasonable pressure to control valve. Control
valve is fixed by an indicator that indicates direction in
which oil is moving. As of the control valve, oil can be
delivering to each side of the piston.
41. Note:
The quick return motion is effected due to the difference in
stroke volume of the cylinder at both ends
The left end is smaller due to the presence of the piston rod
As the pump is a constant discharge one, within a fixed period
, the same amount of oil will be pumped into the right or left
hand side of the cylinder.
i. e the same amount of oil will be packed within a smaller
stroke volume causing the oil pressure to rise automatically
and increasing the speed during return stroke.
The length and position of stroke is adjusted by shifting
the position of reversing dogs.
42. Advantages
The cutting and return speeds are partially constant throughout
the stroke which permits the cutting tool to work uniformly
during cutting stroke.
The reversal of ram is obtained quickly without any shock as
the oil on the other end of cylinder provides cushioning effect.
Infinite number of cutting speed may be obtained from zero to
the maximum value and control is easier.
With high rate of return speed, a greater number of cutting
strokes may be available within the range of cutting speed
The relief valve ensure safety to the tool and the machine
when the machine is overloaded.
43.
44. Machining time for shaper
Let
L = the length of stroke(m) of shaper
Vo=cutting speed in m/min
Vr=return speed in m/min
f= feed per cycle in m
• Threfore, time for cutting stroke, tc=Length of
the stroke/cutting speed
Speed
)L(travelectanDis
imeMachiningt
c
c
V
L
t
45. • Similarly, time for return stroke
• Total time for one cycle T= tc+ tr
• Now, Shaping width W= width of the workpiece +
distance the tool moves on either side of the
workpiece to ensure that the full width of the
workpice has been machined
• No. of cylce required to machine the
workpice=W/f
• Machining time Tm=No. of cycles x time per cycle
R
R
V
L
t
T
f
W
Tm
46. • Q1-Calculate the time to machine 250mm
long plate, 100mm wide. Tool clearance at
each end of stroke is 30mm and 20mm
repctively. Cutting speed is 10m/minute and
return speed is 20m/min. feed is 1mm per
cycle and the distance the tool moves on
either side of the work in width direction is
10mm each.
47. • In Shaper machine, tool is having reciprocating
motion and w/p is clamped on table which is
stationary.
• It is mostly suitable for light duty operation. In
Shaping large cutting force is transferred to tool.
• In Planer machine, tool is having stationary and
w/p is clamped on table which is reciprocating
motion.
• It is mostly suitable for Heavy duty operation. In
planner large cutting force is transferred to table.
48. 1- Light duty machine used for finishing of
material object.
2- job is stationery whereas cutting tool is
moving.
While PLANER is
1- Heavy duty machine used when more
finishing is required.
2-job can be moved but cutting tool is
stationery.
