Reciprocating machine tools shaper

1. RECIPROCATING
MACHINE TOOLS
SHAPER…..
COMPILED BY
M.BALASUBRAMANIAN

2. WORKING PRINCIPLE
The tool held in the tool
holder mounted on the ram
moves forwards and
backwards in a straight line
over the work piece rigidly
held in a vice clamped over
the work table.

3. WORKING PRINCIPLE
Each time the tool moves
forward it cuts a slice of
metal from the workpiece.
Each time the tool moves
backward the tool lifts clear
of the workpiece.

5. Cutting stroke Return stroke
A - Work A - Work

6. PARTS OF SHAPING MACHINE
1. Base.
2. Column or pillar
3. Cross rail.
4. Saddle.
5. Table.
6. Ram.
7. Tool head.
8. Drive mechanism

7. A - Swiveling Head G - Outboard clamp M - Bull Gear S - Crank pin
B - Stroke position
Adjustment
H - Ratchet power
cross feed
N - Rocker arm T - Ram
C - Ram clamp I - Cross feed Screw O - Drive Pinion U - Base
D - Tool Holder J - Ways
P - Stroke Adjustment
for Ram
V - Vertical feed
E - Crossrail K - Elevating Screw Q - Scotch york W - Column or pillar
F - Saddle L - Cross feed arm R - Link X - Pawl

9. 1. Base
The base of the shaper
supports the column or pillar
which supports all the working
parts such as ram, work table,
drive mechanism etc. Base is a
heavy cast iron body.

10. 2. Column, Pillar or Body
It is a ribbed casting of cellular
construction. The top of the
column carries the ram
slideways. The crank and
slotted link mechanism that
drives the ram is contained
within the column. The driving
motor, the variable speed
gearbox, levers, handles and
other controls of shaper are
also contained in the column.

11. 3. Cross rail
It carries the horizontal table
slideways and is mounted on
the vertical slideways of the
column. The cross rail can be
raised or lowered by means of
an elevating screw in order to
suit different thicknesses of
work. It also carries the table
cross feed screw together with
the pawl and ratchet
intermittent drive mechanism.

12. 4. Saddle
Saddle is attached to the cross
rail and supports the table. If
the table is removed, the work
can be bolted or clamped to
the T-slots in front of the saddle.
Crosswise movement of the
saddle causes the work table
to move sideways.

13. 5. Table The work table is a box
shaped casting with T-slots in its
upper surface and down one
side. It also has a vee
machined in the vertical side
to carry cylindrical work.

14. 6. Ram
Ram is a rigidly braced casting
and is located on the top of
column. The ram is driven back
and forth in its slides by the
slotted link mechanism.

15. 7. Tool head
The tool head can swivel from
0° to 90° in a vertical plane:
The tool head can be raised a
or lowered by hand feed for
vertical cuts on the workpiece.

16. Direction of Movement
A - Tool post
B - Clapper box
C - Tool Slide
D - Protractor scale
E - Ram

17. SPECIFICATIONS OF A SHAPERMaximum ram stroke
700mm
Maximum
tooloverhang840mm
Distance between table
surface and ram
Maximum 400 mm
Minimum 80 mm
Dimensions of table working
surface
700 mm * 450 mm
Maximum travel of table
Horizontal 700 mm
Vertical 320 mm
Horizontal feed per double
stroke
0.25--5 mm
Motor power 7 kw
Overall dimensions 2785 * 1750 * 1780 mm

18. TYPES OF SHAPER
(a) Design of work table as
Standard shaper
Universal shaper
(b) Driving mechanism as
Crank shaper
Geared shaper
Hydraulic shaper

19. (c) Direction of travel of ram as
Horizontal shape
Vertical shape
(d) Nature of cutting stroke as
Push cut shaper
Draw cut shaper

20.  In a standard shaper the work
table has only vertical and
horizontal movements.
 Universal shaper has a work
table-which may be swivelled
around horizontal axes and
also adjusted horizontally

21. Crank shaper
Have a crank and slotted
link mechanism to constitute
the quick return motion in
the driving mechanism. The
crank changes the circular
motion of the power source
to the reciprocating motion
of the ram or cutting tool.

22.  Geared shaper
It is not commonly used. A geared
shaper has got a rack under its ram.
The rack (and hence the ram) is driven
by a spur gear.
 Hydraulic shaper
The drive is neither a crank nor gear,
rather it is a hydraulic circuit. Though
expensive, it is very efficient. The
reciprocating movements of the ram
are obtained by the application of oil
pressure on the piston in a cylinder.

23. HYDRAULIC SHAPER

24.  Oil is pumped to Right side of Cylinder
 Piston moves Left Hand Side, Forward
Stroke
 Shaper dog hits the reversing lever
 Reversing lever alters valve position
 Oil is now pumped to Left side of Piston
 Piston moves Right Side, return Stroke
 Oil on the Right side of Piston goes to
reservoir
 At the end of Return stroke another trip
dog hits reversing lever, reversing lever
changes direction of stroke of Piston
 Thus the Cycle is repeated

25. QRM is obtained due to the
difference in stroke volume
volume on Left side of piston is
small due to presence of piston
rod. Right side volume is larger
( absence of piston rod). Pump
pumps same amount of oil both
sides. As volume is small on Left
side, pressure increases causing
Speed of ram to increase in
return stroke

26. ADVANTAGES OF HYDRAULIC
SHAPER
 Cutting tool works uniformly during
cutting stroke.
 Reverse stroke is obtained without any
shock
 More no. of cutting speeds are obtained
 Good control on cutting speed
 Relief valve ensures safety i.e. Machine is
not overloaded

27.  Horizontal shaper has a ram
which reciprocates in the
horizontal plane only and are
very commonly used to produce
flat surfaces.
 Vertical shaper (also known as
slotter) has the ram which
reciprocates in vertical plane. It
possesses a rotary work table.
used to generate internal
surfaces, keyways, grooves, slots

28.  Push cut shapers are of the
horizontal push cut type. In this
type, cutting occurs as the ram
pushes the tool across the
workpiece.
 Draw cut shapers are used primarily
in tool and die shops. Cutting is
done during the return stroke as the
tool is set in a reversed direction to
that of the standard shaper. It can
take heavy cuts with 'less vibration
and strain on the work table.

29. SHAPER FEED MECHANISM
 The feeds of a shaper are usually
obtained by means of a pawl and
ratchet actuating the feed (lead)
screw
 The driving disc is linked by
connecting rod to the rocker arm
which carries a spring loaded
reversible pawl. As the disc rotates
it causes pawl to oscillate about
the centre of the feed screw.

30. RATCHET AND PAWL

31.  By offsetting the driving pin on
the slotted disc, the rocker arm
is made to oscillate sufficient to
move the pawl over one or
more teeth of ratchet and so
transmit intermittent motion to
the Crossfeed lead screw
which moves the work table.

32.  To reverse the direction of
table traverse, the pawl is lifted
and turned round so that it
moves the ratched wheel in
the opposite direction. When
no feed is required, the pawl is
lifted and turned through 90°
so that the pin is out of the
groove and the pawl is held
clear of the ratchet.

33. SHAPER OPERATIONS
(a) Horizontal shaping (facing top job
surface).
(b) Vertical shaping (facing side),
(c) Shaping of grooves, slots, steps
and keyways
(d)Angular shaping (Dovetail cutting)
(e) Cutting of splines and gear teeth.
(f) Irregular cutting.

34. Angular(dovetail) Slotting(grooves)

35. SHAPER

36. WORK HOLDING DEVICES
(i) Vices
(ii) Parallel strips
(iii) Clamps
(iv) Jack
(v) Angle plate
(vi) Vee blocks
(vii) Stop pins and toe dogs
(viii) Centres.

37. WORK HOLDING DEVICES
 Shaper Vice
 Parallel Strips
 Stop pins and Toe Dogs

38. ADJUSTING THE LENGTH OF
THE STROKE
 The closer the pin
is brought to the
centre of the bull
wheel, smaller will
be the stroke.
 Maximum stroke
of the ram is
obtained when
the crank pin is
shifted towards
the farthest end
of the slide.
1. Crank pin
Short stroke Long stroke

39. ADJUSTING THE POSITION OF
STROKE
 Clamping lever is loosened and by
rotating the hand wheel, screwed
shaft will rotate within the ram
block.
 Rotation of the screwed shaft will
cause the ram to move forward or
backward. Thus position of the
ram is adjusted to desired position.
Now the clamping lever is

41. QUICK RETURN MECHANISM
Since return stroke does no
cutting, the ram should move
faster during return stroke. The
shaper drive system
incorporates quick return
mechanism enabling the ram to
move faster during return stroke
Thus minimizing the (idle time)
Quick Return time.

42. SHAPER DRIVE MECHANISMS
 Slotted link quick return
mechanism
 Whitworth quick return mechanism
 Hydraulic quick return mechanism

43. CRANK AND SLOTTED LINK
A - Clamping nut
B - Ram
C - Link
D - Crankpin
E - Slotted crank
F - Bull Wheel
G - Slot
A - Path of crankpin
B - Length of stroke
C - Cutting stroke
D - Idle or return

44.  When the bull wheel
rotates, the crank pin
rotates and also slides
through the slot in the
slotted crank. This
makes the crank to
oscillate about its one
end E. This oscillating
motion of the crank
makes the ram to
reciprocate. Rise and
fall of the crank is
taken care by the
lever ‘C’

45.  The position of the
crank pin in the
slot in the bull
wheel decides the
length of the stroke
of the shaper. The
further it is away
from the centre of
bull wheel, the
longer is the stroke.

46.  The cutting stroke of the
ram is completed while
the crank pin moves
from A to A1 and the
slotted link goes from
left to right. Similarly,
during return stroke
crank pin moves from
A1 to A and the link
changes its position
from right to left.

47.  Since the crank
pin rotates with
uniform velocity
and angles of A1A
is smaller, it is
obvious that the
idle return stroke is
quicker than the
forward cutting
stroke and hence
the slotted link
mechanism is
known as quick
return mechanism.
Cutting time/Idle time =
angles of AA1/angles of
A1A

50. WHITWORTH QUICK RETURN
MECHANISM
1. Driving pinion
2. Crank pin
3. Sliding block
4. Crank plate
5. Pivot for crank plate
6. Connecting rod
7. Connecting pin for ram
8. Ram
9. Pin

51.  Bull gear rotates at constant speed.
Crank pin 2 with the sliding block 3 will
rotate on a crank circle of radius A2 and
the sliding block 3 will cause the crank
plate to rotate about the point 5 with a
variable angular velocity.

52.  Rotary motion of the crank pin 9 will be
converted in to reciprocating motion
of the ram. When the pin 2 is at
position C, the ram will be at the
extreme backward position. At position
B, ram is at the forward position.

53.  Length of the stroke is adjusted by
shifting the position of pin 9 closer
or away from pivot 5
 Position of stroke may be altered
by shifting the position of pin 7 on
the ram.

54. DIFFERENCE BETWEEN THE
TWO QRM
 In whitworth the slotted or driven
member is inside of the crank pin
circle, whereas in crank and
slotted link, the pivot is outside of
the crank pin circle.
 As a result of this difference, part 4
in ww, has a continuous rotary
motion, while slotted link E swings
through a definite angle

55. DIFFERENCE BETWEEN THE
TWO QRM
 On entering the cut, the
highest pressure on the tool
and the slowest speed is
available.
 On entering the cut the
maximum pressure is holding
the ram down in its slides and
so steadying the ram when
most necessary.

56.  The slotted link motion is
directly opposite to all the
three points enumerated
above

57. Machining time
 L = Length of the cutting stroke in mm
 M = Ratio between return time to cutting time
 n= Number of double strokes of the ram per
minute or RPM of the bull wheel
 v= Cutting speed in m/min

58. CUTTING SPEED, FEED, DEPTH OF CUT
CUTTING SPEED = Length of the cutting stroke in mm/1000
(m/min) -------------------------------------------------
Time required by the cutting stroke in min
Time taken by the cutting stroke = L / (1000 x v)
Time taken by the return stroke = m x cutting stroke time
= (m x L)/(1000x v)
Time taken to complete = cutting stroke + return stroke time
one double stroke
)1(
1000
m
v
L



59. Machining time
Number of double strokes per minute (n)
=
Total number of double strokes to complete the job = B / S
B = breadth of the work in mm, S = feed in mm/double
stroke
Total time taken to complete the cut
= Time to complete one double stroke x number of double
strokes
)1(
1000
mL
v
n



)1(
1000
m
Sv
BL




60. ADVANTAGES OF SHAPERS
 The single point tool used is in-expensive
 Setup of shaper is very quick
 Thin jobs can be easily machined because
of lower cutting forces

61. Problem 1…
 In a shaper, the length of stroke is 200mm,
number of double strokes per minute is 30
and the ratio of return time to cutting time
is 2:3 (normally). Find the cutting speed

62. Solution
 V = length of the cutting stroke / Time
taken by the cutting stroke
m=2/3
V=30x200(1+2/3)
-------------------- = 10m/min
1000

63. Problem 2…
 Find the time required for taking a
complete cut on a plate 600 x 900mm, if
the cutting speed is 9m/min. The return
time to cutting time ratio is 1:4 and the
feed is 3mm. The clearance at each end is
75mm.

64. Solution
 In a shaper a stroke length of more than 900mm is not
ordinarily available so the work is placed on the table to
take a cut of 600mm plus the clearances.
Total length of the stroke = 600 + 75 + 75
= 750mm
m=1/4 , v=9m/min
750x900
-------------(1+1/4)=31.25min
1000x9x3
)1(
1000
m
Sv
BL




65. Problems….
 Find the correct number of strokes per
minute to use on a shaper cutting a m.s
piece 250mm long and 150mm wide. The
cutting speed is 20mpm for HSS tool. If a
feed of 1mm be used then how much time
will be taken in machining one surface of
job. What will be the machining time if
carbide tool be used to cut at 100mpm.