2. INTRODUCTION
Planing, shaping and slotting machines
constitute a class of machine tools in
which a cycle of operation is complete by
a cutting stroke, followed by a return
stroke in which no metal removal takes
place, As this latter stroke is non
productive, means are provided to effect
a rapid reversal to reduce the idle time.
3. INTRO…..
Whereas in a slotter, the tool cuts
while moving vertically up and down,
in shaper and planer the direction of
cutting action of the tool is horizontal.
The shaper is unsuitable for
generating flat surfaces on very large
parts because of limitations on the
stroke and over hang of the ram.
4. INTRO…
This problem is solved in the planer
where unlike shaper the large workpiece
is moved past one or more stationary,
single point cutting tools, Planers are
used primary to produce horizontal,
vertical or inclined flat surfaces on
workpieces that are too large to be
accommodated on shapers.
5. PRINCIPLE
The workpiece is clamped onto the
worktable rides on the grooves on the
base of the planer and is accurately
guided as it travels back and forth.
Cutting tools are held in tool heads that
can travel in a direction at right angle to
the direction of motion of the worktable.
Tool heads are mounted on a horizontal
cross rail that can be moved up and
down.
6. DIFFERENCE BETWEEN
PLANER AND SHAPER
(i) In shaper, the work is held stationary
and the cutting tool on the ram is moved
back and forth across the work, whereas
in a planer, the tool is stationary and the
workpiece travels back and forth under
the tool.
(ii) A planer is a rigid and heavy duty
machine when compared to shaper meant
for larger jobs as large as 6 metre wide
and twice as long can be machined on a
planer.
7. DIFFERENCE BETWEEN
PLANER AND SHAPER
(iii) A shaper uses one cutting tool at a
time, whereas several tools can cut
simultaneously on a planer.
(iv) The drive on the planer table is either
by gears or by hydraulic means. The
shaper ram can also be driven in this
manner, but many times a quick return
link mechanism is used.
8. PLANER SIZE AND
SPECIFICATION
The size of a planer is specified from the
measurement of the largest job that can be
held on its table and pass under and between
housings.
Distance between the vertical housings in mm
The distance from the table to the rail in its
uppermost position in mm,
The maximum length of the table travel in
metres.
10. PLANER PARTS
(i) Bed
(ii) Work table
(iii) Column or housing
(iv) Cross rail
(v) Saddle
(vi) Tool head
(vii) Driving and feed mechanism.
11. PLANER PARTS…
(i) The Bed of a planer must be a
weldment or casting twice as long
as the table. The other parts are
attached to, or supported by the
bed. The bed has accurately
finished ways on which the
worktable slides. The gearing or
hydraulic cylinder for driving the
table is housed under the bed.
12. PLANER PARTS….
(ii) The table is a heavy rectangular
casting. It travels on vee or flat ways
of the bed. The table is driven either
by a hydraulic cylinder or by a pinion
gear driving a rack which is fastened
under the center of the table. The
motor driving the pinion gear is of
reversible type with variable speed.
13. PLANER PARTS….
The upper surface of the table has
T slots to facilitate the clamping of
the work or vises and special
fixtures. The top surface of the
table also has accurate holes for
supporting the stop pins etc.
The side of the table has a groove
for clamping planer reversing dogs
at different positions.
14. PLANER PARTS….
(iii) Column or Housing The frame of the
planer is of hollow box type. The frame is
basically two heavy columns fastened
together at the top with a large bracing
section and fastened at the bottom to the
machine bed.
15. PLANER PARTS….
It is a very strong rigid structure which
will handle heavy loads without
deflection. On a double housing
planer, two columns rise vertically at
the sides of the machine. They
support the crossrail and house the
elevating screws and controls for the
machine.
16. PLANER PARTS….
(iv) The Crossrail is a heavy box
construction. It is mounted on the
vertical ways of the housing. It slides
up and down on vee or flat ways,
controlled by hand or by power
operated screws. These cross rails are
so heavy that they are
counterweighted, with either cast iron
weights or hydraulic cylinders, in order
that they may be moved easily and
positioned accurately.
17. PLANER PARTS….
The purpose of the crossrail is to
carry the vertical tool heads which
by means of feed screws may be
moved from left to right. It is very
essential that the crossrail, when
clamped, be parallel to the table
for obtaining accurate machined
surfaces.
18. PLANER PARTS….
(v) The saddle is fitted to the ways of
the crossrail. On its front surface are
ways to which the toolhead is fitted,
together with a vertical feed screw that
provides for a vertical movement of the
toolhead. There are two saddles one for
the left toolhead, the other for the right
toolhead. Each one may be operated
independently of the other.
19. PLANER PARTS….
(vi) The toolhead contains the tool post
which in turn, holds the cutting tool. The
tool post is hinged to the head so that
on the return movement of the table the
cutting tool will be raised and ride on the
top of the work.
This saves the cutting edge of the tool
from being damaged and permits the
automatic traverse feed to operate
without interference.
20. PLANER PARTS….
The toolhead can be swiveled for
taking angular cuts. There are four
toolheads, two in vertical position
on the crossrail, and the other two
known as side tool heads mounted
one each on the two columns
below the crossrail.
21. PLANER TYPES
Double housing planer
Open side planer
Pit planer
Edge or Plate planer
Divided table planer
22. Double Housing Planer
Length of the bed is little over twice
the length of the table
Two massive vertical housings
mounted on the base
Two tool heads on the horizontal cross
slide
Two tool heads on the vertical face
24. Open side Planer
Has housing only on one side of the
base
Allows large and wide jobs to be
machined
Since only one column no limitation to
width of the jobs
Consist of three tool heads
25. Pit Planer
Table is stationary
Column carrying the cross rail reciprocates on
massive horizontal rails mounted on both sides
of the table.
This design saves much of floor space
Pit planers are used only for very large work,
where the weight of the workpiece and the
required table would make reciprocation
difficult and severely limit cutting speeds.
26. Edge or Plate Planer
Intended for squaring and beveling
the edges of steel plates.
One end of the long plate which is
stationary is attached to the frame of
the machine and the carriage carrying
the tool reciprocates past the edge of
the plate
28. Divided Table Planer
Two tables present, which can be
reciprocated separately or together
For continuous production, one table is
used to set the job and other table on
which the job is already fixed
reciprocates past the tool.
29. PLANER DRIVING
MECHANISM
A planer driving mechanism provides the
longitudinal to and fro motion of the
planer worktable. The following methods
are employed for the said purpose.
(a) Open and cross belt drive.
(b) Gear drive
(c) Reversible motor drive.
(d) Hydraulic drive.
30. Open Drive Mechanism with
Rack and Spur Gears
A - Crossed Belt
B - Crossed Belt
C - Rack
D - Table
E - Bull Gear
F - 2 ND Intermediate
G - 1 ST Intermediate
H - Drive Pinion
31. CLOSED BELT DRIVE
A - Counter Shaft, B - Crossed Belt
C - Open Belt, D - Belt Shifter
E - Table, F - Rack
G - Drive pinion and Tight pulley
Shaft
H - Bull Gear
I - 2 ND intermediate
J - 1 ST Intermediate,
K - Tight pulleys(outer), L - Loose
Pulleys
32. OPEN AND CROSS BELT
Two belts, one open and one crossed
operate on loose and tight pulleys.
Crossed belt is used for forward or
cutting stroke and the open belt for
return motion. The crossed belt
making a greater arc of contact on the
pulley is considered better for driving
the table on the cutting stroke.
33. OPEN AND CROSS BELT
Crossed belt drive mechanism permits
operation of the gear train in such a
manner that the table will travel slowly on
the cutting stroke and travel faster on the
return stroke. Pulleys keyed to the drive
pinion shaft are called tight pulleys and
those which turn freely on the shaft are
called loose pulleys.
There are two tight pulleys and two loose
pulleys. Larger tight pulley - Cutting stroke
smaller tight pulley - quicker return stroke.
34. Drive Mechanism
For obtaining continuous forward and
return motion of the planer table both
the open and crossed belts run
continually and are shifted back and
forth by the belt shifter which is linked
to the reverse lever.
During cutting stroke the crossed belt
is on the tight pulley, the open belt is
on the loose pulley and the position is
reverse during the return stroke.
35. Drive Mechanism
Trip dogs are provided, one each at
both ends of the planer table. At the
end of each stroke, the trip dog meets
against the reverse lever, actuates the
belt shifter and thus the table
movement is reversed.
37. PLANER REVERSIBLE MOTOR
WITH RACK AND WORM
Commonly used on modern planers as it
provides a wider range of table speeds and
a better control. Most planers are driven
direct by a coupled motor in place of the
old method of open and crossed belt drive.
The reciprocating motion of the planer
table is obtained by driving through a worm
on to a rack attached to the length of the
underside of the table. The reversal of the
drive is obtained by reversing the motor
itself either by field or phase changing.
38. PLANER FEED MECHANISM
The feed may be given by hand or
by power. The methods employed
for power feed are:
(i) Friction disc mechanism
(ii) Electrical drive
(iii) Hydraulic drive.
39. NEED FOR FRICTION DISC
MECHANISM
In shaper when bull gear rotates through
one revolution, the ram completes one
double stroke. Using pawl and ratchet
mechanism, for one half revolution of bull
gear, feed is imparted and other half no
feed is given.
In planer since the length of the table is
long, bull gear will make large number of
revolutions in forward and return stroke.
41. FRICTION DISC
Driving disc 16 rotates
The disc consists of two parts
having a cylindrical opening
which encloses flange 4
connected to shaft 5.
Leather washers 6 are placed
between the flange 4 and disc
openings.
Hence a flexible connection is
made between the shaft 5 and
disc 16.
42. Shaft 5 rotates during the
forward stroke and motion
is transmitted to disc 16 by
flange 4 and the disc 16
starts rotating.
The motion of the disc is
limited by the projecting pin
3 hitting against a fixed pin
17.
43. FRICTION DISC
Thus when disc 16 rotates
through a part of the
revolution, flange 4
connected to the shaft 5
continues to rotate within
the disc 16 slipping over
the leather washers 6
throughout the cutting
stroke.
45. FEED MECHANISM
Rotary movement of the disc 16 is
transmitted to rack 14 through the
connecting rod 15 and a pinion
mounted on shaft 12 meshes with the
rack.
Thus gear 11 will rotate through a part
of the revolution in one direction only
during a complete double stroke.
46. FEED MECHANISM
The direction of the feed may be
reversed by changing the position of
the double pawl 10.
Amount of feed movement may be
varied by shifting the position of block
1 with respect to centre.
