UNIT-III
SHAPING, SLOTTING & PLANING MACHINES
shapers and planers & slotting machine tools which produce a flat surface.
They are capable of machining a horizontal, vertical or inclined flat surface.
They employ single-point cutting tools which are essentially similar to singlepoint cutting tools used on lathe. In both these machine tools, the cutting tool
is subjected to interrupted cuts, the tools cuts in forward direction and is idle
in the return direction
Types of shapers
1 According to type of mechanism used for ram:
a) Crank type
b) geared type
c) Hydraulic type
2. According to position & travel of ram:
a) Horizontal type
b) Vertical type
c) Traveling type
3. According to type of design of table:
a) standard shaper
b) universal shaper
4. According to type of cutting stroke:
a) push type
b) draw type
Working principle of shaper:
It consists of a hollow machine bed made of cast iron which rests on
the ground. Inside the hollow portion the machine drive mechanism is housed.
This mechanism is called slotted lever quick return mechanism and it drives a
horizontal ram which reciprocates in the guide ways provided on the top
surface of the machine frame. In the front face of the ram, a tool post is fitted.
This is a very special kind of tool post. It carries a slide which can be operated
by a hand wheel and the entire tool post can be lowered or raised. Besides, the
tool slide can be swiveled in a vertical plane and its inclination to the vertical
(amount of swiveling) can be read off on a scale marked in degrees. The tool is
inclined, when an inclined surface has to be machined. In the front portion of
the base, a table is fitted. The table can be raised or lowered to vary its height.
It can also be moved horizontally to left or right. A vice to hold the work piece
is provided on the table top. The tool does useful work i.e., cutting only in
the forward stroke of the ram. It does not cut in return stroke i.e. it is idle
during the return stroke of ram. In order that while returning, the tool may not
rub and spoil the strip of the metal machined in the forward stroke, a special
device called the “clapper box” is provided in the tool post. It lifts the tip of the
tool during the return stroke.
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. Sliding along the cross
rail is a saddle which carries the work table.
Ram and tool head: 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 work piece to be-machined.
Shaper specifications:
 Maximum length of stroke or cut it can make ranges from- 175 to 900
mm.
 Drive- belt or individual motor drive
 Power input
 Floor space
 Weight of machine
 Cutting to return stroke
 Number & amount of feed
Shaper mechanism:
The shaper machine should be so designed that it can allow the ram
holding the tool to move at a comparatively slower speed during the forward
cutting stroke the cutting speed depending upon the type of material &
machining conditions, whereas during the return stroke it can allow the ram to
move at a faster rate to reduce the idle return time. This mechanism is know as
Quick return mechanism
1. Crank & slotted link mechanism
2. Whit worth quick return mechanism
3. Hydraulic shaper mechanism
1. Crank & slotted link mechanism:
Since useful work is done only during the forward stroke of
ram, the mechanism driving the ram is so designed that the return stroke
is completed in much less time than the forward stroke. The slotted lever
quick return mechanism is illustrated in Figs. 2(a) & 2(b)
The crank AB(of adjustable length R) rotates with a uniform angular speed. The
crank pin B is in the shape of a die block which is free to slide inside the slot in
the slotted lever OBC . This slotted lever is pivoted at O and the other end C is
connected to the ram by a short link arm as shown in Fig. 2 (a). When the
crank AB rotates clockwise from position AB1to AB2, the ram moves forward
from left to right and when it rotates from positionAB2to AB1the ram returns
back to its original position. Clearly the time taken to complete forward stroke
is proportional to angle α (refer to Fig. 2 (b) and the return stroke is completed
in less time which is proportional to angle β.
The ratio between the cutting time & return time may be determined by
Cutting time/ Return time
2. Whit worth quick return mechanism:
Shapers operations:
1. Machining vertical surface
2. Machining horizontal surface
3. Machining angular surface
4. Cutting slots, grooves & key ways
5. Machining irregulars surface
6. Machining splines or cutting gears
Work holding devices
1. Clamped in a vise
2. Clamped on the table
3. Clamped to the angle plate
4. Clamped on a v- block
5. Held between shaper index centers
Planning machines:
The planer is a machine tool designed to produce plane and flat surface
on a work piece which is too large or too heavy. The work piece is securely
fixed on a table called platen, and it reciprocates horizontally against a single
edged cutting tool. The surface machined may be horizontal, vertical or at an
angle.
Types of planning machines
1. Double housing planer
2. Open side planer
3. Pit type planer
4. Divided table planer
5. Edge or plate planer
1. Double housing planer:
It is the most common type of planer. It consists of mainly a
massive bed on which the work table reciprocates, and two vertical
columns or housing, one on each side of the bed. Each column carries a
tool head that can be slide up and down on the column. A cross rail
fitted between the two columns may carry one or two tool heads that
can slide horizontally on the cross rail. All the tool heads can be clamped
in position, and can be used collectively or individually depending on the
requirements.
2. Open side planer:
Open side planer consists of only one vertical column or
housing on which the cross rail is mounted. The column and the cross
rail carry single and double tool heads respectively. This type of machine
permits machining of wide work piece.
3. Pit type:
A pit type planer differs from other planer in the sense that,
the table and the work piece resting on it remain stationary and the tool
reciprocates across the work surface. This type of machine is preferred
for very large work, where the weight of the work piece and the tool
required table would make reciprocating movement difficult. The job is
either mounted on a stationary table, or on the floor inside a pit, and
hence the name pit type planer. One or two tool heads can be mounted on the
cross rail and two side tool posts the housings, if required. The entire
unit travels along the horizontal ways and fro and, thus the tool moves
past the work surface during operation.
4. Edge or plate planer:
This type of machine is used for machining the edges of heavy
work pieces. The work piece is clamped on the bed and the side
mounted carriage supporting the cutting tool is reciprocated along the
edge of the work piece. Cutting can take place during both directions of
carriage travel.
5. Divided table planer:
It is also called tandem planer and consists of two
worktables, which may be reciprocated together or separately. It is quite
well known that, mounting and setting of work pieces on the worktable
consumes more time thereby restricting the machine for continuous
mass production applications. In such cases, divided table planer can be
used, where in, one worktable can be used for setting up a new work
piece, while the second worktable carrying work piece is being
machined. The two tables can be joined together to hold large work
piece.
Planing Machine parts:
Construction: The main parts of the double Housing Planer machine is
Bed and table, Housings, Cross rail, Tool heads, Driving and feed mechanism.
Bed and table: The bed is a long heavy base and table made of cast iron. Its top
surface is flat and machined accurately. The flat top surface has slots in which
the work piece can be securely clamped. The work piece needs rigid fixing so
that it does not shift out of its position. The standard clamping devices used on
planer machine are: Heavy duty vice, T-holders and clamps, angle plate, planer
jack, step blocks and stop. The table movement may be actuated by a variable
speed drive through a rack and pinion arrangement, or a hydraulic system.
Housings: The housings are the rigid and upright column like castings. These
are located near the centre on each side of the base.
Cross rail: The cross rail is a horizontal member supported on the machined
ways of the upright columns. Guide ways are provided on vertical face of each
column and that enables up and vertical movement of the cross rail. The
vertical movement of the cross rail allows to accommodate work piece of
different heights. Since the cross rail is supported at both the ends, this type of
planer machine is rigid in construction.
Tool heads: Generally two tool heads are mounted in the horizontal cross rail
and one on each of the vertical housing. Tool heads may be swiveled so that
angular cuts can be made.
Driving and feed mechanism: The tool heads may be fed either by hand or by
power in crosswise or vertical direction. The motor drive is usually at one side
of the planer near the centre and drive mechanism is located under the table.
Planer mechanism :
Two important mechanism of a planer are
1. Table drive mechanism
2. Feeding mechanism
Different mechanism used to drive the table.
1. Open & belt drive mechanism
2. Receivable drive mechanism
3. Hydraulic drive mechanism
Planer operations:
1.
2.
3.
4.
Planing flat horizontal surfaces
Planing vertical surfaces
Planing at an angle & machining dovetails
Planing slots & grooves
1. Horizontal surfaces:
While machining horizontal surface, the work is given a
reciprocating movement along with the table & the tool is fed crosswise
to complete the cut. Both the rail heads may be used for simultaneous
removal of the metal from two cutting edges.
2. Vertical surfaces:
The vertical surface of a work is planed by adjusting the
saddle horizontally along the cross rail until the tool is in a position to
give the required depth f cut. The vertical slide is adjusted perpendicular
to the planer table & the apron is swiveled in a direction so that the tool
will swing clear out of the machined surface during the return stroke.
3. Planing at an angle & machining dovetails
For dovetail work, cutting v- grooves etc., the tool head is
swiveled to the required angle &the apron is then further swiveled away
from the work to give relief to the tool cutting edges during return
stroke.
4. Planing slots & grooves
Slots or grooves are cut by using slotting tools. The
operations are similar to that of a shaper.
Slotting machines:
The slotting machine is a reciprocating machine tool in which, the ram holding the tool
reciprocates in a vertical axis and the cutting action of the tool is only during the downward
stroke.
Construction:
The slotter can be considered as a vertical shaper and its main parts are:
1. Base, column and table
2. Ram and tool head assembly
3. Saddle and cross slide
4. Ram drive mechanism and feed mechanism.
The base of the slotting machine is rigidly built to take up all the cutting forces.
The front face of the vertical column has guide ways for Tool the reciprocating ram. The ram
supports the tool head to which the tool is attached. The workpiece is mounted on the table
which can be given longitudinal, cross and rotary feed motion.
The slotting machine is used for cutting grooves, keys and slotes of various shapes making
regular and irregular surfaces both internal and external cutting internal and external gears
and profiles .The slotter machine can be used on any type of work where vertical tool
movement is considered essential and advantageous.
Types of slotting machines
1. Puncher slotter
2. Precision slotter
Puncher slotter:
It is a heavy , rigid machine designed for removal of large amount of metal from large
forging or casting. It may be as long as 1800 to 2000 mm. It is usually driven by spiral pinion
meshing with rack teeth cot on the under side of the ram. It is driven by an electric motor.
Precision slotter:
It is a lighter machine & is operated at high speed. It is designed to take light cuts giving
accurate finish. Used for jigs, & handle a number of identical works on a production basis.
Slotter operations:
1.
2.
3.
4.
Machining flat surface.
Machining cylindrical surface.
Machining irregular surface & a cam machining
Machining slots, key ways & grooves.
Difference between the three types
1
2
Shaper
Planer
Slotter
The work is held stationary
and
the tool on the ram is
moved
back and forth across the
work
Used for shaping much
smaller jobs
The tool is stationary and
the workpiece on the table
travels
back and forth under the tool
The work is held
stationary and
the tool on the ram
is moved up
and down across
the work
It used for making
slots in
smaller jobs.
Slotting is light
machine
Can employ light
cuts and finer
feeds
Meant for much larger jobs are
of 6 mts wide & twice as long can
be machined
It is a heavy duty machine
3
Is a light machine
4
Can employ light cuts and
finer
feed.
Can employ heavier cuts and
coarse feed
5
Driven using quick- return
link
The drive on the planer table is
either by gears or hydraulic
means
The rams are either
crank-driven
or by hydraulic
driven
6
It is less rigid and less
robust
7 Smaller jobs can be fixed
quickly & simply in a vice
. job sizes 900 mm cube(
max)
Better rigidity that give more
accuracy on machined surfaces
It is less rigid and
less robust
Bigger jobs require fixtures for Same as shaper
fixing & hence more fixing
time & skillness are requird .
max job size: 3m*3m*2.5m