CHAPTER NO:6

SHAPER MACHINE

PREPARED BY: BRAMHAKSHATRIYA GIRISH

M.

INTRODUCTION:• A shaper is a type of machine tool that uses linear relative motion

between the work-piece and a single-point cutting tool to machine a linear tool path

• Its cut is analogous to that of a lathe, except that it is linear instead of helical

• A shaper is analogous to a planer, but smaller, and with the cutter riding a ram that moves above a stationary work-piece, rather than the entire work-piece moving beneath the cutter.

• The ram is moved back and forth typically by a crank inside the column; hydraulically actuated shapers also exist

Types of shaper machine:• According to the type of mechanism used for giving reciprocating

motion to ram:• Crank type• Geared type• Hydraulic type

• According to the position and travel of ram:• Vertical type• Horizontal type• Travelling head type

• According to type of design of the table:• Standard shaper• Universal shaper

• According to the type of cutting stroke:• Push type• Draw type

Principle parts:

Principle parts:

Contd...• BASE:

• It is heavy and robust cast iron body• The base supports the pillar or column which supports all the working

parts such as ram, work-table, drive mechanism etc.• COLUMN OR PILLAR:

• The column is ribbed casting of cellular construction• The ram slide ways provided on the top of the column while the table

slide ways are machined on the front• The crank and slotted link mechanism that drives the ram is contained

with in the column• The driving motor, variable speed gear box, levers, handles and other

control of shaper are also contained in the column• CROSS RAIL:

• The cross rail is heavy casting attachment to the column at its fronton the vertical guide way

• It carries the horizontal table slide ways• It can be raised or lowered by means of an elevating screw in order to

compensate for different thickness of work

Contd…• TABLE:

• It is a made of cast iron and has box type construction• It holds and supports the work during the operation and slides along the

cross-rail to provide feed to work• T-slots are provided on its top and sides for securing the work to it

• RAM:• Ram is rigidity 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• The ram contains a stroke positioning mechanism and down feed

mechanism • TOOL HEAD:

• It is device which holds the tool• The tool head slides in a dovetail at the front of the ram by means of t-

bolts• It can swivel from 0 to 90 degree in vertical plane• The tool head can be raised or lowered by hand feed for vertical cuts on

the work-piece

Shaper mechanism:

A shaper drive mechanism changes the rotary motion of the power source (Electric motor) into the reciprocating motion of the ram.

Metal cutting is carried out during the forward stroke of the ram only; the return stroke of the ram does no cutting and hence is called idle stroke.

Since return stroke does no cutting the drive system incorporates a quick return mechanism so that the ram moves faster during return stroke in order to minimize the idle time. The two common mechanism used for this purpose are,◦Crank and slotted link quick return mechanism◦Whitworth quick return mechanism◦Hydraulic quick return mechanism

Crank and Slotted link mechanism:

B2LB1

B2KB1

timereturn

timecutting

Principle of quick return

mechanism

Contd….

◦Cutting time to return time ratio varies between 2:1 and the practically limit is 3:2

◦Disadvantages is that the cutting speed and return speed is not constant throughout stroke

◦ It is minimum when the rocker arm is at the two extremities and the speed is maximum when rocker arm is vertical

In the illustration, the bull gear b, driven by drive pinion a, revolves about the large boss c, extending off support d.

The slotted section e, is pivoted about f, which is bored eccentric in boss c. g,  a pin that is fixed in bull gear b, is free to slide in a slot in the back of e. 

As b revolves, it forces e to revolve about f, but owing to the eccentric position of f,  the pin l makes one half revolution while the gear revolves from h to i, and the other half while the gear revolves from i to h.

Whitworth quick return mechanism:

k which pins the link m, to the ram n, can be loosened to position the ram where required

As can be seen, this type of actuation makes for a simple frame for the saddle o in which the ram reciprocates, to traverse the machine.

This is also a motion that the majority of mechanical slotting machines utilized

Whitworth quick return mechanism:

Hydraulic quick return mechanism:

The constant discharge from the oil pump develops moderate oil pressure

This pressure is then transmitted through piping and a reversing valve to an operating cylinder

This pressure acts on the piston and moves the shaper ram forward on its cutting stroke, the same movement expels the oil from the other side of the cylinder and returns it to the sump through the piping and the throttle valve

At the end of the stroke, a limit switch actuates the reversing lever which pulls the reversing valve towards the lever side and thus directs the oil under pressure to the other end of the operating cylinder

The stroke of the shaper is controlled by adjusting the limit switches

the discharge rate of gear pump is constant The same volume of oil is delivered to both the sides of the piston

Contd…

Advantages of hydraulic shaper:

• The cutting and return speeds are constant throughout the stroke practically

• The reversal of the ram is obtained quickly without any stroke as the oil on the other side of the cylinder provides cushioning effect

• Infinite number of cutting speeds may be obtained from zero to the maximum value and the control is easy

• With a high rate of return speed, greater cutting strokes within range of cutting speed

• The relief valve ensures safety to the tool and the machine, when the machine is over loaded. But it is costly and difficult for service and maintenance

Feed mechanism:

• Automatic feed of tableis obtained by aRatchet and Pawl mechanism

• It consists of a slotted disc carries T-slot which is rotated by bull gear

• In this T-slot an adjustablepin is fitted

• A connection rod is attached to the pin and other end of rod is attached to lower end of rocker arm of pawl mechanism

• Rocker arm swings about screw and its upper end carries a spring loaded pawl

• Adjustable pin is set eccentric with the slotted disc centre

Feed mechanism:

• The slotted disc at its back carries a spur gear, driven by a bull gear

• As disc rotates the adjustable pin being eccentric with disc centre, causes connecting rod to reciprocates

• Thus rocker arm swing to move the pawl over one or more teeth and transmit motion to cross-feed screw which moves the table

• Feed may be altered by shifting position of crank pin with respect to centre of driving disc

Specifications of a shaper:

• Maximum length of the stroke• For small bench models stroke of 175 to 200mm and for

heavy duty strokes as much as 900mm• Power feed ranging from 0.2 to 0.5 mm/stroke

• Size of the table (length, width and depth of the table)• Maximum vertical and horizontal ravel of the table• Maximum number of strokes per minute• Type of quick return mechanism• Power of the drive motor• Floor space required• Weight

Cutting tools:

• Tools used in shapers are similar to those used in lathe work

Shaper operations:

The different operations can be performed on shaping machine are listed as:• Machining horizontal surface• Machining vertical surface• Machining angular surface• Machining a V or keyway centrally in the bock• Cutting spines or gears• Machining an irregularly curved surface

Machining Horizontal Surface:

• Set the vice jaws length perpendicular to the ram movement.

• Hold the job length-wise parallel to the tool stroke so that maximum stroke of the tool may be utilized.

• Adjust the cutting speed and feed depending upon the surface finish required, rough or finish.

• Hold the appropriate tool in tool head. Set the proper inclination of the tool and depth of cut.

• Give cross feed to the tool initially by hand till the cut start and then employ power feed.

• After the tool has cut the full width of the job, stop the shaper, inspect the job and set another depth of cut.

• Repeat the above said procedure.

Machining vertical surfaces:

• The tool is fed downward in vertical cutting so swivel the clapper box from the face of the work to be cut

• The tool is fed downwards by rotating the down feed screw by hand at the end of return stroke. Give the feed

• On the return stroke the tool swings away from the work and gives clearance, which prevents the work from being scored

• Start cutting from highest point towards the bottom

• Repeat the procedure for another cut

Machining Angular surfaces:

• Set the swivel head to the required angel for shaping angular faces

• The clapper box is to be swung away from the face to be machined.

• The tool is to be fed by the slide hand wheel.

• The apron top is also swiveled in the direction away from the surface to be machined.

• Feed the tool during return stroke.• Repeat the procedure to finish the

work

Machining slots and keyways:

• For shaping grooves, slots and keyways, a square nose tool to be used

• Fix tool rigidly• Avoid excessive overhang• Start machine and apply feed

during return stroke• Repeat the procedure to finish the

work

Machining Irregular surfaces:

• Secure the work-piece position • Guide the cutting tool vertical and

horizontal feeds so follow the layout lines

• First rough machine the surface• Then finish the machining surface• Repeat the same method to

machine right marked shape