Shaper or Shaping Machine

Shaper or Shaping Machine with Quick Return Mechanism

               The shaper is a reciprocating type of machine tool intended primarily to produce flat surfaces. These surfaces may be horizontal, vertical or inclined. In general, the shaper can produce any surface composed of straight line elements. Modern shapers can generate contoured surface. The meta] working shaper was developed in the year 1836 by James Nasmyth.

Classification of Shapers:

Basic types;

• Horizontal shaper

• Vertical shaper

• Travelling head shaper

Horizontal Shaper:

Ram holding the cutting tool moves in horizontal plane.

Vertical shaper:

The cutting tool moves in vertical plane.

Travelling head shaper:

Cutting tool reciprocates and moves cross wise simultaneously.

Working Principle of Shaper:

               Cutting tool repeatedly travels along line A B. Work is fed a small distance each time. Feed of work and line of tool motion are in same plane but perpendicular.

The tool line eventually reaches position C D. Combination of two movements results in the flat plane ABCD being machined.

Principle of Operation:

               The tool head is fitted on the front end of the ram. The job is rigidly held over the table using a vice. The ram reciprocates to makes the tool to cut the material in the forward stroke. During the return stroke, the tool does not cut any material is called as idle stroke. Combination of one cutting stroke and one idle stroke is called one pass.

Main Parts of a Shaping Machine

Principle Parts of Shaper:

The different parts of a standard shaper are;

•  Base:

It is made of cast iron. It supports the whole of the machine and is bolted to the floor with the help of foundation bolts. Acts as a reservoir of lubricating oil.

• Column:

It is a box type structure and made of cast iron. The inside surface of the column is hollow. column is mounted on the base. Quick return mechanism is housed inside the column. Two guide ways are provided on the top of column and the ram reciprocates on this guide ways.

• Ram:

It is made of cast iron with cross ribs for rigidity. Ram slides over the guide ways on the top of the column. It carries tool head and connected with any one driving mechanism.

• Table:

It is a box type rectangular hollow casting. The table slides along the horizontal guide ways of the cross rail. T - slots are provided on the table for clamping the work pieces. Elevating screw is used for moving the table vertically.

• Cross Rail:

The cross rail slides on the guide ways provided at the front vertical face of the column. A saddle slides over two guide ways provided in the front face of the cross slide. Cross feed screw is for moving the table crosswise. Elevating screw is used for moving the table in vertical direction.

• Saddle:

It is mounted on cross rail. It supports the table. Moves across the cross rail left to right. Movement obtained by a cross feed screw.

• Tool Head:

It is attached to the front end of ram. Carries clapper box & tool post on it. Can be swivelled at any angle on either side.

• Clapper Box:

It is hinged to the tool head. It houses clapper block. Swings outward in return stroke. Tool post mounted on clapper block.

Specifications of Shaping Machine:

• Maximum length of the stroke [in mm].

• Size of the table i.e., length, width and depth of the table.

• Maximum horizontal and vertical travel of the table.

• Maximum number of strokes per minute.

• Type of quick return mechanism.

• Power of the drive motor.

• Floor space required.

• Weight.

Note:

• Horizontal shapers range in size from small bench models with stroke of 175 mm or 200 mm to heavy duty models with strokes as much as 900 mm.

• Shaping machines are commonly provided with power feed ranging from 0.2 to 0.5

mm stroke.

Shaping Mechanism:

               In a shaper machine, ram reciprocates to and fro along with the tool to cut the material. Mechanism involves converting the rotary motion of the drive into reciprocating motion of the ram. In a shaper, material is removed only in the forward cutting stroke and no material is removed during the return stroke. The shaper mechanism allows the ram to move at a slower speed during forward cutting stroke. Since the return stroke is idle, quick return mechanism is used which allows the ram to move faster speed than the cutting stroke. There are three types of Quick Return Mechanism. They are:

• Hydraulic mechanism.

• Crank and slotted lever mechanism.

• Whitworth mechanism.

Slotted Link/Lever Quick Return Mechanism of Shaper:

               Slotted link mechanism is very common in mechanical shapers. The slotted link mechanism gives the ram a higher velocity during the return non-cutting stroke.  Pinion gear gets the power from the motor and drives the bull gear which rotates in opposite direction. A radial slide is provided on the bull gear and a sliding block is assembled on this slide. The sliding block has a crank pin and rocker arm is freely fitted on this crank pin. When the pinion gear rotates, the rocker arm rotates along with the bull gear. The other end of the rocker arm is connected to the ram. The rotary motion of the bull gear is converted to the reciprocatory motion of the ram. The slotted link mechanism gives the ram a higher velocity during the return non- cutting stroke as the angle turned by the rocker [thita] is less during return stroke.

Shaper Operations:

               Punches are used in sheet metals and other work to mark position on work. We shall now learn the operations that can be performed on a shaping machine:

• Machining horizontal surfaces.

• Machining vertical surfaces.

• Machining angular surfaces.

• Cutting slots, grooves & key ways

• Machining irregular surfaces.

• Machining sp1ines/ cutting gears.

Machining Horizontal Surfaces:

Steps involved:

• Fix the work properly on the table.

• Adjust the length of stroke.

• Set the required cutting speed.

• Give required feed of the table.

• Fix an appropriate tool in the tool head.

• Give suitable depth of cut for rough cuts.

• Finishing the job by giving less depth of cut.

Machining Vertical Surfaces:

Steps involved:

• Fix the job on the table firmly.

• Align the surface to be machined properly.

• Fix the side cutting tool in the tool head.

• Set the vertical slide exactly at zero.

• Swivel the apron away from the job.

• Switch on the machine.

• Rotate down feed screw by hand to give down feed

• Feed is above 0.25 mm.

Machining Angular Surfaces:

Steps involved:

• Angular shaping is carried out to machine inclined surfaces, beveled, dove tail etc.,

• Set the work on the table.

• Swivel the vertical slide of tool head to the required angle [to the left or right].

• Set apron away from work.

• Give down feed as per requirement.

Cutting Key Ways:

Steps involved:

• Fix up the job between two centers.

• Cut first spline similar to a key way.

• Move / rotate work by the required amount.

• Use index plate for this purpose.

Machining Irregular Surfaces:

Steps involved:

• Fix the forming too] in tool post.

• Give cross feed in conjunction with down feed.

• Swivel the apron suitably according to the contour required.

Cutting Speed in Shaper:

In a shaper, the cutting speed is the rate at which the metal is removed by the

cutting tool.This is expressed in m/min. The cutting speed of a shaper may be obtained from,

Cutting speed = (Length of the cutting stroke) / (Time required by the cutting stroke)
So, Cutting speed, V = [nL(1 + m)] / 1000  m/min
Where,

L = Length of cutting stroke in mm.

m = Ratio between return time to cutting time

n = No of double strokes of the ram/min.

Feed in Shaper:

Feed [s] is the relative movement of the tool or work in a direction perpendicular to the axis of reciprocation of the ram per double stroke and is expressed in mm. The feed is always given at the end of return stroke when the tool is not cutting the metal. The selection of feed is depended upon the kind of metal, type of job, etc.

Depth of Cut in Shaper:

Depth of cut [t] is the thickness of metal that is removed in one cut. It is the perpendicular distance measured between machined surface and non - machined surface of the workpiece.

Machining time:

If the length of cutting stroke, breadth of the job, feed and cutting are known, the time required to complete the job may be calculated as,

Let,

L = Length of the stroke in mm

B = Breadth of the work in mm

s = Feed expressed in mm/double stroke

m = Ratio return time to cutting time

v = Cutting speed in m/min 

Time taken to complete one double stroke = [L(1 + m)] / (1000 × v)

Total number of double strokes required to complete the job = B / s

So, Total time taken to complete the cut = [L × B(1 + m)] / (1000 × v × s)

END