Shaping Machine – Introduction
- Shaping is a process of machining a flat surface which may be horizontal, vertical, inclined, concave, or convex using a reciprocating single point tool. A shaping machine is a reciprocating type of machine tool.
- The work is held firmly on the table and the ram is allowed to reciprocate over it. A single point cutting tool is attached to the ram. When the ram moves horizontally in the forward direction, the tool removes metal from the work. On the return stroke, metal is not removed. The ram moves at a slow speed during the forward stroke. But during the return stroke, the ram moves at a faster speed.
- Though the distances of ram movement during the forward and return stroke remain the same, the time taken by the return stroke is less as it is faster. It is possible by the ‘Quick return mechanism’. In a shaping machine, a flat horizontal surface is machined by moving the work mounted on the table in a cross direction to the tool movement.
- When vertical surfaces are machined, the feed is given to the tool. When an inclined surface is machined, the vertical slide of the tool head is swiveled to the required angle and the feed is given to the tool by rotating the down feed handwheel.
Classification Of Shaper Machine :
1. According to the reciprocating motion to the ram:
a) Crank type shaper.
The crank and slotted link mechanism of a crank type shaper converts the rotation of an electric motor into the reciprocating movement of the ram. Though the lengths of both the forward and return strokes are equal, the ram travels at a faster speed during the return stroke. This quick return is incorporated in almost all types of shaper.
b) Geared type shaper.
The reciprocating motion of the ram in some type of shaper is affected utilizing a rack and pinion. The rack teeth which are cut directly below the ram mesh with a spur gear. The pinion meshing with the rack is driven by a gear train. The speed and the direction in which the machine will traverse depend on the number of gears in
the gear train. This type of shaper in not very widely used
c) Hydraulic shaper
The ram of a hydraulic shaper is connected to a piston. Oil at high pressure is pumped to the cylinder of the hydraulic system. As the oil pushes the piston, the ram reciprocates. Hydraulic shapers are high power machines and are used for heavy-duty work.
2. According to the position and travel of the ram:
a) Horizontal shaper. –
In a horizontal shaper, the ram holding the tool reciprocates in a horizontal axis. Horizontal shapers are mainly used to produce flat surfaces.
b) Vertical shaper.-
In a vertical shaper, the ram holding the tool reciprocates in a vertical axis. In some of the vertical machines provision is made to allow adjustment of the ram to an angle of about 10 degrees from the vertical position. Vertical shapers may be crank driven, rack driven, screw-driven, or hydraulic power-driven. The worktable of a vertical shaper can be given cross, longitudinal, and rotary movement. The tool used on a vertical shaper is entirely different from that used on a horizontal shaper. Vertical shapers are very convenient for machining internal surfaces, keyways, slots, or groves. Large internal and external gears may also be machined by the indexing arrangement of the rotary table. There are vertical shapers that are specially designed for machining internal keyways. They are then called key seaters.
c) Travelling Shaper-
In a traveling head shaper, the ram carrying the tool while it reciprocates moves crosswise to give the required feed. Heavy and unwieldy jobs which are very difficult to hold on the table of a standard fed past the tool are held static on the basement of the machine while the reciprocate and supplies the feeding movements.
3. According to the type of design to the table
a) Standard shaper.
A shaper is termed as standard or plain when the table has only two movements, vertical and horizontal, to give the feed. The table may or may not be supported at the outer end.
b) Universal shaper.
In a universal shaper, in addition to the two movements provided on the table of the standard shaper, the table can be swiveled about an axis parallel to the ram ways, and the upper portion of the table can be tilted about a second horizontal axis perpendicular to the first axis. As the work mounted on the table can be adjusted in different planes, the machine is most suitable for different types of work and is given the name “Universal“. A universal is mostly used in tool room work.
4. Based on cutting stroke.
a) Push cut type.
This is the most general type of shaper used in common practice. The metal is removed when the ram moves away from the column, i.e pushes the work.
b) Draw cut type.
In a draw shaper, the metal is removed when the ram moves towards the column of the machine, i.e., draws the work towards the machine. The tool is set in a reversed direction to that of a standard shaper. The ram is generally supported by an overhead arm which ensures rigidity and eliminates deflection of the tool. In this shaper the cutting pressure acts towards the column which relieves the cross rail and other bearings from excessive lading and allows staking deep cuts. Vibration in these machines is practically eliminated.
Parts Of Shaper Machine :
It is a heavy and robust cast iron body. The base supports the column or pillar which supports all the working parts such as ram, work-table, drive mechanism, etc.
Column or Pillar:
The column is a ribbed casting of cellular construction. The ram slideways are provided on the top of the column while the table slideways are machined on the front. The crank and slotted link mechanism that drives the ram is contained within the column. The driving motor, variable speed gearbox, levers, handles, and other controls of shaper are also contained in the column.
Ram is a rigidly braced casting and is located on the top of the column. The ram slides back and forth in dovetail or square ways to transmit power to the cutter. The starting point and the length of the stroke can be adjusted using stroke positioning mechanism and the down feed mechanism.
It is the device which holds the tool. The tool head slides in a dovetail at the front of the ram utilizing T-bolt sand is fastened to the ram on a circular plate so that it can be rotated for making angular cuts. It can swivel from 0° to 90° in a vertical plane. The tool head can be raised or lowered by hand feed for vertical cuts on the workpiece by its hand crank for precise depth adjustments.
The clapper box is needed because the cutter drags over the work on the return stroke. The clapper box is hinged so that the cutting too] will not dig in. Often this clapper box is automatically raised by mechanical, air, or hydraulic action.
The Cross Rail is a heavy casting attached to the column at its front on the vertical guideways. It carries the horizontal table slideways. The cross rail can be raised or lowered using an elevating screw in order to compensate for different thicknesses of work.
It is 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 the work. T-slots are provided on its top and sides for securing the work to it. The table is moved left and right, usually by hand, to position the work under the cutter when setting up. Then, either by hand or more often automatically, the table is moved sideways to feed the work under the cutter at the end or beginning of each stroke.
The saddle moves up and down (Y-axis), usually manually, to set the rough position of the depth of cut. The final depth can be set by the hand crank on the tool head.
Tool holders are the same as the ones used on at engine lathe, though often larger. The cutter is sharpened with rake and clearance angles similar to lathe tools though the angles are smaller because the work surface is usually flat. These cutters are fastened into the tool holder.
Work holding is frequently done in a vise. The vise is specially designed for use in shapers and has long ways which allow the jaws to open up to 14″ or more, therefore quite large workpieces can be held. The vise may also have a swivel base so that cuts may be made at an angle. Work that cannot be held in the vise (due to size or shape) is clamped directly to the shaper table in much the same way as parts are secured on milling machine tables.
A shaper is a machine tool primarily designed to generate a flat surface by a single-point cutting tool. Besides this, it may also be used to perform many other operations. The different operations, which a shaper can perform, are as follows:
1. Machining horizontal surface
2. Machining vertical surface
3. Machining inclined surface
4. Slot cutting
5. Keyways cutting
6. Machining irregular surface
7. Machining splines and cutting gears
Machining horizontal surface
Set the vice jaws length perpendicular to the ram movement. Hold the job lengthwise parallel to the tool stroke so that the maximum stroke of the tool may be utilized. Hold the appropriate tool in the 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. Repeat the above-said procedure.
Machining Vertical Surface:
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 the return stroke. On the return stroke the tool swings away from the work and gives clearance, which prevents the work from being scratched. Start cutting from the highest point towards the bottom. Repeat the procedure for another cut.
Machining Angular Surface :
In this shaper machine operation, an angular cut is done at any angle other than a right angle to the horizontal or to the vertical plane. The work is set on the table and the vertical slide of the tooth head is swiveled to the required angle either towards the left or towards right from the vertical position.
The apron is then further swiveled away from the work so that the tool will clear the work during the return stroke. The down feed is given by rotating the down feed screw. The angular surface can also be machined in a universal shaper or by using a universal vice without swiveling the tool head.
Read More about Shaper Operation: Operation Performed On Shaping Machine Or Shaper.
The size of a shaper is determined by the maximum length of cut or stroke it can make. A standard shaper is usually capable of holding and machining a cube of the same dimensions as the length of stroke. The length of stroke is always the principal dimension, but a number of other details are also required for specifying a shaper fully.
The complete specification of a typical shaper is given below.
1. Length of stroke
2. Maximum horizontal travel of table
3. Maximum vertical travel of table
4. Maximum distance from table to ram
5. Maximum vertical travel of tool slide
6. Length and width of table top
7. Length and depth of table side
8. Power of motor
Shaper Machine Mechanism :
In a shaper rotary movement of the drive is converted into reciprocating movement by the mechanism contained within the column or frame of the machine. The ram holding the tool gets the reciprocating movement. In a standard shaper, metal is removed in the forward cutting stroke, while the return stroke goes idle and no metal is removed during this period. This mechanism is known as the quick return mechanism. The reciprocating movement of the ram and quick return mechanism of the machine usually obtained by anyone of the following methods:
1. Crank and slotted link mechanism
2. Whitworth quick return mechanism
3. Hydraulic shaper 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. a and 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. (a).
- When the crank AB rotates clockwise from position AB1 to AB2, the ram moves forward from left to right and when it rotates from position AB2 to AB1 the ram returns back to its original position.
- Clearly the time taken to complete forward stroke is proportional to angle (refer to Fig. (b))and the return stroke is completed in less time which is proportional to angle β
Hydraulic Shaper Mechanism
In a hydraulic shaper, reciprocating movement of the ram is obtained by hydraulic power. Oil under high pressure is pumped into the operating cylinder fitted with a piston. The end of the piston rod is connected to the ram. The high-pressure oil first acts on one side of the piston and then on the other causing the piston to reciprocate and the motion ist5ransmitted to the ram. The piston speed is changed by varying the amount of liquid delivered by the pump. One of the most important advantages of this type of shaper is that the cutting speed and force of the ram drive are constant from the very beginning to the end of the cut. It also offers great flexibility of speed and feed control., eliminates shock and permits slip or slowing up of motion when the cutting tool is overloaded, protecting the parts or the tools from breakage. Another advantage is that the machine does not make any noise and operates very quietly.
Shaping Machine Parameter :
Feed (S) is the relative movement of the work or tool in a direction perpendicular to the axis of reciprocation of the ram per double stroke. It is expressed in mm per stroke.
In a shaper, the cutting speed is the speed at which the metal is removed by the cutting tool in a period of one minute.
3) Stroke length calculation and adjustment
The length of the stroke is calculated to be nearly 30mm longer than the work. The position of the stroke is so adjusted that the tool starts to move from a distance of 25mm before the beginning of the cut and continues to move 5mm after the end of the cut. The figure shows the adjustment required for the stroke length calculation.
Question and Answer on Shaping Machine Click here
Reference : https://en.wikipedia.org/wiki/Shaper
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