Shaper construction
The function of the shaper is, primarily, the production of flat surfaces. The work is held on an adjustable worktable, or more oftenin a vise fastened to the worktable, while the cutting tool, which is given a reciprocating motion, that is, caused to move forward and back, peels off a chip on the cutting stroke. At the end of the return stroke the feed operates to move the table (and work) the desired amount.
Shapers are classified as to size (14, 16, 20 in., etc.) by the maximum length of the cut that may be taken, and a standard shaper of a given size will hold and machine a cube of that size.
The crank shaper, in which the tool carrier is driven forward and backward by an oscillating arm operated by a crankpin in the main driving gear, or "bull wheel," and in which the feed is transmitted to the worktable by ratchet-and-pawl mechanism, is so commonly used as to be termed standard.
It should be noted, however, that the hydraulic shaper is becoming increasingly popular . the tools used, the work holding devices the methods, and the general operations are the same for either type .
Parts of Shaping Machines OR Shaper
1. Base. 5. Table.
2. Column or pillar 6. Ram.
3. Cross rail. 7. Tool head.
4. Saddle. 8. Drive mechanism.
1. Base :- The base of tbe shaper supports the column or pillar which supports all tbe working parts such as ram, work table, drive mechanism etc. Base is a heavy cast iron body.
2. Column or pillar 6. Ram.
3. Cross rail. 7. Tool head.
4. Saddle. 8. Drive mechanism.
1. Base :- The base of tbe shaper supports the column or pillar which supports all tbe working parts such as ram, work table, drive mechanism etc. Base is a heavy cast iron body.
2. Column:- Pillar or Body:- The shaper has a column which is a ribbed casting of cellular construction. The top of the column carries the ram slideways, whilst the table slideways are machined on the front of the casting. The crank and slotted link mechanism that drives the ram is contained within the column. The driving motor, the variable speed gearbox, levers, handles and other controls of shaper are also contained in the column.
3. Cross rail:- The cross rail carries the horizontal table slideways and is mounted on the vertical slideways of the column. The cross rail can be raised or lowered by means of an elevating screw in order to compensate for different thick nesses of work. The cross rail is a, heavy casting and it also carries the table cross feed screw together with the pawl and ratchet intermittent drive mechanism.
4. Saddle:- Saddle is gibbed to the cross rail and supports the table. If the table is removed, the work can be bolted or clamped to the Tslots in front of the saddle. Crosswise movement of the saddle causes the work table to move sideways.
5. Table:- The work table is a box shaped casting with Tflots in its upper surface and down one side (Fig.). It also has a vee machined in tbe vertical side to carry cylindrical work.
The upper surface of the work table is machined in situ after assembly to ensure that the working surface of the table is a true datum for work setting.The work table is bolted to the saddle and can be moved vertically and crosswise with the help of saddle and cross rail.
6. Ram:- Ram is a rigidly 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 the downfeed mechanism.
7. Tool head:- 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° in a vertical plane: The tool head can be raise a or lowered by hand feed for vertical cuts on the workpiece.
The tool head holds the tool. The tool head imparts the tool, the necessary vertical and angular feed movements. The tool slide controls the in feed of the cutting tool into the workpiece. In other words, it controls the depth of cut and is adjusted by a lead screw.
The clapper box allows the cutting tool to lift on the return or idle stroke so that the tool is not dragged back through the uncut workpiece and gets damaged. The tool post carries the cutting tool.
8.Slotted Link Quick Return Shaper Drive Mechanism:-
Slotted link mechanism is very common in mechanical shapers. The mechanism is simple and compact. It converts the rotary motion of the electric motor and the reciprocating motion of the ram.The slotted link mechanism gives the rain a higher
velocity during the return non cutting stroke than during its forward cutting stroke thereby reducing the time wasted during the return stroke. The bull gear is driven by a pinion which is connected to the motor shaft through a gearbox with four, eight or more speeds available. The bull wheel has a slot. The crank pin A is secured into this slot; at the same time it can slide in the slotted crank B.
When the bull wheel rotates, the crank pin A also rotates and side by side slides through the slot in the slotted crank B. This makes the slotted crank to oscillate about its one end C. This oscillating motion of slotted crank (through the link D) makes the ram to reciprocate. The intermediate link D is necessary to accommodate the rise and fall of the crank. The position of the crank pin A in the slot in the bull wheel decides the length of the stroke of the shaper. The further it is away from the centre of bull wheel, the longer is the stroke. The cutting stroke of the ram is completed while the crank pin moves from A to A1 and the slotted link goes from left to right. Similarly, during return stroke crank pin moves from A1 to A and the link changes its position from right to left. The time taken by cutting and idle strokes of the ram is proportional to the angles AZA1 and A1ZA respectively.
