Shaper Machine Drive Mechanism- How Shaper Machine Works
Introduction To Shaping /Principle Of Shaping Machine:
Shaper is machine tools which produce a flat surface. It is capable of machining a horizontal, vertical or inclined flat surface. Shaper and planer employ single-point cutting tools which are essentially similar to single-point 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.
Shaper 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 swivelled in a vertical plane and its inclination to the vertical (amount of swivelling) 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 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.
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).
|Quick return shaping mechanism|
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 Alpha (refer to Fig. (b)) and the return stroke is completed in less time which is proportional to angle Beta.