Introduction to Basic Manufacturing Processes and ... - always yours

360 Introduction to Basic Manufacturing Processes and Workshop Technology
Sheet metal work consists mainly of cutting, forming and assembling the object that has
been laid out on flat metal sheet. The outline of the object or pattern is first either scratched
on the sheet or drawn on a paper and then transferred to the sheet. Metal sheet is then cut
to various shapes and sizes as per the pattern or shape of object, which may be later,
transformed to various articles by using different sheet metal processes. In the process of
laying out a pattern, certain allowances are kept for making edges and seams. The development
of surface is the unfolding or unrolling sheet in one plane. The sheet is used to mark correctly
using scriber. Important attention is also invited regarding accounting for the allowance in
preparing edges and seams to be made for making joints. The notches of metal pieces are
then cut. Finally the edges are then turned to form box as shown through step in Fig. 18.12.
Square notch
Notched pattern
Edge turned to form pan
Fig. 18.12 Pattern development of sheet metal part
18.7 MACHINES USED IN SHEET METAL SHOP
The various machines, which are in use to perform different operations on metal sheets,
can be listed as follows:
1. Shearing machine
2. Bending machine
3. Folding machine
4. Grooving machine
5. Peining machine
6. Beading machine
7. Swaging machine
8. Burring machine
9. Double seaming machine
Apart from the above, many other special purpose machines are also manufactured to suit
a particular kind of work especially in mass production of identical parts. The above machines
vary in shape and also slightly in the procedure of operating according to the mechanism
adopted by different manufactures. Some important machines are discussed as under.
A shearing machine consists of a base or frame, which can be conveniently fixed on a
bench in any position as desired. Two shearing blades are provided in the machine. One called
the fixed blade is rigidly fixed with the frame whereas the other known as movable blade is
operated by means of the hand lever provided at the rear. In operation, the metal sheet is
placed between the shear blades in such a way that the markings of the layout come exactly
under the cutting edge of the upper blade. Out of the two blades one is fixed and the other