Sheet Metal Processes

UNIT - 4

SHEET METAL PROCESSES

Sheet metal characteristics - shearing, bending and drawing operations - Stretch forming operations - Formability of sheet metal - Test methods – special forming processes - Working principle and applications - Hydro forming - Rubber pad forming - Metal spinning- Introduction of Explosive forming, magnetic pulse forming, peen forming, Superplastic forming - Micro forming.

INTRODUCTION

The working of metal thickness from 3 mm to 5 mm with hand tools and simple machines into various forms is known as sheet metal work. These are formed by cutting, forming and joining processes. It plays an important role in engineering works in day-to-day life. Sheet components are less expensive, lighter in weight and easily replaceable. Example: Funnels, bends, boxes, pipes covers etc.

Before doing sheet metal work, one should have thorough knowledge about geometry, development of surfaces and properties of metal to be used. It provides the saving in time and money in sheet metal work.

The sheet metals used in press working are black iron, galvanized iron, stainless steel, copper, brass, zinc, aluminium, tin plate and lead. According to the components produced, the suitable sheet metal is selected.

The basic sheet metal hand tools used in sheet metal work are as follows:

1. Measuring tools

2. Straight edge

3. Steel square

4. Scriber

5. Divider

6. Trammel points

7. Punches

8. Chisel

9. Hammers

10. Snips or shears.

11. Pliers

12. Stakes

13. Groovers

14. Rivet set and

15. Soldering iron.

Measuring tools are steel rule, folding rule, circumference rule, vernier caliper, micrometer, thickness gauge and sheet metal gauge.

1. Classification of Sheet Metal Operations

Sheet metal processes are classified as follows:

1. Shearing process:

The process which applies shearing force to cut, fracture or separate the material is called shearing. The following shearing processes are commonly carried out:

(a) Punching

(b) Blanking

(c) Perforating

(d) Parting

(e) Notching

(f) Lancing

2. Forming process:

The process which causes the metal to undergo desired shape changes without failure, excessive thinning or cracking is called forming. Various forming processes generally used in

sheet metal work are as follows:

(a) Bending

(b) Stretching

(c) Drawing

(d) Roll forming.

3. Finishing process:

The process which improves the final surface characteristics is called finishing.