Sheet metal basics cover all the necessary topics needed for an engineer. We will explore topics step by step starting with what is sheet metal, sheet metal design guidelines, etc.
What is sheet metal, let us understand the sheet metal basics?
Sheet metal is a thin and flat piece of metal formed by rolling or hammering. Sheets are available in many different metals, namely aluminium, copper, brass, steels, gold, silvers, and certain alloys.
Sheet vs Plate vs Foil
What is sheet? A sheet is anything whose thickness is between 0.006 inch (0.154mm) to 0.25inch (6.35mm).
What is Plate? Anything of thickness above 0.25inch (6.35mm).
What is foil? Material whose thickness is less than 0.006 inch (0.154mm) is foil.
Sheet metals were usually classified by gauge numbers, but various organisations discontinued using them. Presently only US is using traditional gauge method for sheet metal measurement.
Examples of sheet metal
After you have understood sheet metal basics, we will explore examples of sheet metal. Sheet metal objects are commonly used in day to day products. Right from bear or coke cans to cars bodies, it is everywhere. Sheet metal has a variety of applications. As sheet metal finds its way to daily use, the critical part is present in its designing. Sheet metal designing is a crucial part, and designers must consider tooling while designing part.
Let us see different sheet metal operations.
Basics of sheet metal component design
Sheet metal basics design is a very vast topic. Design considerations are a matter of experience, one achieves after designing, failing and succeeding of parts. Predefined calculations give desired results to a certain extent, but they too have some limitations, so we present you with the basics of sheet metal component design because you have now understood sheet metal basics.
The problems most of the manufacturers face while making a sheet metal part is the size of sheet metal. The thickness of sheet metal varies from sheet to sheet. Minor change in sheet thickness can cause variations in part. Tool designer faces the heat of the manufacturer, and the manufacturer faces the heat of the designer. So while designing a part, one must consider all aspects of sheet metal blanks.
It is not possible to control the thickness of the sheet as different batches may produce different sheet thickness. This minor change in thickness is reflected on forming dies. During any of the forming operation, the clearance between the punch, sheet and die varies, depending on the sheet thickness, causing variations in features.
Sheet metal design rules
Hence while designing any sheet metal component, designers must try to optimise tolerances on the features considering all the above points.
Basic factors to be considered during sheet metal design:
- What type of sheet is being used?
- What type of operations is going to be performed on the designed part?
- Bend radiuses
- Total number of operations being performed on the part
Few thumb rules for sheet metal design
- The minimum hole diameter should be equal to or more than the sheet thickness.
- Distance from the bend to the hole edge should be equal to or more than twice the thickness of the sheet.
- Inner radius should be decided on the ductility of the material, more ductile the sheet the smaller the inner radius.
- Spring back to be decided during the design stage with proper tolerance.
Deep drawing design calculation varies based on different factors. Exact calculations are not achieved, so this formula provides a basic idea for Blank OD for a cup drawing operation.
Deep Drawing Blank Size Calculation (D) = √(d²+4dh) - 0.5r
Where d = diameter of the desired cup
h = height of the cup
r = radius at inside corner (0.5r value is considered based on different factors)