Sheet Metal Bending Operation

The Sheet Metal Bending process involves the application of external force using a punch and a die at the specified length of the workpiece. This external force results in the plastic deformation of the workpiece. The type of bend and bend length depends on punch and die design. 

In this article, we will discuss various types of sheet metal bending operationsWe suggest you also read this article on sheet metal cutting operations.

Types of Sheet Metal Bending Operations

According to the type of sheet metal bend, bend shape, and production volumes, the following types of sheet metal bending operations are used to bend sheet metal parts.

  1. Press-Brake-Bending
  2. Roll-Bending
  3. Deep Drawing

1. Press Brake Bending

Press brake or Brake Press in sheet metal parts utilizes v-types of flat punch and die to make straight sheet-metal bend at required angles. During bending, the sheetmetal workpiece is placed in a V-Die where the bending punch is pressed against the sheet metal workpiece at the bending line. 

Sheet metal bending angle depends on the travel of punch against the sheet metal workpiece. Whereas internal bend radius depends on the punch radius. As a result, the same punch and die can be used to bend different sheet metal parts.

Brake Press Machine
this image shows sheet metal Brake Press Bending Tool
Bending Tool for Brake Press

Brake press machines are used to bend sheet metal parts with low production volumes. Because the same punch and die can be used to bend multiple different sheetmetal parts. Press bending machines are used to manufacture in the following industries:

  • Electrical and electronics enclosure.
  • Racks
  • Doors etc.

Press brake bending operations can be classified into the following types.

  1. Air Bending
  2. Coining
  3. Bottoming
1.1) Air Bending

In Air bending Process, the sheet metal workpiece does not come in contact with outside edges or the bottom of the V-die. Therefore the inside diameter of the sheet metal part is controlled by V die Opening. The larger the v-opening, the larger will be the inside bend radius.

This image Indicates air bending process in sheet metal using brake press Bending machine.
Air Bending in Sheet Metal
  • The V-die angle should be greater than the bending angle of the sheet metal part. Because in the air bending sheet metal part does not come in contact with the die wall.
  • In Air bending, the bend angle is controlled by the travel of the punch.
  • Spring-back in air bending is compensated by bending the sheet metal part at an angle larger than the required angle.
1.2) Bottom Bending

Bottom Bending or Bottoming in sheet metal involves bending sheet metal parts in such a way that the material makes contact with the punch tip and sidewall of the V-die Opening. But punch and die do not make complete contact with sheet metal. In this, the sheet bend angle is equal to the V-Die angle.

Indicates bottom bending process in sheet metal using brake press Bending machine.

As shown in the above image. bottoming involves following three steps.

Step-1: The sheet metal workpiece is bottomed against V-Die.

Step-2: To compensate for the impact of spring-back, Sheet metal punch bends the workpiece up to the punch angle. Where the punch angle is always less than the die angle. For example, to bend a sheet metal part at 90° angle. 90° angle V-die and 88° angle punch are required.

Step-3: When the punch is released. Due to the spring-back action sheet metal part takes the angle equal to the die angle.

1.3) Coining

Coining in sheet metal involves bending a sheet metal workpiece using a punch and die in such a way that the punch penetrates the sheet metal part. In this way, coining gives highly accurate and precise sheet metal parts. But the high impact of punch and die can cause thinning in the bending region.

This image shows coining sheet metal bending process.
Advantages of Coining Sheet metal operation
  • Highly accurate, precise, and repeatable.
  • Can be performed on old or less sophisticated machines.
  • Inside bend radius is equal to the radius of the punch.
  • No spring back action.
Disadvantages of Coining Sheet metal operation
  • High tonnage machines are required compared to air bending or bottoming.
  • High tear and wear.

2. Roll Bending

Roll Bending process in sheet metal is used for manufacturing tubes, cones, or other revolved sheet metal parts. It utilizes revolving rollers to apply force on a sheet metal part and form it in round shapes.

Roll Bending Machine
Sheet Metal Bending Using rolling Operation
Roll Bending Operation

For roll bending minimum recommended bend radius for steel sheet is 1 to 3 times of sheet thickness. Whereas the minimum recommended bending radius for aluminum is 0.8 to 1 time of sheet thickness.

3. Sheet Metal Drawing

Sheet metal Deep Drawing Process can be divided into four simple steps
Deep Drawing Process

Sheet metal Drawing Operation involves drawing sheet metal parts in a cup-like shape by utilizing a bending press. This process is very extensively used in the automobile industry to achieve a high production rate.

We will keep adding more information on various sheet metal bending operations. Please add your comments, questions or suggestions on various types of sheet metal bending operations in the comment box.

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