Short Answer:

Sheet metal bends are represented in drawings using specific conventions that clearly show the bend angle, location, and type of bend. These conventions include using bend lines, bend symbols, and indicating the bend radius or angle. The flat pattern and the bent shape are often shown separately to help manufacturing and inspection.

These standard ways of representing bends ensure that the fabricator understands exactly how to form the metal sheet, maintaining accuracy and avoiding errors during production.

Detailed Explanation:

Conventions for representing sheet metal bends

Sheet metal bending is a common process in manufacturing where flat metal sheets are shaped by bending at specific angles. To communicate how a sheet should be bent, engineering drawings follow established conventions that make the instructions clear and unambiguous for fabricators.

Bend lines

Bend lines are shown as long dashed lines (often with alternating long and short dashes) on the flat pattern view of the sheet metal.
These lines indicate where the sheet is to be bent.
They are usually drawn perpendicular to the direction of the bend.
Sometimes bend lines are labeled or numbered for reference.

Bend angle symbols

The bend angle is indicated by a bend symbol, usually a curved arrow or an angular dimension near the bend line.
The angle shows how much the sheet metal should be bent (e.g., 90°, 45°, or 135°).
Sometimes a note or callout specifies the angle more clearly.
Some drawings include both the angle and the radius of the bend.

Bend radius

The bend radius is the radius of the inside curve of the bent metal sheet.
It is usually specified next to the bend symbol or in a note.
The radius affects how tightly the sheet can be bent without cracking or deforming.
A minimum bend radius is important for manufacturing and must be shown clearly.

Flat pattern and bent shape views

Flat pattern view shows the sheet metal in its unfolded, flat state with bend lines marked.
Bent shape view shows the final shape after bending, often in isometric or side views.
Both views are important to understand the full process and final shape.

Additional conventions

Material thickness is usually specified, as it affects bend allowances.
Bend allowance or bend deduction might be noted to help with cutting the flat sheet to the correct size.
Bend direction may be indicated with arrows or notes (e.g., inside or outside bend).
For complex bends, multiple bend lines and angles are shown clearly.

Importance of following conventions

Helps fabricators bend the sheet metal accurately according to design.
Prevents errors like incorrect angles, wrong bend locations, or improper radius.
Saves time and cost by avoiding rework and scrap.
Ensures that the part fits correctly in assembly and performs as intended.

Conclusion:

Sheet metal bends are represented in drawings using standard conventions like bend lines, angle symbols, and radius specifications. Both flat pattern and bent views are used to clearly communicate how the sheet should be formed. Following these conventions ensures precise bending, reduces manufacturing errors, and helps produce high-quality sheet metal parts.