In the world of metalworking, the type of bending die used can significantly influence the outcome of the bending process. Bending dies are essential tools that shape metal sheets into desired angles and forms. This article delves into the types of bending dies, their applications, and how they affect the bending process and calculations. Understanding these factors is crucial for achieving precise and efficient metal bends.
Types of Bending Dies
Bending dies are primarily categorized into standard dies and special dies, each serving distinct purposes in the bending process.
Standard Bending Dies
1. Definition and Use
- Standard Bending
- Standard bending dies are typically used for straightforward bending tasks such as creating right angles and other simple bends. They are the go-to choice for most routine bending operations.
2. Selecting V-Groove Sizes
- V-Groove Selection Based on Thickness
- The size of the V-groove in the die is selected based on the thickness of the metal sheet. The general rule of thumb is to choose a V-groove opening size that is 6-10 times the thickness of the sheet:
- For 0.5 to 2.6mm thickness: 6 times the thickness
- For 3 to 8mm thickness: 8 times the thickness
- For 9 to 10mm thickness: 10 times the thickness
- For thickness above 12mm: 12 times the thickness
- For example, for bending a 2mm thick sheet, a 12mm V-groove would be appropriate.
3. Bending Size Calculation
- Bending Coefficient
- The bending coefficient is a crucial factor in determining the unfolded length of the metal sheet. It varies depending on the bend angle and the material thickness:
```
Bending Coefficient = 0.35 * Sheet Thickness (for angles less than 45 degrees)
Bending Coefficient = 0.18 * Sheet Thickness (for 90-degree bends)
```
- For a 90-degree bend, if the sheet thickness is 2mm:
```
Bending Coefficient = 0.18 * 2 = 0.36
Unfolded Length = 98 + 98 + 0.36 = 196.36mm
```
Special Bending Dies
1. Definition and Use
- Special Structures
- Special bending dies are required for creating complex structures such as offset bends, hemming, and other intricate shapes that standard dies cannot achieve.
2. Types of Special Dies
- Offset Bending Dies
- Used for creating steps or offsets in the metal sheet.
- Hemming Dies
- Designed for folding the metal sheet back onto itself to create a hem.
Segmented Bending Dies
1. Importance of Segmented Dies
- Flexibility in Bending
- Bending machine dies typically come in standard lengths of 835mm. However, using segmented dies, which are shorter sections of different lengths, allows for greater flexibility in bending various sizes of box-shaped workpieces or enclosures.
2. Standard Segmentation
- Industry Standards
- There is an industry standard for segmenting bending dies, which allows for the creation of a combination of different lengths to suit specific bending needs.
Metal Bending and Forming
1. Bending and Forming Process
- Placement and Bending
- Metal sheets are placed on the bending machine, and a brake shoe is lifted by a lever. The workpiece is then slid into the correct position. Lowering the brake shoe onto the workpiece and applying force via a bending lever achieves the desired bend.
Common Issues and Solutions
1. Minimum Bending Radius
- Definition
- The minimum bending radius is a function of the material’s ductility and thickness. It is the smallest radius at which the sheet can be bent without cracking.
2. Preventing Bend Marks
- Surface Smoothness
- To avoid marks during bending, ensure that the surface of the bending die is polished and smooth. Avoid pressing the material too hard, as excessive pressure can cause indentations.
3. Sheet Metal Flanging
- Process
- To create flanges, typically start with vertical bends, then adjust the part and press it down. Final shaping can be done with additional tools to achieve the desired flange.
Conclusion
Understanding the different types of bending dies and their applications is essential for any metalworking professional. Standard bending dies are ideal for routine bends, while special dies are necessary for more complex shapes. Proper selection, use, and maintenance of these dies are crucial for achieving precise and high-quality bends. By mastering the use of these tools, metalworkers can enhance their efficiency and output quality.
Frequently Asked Questions
What are standard bending dies used for?
- Standard bending dies are used for straightforward bending tasks, such as creating right angles and simple bends.
How do you select the V-groove size for bending dies?
- The V-groove size is selected based on the metal sheet thickness, typically 6-10 times the thickness of the sheet.
What is a bending coefficient?
- The bending coefficient is a factor used to determine the unfolded length of a bent metal sheet, varying with the bend angle and sheet thickness.
What are special bending dies?
- Special bending dies are used for complex bends and shapes that standard dies cannot achieve, such as offset bends and hemming.
Why are segmented bending dies important?
- Segmented bending dies allow for greater flexibility in bending various sizes of workpieces, making them essential for custom bending tasks.
How can you prevent marks during the bending process?
- Ensure the bending die surface is polished and smooth, and avoid excessive pressure to prevent indentations.
