Types of Punches and Dies for Press Brakes | Explanation + Photos and Videos

Table of Contents

• Explanation of Punches and Dies
• Standards for Press Brake Punches and Dies
• Die Segmentation
• Types of Punches and Dies
• Selection of Punches and Dies
• V-Opening and Workpiece Radius
• Rule of 8
• Application of the Rule of 8 in Die Selection
• Materials and Quality of Punches and Dies
• Maintenance of Punches and Dies

Introduction

Metals play a vital role in modern industry and human life. Various processes are applied to metals to achieve the desired results, and one of the most commonly used processes is bending. There are several methods for bending metals, and one of the most widely used is the press brake machine. Press brakes come in different sizes, types, and capacities. To perform bending operations with a press brake, specific tools called punches and dies are required.

Explanation of Punches and Dies

A punch is a tool installed on the upper ram of the press brake, while the die is positioned on the lower table of the machine. To perform the bending operation, the press brake applies force to the punch, moving it downward toward the workpiece placed on the die (as shown below).

The force applied to the ram and consequently to the punch depends on the type of press brake and its power source. The main power sources used in press brakes are mechanical motors, pneumatic systems, servo-electric motors, and hydraulic systems.

For more details about press brake machines, click here.

Standards for Press Brake Punches and Dies

With a wide variety of punches and dies available, selecting the right ones can significantly improve the quality and efficiency of metal bending.

Since parts are designed and manufactured to standard dimensions, using standard-sized punches and dies in press brakes makes it easier and faster to replace these tools, reducing the need for extensive adjustments during tool changes.

A set of clamping devices is required to secure punches to the upper ram, and similarly, clamps are needed to position dies correctly on the lower table to ensure smooth and accurate bending operations.

Die Segmentation

Die segmentation in press brakes simplifies the bending process for workpieces of different sizes.

Punches and dies for press brakes require high precision and quality, especially in the punch tips and die edges, as these parts come into direct contact with the metal during bending. High-quality tools also reduce installation time.

Grand Dayyani Machine Manufacturing a variety of punches and dies for press brake machines. These tools are of the highest quality and can be customized according to customer requirements.

Types of Punches and Dies

Press brake dies are categorized into three main types:

1. V-dies
2. U-dies
3. Z-dies

The most common type is the V-die.

The minimum flange length should be four times the material thickness; otherwise, it is impossible to accurately calculate the bending angle.

The width of the die openings corresponds to the punches used, allowing the press brake to bend materials at various angles.

Press brake punches are mainly classified into three types:

1. Straight punch
2. Gooseneck punch
3. Acute punch (less than 90 degrees)

Other types include sash punches, burring punches, standard thin punches, and standard punches.

Press brake dies are categorized into single V-die (1V), double V-die (2V), and multi-V dies. Below is an example of 1V and 2V dies.

Watch the video below to see how punches from Grand Dayyani Machine Manufacturing   are installed on their press brake machines.

Selection of Punches and Dies

When selecting punches and dies, the following factors must be considered:

• The type and mechanical properties of the metal.
• Thickness of the metal.
• Die opening width.
• Bending radius and angle.

For example, some types of steel are stronger than others and require more resistant dies due to their ultimate tensile strength (UTS).

Tools designed for thin sheets may not be suitable for thicker workpieces, which could cause premature wear or damage to the tools and the press brake machine.

V-Opening and Workpiece Radius

Excessive force on the workpiece during bending should be avoided to prevent damage. If the inner radius is smaller than the sheet thickness, the sheet may stretch, causing deformation. If the inner radius is larger than the sheet thickness, no deformation occurs.

When choosing a V-die opening, it is essential to prevent deformation while also considering a smaller radius.

Rule of 8

The “Rule of 8” applies to V-die openings in press brake machines. Based on 60,000 PSI tensile strength for cold-rolled steel, this rule is used for most bending processes. The rule states that the V-die opening should be eight times the material thickness.

Although widely accepted, the Rule of 8 is not absolute. As material thickness changes, the ratio increases or decreases. For thicker sheets, a V-die opening of 10 times the material thickness is often required to distribute the force over a larger area and prevent cracking.

Application of the Rule of 8 in Die Selection

To select the correct V-die size:

1. Determine the thickest and thinnest sheet metal to be bent.
2. Use the Rule of 8 to select the smallest V-die, then double its size for the next die. Continue this process until the maximum die size is reached.

If an exact match is unavailable, round to the nearest standard die size. The V-die opening also affects the bending radius; ideally, the inner radius should equal the material thickness.

Materials and Quality of Punches and Dies

The material composition of punches and dies significantly impacts bending quality, workpiece accuracy, and tool longevity. The production cost of punches and dies varies depending on material type and bending precision.

High-quality materials include hardened steel, high-speed steel (HSS), and tungsten carbide.

• Hardened steel: Durable, wear-resistant, and capable of handling high loads.
• High-speed steel (HSS): Wear-resistant and long-lasting but more expensive than hardened steel.
• Tungsten carbide: Offers the highest quality and cost.

Maintenance of Punches and Dies

To prolong the service life of punches and dies and ensure bending quality, proper maintenance is essential:

• Regular lubrication.
• Grinding as needed.
• Storing tools in specialized cabinets with drawers or compartments.

To prevent wear, separate punches and dies with foam or plastic. Clean them regularly with a soft cloth and apply anti-rust spray to prevent corrosion.

Punches and dies play a critical role in determining the shape and quality of the bent workpiece. Before bending, select the appropriate tools based on the sheet’s material, thickness, and desired bending angle and radius. Proper tool selection enhances bending precision.