In the sheet metal processing industry, the press brake and laser cutting machine are known as the “golden pair.” A suitable press brake directly determines product forming accuracy, production efficiency, and a company’s profitability. However, faced with numerous model parameters—from tonnage to table length, from CNC systems to tooling configurations—many buyers often find themselves in a dilemma. This article systematically outlines the five core factors for press brake selection from a practical application perspective, helping you precisely match the equipment that best suits your business needs.
Part 1: Tonnage Selection – Starting from Material Thickness and Length
Tonnage is the core indicator of a press brake, directly determining how thick and how long a sheet the machine can bend. Too low and it won’t bend; too high and it creates waste.
1.1 Tonnage Calculation Formula and Quick Reference Table
The basic formula for calculating required bending tonnage is:
P = (1.42 × σb × S² × L) / V
Where:
- P: Required bending force (tons)
- σb: Material tensile strength (MPa), approximately 450MPa for ordinary carbon steel Q235
- S: Sheet thickness (mm)
- L: Bending length (m)
- V: Die opening width (mm), typically 8-12 times the sheet thickness
Quick Reference Table (for ordinary carbon steel Q235, V-die opening at 8× sheet thickness):
| Thickness (mm) | Tonnage Required for 1m Length (tons) | Tonnage Required for 2.5m Length (tons) | Tonnage Required for 4m Length (tons) |
|---|---|---|---|
| 1.0 | Approximately 8 tons | Approximately 20 tons | Approximately 32 tons |
| 1.5 | Approximately 18 tons | Approximately 45 tons | Approximately 72 tons |
| 2.0 | Approximately 32 tons | Approximately 80 tons | Approximately 128 tons |
| 3.0 | Approximately 72 tons | Approximately 180 tons | Approximately 288 tons |
| 4.0 | Approximately 128 tons | Approximately 320 tons | Approximately 512 tons |
| 5.0 | Approximately 200 tons | Approximately 500 tons | Approximately 800 tons |
| 6.0 | Approximately 288 tons | Approximately 720 tons | Approximately 1150 tons |
Selection Suggestion: It is recommended to add a 20%-30% safety margin to the theoretical value to account for factors such as material hardness fluctuations and tooling wear.
1.2 Common Industry Tonnage References
| Industry Sector | Common Thickness Range | Recommended Tonnage Range | Typical Workpieces |
|---|---|---|---|
| Advertising Signs, Decoration | 0.5mm-1.5mm | 40 tons-100 tons | Light box frames, letter shells |
| Electrical Cabinets, Enclosures | 1.0mm-2.5mm | 80 tons-160 tons | Control cabinets, distribution boxes |
| Automotive Parts | 1.5mm-4.0mm | 120 tons-250 tons | Brackets, reinforcement plates |
| Construction Machinery | 3.0mm-8.0mm | 200 tons-500 tons | Buckets, track plates |
| Steel Structures, Shipbuilding | 6.0mm-16mm | 400 tons-1000 tons+ | Beams, columns, hull plates |
Part 2: Table Length and Ram Stroke – Matching Workpiece Dimensions
2.1 Table Length Selection
Table length determines the maximum workpiece length the machine can bend. Selection principle: Cover 80% of regular workpiece lengths; consider multiple bends or outsourcing for extra-long workpieces.
| Table Length | Applicable Scenarios | Typical Industries |
|---|---|---|
| 1.5m-2.5m | Small workpieces, limited space | Advertising production, small hardware |
| 3m-3.2m | Standard sheets (common sheet size 1.25×2.5m) | Electrical cabinets, enclosures, general sheet metal |
| 4m-4.2m | Long workpieces, architectural decoration | Door frames, curtain walls, elevator door panels |
| 6m and above | Extra-long workpieces, high-volume production | Steel structures, ventilation ducts, large equipment |
Important Considerations:
- Standard sheets are often 1.25×2.5m; selecting a table length of 3m or more allows one-time forming without the need for repositioning.
- The longer the table, the higher the overall rigidity requirements; for the same tonnage, longer table machines are more expensive.
2.2 Ram Stroke and Open Height
Ram stroke determines the height of workpieces the machine can accommodate (such as box-shaped parts, enclosures) as well as tooling height.
- Standard Stroke: 100mm-200mm, meets 80% of conventional bending needs
- Extended Stroke: 200mm-400mm, suitable for deep box-shaped parts, high flanges
- Open Height: The distance from the table surface to the bottom of the ram when the ram is at top dead center, typically between 300mm-500mm. Deep box-shaped parts require greater open height for workpiece insertion.
Part 3: CNC System Selection – Determining Operational Efficiency and Accuracy
The CNC system is the “brain” of the press brake, directly affecting programming efficiency, operational convenience, and bending accuracy. Mainstream system brands currently include Delem, Cybelec, ESA, and domestic self-developed brands.
3.1 System Level Classification
| System Level | Axis Control | Features | Applicable Scenarios |
|---|---|---|---|
| Economy (2-axis) | Y-axis (ram) + X-axis (back gauge) | Manual programming, basic bending | Simple workpieces, single batch, limited budget |
| Standard (3+1 axis) | Y1/Y2 (ram sides) + X + R | Automatic angle calculation, adjustable back gauge height | General sheet metal, high-mix low-volume |
| High-End (6+ axes) | Full servo control, including Z1/Z2, X, R, Y1/Y2, C-axis (deflection compensation) | 3D graphical programming, automatic collision detection, remote diagnostics | Complex workpieces, high precision requirements, automated production lines |
3.2 Key Functional Highlights
- 3D Graphical Programming: A 3D graphical interface intuitively displays bending sequences and tooling interference, significantly reducing programming difficulty and setup time.
- Automatic Deflection Compensation: During bending, the middle of the table deforms elastically due to force, causing inconsistent bending angles. The automatic compensation system uses a pre-convex mechanism to counteract deformation, ensuring consistent angles across the entire length.
- Real-Time Angle Measurement: Equipped with an angle measurement system (such as a laser angle sensor), it can measure the angle in real-time during bending and automatically compensate, suitable for workpieces with high precision requirements.
3.3 Selection Suggestions
- Beginners / High-Mix Low-Volume: Choose a high-end system with 3D graphical programming to lower operational barriers.
- Skilled Operators / High-Volume Single Product: A standard system offers better cost-effectiveness.
- High Precision Requirements: Must be equipped with automatic deflection compensation and angle measurement systems.
Part 4: Tooling Configuration – Key Factor Affecting Bending Results
Tooling is the “teeth” of the press brake, directly determining bending radius, appearance quality, and the ability to create specific shapes.
4.1 Upper Punch Selection
| Type | Characteristics | Applicable Scenarios |
|---|---|---|
| Straight Punch | 90° standard bending | General bending, over 90% of applications |
| Sharp Punch (Acute Angle) | Can bend acute angles less than 90° | Acute angle bending, complex shapes |
| Gooseneck Punch | Avoids interference with already bent flanges | U-shaped parts, box-shaped parts, prevents collisions |
| Flattening Punch | Used for flattening hems | Sheet metal hemming, reinforcement ribs |
4.2 Lower Die (V-Die) Selection
The lower die V-opening width is typically 8-12 times the sheet thickness:
- V = 8×S: Smaller inside bend radius, suitable for thin sheets (<3mm)
- V = 10×S: Standard bending, general choice
- V = 12×S: Larger inside bend radius, suitable for thick sheets (>5mm)
Segmented Tooling: It is recommended to choose segmented tooling (such as 835mm segments) to facilitate combination for different workpiece lengths, avoiding the purchase of full sets of multiple specifications and reducing initial investment.
Part 5: Machine Structure – Choosing Between Torsion Bar Synchronization and Electro-Hydraulic Servo
5.1 Torsion Bar Synchronization vs. Electro-Hydraulic Servo
| Type | Principle | Advantages | Limitations | Applicable Scenarios |
|---|---|---|---|---|
| Torsion Bar Synchronization | Mechanical linkage forces synchronization on both sides | Simple structure, lower price, easy maintenance | Limited precision, weak resistance to off-center loads | Thin sheets, general bending with moderate accuracy requirements |
| Electro-Hydraulic Servo | Independent cylinders on both sides + linear scale closed-loop control | High precision (±0.01mm), strong resistance to off-center loads, fast speed | Higher cost | Medium-thick plates, high precision, complex workpieces |
5.2 Servo-Driven Press Brakes (All-Electric)
In recent years, servo-driven press brakes have emerged, using servo motors to replace hydraulic systems:
- Advantages: Energy efficient (50%-70% energy savings compared to hydraulic models), fast speed, high precision, no hydraulic oil leakage risk
- Limitations: Higher initial cost, large tonnage models not yet fully mature
- Applications: Thin sheets, high-speed production, applications with high environmental requirements
5.3 Quick Selection Table
| Processing Requirements | Recommended Configuration |
|---|---|
| Thin sheets (<2mm), moderate precision, limited budget | Torsion bar synchronization + 2-axis CNC |
| Medium-thick plates (2mm-6mm), general sheet metal, high-mix | Electro-hydraulic servo + 3+1 axis CNC + automatic compensation |
| Thick plates (>6mm), high precision requirements, complex shapes | Electro-hydraulic servo + 6+ axis system + angle measurement |
| High-speed thin sheet processing, high environmental requirements | Servo-driven press brake (all-electric) |
Summary: Five-Step Press Brake Selection Process
- Calculate Tonnage: Based on maximum sheet thickness and maximum length, calculate tonnage using the formula and add a 20%-30% safety margin.
- Determine Length: Select table length based on regular workpiece dimensions; it is recommended to cover 80% of workpieces.
- Choose System: Select the appropriate level of CNC system based on operator skill level and workpiece complexity.
- Configure Tooling: Configure standard punches and dies according to common sheet thickness; consider segmented tooling when necessary.
- Decide Structure: Choose between torsion bar synchronization and electro-hydraulic servo based on precision requirements and budget.
Common Selection Mistakes to Avoid:
- Blindly pursuing high tonnage: Increases equipment cost, energy consumption, and floor space.
- Overlooking deflection compensation: Leads to inconsistent bending angles on long workpieces.
- Underestimating the importance of the CNC system: Difficult programming for complex workpieces leads to long setup times.
- Insufficient tooling configuration: Inability to form specific shapes, limiting product design.
For further technical consultation, please bring your typical workpiece drawings and contact our engineers. We will provide you with a customized selection solution and trial bending service.