Introduction to the Press Brake Stroke
A press brake, also known as a precision metalworking tool, is designed to bend metal sheets with great accuracy. stroke is one of the most important specifications for these machines. It directly affects the machine’s performance and capabilities.
The maximum vertical distance the upper beam (ram) can travel is called the press brake stroke. This measurement is used to determine the machine’s capability to handle different material thicknesses, and bend at different angles. Understanding press brake strokes is important for choosing the right machine and tooling combination, as well as ensuring efficient manufacturing.
Determining the Press Brake Stroke Exactly
The stroke of a machine can be described as the distance between the top dead centre (TDC), and the bottom dead central (BDC), of its ram movement.
- Top dead center (TDC): The highest position that the ram will reach when fully retracted
- Bottom dead center (BDC): The lowest position that the ram will reach when fully extended
The stroke is the distance that the upper punch travels from its fully opened position to its closed position when it comes into contact with the lower die. This measurement is usually expressed in millimeters and inches.
Press Brake Stroke: It’s Critical!
The stroke parameter has a significant impact on the operation of the press brake.
1. Material Processing Capabilities
- Maximum Thickness of Material: A machine that has an insufficient stroke might not be able process thicker materials, which require a greater vertical clearance
- Bending angle range: Larger angles require more vertical travel in order to accommodate material movement during forming.
2. Tooling compatibility and versatility
- Tooling Heights: Different bend applications require different tool heights. A stroke that is adequate ensures compatibility across a range of tooling.
- Special Forming Operation: Complex shapes like box and pan bending requires additional clearance directly related to stroke
3. Production Efficiency
- Cycle Times Impact: Excessive stroke increases cycle times, as the ram has to travel further than necessary during each operation
- Energy Consumption: Larger strokes may require more hydraulic power and increase operational costs
4. Relationship with other Parameters
The stroke is closely related to other press brake specifications.
- Daylight: Maximum opening between the upper table and the lower table at TDC
- Shut height: Distance between the top and bottom of the lower die when the machine is in BDC mode with tooling installed
Calculating the required press brake stroke
In order to determine the correct stroke, you must consider multiple factors relating to your specific bending application. Here is a methodical approach to calculating the stroke requirements.
Stroke Calculation Formula
Stroke= Daylight (Total height bottom die) (Height top punch) (Height clamping) +(Depth die notch) (Plate thickness).Example of Step-by-Step Calculation
Let’s look at a real-life example to demonstrate the calculation process.
Given Parameters
- Daylight: 400mm
- Bottom die total height (including die holder): 75mm + 26mm = 101mm
- Upper punch height 70mm
- Clamping Height: 120mm
- The notch depth is 8mm (half being 4mm).
- Material thickness: 1mm
Calculation:
Stroke = 400mm - 101mm - 70mm - 120mm + 4mm - 1mm = 112mm The stroke required for this particular tooling and materials combination is therefore 112mm.
Factors that influence stroke requirements
When determining the best stroke for your applications, you must consider several factors:
1. Workpiece Characteristics
| Factor | Influence on Stroke Requirements |
|---|---|
| Material Thickness | More strokes are required for thicker materials. |
| Bend Angle | Increased stroke may be required for larger angles |
| Dimensions of the Workpiece | The clearance of larger parts may require extra consideration. |
| Material Type | The springback characteristics of different materials can vary |
2. Tooling Configurations
| Tooling Element | Impact on Stroke calculation |
|---|---|
| Upper Punch Height | Taller punches reduce available stroke |
| Lower Die Height | The higher the die, the lower is the available stroke |
| Die Adapters/Holders | The components in these products consume a portion of the daylight |
| Specialized Tooling | Gooseneck tools and hemming tool, etc. have unique requirements |
3. Bending Operations
| Operation Type | Stroke Considerations |
|---|---|
| Air Bending | Bottoming requires a smaller stroke. |
| Bottoming | For accurate forming, you need to have a precise stroke control. |
| Coining | Needs maximum force with precise stroke control |
| Box/Pan Forming | Additional clearance is required for flanges |
Practical Considerations in Stroke Adjustment
Modern press brakes have a variety of mechanisms to control and adjust stroke:
Electronic Stroke Control
The advanced CNC press brakes have programmable stroke limitations that allow operators:
- Set the top of stroke to minimize unnecessary ram movement
- Define bottom positions precisely (up to 0.01mm on high-end machines).
- Different stroke settings can be programmed for different stages of the bending procedure
Manual Adjustment Mechanisms
For basic hydraulic or mechanical press brakes
- Limit switches can be physically moved to adjust stroke ends
- The bottom position can be defined precisely by using mechanical stops
- The hydraulic pressure setting indirectly affects bottom dead center positions
Safety Considerations
Always ensure that:
- The stroke limits are adequate to avoid tool collisions
- The bottom dead center position (maintaining the material thickness clearance), prevents die crush.
- The emergency stop works throughout the entire stroke range
Stroke Management: Best Practices
Follow these guidelines to optimize the performance of your press brake and tool life.
Test before Production
- Test stroke settings on sample materials before production.
- Check that the punch is not completely pressed against the die
Maintain Proper Clearances
- Make sure the stroke bottom maintains a space equal to the material thickness
- Avoid collisions between dies that can cause tooling damage and machine wear.
Optimize Efficiency
- Set the top stroke limit to minimize unnecessary ram movement
- Reduce cycle times by using programmable stroke settings
Regular Verification:
- Check stroke settings regularly, particularly after tooling changes
- Regular maintenance includes confirming stroke calibration.
The Common Stroke Problems and Their Solutions
| Problems with the? | Potential Cause | You can also find out more about the solution by clicking here. |
|---|---|---|
| Unable to achieve desired bent angle | The stroke is not sufficient | Consider modifying the tooling or adjusting stroke settings |
| Tool damage or collision | Stroke excessive | Add material thickness clearance to the bottom dead center limit |
| Uneven bend angles | Stroke variation | Verify CNC settings and hydraulic system |
| Reduced production speed | Stroke travel that is unnecessary | Optimize the top of stroke settings |
| Unable to accommodate tooling | The stroke-to-daylight is not adequate | Consider using a machine or tool with better specifications. |
The Right Press Brake for Your Stroke Needs
Consider these factors when buying a new press break:
Analyze your typical workpieces
- Document the thickness ranges of materials you process
- Maximum bend angles for bends
- Consider special forming operations (boxes, pans, etc.)
Tooling Evaluation
- List the different tooling heights that you will need
- Specialty tools that may require extra clearance
- Future tooling requirements may change the stroke requirement.
Calculate the optimal daylight-to-stroke ratio
- The daylight of most versatile machines is usually 2-3 times greater than the stroke
- This ratio allows for a wide range of tooling combinations.
Consider Adjustability Feature
- Search for CNC-controlled stroke adjustments
- Test the precision of the bottom dead center control
- Look for top-of stroke features that can be programmed to improve cycle times
Conclusion
The press brake stroke has a much greater impact than a simple technical specification. It directly affects your manufacturing capabilities, tooling compatibility, and efficiency. Understanding how to calculate the stroke requirements and managing stroke settings will help you maximize your press brake’s performance, while also ensuring consistent quality and tool life.
Consider the relationship between stroke, daylight, dimensions of tooling and requirements for workpieces when selecting a press-brake or configuring your tooling. You can improve the quality of your bending operations and increase productivity with proper planning and adjustments.
It is important to remember that the optimal stroke setting must balance the clearance needed for your tooling and material, while also minimizing unnecessary ram movement. This optimization will lead to shorter cycle times, lower energy consumption and an overall improvement in efficiency for your sheet metal forming operation.
