How is the bending accuracy of the sheet affected? How to avoid it?
Hello, everyone, today we talk about the use of press brake bending sheet metal may appear a variety of errors, including inaccurate bending radius, insufficient bending force, improper mold clearance, post-specified bit error and bending calculation error and so on.
In addition to this, the Angle of the workpiece may also deviate from the calculated Angle if the press brake is not level or if the coronation mechanism is not working properly. Over time, the ram and bench of the press brake will experience deformation, which can lead to uneven forces on the sheet metal and reduced bending accuracy.
Therefore, in order to counteract this, the overhead mechanism must compensate for the deformation of the ram and table.
There are two kinds of overhead mechanism of press brake: hydraulic overhead and mechanical overhead.
The hydraulic top mechanism on the electro-hydraulic press brake compensates for deformation by a hydraulic cylinder that produces downward and upward forces on the beam and under the workbench, respectively.
The compensation force can be adjusted according to the thickness of sheet metal, tensile strength and mold size, and is controlled by the numerical control system.
The mechanical top adopts a triangular wedge structure, and two bottom plates composed of several wedges need to be placed above and below the table. The bottom plate is connected by dish-shaped springs and bolts, and a motor is used to move the wedge relative to the bottom plate, forming a curve that cancels out the original bulges.
一、Proper sheet metal bending methods
The bending accuracy of the sheet is also affected by the bending method, and there are three main bending methods: air bending, bottom bending and compression, which are distinguished according to the relationship between the end die position and the sheet thickness.
二、Air bending method
This method requires a relatively low bending force, does not require the mold to be in full contact with the workpiece, and the press brake uses two points on the shoulder of the mold to press the sheet metal into the U or v mold. The Angle of air bending is determined by the shape and stroke of the punch and the lower die, and the appropriate stroke depth can obtain more accurate bending. However, due to the rebound after the load is released, the Angle at which the air bends will change, depending on the compressive strength of the material.
In order to adjust the Angle, some pressure needs to be applied to make the adjustment.
The bending Angle error of air bending is usually about 0.5 degrees. In the bottom pressing method, the workpiece is positioned at the opening of the punch and V-shaped die. The opening size of the V-mold is 6 to 10 times the thickness of the sheet metal, and the opening size varies according to the bending Angle and the thickness of the material. After the load is released, the sheet material has less rebound and high precision.
Finally, in the die method, the press brake the material completely into the lower die, which requires a high bending force and can permanently shape the material. The rebound after stamping is minimal, making this method highly accurate for bending.
三、Sheet bending parameter
In addition to choosing the appropriate bending method, it is also crucial to determine the bending parameters of the workpiece.
During metal bending, the inner surface of the metal is compressed while the outer surface is stretched. In order to ensure the accuracy of the bending pipe, it is necessary to know the tensile value of the material and calculate the minimum flange tolerance length. The parameters involved include bending radius, K coefficient, bending deduction, bending allowance, frustration and so on. If the material properties are inconsistent, the bending Angle of the workpiece may be affected when bending with air. In addition, if the thickness of the plate remains the same, the die is narrowed, and the bending Angle will be more obvious.
四、Material property
If the material properties are inconsistent, the Angle of the workpiece may change when using air bending, if the plate thickness is unchanged, but the mold opening is narrowed, the bending Angle of the workpiece changes more. It is important to note that even though material properties may not be consistent, they may still fall within the thickness and strength tolerances of the mill. This is because the tensile strength of many materials falls within certain tolerances.
Another factor to consider is the outer surface of the sheet, as different natural texture directions require different bending pressures. It is important to remember that these values may not be the most accurate, so the Angle and length may need to be adjusted during bending.
In order to prevent the above factors from affecting the accuracy of the press brake die, there are several ways to avoid:
1. Perform regular maintenance
Regular maintenance of press brake molds and machines is essential to maintain their accuracy. Replace worn tooling and machine parts to ensure even bending force. Perform regular inspections to detect any potential problems early.
2. Check the tooling gap
Check the upper and lower mold clearance regularly. Adjust the clearance to ensure accurate bending.
3. Locate materials correctly
Correct material positioning is the key to achieving accurate bending. Before the bending process begins, use a back gauge or stopper to make sure the material is in the correct position.
4. Invest in high-quality molds
High quality tooling can ensure the precision and accuracy of bending processing. Invest in tools made of high-strength materials that can withstand bending forces and reduce premature wear.
In short, the precision of the press brake die is crucial to the success of any metalworking project. The factors that affect the bending accuracy include bending force, die clearance and material positioning. These factors can be avoided by regularly maintaining press brake molds and machines, checking mold gaps, using proper material positioning, and investing in high-quality molds. By following these steps, you can ensure that your press brake mold is precise and accurate, resulting in a high quality product.
After knowing this, you can visit our website, if you need to learn more about CNC press brake machine knowledge or buy a machine, you can also consult our sales staff, they can recommend you the best smart press brake for you.
