Narrow and elongated workpieces are a type of workpiece with a large length-to-width ratio, where the short edge is used for positioning during bending. Often, the contact size between the workpiece positioning edge and the back gauge of the bending machine is too short, resulting in poor workpiece accuracy. This article introduces an optimized fixture structure for positioning narrow and elongated workpieces during bending, which effectively solves the difficulties and low precision associated with positioning such workpieces.
With the rapid advancement of sheet metal forming technology, CNC bending machines have become important production equipment for cold deformation processing of sheet metal. They are widely used in the field of sheet metal fabrication. Existing bending machine equipment generally uses a back gauge as a positioning device for safety and convenience. Through simple programming, the back gauge can be synchronized or operated individually, providing sufficient capabilities to meet the processing requirements of various shaped bent parts. However, the back gauge positioning used in CNC bending machines also has its limitations. When the width of the workpiece's positioning edge is too narrow, such as in the case of narrow and elongated workpieces, using the back gauge for positioning results in insufficient contact size between the workpiece and the back gauge. This can lead to inaccurate positioning dimensions, misalignment between the bending position and the designed bending line, and poor quality of the formed product. Often, rework and repair are required, resulting in significant waste of materials, energy, and labor.
Bending Deformation Mechanism
In production, it is often necessary to bend workpieces (steel plates) to a certain angle, with a smaller bending radius at the curved section. This process is known as bending. Bending is the process of applying external force to the sheet metal using a mold to bend it to a certain angle or shape. The bending deformation of the workpiece can be divided into several stages. In the initial stage, the material undergoes free bending. As the upper die presses down, the material gradually comes into contact with the lower die surface. As the upper die continues to press down, the bending area of the material becomes smaller until it contacts the upper die at three points. When the upper die reaches its lowest point, the material is fully pressed against the upper die.
During the free bending of the material, the inner fibers shorten longitudinally due to compression, while the outer fibers lengthen transversely due to tension. As plastic deformation occurs without a change in volume, the width of narrow workpieces slightly fans out after bending. For wide plate-like workpieces, there is no significant deformation in the cross-section after bending.
Basic Positioning of Bending
CNC bending machines generally use a back gauge for workpiece positioning. The basic principle is as follows: during the bending process, a bending program is first created, and the shape of the workpiece is input into the machine. The machine automatically calculates the position of the bending line for the workpiece. The CNC system controls the servo motor to move two back gauges to the bending positioning position through a high-precision screw and nut assembly. The operator only needs to align and snugly fit the positioning edge of the workpiece with the back gauge of the bending machine to complete the positioning process. At this point, the centerline position of the lower die of the bending machine corresponds to the bending line of the workpiece.
Limitations of Bending Machine Positioning Device
In production, it has been observed that when using the commonly used back gauge positioning in CNC bending machines, if the contact size between the processed workpiece and the back gauge is too short, it is difficult to align the workpiece with the back gauge accurately. As shown in Figure 2, even a slight deviation of the workpiece to the left or right can result in inaccurate positioning, leading to workpiece rejection or uneven bending edge dimensions. To ensure a satisfactory forming result, operators often need to repeatedly readjust the positioning, but the results are often unsatisfactory, significantly impacting production efficiency and product quality.
Optimized Positioning Device for Narrow and Elongated Workpiece Processing
Considering the limitations of the positioning device in CNC bending machines, a positioning optimization device has been designed for use in such machines. The back plate is used to align and position with the side of the lower die of the bending machine, the movable locking block is used to secure the entire device to the lower die, the front plate is used to install the screw, the locking screw is used to fix the movable locking block to the lower die, and the positioning top plate is used for workpiece positioning.
Usage of the Positioning Optimization Device
When using the aforementioned positioning optimization device, it is first aligned and clamped to the lower die of the bending machine. The device's status is checked using a square ruler. During workpiece positioning, the end of the workpiece is aligned with the back gauge of the bending machine, while the positioning optimization device is used for side positioning, ensuring accurate and stable workpiece positioning, as shown in Figure 4.
Effectiveness of the Auxiliary Positioning Device
1. Improved production efficiency:
Before using this device, narrow and elongated workpieces often required repeated measurements to ensure accurate positioning, which often resulted in significant errors. With the use of this device, operators can quickly align the workpiece to be processed, greatly improving production efficiency. Processing time for individual workpieces is reduced by more than half.
2. Enhanced product quality:
Prior to using this fixture, the defect rate of narrow and elongated workpieces was high, with issues such as workpiece rejection due to excessive bending edge dimensions or uneven bending edge dimensions. With the application of this optimization device, quality issues caused by inaccurate bending line positioning no longer occur, significantly improving product quality.
With the rapid advancement of sheet metal forming technology, CNC bending machines have become important production equipment for cold deformation processing of sheet metal. They are widely used in the field of sheet metal fabrication. Existing bending machine equipment generally uses a back gauge as a positioning device for safety and convenience. Through simple programming, the back gauge can be synchronized or operated individually, providing sufficient capabilities to meet the processing requirements of various shaped bent parts. However, the back gauge positioning used in CNC bending machines also has its limitations. When the width of the workpiece's positioning edge is too narrow, such as in the case of narrow and elongated workpieces, using the back gauge for positioning results in insufficient contact size between the workpiece and the back gauge. This can lead to inaccurate positioning dimensions, misalignment between the bending position and the designed bending line, and poor quality of the formed product. Often, rework and repair are required, resulting in significant waste of materials, energy, and labor.
Bending Deformation Mechanism
In production, it is often necessary to bend workpieces (steel plates) to a certain angle, with a smaller bending radius at the curved section. This process is known as bending. Bending is the process of applying external force to the sheet metal using a mold to bend it to a certain angle or shape. The bending deformation of the workpiece can be divided into several stages. In the initial stage, the material undergoes free bending. As the upper die presses down, the material gradually comes into contact with the lower die surface. As the upper die continues to press down, the bending area of the material becomes smaller until it contacts the upper die at three points. When the upper die reaches its lowest point, the material is fully pressed against the upper die.
During the free bending of the material, the inner fibers shorten longitudinally due to compression, while the outer fibers lengthen transversely due to tension. As plastic deformation occurs without a change in volume, the width of narrow workpieces slightly fans out after bending. For wide plate-like workpieces, there is no significant deformation in the cross-section after bending.
Basic Positioning of Bending
CNC bending machines generally use a back gauge for workpiece positioning. The basic principle is as follows: during the bending process, a bending program is first created, and the shape of the workpiece is input into the machine. The machine automatically calculates the position of the bending line for the workpiece. The CNC system controls the servo motor to move two back gauges to the bending positioning position through a high-precision screw and nut assembly. The operator only needs to align and snugly fit the positioning edge of the workpiece with the back gauge of the bending machine to complete the positioning process. At this point, the centerline position of the lower die of the bending machine corresponds to the bending line of the workpiece.
Limitations of Bending Machine Positioning Device
In production, it has been observed that when using the commonly used back gauge positioning in CNC bending machines, if the contact size between the processed workpiece and the back gauge is too short, it is difficult to align the workpiece with the back gauge accurately. As shown in Figure 2, even a slight deviation of the workpiece to the left or right can result in inaccurate positioning, leading to workpiece rejection or uneven bending edge dimensions. To ensure a satisfactory forming result, operators often need to repeatedly readjust the positioning, but the results are often unsatisfactory, significantly impacting production efficiency and product quality.
Optimized Positioning Device for Narrow and Elongated Workpiece Processing
Considering the limitations of the positioning device in CNC bending machines, a positioning optimization device has been designed for use in such machines. The back plate is used to align and position with the side of the lower die of the bending machine, the movable locking block is used to secure the entire device to the lower die, the front plate is used to install the screw, the locking screw is used to fix the movable locking block to the lower die, and the positioning top plate is used for workpiece positioning.
Usage of the Positioning Optimization Device
When using the aforementioned positioning optimization device, it is first aligned and clamped to the lower die of the bending machine. The device's status is checked using a square ruler. During workpiece positioning, the end of the workpiece is aligned with the back gauge of the bending machine, while the positioning optimization device is used for side positioning, ensuring accurate and stable workpiece positioning, as shown in Figure 4.
Effectiveness of the Auxiliary Positioning Device
1. Improved production efficiency:
Before using this device, narrow and elongated workpieces often required repeated measurements to ensure accurate positioning, which often resulted in significant errors. With the use of this device, operators can quickly align the workpiece to be processed, greatly improving production efficiency. Processing time for individual workpieces is reduced by more than half.
2. Enhanced product quality:
Prior to using this fixture, the defect rate of narrow and elongated workpieces was high, with issues such as workpiece rejection due to excessive bending edge dimensions or uneven bending edge dimensions. With the application of this optimization device, quality issues caused by inaccurate bending line positioning no longer occur, significantly improving product quality.
