Analysis of the current status of bending process in sheet metal industry

In the sheet metal industry, most companies are currently engaged in traditional bending processes. In the production process, due to the variety of products, multiple specifications, small batches, multiple bending machines and a large number of skilled and experienced sheet metal bending operators are still needed to complete the workpiece bending. However, in the actual work, there are the following problems: First, because the operator works for a long time, the endurance of the endurance is not continuous, resulting in inconsistent position of the workpiece placed each time; second, the operator does not maintain stability as the robot, so the fold Due to the influence of man-made bending, the size and bending precision are not guaranteed, resulting in poor quality of the finished product. Thirdly, in the face of large workpieces, 3-4 operators are generally required to complete the handling and operation, and the recruitment is difficult and the cost is high. The dilemma; the fourth is that the operator's work safety is poor, carrying a workpiece to work has a large potential safety hazard, prone to work-related accidents.

At present, the manufacturing and precision of sheet metal equipment bending machines have been greatly improved compared with the past, but there is still a big gap between the current requirements for intelligent manufacturing, and “intelligent production, personalized customization, and service extension. And networked collaboration, etc., also need the joint innovation and development of the sheet metal equipment manufacturing segment and the demand side. This kind of innovation development and promotion is another improvement and liberation of productivity.

2. The traditional bending needs of the sheet metal industry need to be solved

The traditional bending of the sheet metal industry needs to solve the following problems: ① can not achieve multi-variety, small batch, fast switching; ② high precision workpiece bending in the sheet metal industry with low precision and unstable quality; ③ sheet metal folding Bending operators are scarce, workers are labor intensive; ④ personnel costs, safety hazards, process layout, management operations.

The above problems can be solved by selecting an intelligent robot bending unit (see Figure 1). The unit includes: CNC bending machine, German KUKA6 axis robot and seventh axis guide rail, loading station, magnetic sheet separation. 

Equipment, pre-alignment positioning workbench, sheet turning mechanism, loading gripper, finished product stacking, mold library, off-line programming software, parametric programming software and secondary development of bending software and extension services.

Figure 1 Robot bending unit

3. The technical characteristics of the robot bending unit

1） Design and development

Design and development focus on the user's individual needs and customization characteristics, with the customer's needs and goals as the top priority, in the development of each technical solution with the customer for detailed technical exchange; Second, the customer's workpiece processing drawings Computer simulation analysis; third, on-site proofing test for typical workpieces of customers; fourth, classification analysis and data processing of customer's workpieces. After confirming the completion of the above procedural work, the technical plan is formulated, and the technical plan and plan map are fully approved after the customer's approval.

LAG Geshi International Robot Bending Unit (see Figure 2, Figure 3) adopts advanced 3D design in materials, structure, sensor, real-time compensation, follow-up, laser angle measurement, automatic mold change, automatic change of hand , software and control, parametric programming, offline programming, production management software and bus control technology all adopt and select world-class brand software and hardware. The design of the bending machine body adopts the world's more advanced design software and design method for structural mechanics analysis. With years of design experience and understanding of the structural characteristics of the bending machine frame, finite element analysis is performed on each force point. The mechanical analysis of the structural points of the side shoulder, upper beam, lower beam and lower beam of the bending machine is realized, which fully guarantees the rationality, reliability and stability of the machine tool design.

Figure 2 3D design of the robot bending unit - stand-alone

Figure 3 3D design of the robot bending unit - dual machine

The robot bending unit is designed to implement intelligent product concepts with the latest technology (software, hardware) for real-time data exchange, real-time compensation and bend tracking follow-up in the production process. The main problems solved and the effects obtained are:

2）Solved the technical problems of customized production of sheet metal, and solved the problem of rapid switching production of multi-products, small batches (5-10 pieces) and multi-variety parts in the elevator industry. (2) Solving the problem of unstable product quality, low precision of parts and poor product consistency. (3) Solved the problem of low production efficiency, unreasonable production layout and process route. (4) Solved the problem of difficulty in recruiting labor, high labor cost, and labor intensity of manual bending. (5) Improve the precision of bending and automation, improve the ability of enterprise intelligent manufacturing, and enhance the visual effect of customer visits.

3）Unique rack structure

(1)Conventional bending machines generally use welded frames, including left and right columns, lower beams (workbench), fuel tanks and supporting square beams. The bending machine frame (see Figure 4) in the LAG Gesch International 

Robot Bending Unit does not use a welded frame structure, but uses an exclusive rack riveting technique. High strength is used between the lower beam (workbench) and the column. The steel bolts are fastened and connected. This flexible connection fully guarantees that the body can greatly reduce the stress and deformation of the frame under high load conditions and maintain the long-term stability of the machine.

(2)Its structural features: ① to ensure that the machine has no welding stress deformation; ② improve the assembly accuracy of the machine; ③ improve the service life of the machine; ④ greatly improve the accuracy of hydraulic compensation.

Figure 4 Rack riveting technology

4） Sensor Technology (Precision Potentiometer) Applications

In order to ensure high-precision sheet metal bending, sensors are installed on the upper beam (slider) and the lower beam (workbench) of the bending machine (see Fig. 5). In the working state, the deformation of the upper and lower beams is Real-time accurate feedback to the CNC system (PC), after the CNC system is calculated and compared, the corresponding compensation value is output to drive the compensation cylinder for dynamic compensation to obtain satisfactory workpiece precision.

Figure 5 sensor application

5） Compensation technology

The G-FLEX wallboard proportional variable compensation system is a patented compensation technology that guarantees each bending angle on the bending machine regardless of the bending conditions and any changes in the thickness, length or bending position of the sheet. Completely consistent over the entire length, eliminating the measurement error of the scale and ensuring the accuracy of the machine.

The G-CS automatic flexing system simplifies the complicated trial bending process under the condition of a certain bending of the plate thickness through closed-loop control, even if the length of the bending workpiece is different, or the folding machine can ensure the folding at different positions of the bending machine. The bent workpiece has a completely consistent angle and straightness without manual intervention. It can achieve the highest bending accuracy, the best stability, and real-time dynamic compensation.

4. Bending follow-up technology

HARSLE International Robot Bending Unit handles workpieces of different sizes and thicknesses during the bending process. It can be automatically followed according to the running speed of the bending machine slider (see Figure 6) and automatically adjusted. The technology is realized by the Italian LAG Gesch special robot bending application software package LK-RBC-Rev4.0.

Figure 6 Bending follow

5. Laser angle measurement technology

The AMS angle measurement system (see Figure 7) works with the G-CS system through the closed-loop laser angle on-line measurement system. During the automatic bending process of the robot, the automatic application of the AMS and the automatic angle measurement system of the built-in laser angle measuring device work together with the G-CS system. Guaranteed bending angle accuracy. Its main features are:

①The bending angle of the workpiece after rebound is detected by laser on-line; ② the force detection system automatically calculates the amount of bending rebound; ③ the piece can automatically adjust the depth according to the width of the lower die; ④ The closed-loop laser angle on-line measurement system ensures that the yield of bending is over 99.5%.

Figure 7 AMS angle measurement system

6. Robot automatic (ATC) change hands, change models

Robot automatic (ATC) change the gripper (see Figure 8), the mold change is a complete intelligent automatic operation mode in the sheet metal field, which consists of automatic mold change software, robot and mold library (see Figure 9). When the automatic mold change system is selected, the precision bending center can automatically and randomly bend small batches of different products. With the automatic mold change function, the mold in the press brake is no longer a limiting factor, and the parts can be unprocessed at all times. The robotic robotic gripper changes the mold very quickly and can bend the next part at any time.

Figure 8 Handle Library

Figure 9 mold library

（1） Automatic mold change software

The main features of the automatic mold change software are:

① Through the graphical interface of the attachment, the user can immediately see the current status of the entire system; on the right side of the interface, there is a graphic indicating the state of the mold, and the current position of the mold is partitioned. ② The entire interface includes the bending upper mold area, the bending lower mold area and the mold base; the mold display follows the size of the mold itself, and the position of the clamped work station. ③ The upper and lower molds are distinguished by different colors; on the upper left side of the interface, there is a detailed description of the molds mounted on the bending machine. Two parts: one is to explain the upper mold, the other is to explain the lower mold, and the clamped mold is described by the identification code and the existing position.

2）Management function

Pressing the mold management (see Figure 10), product management, mold library management, mold settings management and other icons will pop up a corresponding window to set or manage related tasks.

Figure 10 mold management

7. CNC sequential bending technology

CNC sequential bending technology is a high-precision bending control system suitable for workpiece shape tolerance machining (see Figure 11). The device consists of a set of two sets of numerical control pre-pushing device operating systems with rails. The displacement is transmitted by the sensor. The whole operation is controlled by the numerical control system. The control axes are composed of X3\X4 and Z3\Z4. By configuring the displacement of the CNC front pusher and the rear stop for bending, even if the workpiece blanking size reaches ±1mm, it is easy to ensure that the critical dimensions are within the controllable error and improve the accuracy and efficiency of the workpiece.

Figure 11 sequential bending

8. Software and control

In the robot bending unit, we applied parametric programming software, off-line programming software (see Figure 12) and production management software, and at the same time developed the following functions: bending follow-up, automatic mold change, automatic change of hand, flexible palletizing, Real-time compensation, edge-to-edge edge finding, flexible flipping technology and bus control technology. It can greatly meet the technical and software requirements of various customers' sheet metal bending.

Figure 12 Offline programming

9. The conclusion

With the improvement of the overall level of China's machinery industry, sheet metal manufacturing will have a new level of requirements for production equipment. In the end, devices that can solve problems for users will be favored by users. LAG Geshi International Robot Bending Unit has a production method suitable for customers. It is best combined with hardware and software. It is suitable for customers with multiple varieties, small batches, fast switching and no need for first-piece trial production.