Application of modern numerical control technology in sheet metal processing

With the development of microelectronics and computer technology, the development of numerical control technology in China has been promoted. The domestic numerical control system has been successfully developed, which ensures the quality and performance of numerical control machine tools in China. Numerical control machine tools have been widely used in various fields because of their strong adaptability to workpiece modification, high machining accuracy and high productivity.

Numerical control technology has been widely used in sheet metal machine tools. It solves the problems of high precision, complex shape and large batch in sheet metal processing. Numerical control sheet metal machine tools include numerical control plate cutting machine, numerical control laser cutting machine, numerical control punch, numerical control bending machine, welding machine, flame cutting machine, etc. Their application in production greatly improves the sheet metal processing capacity, ensures the quality and output of sheet metal parts, and greatly reduces the labor intensity of workers.

Plate cutting is the first process in sheet metal processing. The accuracy of cutting directly affects the processing quality of subsequent processes. The application of CNC plate cutting machine ensures the size of cutting and the work difference of the diagonal of cutting. The numerical control plate cutting machine is composed of numerical control device, servo system, measuring device and machine tool. The servo system is composed of three servo motors and servo drive devices. There are two servo motors positioned in front of the machine tool. Usually, one main motor works alone, with a processing range of 2-500mm. If the bevel is processed, the auxiliary motor works. The CNC system gives two different commands to form the bevel. A servo motor is located at the rear, which is mainly used to process products with large plate surface, and the processing range is 150-4000mm. For example, the QC12K series CNC plate shears made in Shanghai are equipped with Swiss cybelec dnc60 series, which can store 36 sequences, and the internal memory capacity is 100 sequences.

S stamping is an important link in sheet metal processing. CNC punch can replace the processing capacity of the past three punch presses. Which greatly improves the productivity. Numerical control punch is a kind of machine tool with wide use, including single punch and turret. Taking cnc1000 as an example, this machine tool is produced in Italy. Machine tool with C-type structure, processing range: 1270 × 1000mm, the turret has 19 mold stations, which are divided into upper and lower parts to respectively install the punch and die of the mold. The external dimensions of the die are 25.4mm, 47.62mm, 88.9mm, 125.43mm, 158.4mm and 210.00mm. The CNC punch generally has x, y and Z axes. The X axis is the 0 degree direction of the machine tool, the Y axis is the 90 degree direction of the machine tool, and the Z axis is installed on the turret to control the angle of the mold.

The machine operator shall determine the processing scheme and prepare the program sheet according to the part drawing and process requirements. The operator directly writes the program into the program memory in the edit mode through the operation panel of the machine tool; With the development of CAD / CAM and CIMS technology, operators can input graphics into the computer through computer related software to generate programs, copy them into the disk and input them into the CNC system through the disk drive. It can also be input by the serial method of computer and numerical control system. The programming instructions of the CNC punch are divided into G code and M code. G code is used to instruct the machine tool to carry out machining movement and interpolation mode. Such as G91 increment command, G90 absolute command, g29 arc punching, g68 step arc punching. M code is the code that instructs the machine tool to perform some auxiliary actions. For example, the M30 program stops. After the inspection procedure is correct, loosen the caliper, put in the workpiece and close the caliper. Start the oil pump and punch to complete the processing.

The CNC punch has the following characteristics:

(1) Full automatic centralized lubrication;

(2) Automatic cooling and lubrication of punch die

(3) Screen display and automatic reset of hydraulic overload protector;

(4) Equipped with pneumatic / hydraulic operated variable pressure sheet clamp;

(5) Large worktable that can fully support large plate materials;

(6) High accuracy, high speed and low noise hydraulic numerical control punch;

(7) A sliding table that can easily change the mold and safely interlock;

(8) Polyurethane free ball device prevents scratch on the material surface.

The processing technology of CNC punch has the following characteristics:

 (1) High processing accuracy. The working deviation of hole edge distance is 0.2mm, and the working deviation of hole distance is 0.5mm/m.

 (2) Because there are many kinds of molds installed on the turret, the workpiece can complete all the processing contents at once.

 (3) The machine tool can process the workpieces individually or use the group command g98 to process the workpieces in batch, so as to improve the productivity.

The workpiece reaches the bending process after two processes of blanking and stamping. Numerical control bending machine has the advantages that ordinary machine tools can not compare. For example, the origin of casprini is Italy and Siemens CNC system. The input method is manual programming, (1) the plate thickness, mold number, tensile strength, X-axis dimension, angle, workpiece length and stroke height are directly input through the control panel to complete the preparation. (2) For some workpieces with complex shape and high precision requirements, input 2D or 3D graphics, plate thickness and die number through the control panel, and determine the bending sequence generation program through the function of human-machine dialogue. After the program is generated, it is stored in the program buffer area. If it needs to be used in the future, it is stored in the memory of the machine tool. If the program needs to be used repeatedly, it must be copied out and backed up by a special disk. The CNC bending machine usually has two trailing frames at the front and rear. The CNC system controls the bending angle to determine the lifting height of the trailing frame, thus reducing the labor intensity of the operator. The common CNC bending machine has two servo motors to drive the x-axis and Y-axis of the machine tool. The detection assembly adopts grating ruler, inductosyn, encoder, etc., which are usually installed on the lead screw of the machine tool. The detection feedback device converts the displacement of the lead screw into an electrical signal and feeds it back to the numerical control device. If there is an error of 0.02mm from the command value, the lead screw is controlled to make adjustment. The high-performance bending machine is equipped with a motor on both sides of the x-axis, so that the x-axis can process bevels. A motor is installed on each shaft to process workpieces with different angles on both sides. A motor is added under the rear baffle so that the rear baffle can move up and down, which is more convenient for operation and processing. Because the hydraulic system is used on the machine tool for a long time, the lower die of the common up-down bending machine is bent. Therefore, the CNC bending machine is equipped with a set of hydraulic system under the machine tool. When the upper and lower dies work together, the system applies force to the lower die to reduce the deformation of the lower die and prolong the service life of the lower die.

Features of CNC bending machine:

 (1) After the program is established, it can work automatically or semi automatically. The automatic cycle of the program enables the workpiece to be processed at one time, thus changing the inconvenience of large batch of workpieces and complex processes during semi-automatic processing.

 (2) The numerical control system automatically calculates the oil pressure to avoid damage to the machine tool caused by overpressure.

 (3) The introduction of 2D and 3D graphic input functions facilitates the processing of complex workpieces and improves the processing efficiency.

 (4) The addition of various devices improves the processing technology and reduces the labor intensity of the operator.

With the wide application of sheet metal machinery in aerospace, railway transportation, environmental protection equipment, air conditioning appliances, tobacco machinery, packaging and printing, engineering machinery, textile machinery and many other industries. Sheet metal processing also needs more high-tech workers to operate. Good equipment and excellent employees can produce good products, so that there are more excellent products made in China in the world.