Application and development trend of CNC turret punch

Application and development trend of CNC turret punch

CNC turret punch press (NumericalControlTurretPunchPress, abbreviations NCT) is an important category of nc machine tools, mainly by the control system, the main transmission system, feed system, the turntable, mold and peripheral components, such as the programming software is a set of machine, electricity, liquid, gas in integration, High-speed, precise, flexible processing equipment capable of blanking and other forming processes on sheet metal, as shown in Figure 1. CNC turret punch as a key equipment in the field of sheet metal processing, so far there have been more than 70 years of application and development history, has become automobile manufacturing, engineering machinery, hardware, household appliances, computers, instruments and meters, electronic information, textile machinery and other industries for the important process equipment.

Classification and characteristics of CNC turret punch

According to the power source of the main drive, CNC turret punch can be divided into the following three categories:

The mechanical turret punch press. This kind of structure has single movement characteristic, narrow processing range, low stamping frequency, high noise, easy wear of clutch and brake, low life, and has been basically eliminated by the market.

Hydraulic turret punch press. Through the hydraulic cylinder drive hitting head, by the electro-hydraulic servo valve stamping control, this type of products in the past quite a long period of time are the mainstream products in the market. Compared with mechanical type, its advantage is that the stamping process is expanded, the stamping frequency is improved, and the noise is reduced. But there are oil pollution, large power consumption, poor environment and temperature tolerance, low reliability, difficult maintenance and other disadvantages.

⑶ All-electric servo turret punch press. With the improvement and promotion of high-torque servo motor and drive system in recent years, all-electric servo turret punch has made great progress, and gradually replaced the hydraulic structure, become the mainstream product of the industry.

Compared with the traditional mechanical and hydraulic type, the all-electric servo main drive has many advantages:

1) Good versatility and high level of intelligence. Because of the servo function, the punch movement curve is no longer just a sinusoidal curve, but an arbitrary curve that can be optimized according to the technological requirements, greatly improving the processing performance and expanding the processing range.

2) High accuracy. Encoder on the servo motor to the rotation of the crank Angle information feedback to the CNC system, and then through the punch displacement as a function of crank Angle between processing and can obtain the punch position of real-time data, forming half closed loop control, realize the accurate control of the punch movement, bottom dead center precision can be controlled within + / - 0.05 mm.

3) High production efficiency. Servo punch can adjust the stroke of punch according to different processing technology. In a working cycle, there is no need to complete 360° rotation, only a certain Angle of swing can complete the processing, which further shorten the cycle time, greatly improve the production efficiency.

4) Energy saving and environmental protection. The CNC turret punch driven by servo motor completely depends on the torque of the motor. The motor rotates only when the punch moves, and the energy saving effect is very obvious.

5) Small vibration and low noise. By setting the speed characteristic curve of the punch, when the upper die contacts the plate, the movement speed of the punch can be appropriately reduced, and the noise can be reduced by 8 ~ 12dB compared with the traditional mechanical and hydraulic CNC turret punch.

At present, the main servo drive structure mainly has three forms. These three forms of institutions have mature technology, and each has its own characteristics, and all occupy a large market share.

(1) Double motor driven crank slider mechanism, on behalf of the model of Japan AMADA company EM2510NT CNC turret punch. The double motors are symmetrically arranged on both sides of the fuselage, compact and compact, which can ensure sufficient torque output of the crankshaft and obtain high stamping frequency.

The crank and elbow type mechanism, the representative model is MOTORUM - 2048LT CNC turret punch from MURATEC Company in Japan. Although the structure is more complex, it can reduce the load torque of the servo motor by using the unique force enhancement characteristics of the crank elbowed mechanism, and the crank rotates once, and the slider moves up and down twice, so as to achieve a higher stamping frequency.

(3) A single water-cooled large torque servo motor driven crank slider mechanism, representative model for Jiangsu Yangli CNC Machine Tool Co., LTD. EP series and H series full electric servo CNC turret punch. Due to the use of a single water-cooled large torque servo motor as power source, continuous load capacity is strong, there is no synchronous control problem driven by double motors, mechanical efficiency is higher, stability and reliability is better, the product has a high cost performance.

Typical processing technology

CNC turret punch typical processing technology mainly includes punching and forming two.

The blanking process

Blanking process is usually also called material separation process, refers to the processing of materials under the action of external forces, along the closed or not closed contour shear crack and separation. Blanking processing can be directly blanked into finished parts, but also for bending, drawing, forming and other processes to prepare blank.

Generally, the blanking process is mainly divided into the following four modes:

(1) single shot. Punching in one time, including linear distribution, circular distribution, circular distribution, grid hole stamping.

The continuous impulse in the same direction. The use of rectangular mold overlapped processing way, you can process long holes, cutting edges, etc. When the cutting mode is used, in the process of blanking die stack will deviate from mold cutting load by the center (partial), will cause the torsional deformation of machine tool structure, serious when it might damage the mould, so in the big pore diameter and thick plate cutting load, should as far as possible the reduction of mould amount of overlap, reduce the partial load.

(3) Multi-directional continuous punching. This is a small mold processing large hole processing method, can increase the flexibility of the machine tool, expand the mold processing range. Using this blanking mode, usually need to rotate the punch at different angles through the rotation station, with the positioning movement of the feeding mechanism in the XOY plane to complete.

(4) Nibbling blanking. This is a kind of machining mode of circular arc or spline curve by using small circular die with small step. It is a common machining mode. Due to the use of small circles for fitting, so the profile accuracy and section quality is usually not high, and the punching efficiency is low, when the punching size is large and the number is large, it is recommended to use a special punching die.

Forming process

Forming technology refers to the plate under the action of external force, the stress exceeds the yield point of the material, through plastic deformation and get a certain shape and size of the processing method, mainly including rolling, shallow deep drawing, flanging, bending, etc., some typical parts of the main forming characteristics and supporting mold.

(1) Single forming, according to the mold shape of a shallow deep drawing forming processing mode, using this forming mode, the shape and size of the mold must correspond to the characteristics of the processing, and the common press processing mode is exactly the same, is a completely "rigid" processing mode.

Continuous forming, forming larger than the mold size of the forming method, such as large size shutter, rolling ribs, rolling steps and other processing methods.

Sheet forming process of the material mechanical properties, plate thickness, forming temperature and forming rate of various factors such as comprehensive effect of elastic deformation, plastic deformation involves the anisotropy, strain hardening, material aspects of content, present a highly nonlinear and its forming mechanism is very complex, it is difficult to through the traditional mechanics formula in practical production were analyzed. In the computer virtual environment, the finite element method is used to simulate the process of material forming, which can realize the prediction and evaluation of elastic rebound, crack and fold in the process of forming, which is conducive to the in-depth study of the forming mechanism. In industrial production, finite element analysis can guide mold design and optimize forming process parameters, which has immeasurable practical application value. At present, the commonly used software mainly includes ANSYS, ABAQUS, MAC, LS-DYNA, DYNAFORM and so on.

Future trends

With the development of CNC technology, network technology, servo control technology and large torque servo motor, CNC turret punch is the following development trend.

The high speed, high precision.

High speed, high precision machine tool industry is the eternal pursuit of development, improve the speed and precision of the CNC turret punch press content mainly includes the following aspects: 1) improve the dynamic performance of conveying mechanism, the conveying mechanism with ball screw and gear rack and two main traditional way of mechanical transmission is given priority to, and half closed loop control is adopted to locate the speed, acceleration and location accuracy is usually not high. With the development and application of linear motor drive technology in recent years, the use of linear motor drive technology, through the grating ruler real-time motion position feedback, the formation of closed-loop control, it is possible to improve the positioning speed, acceleration and positioning accuracy of CNC turret punch feeding mechanism to an unprecedented height; 2) The use of full electric servo main drive, on the one hand, its lower dead point accuracy is high, can be controlled within the range of ±0.05mm, on the other hand, this transmission mechanism has a rich stamping mode, such as the use of high speed crankshaft positive and negative swing processing mode, complete a 4mm stroke required time can be controlled within 40ms; 3) Adopt new technology to reduce downtime as much as possible, such as automatic detection technology of mold wear, automatic replacement technology of mold, automatic loading and unloading technology, etc.

(2) Real-time intelligence.

The development of science and technology up to now, the market for CNC turret punch is no longer limited to accuracy and reliability, but began to be based on intelligent solutions. Key technologies to be promoted: 1) workpiece quality online monitoring technology; 2) Online monitoring technology of die wear; 3) Automatic selection and replacement of molds; 4) Remote intelligent fault diagnosis and elimination; 5) Establishment and optimization technology of process expert database.

⑶ Energy saving and environmental protection.

CNC turret punch mainly involves the following three aspects of the problem: 1) noise pollution, can use silent processing mode, optimize the structure of the machine tool, the use of sound insulation materials and other methods to reduce vibration and noise processing; 2) Oil pollution, it is an inevitable trend for the development of the industry that the all-electric servo main drive mode replaces the traditional hydraulic main drive mode; 3) Based on the life of the green design concept, the use of excellent design concepts and design methods, and strive to rationalize the application of materials, machine tools are no longer stupid.

(4) Single-machine flexible machining unit (FMC) and functional compound.

Large multi-machine flexible machining system, also known as flexible manufacturing system, is the future development trend, but considering the characteristics of the current domestic market and industrial structure, small single-machine flexible machining unit with complex functions has a better market prospect. This small single flexible machining unit to CNC turret punch as the main body, with deburring, tapping and other ancillary functions, at the same time with three-dimensional warehouse, automatic loading and unloading system, with high processing flexibility and efficiency, and even can achieve unmanned operation. Compared with large flexible manufacturing system, it covers a small area, low cost of equipment acquisition, better reliability and stability of operation, more easily accepted by customers, especially suitable for some small and medium-sized professional sheet metal processing enterprises. The flexible sheet metal blanking processing unit developed by the company in 2009 has mature technology and stable performance. At present, more than 30 sets have been sold, bringing considerable economic benefits to customers. The two sets of CNC turret punch press machining unit adopts the symmetrical layout, equipped with automatic stereo warehouse and loading mechanism, significantly improve degree of automation, and only operators monitoring on time, but in order to realize the real unmanned operation and some key technologies needed breakthrough, such as on-line monitoring technology, mould wear mold automatic selection and replacement technology, On-line monitoring technology of workpiece quality, intelligent fault diagnosis and elimination technology.