Brief Introduction to the Corrugated Paper Computer Cross-Cutting Control System Process

Brief Introduction to the Corrugated Paper Computer Cross-Cutting Control System Process

--Product Technology Department, Guangzhou Bowei Servo Technology Co., Ltd. 1. Hardware Components

For the dedicated control system of corrugated paper flying shear equipment, we use BWS-LDNC-70 (for corrugated paper) as the core controller, and PRO-FACE as the user's display and setting window; the servo drive unit of the AC servo motor adopts the Bowei/BWS-BB servo driver; the flying shear servo motor is Guangzhou Bowei/BWS with low inertia and high torque German AMK technology to ensure the flying shear's fast response and precise start and stop.

2. Software Design 2.1 Process Conditions The rotary flying shear completes one cut per revolution. The measuring roller length pulse code disk provides the length of the strip fed by the feeding roller. The shear blade position detection code disk automatically positions the blade. The "dual position approximation - speed synchronization" control method controls the speed of the flying shear blade acceleration section, so that when the shear blade enters engagement, the length of the strip passed is exactly the required sheet length. At the same time, the horizontal speed component of the shear blade is exactly equal to the speed of the strip. After synchronous cutting, the flying shear is decelerated according to the "desired zero-point deceleration method" and stops accurately at the top dead center (when cutting short strip lengths at high speed, the flying shear will switch from deceleration to acceleration at an appropriate switching point to continue the next cut), thus accurately completing one cut to length.
2.2 Working Principle The shearing process of the flying shear mainly involves coordinating the linear motion of the corrugated paper along the machine direction with the circular motion of the shear blade according to process requirements. Since a high-precision fully digital AC control device is used to control the speed of the machine train, the main focus during shearing is controlling the movement of the shear blade. Figure 4 shows a schematic diagram of the shear blade's motion trajectory. X is the top dead center, Y is the engagement point, and the XY arc segment is the acceleration segment of the shear blade. At point Y, the length counting pulse count of the measuring roller is read, and simultaneously, the shear blade pulse and length counting pulse counters are reset and restarted to prepare for shearing the next sheet. The YZ arc segment is the synchronization segment, where the horizontal velocity component of the shear blade is consistent with the machine speed (i.e., the strip speed), ensuring the quality of the sheared section and preventing scratches on the strip surface. The ZX arc segment is the deceleration segment. For medium-length fixed-length shearing, the entry angle and ejection speed can be flexibly adjusted to meet the shearing effects of different strips and sheets according to different user requirements.

The shear blade will stop and wait at the top dead center (X point). For short-length shearing, it needs to smoothly transition from deceleration to acceleration. Figure 5 shows the shear blade speed waveform.

2.3 Mathematical Model By analyzing the motion relationship between the shear blade and the strip in each shearing cycle, and based on the equation of uniformly accelerated motion, the velocity model of the shear blade in the XY acceleration segment is derived as follows:

In the formula, Vr is the shear blade speed, VL is the train speed, a is the shear blade acceleration, and ΔP is the position deviation. The calculation formula is:

Where L is the set shearing length (converted to pulse count), A is the actual length counting pulse count of the strip, BO is the pulse count for one revolution of the shear blade (a fixed number determined by the pulse equivalent of the shear blade position measurement encoder), and B is the pulse count for shear blade position feedback. The position deviation value ΔP serves as a parameter for the flying shear speed reference, controlling the movement of the shear blade so that when the shear blade reaches point Y, the position deviation is reduced to zero, i.e.:

Since point Y is the zero point of the count, and the position feedback value of the blade after one revolution is Bo, the following equation exists when the blade moves to point Y:

In other words, the actual strip feeding length, i.e. the shearing length, is equal to the set length. Of course, during the acceleration process of the flying shear, (LA) and (Bo-B) gradually approach zero, so the position deviation value ΔP also gradually approaches zero. This is the so-called dual position approximation.
Looking at Vr again, when the shear blade moves to point Y, as described above,

It is evident that the shear blade speed at this point equals the unit speed, achieving synchronization between the two speeds. Therefore, the control method for the acceleration phase of the flying shear is called the "dual-position approximation-speed synchronization method".
It is important to note that the shear blade's trajectory is circular, while the strip's trajectory is linear. Therefore, the equivalent pulse values ​​of the two pulses must be unified in the calculation of ΔP. As shown in Figure 4, draw a tangent line through point Y. Assume that the corresponding point of the shear blade B1 on the tangent line is B2, that is, the arc segment B1Y = the line segment B2Y, and B is the equivalent pulse value of the shear blade pulse in the direction of strip movement.
Starting from point Y, the shear blade speed remains equal to the unit speed to shear the strip. When the shear blade reaches point Z, the flying shear enters the deceleration phase. The speed model for the deceleration phase is:

In the formula, β is the deceleration of the shear blade, Co is the number of pulses in the deceleration segment ZX, and Bj is the number of shear blade position feedback pulses relative to point Z. When the shear blade moves towards the desired zero velocity point X, (Co-Bj) gradually approaches zero, and Vr also gradually approaches zero. When it reaches point X, the shear blade velocity Vr is exactly equal to zero. This is the "desired zero-point deceleration method".
The activation conditions for flying shears are:

In other words, when ΔP makes the above equation true, the flying shear begins to accelerate.
During short-length shearing, the flying shear switches from deceleration to acceleration when the shear blade speed Vr calculated by the mathematical model of the acceleration phase equals the shear blade speed Vr calculated by the mathematical model of the deceleration phase. At this point, deceleration stops and acceleration begins.
The flying shear component was jointly developed by NC-70 and PRO-FACE. The main program structure is shown in Figure 6:

The interrupt routine primarily responds to the NC-70 high-speed counting template triggering a main CPU interrupt according to the preset positioning interrupt value when the shear blade reaches point Y. The interrupt routine reads the real-time value of the measuring roller length counting pulse counter, resets the shear blade position pulse counter and the length counting pulse counter, and simultaneously resets the acceleration section flag and sets the synchronization section flag.

3. System Features and Application Effects 3.1 System Features A. The traditional proximity switch positioning (mainly Y point) is replaced by automatic positioning with a shear pulse code disk (automatic positioning is performed once during debugging or when the code disk is replaced), eliminating the shortcomings of proximity switches such as dead zone and susceptibility to temperature, vibration and other factors;
B. The main program's loop execution time is less than 1ms, which fundamentally guarantees control accuracy.
C. Online changes to the unit speed, shearing length, or switching of user bill of materials settings do not affect normal shearing. Furthermore, the NC-70 controller offers powerful setting capabilities for 1000 bills of materials, allowing for the insertion of new bills and lists at any time. To ensure the stability of the acceleration and synchronization sections, the high-speed scanning and fast-response NC-70 controller is the most suitable choice to guarantee the shearing accuracy of the strip.
D. It adopts a special optimized root extraction procedure, which greatly reduces the execution time of the root extraction procedure and is comparable to the world's advanced products from the United States (UNICD) and Japan (NUSCO);

3.2 Application Effect

E. Performance of the NC-70 dedicated corrugated paper controller: It can accurately meet the user's process requirements, with an electrical design accuracy of ±1Pulse (±0.1mm), which fully meets the ±0.5mm error requirement pursued by the corrugated paper industry;

F. Nearly 20 sets of the existing NC-80/70 series products have been applied in the automotive radiator piping, corrugated paper, tubing and sheet industries, and have been well received by users.

3.3 Key Achievements

G. The renovation project of Beijing Hongda Auto Radiator Co., Ltd. is currently operating well using the NC-80 controller.

H. Guangdong Dahua Automotive Radiator Group, which provides one supporting project for Japan. We independently completed the entire electrical system of the second project group, and the NC-80 control system used is currently operating well.

I. Dalian Fudi Heavy Industry Group already has multiple sets of flying saw systems for pipe shearing, and some projects are currently under negotiation and commissioning.

J. Three strip shearing and slitting machines were commissioned at Tongling Jinwei Copper Industry Co., Ltd., and they are currently operating well.

K. Applications in cooperation with Handan Jilong Company in Zibo, Shandong; applications in cooperation with Henan Yuanhang Company in Zhoushan; applications in cooperation with Handan Dazheng Machinery Factory in Shijiazhuang and Hengshui; and applications at Tongliao Haotian Paper Industry are all currently operating well.