Today's corrugated paper cross-cutting machines are mainly divided into mechanical knives and computer knives. From the control system, computer knives are divided into DC systems and AC frequency conversion systems.
The mechanical knife is mainly driven by the main motor to simultaneously drive the double-sided machine and the cross-cutting machine, and the cutting length is adjusted by adjusting the transmission ratio of the mechanical stepless speed regulation box between the main motor and the cross-cutting machine. This determines that the mechanical knife has the following disadvantages:
1. When changing the work order, the transmission ratio of the mechanical stepless speed regulation box and the eccentric device of the mechanical knife must be adjusted. Make the time of the labor exchange order longer and increase the scrap.
2. Since the length of the cardboard is adjusted by the transmission ratio of the governor box, once the governor box is mechanically worn, the gear gap is too large, and the belt of the double-sided machine slips, the accuracy of the cardboard is difficult to guarantee. Therefore, after the machine knife is used for about one year, the length error of the cardboard will be too large. The higher the speed of the cardboard, the greater the length error. The error of the general cardboard length is greater than 5MM.
3. The speed adjustment of the mechanical knife depends on the main motor using a slip motor to adjust the speed. Due to the low speed torque difference and low efficiency of the slip motor, compared with the frequency conversion speed control system, the power consumption is much larger.
The transmission structure of the computer knife is different from that of the mechanical knife: the double-sided machine and the cross-cutting machine are driven by different motors. The cross-cutting machine is composed of a computer, a speed control system, and a detection wheel to form a speed closed-loop control system. The speed is detected and sent to the computer. The computer calculates the speed command of the cross-cutting machine according to the inherent speed of the cardboard and the preset cardboard length, and sends the speed command to the speed control system. The speed control system controls the knife of the cross-cutting machine Speed, to achieve synchronous control of paper speed and knife speed.
According to different speed control systems, computer knives are divided into DC speed control systems and AC servo speed control systems. Compared with mechanical knives, it has the following advantages:
1. Because the computer knife controls the cross-cutting knife separately, the length of the cardboard is adjusted by a predetermined algorithm to adjust the speed of the cross-cutting machine, so there is no mechanical adjustment when changing the order, thereby reducing waste and increasing productivity.
2. The mechanical structure of the computer knife is much simpler than the structure of the mechanical knife, and the accuracy of the cardboard is not achieved by the accuracy of the machine, and there is no problem of mechanical wear of the speed control box. The accuracy of the cardboard of the computer knife is mainly determined by the resolution and control algorithm of the electrical components such as the detection wheel (rotary encoder), speed control system (DC, AC servo), etc. The accuracy is much more reliable than the accuracy of the mechanical knife. The accuracy of the cardboard of the knife is generally within +/- 1 ~ 2MM.
3. The slip of the detection wheel will also cause the accuracy of the length of the cardboard to deteriorate, but the slip of the detection wheel is much lighter and easier to eliminate than the slip of the belt of the double-sided machine.
The DC speed control system of the computer knife and the AC servo speed control system control the paperboard precision and production efficiency of the cross-cutting machine are higher than the precision of the mechanical knife, but the DC speed control system has the following disadvantages:
1. The cost is about 20% higher than the AC frequency conversion speed control system
2. The power consumption is about 10 ~ 15% higher than the AC frequency conversion speed control system
3. The DC system has a dead zone at low speed, resulting in unstable control
4. The carbon brush of the DC motor must be regularly maintained and replaced
Therefore, the full computer AC frequency conversion control system is currently the best control system for the corrugated paper cross-cutting machine.
The paper feeding motor (that is, the spindle drive) adopts variable frequency servo control. In this way, the speed of paper feeding can be stabilized, the cutting accuracy of the cardboard can be improved, and the braking power can be shared with the motor of the Cross Cutting Machine to realize AC servo regeneration Braking, compared with mechanical knives, saves energy by more than 30%.
introduction
QP-Ⅱ type corrugated paper cross-cutting machine full computer AC servo frequency conversion control system was developed by our company, and after two major improvements, it has become the most advanced corrugated paper cross-cutting machine control system in China. The composition of its system is as follows:
The computer control system of the cross-cutting machine is mainly composed of the upper computer, the lower computer, the servo actuator, the signal acquisition component and the conversion circuit, the man-machine dialogue control cabinet, etc .:
1. The basic functions and configuration of the host computer
This system adopts two-level computer control. The host computer mainly completes data giving, screen display and some management control functions. It can arrange hundreds of groups of cutting orders and record production data, and is equipped with self-learning software to compensate and correct each Shear error caused by this situation. The upper computer adopts industrial control computer suitable for industrial site, and the keyboard adopts membrane keyboard with dustproof. It has the characteristics of adapting to the site environment with large dust. The communication with the lower computer is through the RS-232 / 422 serial port communication module, which has the characteristics of strong anti-interference ability.
2. The lower computer (central processor) adopts the programmable controller of Mitsubishi Corporation of Japan, which is the core of the entire control system corrugated box machine spare parts. Responsible for processing the collected signals and issuing instructions according to the principle of servo control to complete a series of control.
3. The speed and position detection components of the spindle drive and servo control of this system all use rotary encoders. The characteristics of high precision and high reliability provide the feasibility for high precision servo control.
4. The execution mechanism of the system adopts AC servo inverter and high-power AC servo motor. The characteristics of its large starting torque and high speed accuracy provide guarantee for high speed and high precision production.
5. The knife holder adopts a computer cross cutter without eccentric device, and the connection between the motor and the knife holder is a deceleration mechanism with clearance elimination.
6. The paper feeding motor (that is, the spindle drive) adopts variable frequency servo control. In this way, the speed of paper feeding can be stabilized, the cutting accuracy of the cardboard can be improved, and the braking power can be shared with the motor of the cross-cutting machine to achieve AC Servo regenerative braking saves energy by more than 30% compared to mechanical knives.
Investment and return
The cost of the corrugated paper cross-cutting machine was changed from a mechanical knife to a QP-Ⅱ type AC servo inverter controlled computer knife, which is ￥ 320000.00.
With a 1.6-meter corrugated paper line, a monthly output value of ￥ 5000000.00, and an electricity cost of ￥ 1.00, the production cycle is calculated for 8 hours per day:
A) The cutting accuracy of the mechanical knife is more than +/- 5MM, the cutting accuracy of the computer knife is +/- 1 ~ 2MM, and the average cardboard length is 1200MM, and the cost of improving the cutting accuracy can save monthly:
Production value * Poor accuracy / average cardboard length = production value * 0.005 = ￥ 25000.00
B) The power consumption of the double-sided machine of 1.6-meter noodle machine knife Corrugated Carton Blade is about 25KW / H, while the power consumption of the double-sided machine and cross-cutting machine of AC servo inverter computer knife is only less than 10KW / H, calculated based on 8 hours of production per day, The monthly electricity saving fee is: (25-10) * 8 * 30 * 1.00 = 3600.00
C) The mechanical knife must guarantee the accuracy of +/- 5MM, the general production speed cannot be greater than 80 meters / minute, and the production speed of the AC servo frequency conversion computer knife can reach 100 ~ 120 meters / minute, plus its quick order change This greatly improves the production efficiency, and at the same time reduces the heating, pressurizing and transmission energy consumption of the single-sided machine, glue coating machine and double-sided machine cardboard Corrugated Roller.
Based on the above, the investment in retrofitting the cross-cutting machine can be recovered within a year.
