With the increasing lack of forest resources, the comprehensive utilization of wood resources has become an important issue in the woodworking equipment manufacturing industry and wood processing industry. At present, this kind of high-precision veneer processing method is used in the production of high-quality veneer. However, due to the existence of the core, when the diameter of the rotary cutting log is about 200 mm, it can not be processed on the rotary cutting machine with the core; and when the diameter of the log is small, the stiffness of the log is reduced, and the quality of the rotary cutting veneer is poor. At this time, if the remaining wood core is discarded or processed into the wood core board, it will cause a great waste of raw materials, thus increasing the production cost of veneer. As a result, the manufacturers generally use the non card round wood rotary cutting machine to cut the remaining wood core again, making full use of the raw materials.
Working principle of round log non card rotary cutting machine
The schematic diagram of the working principle of the card free rotary cutting machine is shown in the figure below. Driven by two fixed rollers with two rotating centers and one moving roller with one rotating center, the log rotates and cuts. The center support of the dynamic driving roller and the rotary cutter are relatively fixed and move together, so that the rotary cutter can plane the thin plate out of the log, and the thickness of the veneer is controlled by the clearance between the dynamic roller and the rotary cutter and the moving speed of the rotary cutter.
The clearance between the rotary roller and the rotary cutting blade is relatively fixed, which is adjusted by the knife edge clearance adjustment device of the machine tool, depending on the thickness of the rotary cutting plate, and the moving speed of the rotary cutter is controlled by the speed of the driving motor through the control system. Therefore, the moving speed of the rotary cutter also indirectly determines the thickness of the veneer.
Because the rotation speed of the driving roller is constant, that is, the linear speed of the log is constant. With the change of the diameter of the log, the angular velocity of the log changes, that is, the time required for the log to rotate one circle also changes. Therefore, the moving speed of the rotary cutter is a variable value, which is a nonlinear relationship. The control of the traditional log centerless rotary cutter is mainly based on 2T Series of electromagnetic speed governor frequency control method, through the use of manual adjustment twist or cam curve adjustment way to change the input voltage of the controller to change the speed of the motor. The error of plate thickness produced by this method is as much as 1 mm. Therefore, it is very important to design a set of system which can accurately control the moving speed of rotary cutter to control the thickness of rotary cutting plate.
The basic idea of system design is as follows
(1) Establish an accurate mathematical model;
(2) Take over the original speed control system to achieve more accurate speed control.
Control system of Tianlang Weichuang rotary cutting machine
Based on the working principle of rotary cutting machine, Tianlang Weichuang independently developed a set of system suitable for various types of rotary cutting machine in the current market. After the actual application in Shandong, Hebei, Guangxi, Jiangxi and other places, it has solved the requirements of many machinery manufacturers for CNC and automation of rotary cutting equipment. The general response was good.
（1） The control system of Tianlang Weichuang rotary cutting machine adopts AC80 high performance vector inverter and special controller for rotary cutting machine. AC80 high performance vector converter adopts Ti new generation DSP chip, innovative use of three core design, ultra-high speed calculation to ensure that the complex vector calculation can be fully realized, torque response of 20ms, steady-state accuracy ≤ 3%. The speed regulation ratio can reach 1:200, the steady-state speed accuracy is ± 0.2%, and the rated torque of 180% can be output at 0.5Hz.
The application of vector converter in rotary cutting machine has the following technical advantages:
1. For complex rotary cutting objects, the starting torque is large, which ensures that the motor has strong cutting force and uniform output in low speed heavy cutting. Ensure the smooth cutting and high-speed stop and restart.
2. The real-time dynamic high-speed operation ensures that the thickness of veneer is always kept at the set value, and the evenness error of veneer is within ± 0.1mm under normal rotary cutting condition. In some mechanical equipment, the lubricity is good, the connection process is accurate, and the error can reach within ± 0.05mm.
3. Strong deceleration and braking capacity, to ensure that the tool table stops instantaneously.
4. Strong adaptability. According to the field characteristics of the rotary cutting machine, a wide range of working voltage is designed. Under the condition of voltage fluctuation, the output torque can be kept constant, and the normal operation of rotary cutting can be met when the rated voltage is more than 60%. This technology is especially effective for many rural power grid environments.
5. Wide range of adjustable speed, high cutting speed, high efficiency, can meet the requirements of high linear speed.
（2） Features of Tianlang Weichuang rotary cutting machine controller
1. Using rotary encoder as ranging sensor, the measurement accuracy can be improved to 0.01mm;
2. Using the rotary encoder to measure the actual speed of the roller can avoid the error caused by the instability of the grid voltage;
3. A variety of sensor combination modes are available, whether single encoder or double encoder and electronic ruler in some areas can operate stably; it can meet the requirements of new and old customers to a large extent;
4. The use of high-end LCD, full Chinese display, bring rich human-computer interface, real-time display of working state;
5. Various working modes can realize the complete automation of the rotary cutting process and effectively ensure the personal safety of the operator;
6. Built in switching power supply makes the system work more stable and has stronger anti-interference ability.
