1. Introduction
The overall structure of the chemical fiber splitting machine includes a withdrawing device, a guide disc, a splitter, a traverse device, a winding device, a frame, etc. It is a device for splitting and winding chemical fiber monofilaments (nylon, polyester monofilaments). The operating principle of the equipment is to divide ten strands of chemical fiber into single strands of monofilaments and rewind them into shape. The control of the forming and tension is particularly important. Since the speed of the splitting machine is relatively high, it is necessary to use variable frequency speed regulation to separate the monofilament spinning part of the previous process, which can not only improve the production efficiency of the spinning in the previous process, but also increase the production efficiency of the entire process of chemical fiber monofilament production.
2. Control requirements
This article only takes the on-site commissioning project content of the chemical fiber splitting machine of the SKI600 general heavy-duty inverter (VFD) produced by Hangzhou Sanke in a certain local enterprise as the main body, and explains the application scheme of variable frequency technology in the chemical fiber splitting machine, as shown above. The customer hopes to use two SKI600s (0.75KW), one to control the overfeed roller motor and one to control the winding motor. In addition, one SKI600 (0.75) is needed for every 5 devices to control the top wheel motor. The stepper controller controls the wire moving forming, and the single pulse Hall element is used for speed measurement in each circle. The requirements mainly include:
(1) Stable speed measurement. Only when the speed measurement is stable and accurate can good speed control be achieved;
(2) Stable tension control. Tension is the core. Too tight or too loose is not allowed;
(3) Large starting torque to overcome friction and large load;
(4) Good communication performance. Frequent communication is required during the acceleration process and speed adjustment;
(5) High precision of stepper motor and high forming precision requirements;
(6) High precision of PLC pulse output and short scanning cycle.
3. System wiring and debugging
The whole system is composed of a SK-C PLC, a 7-inch touch screen of the S series and two SKI600s. In addition, one SKI600 is added for every 5 complete machines, and one-to-many control the rotation of the top wheel. Each machine is divided into two sides, front and back, with a total of two sets.
1. System debugging
Debugging mainly needs to solve several problems:
(1) Timeliness of speed setting, because it involves communication setting, the communication success rate is very high;
(2) Low-frequency torque output capability;
(3) Speed stability during high-speed operation;
(4) Tension control stability;
(5) Speed detection accuracy and stability;
(6) Stepper motor control wire forming accuracy;
-Since the line speed of the whole machine is collected through a Hall element with one pulse per circle, the sampling speed fluctuates greatly. It is necessary to adopt different sampling methods for different speed segments and perform average optimization or response filtering;
-When starting at zero speed, due to the heavy load of the spindle and the large mechanical friction, it is necessary to increase the output torque of the VFD to achieve a faster start-up effect;
-Tension control is actually a speed closed loop. How to adjust the roller and winding speed by detecting the line speed to achieve tension control;
-Wire forming, the wire after separation is very fine, and the winding distance is very long, generally more than 800 kilometers, so there are certain requirements for forming, similar to the roving machine.