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Controller of computerized flat knitting machine

Update:29-11-2019
Summary:

Computerized flat knitting machines have generally adop […]

Computerized flat knitting machines have generally adopted computer control technology and electronic needle selection technology to control flat knitting machines for single needle selection, thereby forming various designs.

In addition, some old machinery also uses electronic needle selectors to replace the old mechanical needle selectors during equipment modification to expand the possibilities and practicability of their patterns. We found in the investigation that many manufacturers are in the process of self-development of the needle selection system. Due to improper selection of the needle selector, the pattern will often be distorted, and it may even cause the mechanism to malfunction and damage the mechanical structure. On the basis of development and experiments, several factors affecting the reliability of needle selection of computerized flat knitting machine selectors were studied, and corresponding measures were put forward to ensure reliable needle selection.

1 The role of the needle selector

The structure of most computerized flat knitting machine needle selection control systems is electromagnetic needle selection.Here, the computerized flat knitting machine adopts two levels of upper and lower computer structures.The upper computer is an industrial control machine and is mainly responsible for management and monitoring.The lower computer uses a single-chip microcomputer and an extended system. It is responsible for controlling the needle selection of the needle selector according to the synchronization signal and the control signal of the host computer. It can be seen that the needle selector is a transducer that sequentially drives the needle selection mechanism according to the electrical signals of the fabric pattern combination. It is an actuator used by the computerized flat knitting machine control system to implement the needle selection control. Therefore, its performance will directly affect the accuracy and reliability of needle selection.

2  Type of needle selector

At present, the commonly used needle selectors are divided into two types: electromagnetic and piezoelectric. The piezoelectric needle selector uses a piezoelectric ceramic material as a conversion element, and uses a pulse signal sent by the controller to act on the piezoelectric element, and the piezoelectric element is bent to a predetermined value by the inverse piezoelectric effect of the piezoelectric material.

Select the shape first to memorize the needle; another type of needle selector uses the electromagnetic coil to pass currents in different directions, so that the polarity of the electromagnetic spiral tube tip changes accordingly, or used in conjunction with a permanent magnet, relying on an electromagnet The suction and repulsive force between the permanent magnet and the permanent magnet are used to achieve the swing of the needle selection head, that is, the needle selection method is used to achieve the needle selection, or the polarity of the electromagnet is used to control the needle selection of the needle selector, so that the knitting needles can be separated into different tracks. The needle selection method is used to complete the needle selection.

Compared with the two needle selection methods, the piezoelectric needle selector has the characteristics of fast response speed and less heat generation, but it is slightly inferior in terms of component force, shock resistance, vibration, etc., and it is easy for the piezoelectric component to lose memory. Therefore, it is used more on circular knitting machines to ensure fast response and adapt to multiple channels. At the same time, the power consumption and heat generation of the needle selector will not be too large. It is more advantageous to use an electromagnetic needle selector on the flat knitting machine.

The main reasons are:

① Knitting machine needle

Thicker, the yarn tension is greater when weaving, so the needle selector is subject to greater force. The electromagnetic needle selector can withstand large forces, and has good shock resistance and long service life.

② The control of the flat knitting machine is complicated, and the precision of the cooperation between each part is high. Therefore, the use of the electromagnetic needle selector can take advantage of its reliable operation. So in the experiment we choose electromagnetic needle selector.

3 Needle selector structure

Electromagnetic needle selector principle:

When selecting a needle, the electromagnetic spiral tube in the needle selector is passed through a certain direction of current to generate a polarity. This polar magnetic field interacts with the magnetic field generated by the long magnet, and pushes and pulls to make the needle selection head of the needle feeder around the shaft. The pendulum does not interact with the teeth of the selector, and the selector rises along the triangle of the selector. General needle selector structure:

1, electromagnetic coil

2, permanent magnet

3.Select needle

4, shaft

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