The thick material computer pattern machine has the functions of automatic tangent, automatic back sewing, automatic needle bar positioning and automatic foot pressing lifting (AK device). The machine automatically cut off the upper and lower lines after sewing, so that the processed products are beautiful and tidy; Can select the product to be able to automatically reverse sewing (including the number of reverse stitches) when the product is put on or off the hand according to the specified requirements; It can make the needle bar select the positioning mode (up and down) in the low speed state according to the machining requirements. These functions are controlled by an electronic and electrical system, which consists of motor body, electronic control box, needle bar positioning and detection device, setting switch and foot pedal detection device.
The speed control of computer pattern machine is a typical speed feedback control system, and the speed control flow. The sewing speed depends on the degree of pedal down. The relationship between the foot stroke and the sewing machine running speed is approximately linear. The whole transportation distance from low speed to maximum speed is only about 12mm, and the sensitivity is very high. When the pedal is set to the lowest position, the sewing machine stops running. During the shutdown, according to the signal from the synchronous detector, the needle stops at the upper and lower stop position accurately. There is also a line and tangent operation before stopping. The function of foot sensor is divided into four positions, namely, reverse step - up and stop needle; Neutral - stop the needle under; Step forward one by one, low speed; Deep forward - high speed. The command signal is input by foot sensor to control the start, stop and speed regulation of sewing machine. They are used to control the friction plate drive coil and brake coil of the clutch part of the motor by cutting the magnetic field to give information. Two driving circuits in the speed control flow mainly control the current in the drive coil and the brake coil. The protection circuit mainly refers to abnormal condition detection, up and down speed limit, current limiting, etc. The amplitude of output voltage of speed command signal is related to the degree of pedal pressing. The output speed of computer pattern machine is fed back to the control end through synchronous detector, and the needle of computer control machine stops at upper or lower position, and automatic sewing pattern is also carried out.
The synchronous detector is directly connected with the sewing machine shaft, which is convenient for detecting the position of the shaft and the position of the needle stop. It is composed of a speed measuring motor, which is divided into two parts: rotor and stator. The machine speed is measured by cutting magnetic field, and information is given to control the upper and lower positioning of needle rod. The needle position detection part is composed of the detecting magnet 2, the non-contact switch 3 and other parts. The rotor of synchronous detector rotates with the detection magnet, and sends out signal from stator 4 to control circuit, which generates up position signal, lower position signal and speed detection signal, and sends it to computer. The former completes accurate positioning and shutdown, and the latter is used as a given signal of speed control.
The electronic control box is composed of a microcomputer system, which is the hub of the whole transmission system through the input voltage of 380v/220v and output working voltage of 30V, 5V and-5v. The whole computer system in the control box constitutes a complete multi-functional circuit. The control circuit is divided into two printed circuit boards, one is a power supply board, including clutch, brake disc and control circuit power, various load power supply of sewing machine and various amplifier circuits; The other is the control circuit board, including speed and positioning circuit, sewing machine load control circuit, landing pin control circuit, safety protection circuit, etc.
The computer system control of computer pattern machine mainly completes two functions: one is to control the upper or lower stop of the needle accurately; Second, automatic sewing of graphic patterns.
