1 Machine Vision System
At present, machine vision systems are widely used in liquid crystal industry, automation industry, etc. The machine vision system mainly has the main advantages:
(1) The use process is fully automated, and the whole process is controlled by computer;
(2) At present, the mechanical alignment can reach one alignment in tens of milliseconds, and the efficiency is very high:
(3) The automatic alignment accuracy using the machine vision system can reach the micrometer level, and the alignment accuracy is very high.
The vision system generally includes several parts: the light path part, the illumination part, the image acquisition part, and the image processing software. The machine vision system based on screen printing machine generally consists of the following parts
1) Optical path part: The optical path part mainly includes a camera and a lens, and its function is to image the object to be studied, that is, image acquisition.
2) Lighting part: The lighting part mainly includes the light source, and its main function is to achieve different lighting effects according to the working environment and improve the imaging quality. The light source is an imaging aid.
3) Image acquisition: It is mainly to transmit the previously imaged images in a certain way.
4) PC platform: including image processing software and various control programs. Image processing software mainly performs image processing algorithms according to requirements.
5) Control unit: After completing the image processing, various execution operations are performed.
2 Workbench
The table is the device that accepts the screen printing substrate (ie liquid crystal glass). The workbench is divided into upper workbench and lower workbench. The upper worktable mainly meets some process and structural requirements of screen printing, such as material receiving, vacuum adsorption, and rough shaping; the lower worktable platform is mainly a motion platform.
The liquid crystal glass enters the screen printing machine from the feeding machine, and is received by the workbench. The upper worktable is mainly composed of three parts: glass holding mechanism, rough shaping and positioning mechanism and glass adsorption mechanism. The lower worktable is a kind of motion platform. During automatic alignment, in order to make the glass target and the target of the machine vision system accurately aligned, the automatic alignment system will give the motor of the motion platform a command to make the motion platform drive in the plane. The liquid crystal glass moves or rotates.
When the system detects that there is liquid crystal glass entering above the worktable, the ejector pin of the worktable lifting mechanism is lifted up to receive the liquid crystal glass, and then the pin is lowered, and the liquid crystal glass is placed on the worktable. Then use the rough shaping positioning mechanism to give the glass a rough positioning, the purpose of which is to make the target on the glass within the range of the CCD camera. After the rough positioning is completed, vacuum adsorption is performed. At this time, there is no relative movement between the glass and the worktable until the vacuum is broken.
glass holding mechanism
The mechanism includes a motor, a gear, a cam, and a lift bracket. When the motor rotates, the motor drives two gears to rotate, the cam is fixedly connected with a gear, and the cam moves in combination.
Thereby, the whole lifting bracket is driven to move up and down.
2.1Rough shaping and positioning mechanism
There are four rough shaping positioning mechanisms on the worktable, which are located on the four sides of the worktable respectively. Each positioning mechanism has two positioning rods. The roughness of the liquid crystal glass is achieved by the pinching between the two positioning rods. position. Before rough shaping and positioning, the positioning rod is under the worktable, and the liquid crystal glass is above the worktable. Therefore, the positioning rod moves both horizontally and vertically. The rough positioning and shaping mechanism uses the air intake and exhaust of the cylinder to achieve rough positioning. When the cylinder inhales, the cylinder drives the special structure to move, and finally the positioning rod can move in the horizontal direction and the vertical direction at the same time.
3 Vacuum adsorption mechanism
The vacuum adsorption mechanism applies the principle of vacuum adsorption. The vacuum adsorption mechanism is composed of upper and lower plates. The upper plate of the adsorption mechanism has many small holes arranged in specifications, and the lower plate of the adsorption mechanism has some lines arranged in specifications. These lines correspond to the upper plate of the mechanism, and the lines are connected to form a smooth air path. When the two boards are combined together, there will be air in them due to the existence of the lines of the lower board and the holes of the upper board. When vacuum adsorption, the air between the two plates will be sucked away,
At this time, the glass will be tightly attached to the workbench; when the vacuum is broken, air will enter between the two plates, and the glass will no longer be adsorbed on the workbench.