Overall design of screen printing machine

Screen printing machine as its name implies is the screen printing equipment, which is divided into manual, semi-automatic, full-automatic printing machine.Due to the development of science and technology and the demand of the market, the proportion of manual screen printing machine is smaller and smaller, and the automatic screen printing machine is more and more important.This paper is to study the liquid crystal industry for the automatic screen printing machine.

Fully automatic screen printing machine is divided into four parts as follows:

(1) Mechanical vision system: Automatic counterpoint detection of the substrate target;

(2) Working table and its driving mechanism: Used to place the substrate and meet various process requirements of screen printing;

(3) Screen frame: screen printing components, more closely related to the printing process;

(4) Lifting system: The part used to lift the screen frame.

Each section is described below.

2.2.1 Mechanical vision system

At present, mechanical vision system is widely used in liquid crystal industry, automation industry and so on.The mechanical vision system has the following main advantages 1) the use process is fully automated and the whole process is controlled by computer;(2) at present, mechanical alignment can reach tens of milliseconds per alignment, with very high efficiency 3) automatic alignment accuracy using mechanical vision system can reach micron level, with very high alignment accuracy.

Visual system generally includes several parts: light path part, lighting part, image acquisition part, and image processing software.The machine vision system based on screen printing machine generally consists of the following parts

L) Optical path part: The optical path part mainly includes camera and lens, whose function is to image the object to be studied, namely image acquisition.

2) Lighting part: The lighting part mainly includes light sources, whose main function is to achieve different lighting effects according to the working environment and improve the imaging quality.The light source is an auxiliary device for imaging.

3) Image acquisition: The previous image is mainly transmitted through a certain way.

4)PC platform: It includes image processing software and various control programs.Image processing software mainly carries on the image processing algorithm according to the demand.

5)) Control unit: Perform various operations after image processing.

1 is the camera and lens, 2 is the light source, 3 is the sensor, 4 is the image acquisition card, 4 is the PC platform, 6 is the visual processing software and 7 is the control unit.

2.2.2 workbench

The working table is a device for bearing screen printing substrate (liquid crystal glass).Workbench is divided into upper workbench and lower workbench.The upper stage is mainly to meet some of the screen printing process and structure requirements, such as feeding, vacuum adsorption, coarse shaping position;The bottom workbench platform is a kind of movement platform mainly.

The liquid crystal glass enters the screen printer by the feeding machine and is received by the working table.The working table is composed of three parts: glass lifting mechanism, coarse shaping and positioning mechanism and glass adsorption mechanism.The lower table is a moving platform. In order to enable the glass target to be precisely aligned with the mechanical vision system target during automatic alignment, the automatic alignment system will give the motor of the moving platform command to make the moving platform drive the liquid crystal glass to move or rotate in the plane.

When the system detects that there is liquid crystal glass coming into the table, the table lifts the top pin of the mechanism to receive the liquid crystal glass, and then the top pin drops, and the liquid crystal glass is placed on the table.Then, a coarse shaping positioning mechanism is used to position the glass, which aims to make the target on the glass within the scope of THE CCD camera.After the coarse positioning is finished, vacuum adsorption is carried out, and there is no longer relative movement between the glass and the table until the vacuum is broken.

1 glass lifting mechanism

The mechanism comprises a motor, a gear, a CAM and a support bracket.When the motor rotates, the motor drives two gears to rotate, the CAM is fixed connected with a gear, and the CAM is combined to move, thus driving the whole supporting bracket to move up and down.The coarse shaping positioning mechanism has four on the working table, which are located on the four sides of the working table respectively. Each positioning mechanism has two positioning rods, and the coarse positioning of liquid crystal glass is achieved through the clamping stroke between the two positioning rods.Before coarse shaping positioning, the positioning rod is under the table and the LIQUID crystal glass is above the table, so the positioning rod moves both horizontally and vertically.Coarse positioning shaping mechanism is realized by cylinder suction and exhaust.When the cylinder is aspirated, the cylinder drives the special structure to move, and finally makes the positioning rod move in both horizontal and vertical directions.

Vacuum adsorption mechanism

Vacuum adsorption mechanism applies the principle of vacuum adsorption.The vacuum adsorption mechanism is composed of two upper and lower plates.The upper plate of the adsorption mechanism has many holes arranged in different specifications, and the lower plate of the adsorption mechanism has some lines arranged in different specifications. These lines correspond to the upper plate of the mechanism, and the lines are connected, which can form a smooth gas path.When two plates are combined together, there will be air in them due to the lower plate grain and the upper plate hole.When the vacuum sucks the air between the plates, the glass sticks tightly to the worktable: when the vacuum breaks, air enters between the plates and the glass is no longer attached to the worktable.