What is Screen Printing
Screen printing is to stretch silk fabric, synthetic fiber fabric or metal mesh on the screen frame, and use the method of hand-carved paint film or photochemical plate making to make screen printing plate. Modern screen printing technology uses photosensitive materials to make screen printing plates (the screen holes in the graphic part of the screen printing plate are through holes, and the screen holes in the non-graphic part are blocked).
Introduction of Screen Printing Consumables
The screen frame material is aluminum or wood. The screen is installed on the screen frame. Requires you to choose different sizes of frame according to the size of the image. The left and right margins should be 60mm to 100mm, and the top and bottom margins should be 20mm to 30mm.
It is also necessary to separate the screen printing from the surface of the printed matter by about 0.5mm to 2mm according to the size and tension of the screen printing. If the screen is too close to the print object, the clarity of the printed image will decrease.
There are two types of squeegee: flat and sharp. Flat blades are suitable when the item is flat or when the surface is hard and smooth. Because the edge of the flat blade is hard and straight. Otherwise, a sharp blade is better. A sharp blade has a soft edge. It sweeps gently across the screen and handles light up and down surfaces and rounded surfaces well.
Others consider the appropriate longitude and type of scraper. The optimum pressure of the printing squeegee on the screen is also an important factor.
Screen Printing Ink Selection:
According to the material and brightness requirements of the printed matter, different inks have different effects. Ink should be diluted to the appropriate level. The ink is too sticky and easy to block the net. But if you dilute too much, the printed colors are not saturated and the image is not clear.
Put The Right Amount of Screen Printing Ink:
If there is too much, the ink will overflow the print area before the ink recycles the blade. This will cause uneven ink diffusion and affect the effect of the next printing.
When the screen is blocked by ink, it is best to clean it with a suitable cleaning agent immediately.
Design suitable fixture: fix tools and jig are designed so that item to be printed is fixed well and also is easy to set and take out.
How Does a Screen Printing Machine Work
Different types of machines have different specific operations. Take cylindrical screen printing machine as an example to introduce how does a screen printing machine work.
Step 1: Preparation
1. Make a halftone from the image.
2. Mix the ink of the appropriate viscosity.
3. Prepare fixtures according to the requirements of the printing project.
4. Prepare cleaning solution for cleaning screens and objects during printing.
Step 2: Adjustment
The air filtration parts including the air supply switch valve, air filter, Lubricant oil injector, pressure gauge.
- The air supply switch
Cut off or connect the air.
Filtrate the moisture of the compressed air.
The knob on the top of the filter is used to adjust the compressed air pressure, lift up the black knob, and turning clockwise will increase pressure, otherwise, the pressure will be decrease.
- Lubricant oil injector
- To supply the gaseous lubricant to the pneumatic components.
- Lubricant oil use no.20 machine oil or equivalent lubricant oil.
- Refill lubricant oil, shut off air supply, turn off black knob, add suitable volume lubricant oil. Lubricant oil consume regulate, turn screw to proceed adjustment, turn clockwise to decrease and vice versa. Generally, first totally shut off the valve, and then turn anticlockwise 90°-180°.
- Pressure gauge
Optimum working pressure, 4-5 kg/c ㎡.
Step 3: Calibration
- Preliminary calibration
According to the requirement of the object to be printed, such as its shape(round or flat, etc.), suitable print speed, time lag between each print circle in automatic mode, etc., start the machine without loading and proceed with preliminary calibration.
- Adjust the distance
Adjust the distance between the screen and the object to be printed. The screen and printing surface leave a 1-2mm distance. Loosen hold tight screw of up down platform, then turn lever wheel and drive the platform to the required level. After, using the screw fixes it.
- Print blade adjustment
Position and speed adjustment: micro-adjust screw is for print blade up down adjustment.
Regulator is for up down speed regulation, since the speed is too fast may arise oscillation and has bad effect on print result. Angle switch is for six and parallel adjustment purpose.
Alignment between print blade and axial line of curve surface, loosen regulator plates of driving printing head part and then slide left and right. After adjustment, screw tight the regulator plates.
Print blade air pressure adjustment: general setting is about kg/c ㎡, and longer print blade, the higher pressure applied is necessary.
Step 4: Shut Down Procedure
First, stop the machine by Stat/Stop. Then cut off the air supply.
Keep back the remaining ink from the screen frame, then use screen cleaner(suitable solvent) to fully clean the screen on both sides. After that, it is better to dry with the soft wind.
If the screen frame is not used within a short time(several days), it is better to seal it with a cover.
The Benefits of Screen Printing
When considering a screen printing machine, you should already know that there are many benefits of screen printing.
Silk Screen printing is not limited by the size and shape of the substrate. General printing can only be done on a flat surface. The screen printing can not only print on the plane, but also print on the special shape of the molding and the concave and convex surface.
Screen printing uses screen printing ink. The printed product pattern not only has good adhesion and thick ink layer, but also does not fade or fade, and maintains a bright color for a long time.
High Printing Quality
The screen printing machine has a multi-color printing electric eye device. The screen printing operator can accurately align the printing colors and dots with a slight adjustment, which improves the quality of the printed products.
High Speed and Efficiency
The screen printing machine can print on a large area. It can evenly print the substrate with a large area of background color and dots. Large-area substrates are prone to blurred dots when printed with other printing machines. On the other hand, the substrates printed on the screen printing machine have a clear coating and maintain long-term color without fading.
Screen Printing Machine Maintenance
Machine maintenance relies on extensive management. We can only point out the basic requirements to keep the machine functioning properly. For other management, such as the internal parts of the machine, the appearance of the machine, the surrounding of the machine, the working environment, etc., it is necessary to formulate rules and regulations for management. Check the compressed air regularly to ensure that the compressed air is free of oil.
Check the operation of the machine before turning it on. Is there any abnormal performance such as movement and sound during operation. You should find out the problem and fix it as soon as possible. Check that there is enough oil for the machine. If not enough, fill them up. The surface of the machine should be cleaned after get off work and the water in the filter should be drained.
When the screen printing machine is running at the end of the month, the joints and moving parts of the screen print machine should be checked, and some lubricating oil should be added.
The screen printing machines should be inspected and tested every six months.
A comprehensive inspection should be carried out after the silk screen printing machine has been in operation for one year. For mechanical components, inspection points include rust, wear, lubricating oil condition, and performance of pneumatic piping.
Different materials have different printing steps, we take plastic parts as an example. The following steps are required to complete the silk screen.
Most plastic materials require prepress before screen printing for better ink adhesion. Such as PP, PE, HDPE, LDPE, Tritan, etc.
There are various methods of prepress treatment, such as plasma, flame treatment, Pyrosil, etc. The most widely used of plastic materials is flame treatment.
After prepress, enter screen printing. As mentioned above, there are several parts:
- Screen printing machine:
Different substrates need to use suitable screen printing machines, such as flat screen printing machines, cylinder screen printing machines, etc.
a. Template: usually an aluminum frame with a screen, and the screen is engraved with an artwork design.
b. Squeegee: It is a rubber piece for scraping ink.
c. Ink: Different materials require different inks. There are usually solvent-based inks and UV inks.
d. Jig (tool or jig): This is the tool that keeps the substrate from moving while printing.
After screen printing, post-printing process is required:
Solvent-Based Inks: Usually oven-dried or naturally dried.
UV ink: UV ink cannot dry on its own and needs to be UV cured after printing.
This article mainly introduces you how does a screen printing machine work. As we all know, silk screen printing is the most popular printing technology today. But when you have a screen printer machine how you use it is a question, even with the instructions. So here is the ultimate guide on how does a screen printing machine work for your reference.