What is screen printing ?

Screen printing consists of five main elements: the screen printing stencil, the squeegee, the ink for screen printing , screen silk printing machine, and the substrate. The principle of screen printing is as follows:prepared stencil as design requirements. Move ink from one end to the other with a squeegee.  During the movement of the squeegee, the pressure forces the ink to pass through the image area and fill the opening mesh apertures,then transfers the image content ink onto the substrate. It is color separation for screen printing , one color can be printed at a time; multiple colors require multiple stencils to print the different image areas.

What is the process of screen printing?

Edit file and output the film , prepare suitable stenciling and exposure, take a suitable squeegee as printed content, and seal off a printing area with transparent tape.  Set the positioning points on the printing press platform, pour the ink into the mesh screen printing, and use the machine to move the squeegee. During the movement of the squeegee, ink will pass through the image area and fill the open mesh apertures, then transfer the ink onto substrate,while the non-image areas will be blocked. Then, put the printed sheet on a drying rack to dry. After the order is completed, immediately return any excess ink to the ink bucket or container, and then clean the screen thoroughly with screen cleaning solution.

What equipment do I need to start screen printing?

Main screen printing equipment or screen printing kit: Screen printing stencils, screen printing presses, squeegees, ink.

Pre-press processing equipment: Computers, film printers, emulsion, squeegee holders (coaters), heat guns or dryers, exposure units, high-pressure water jets or plate washers.

Other required: Ink Thinners, white cloth, substrates, screen cleaning solution.

How does screen printing work？

Screen Printing Process 

Image for screen printing  – Edit – Output Film – Create Stenciling  – Apply Emulsion – Dry – Screen Exposure and Image Developing – Dry – Screen Touch Up  – Select Suitable Squeegee – Edge Sealing – Mix Ink – Pour Ink into Printing Area – Position Substrate – Print – Place Printed Sheets on Drying Rack to Dry – Quality Inspection –  Finished Printing – Clean Mesh with Screen Cleaning Solution.

How to make screen printing files?

For commercial screen printing ,the original files require high resolution, at least 300 DPI or higher. Low-resolution files are not recommended for screen printing, but can be used for inkjet printing. If the file is high-resolution, the next should make sure the type of screen printing,  then edit files and output films.

Type of Screen Printing

Quality screen printing is divided into three types: spot color printing, CMYK full color printing, and a combination of spot color and CMYK full color printing. 

Spot Color Printing:

• 100% solid printing (using spot color inks,  mixed inks as PANTONE colors, transparent inks, silver inks, gold inks, inks containing silver powder or iridescent powder, etc.) ,such as : container decals, hard hat stickers,uk car stickers.
• Single spot color printing is easy. For multi-color printing, consider color depth: typically print dark colors over light ones, printing the darkest color for last, This applies to front printing. For reverse printing, the opposite process—print dark colors first and save light colors for last.
• Multi-color requires registration marks. Without them, registration errors will cause white gaps, seriously affecting print quality. The size of registration marks depends on the file dimensions, material, and client requirements, typically ranging from 0.15 to 1 mm. 

CMYK Full Colour Printing:

Cyan, Magenta, Yellow, and Key represent the four standard process colors used in overprinting. By controlling the size of the dots during overprinting, different patterns can be created. This printing method does not require ink mixing; simply adjusting the dot size creates patterns in various colors. Suck as : butterfly car stickers,business stickers, flower stickers,skull stickers,letter stickers.

Screen printing is a printing method that uses ink passing through open mesh apertures.  Because the mesh openings are relatively large, CMYK files must use a relatively low LPI (lines per inch); screen printing cannot achieve sufficient precision with a high LPI.

Screen Printing File LPI (Lines Per Inch):

20-30

30-60

60-100 

Liyantian uses 75-80 LPI for vinyl screen printing patterns and text all the time. You may select the appropriate LPI based on your specific requirements.

Spot Color + CMYK Screen Printing

When a file has many colors,cannot be divided into different spot colors,or some cost problem ,or if the original file is an image rather than vector graphics, CMYK printing must be used. However, CMYK dots are large and not suitable for tiny or small text. So combining spot colors can overcome this limitation of CMYK color printing. Alternatively, this method is suitable when clients require gradient colors and spot-color printing for logos, company names, URLs, QR codes, etc. Such as ：motorcycle decals,bike decals,truck decals ,jeep stickers,boat decals.

How to make a screen for screen printing? 

A screen printing frame consists of a frame and a mesh screen. The frame serves as the support structure for the mesh screen, and its material directly impacts printing precision and durability. It is primarily made of metal, wood, steel, or other materials. Aluminum frames are the most commonly used, while wooden frames are often preferred for personal or manual screen printing . Steel frames are suitable for high-tension industrial printing. Frames come in fixed or adjustable, but we generally opt for fixed frames.

How to choose the right screen printing mesh material?

The mesh is a primary component of screen printing, and its material, weaving method, and weave density directly impact printing results. Mesh materials are primarily categorized into silk mesh, nylon mesh, polyester mesh, and stainless steel mesh. 

1. Silk mesh: Due to its poor abrasion resistance, chemical resistance, susceptibility to aging, weak tension during weaving, and high cost, it is rarely used anymore.
2. Nylon Mesh: A synthetic mesh woven from nylon monofilament. This mesh features a smooth surface and excellent ink permeability, with low requirements for ink particle size and viscosity.Due to its high tensile strength, good flexibility, and adaptability to various substrates, as well as its wear resistance, chemical resistance, and long service life, it can be used on flat, uneven, and curved surfaces. It is also easy to recycle and is often used for printing fine lines or dots. However, it is not suitable for high-precision printing.
3. Polyester mesh: Low elongation, stable physical properties, highly resistant to solvents, high temperatures, water, and chemicals. Renewable. Commonly used for high-precision printing. However, compared to nylon mesh, it has lower abrasion resistance and exhibits poorer adhesion and flatness when bonded to the printing plate.
4. Stainless Steel Mesh: High tensile strength and elasticity, excellent ink permeability, strong alkali resistance, chemical resistance, and high-temperature tolerance. Suitable for thermoplastic materials such as flat, high-precision circuit boards. However, due to its high rigidity, it is prone to bending and damage under external force, making it suitable only for flat substrates and unsuitable for curved surfaces. The mesh may loosen during printing due to applied forces, affecting print quality. It is expensive and has high production costs.

How to choose the appropriate size of the screen printing frame? 

The size of the screen frame includes the printed image and text content, the surrounding margins, and the size of the aluminum frame. First, determine the size of the printed image and text and the direction of the printing squeegee. Generally, a 10-15 cm ink coverage area needs to be reserved on both sides in the direction of the squeegee, and a 7-10 cm area needs to be reserved on the other two sides. The printed image and text should not be too close to the screen frame, because the screen mesh at the edges of the frame has less elasticity and is affected by the frame, resulting in poor ink penetration and affecting print quality. 

How to choose the right mesh count?

Once the type of mesh material has been determined, it is necessary to select a mesh with the appropriate mesh count based on the printing content and material. 

Mesh Count

1. 20-100 mesh count:screens have larger openings, allowing for a greater volume of ink to pass through, resulting in a thicker ink layer. However, they produce significant serrations and are only suitable for large billboards or as a base layer of ink.
2. 120-180 mesh count:  The mesh size is moderate, allowing for a moderate amount of ink to pass through. However, there are still small serrations. Suitable for textile printing, signage, and general packaging. Best suited for water-based ink printing, such as 3M 3755 adhesive printing.
3. 200-300 mesh count: The mesh is denser, resulting in higher printing accuracy and better detail reproduction. Suitable for control panel printing, fine signage, and some electronic components. Suitable for solvent-based ink printing.
4. 350 mesh count: The mesh is very dense, suitable for high-precision CMYK four-color printing and spot color printing, such as logo stickers, panels, reflective stickers, window stickers, glow in the dark stickers, magnetic stickers, floor stickers, car stickers, etc. It can also be used for printing circuit boards (PCBs). UV screen printing is commonly used with this mesh count.
5. 420 mesh count: The mesh is extremely dense, enabling ultra-fine printing, such as CMYK screen printing and printing of small characters like different kiss cut sticker or die cut stickers. It can also be used for semiconductor chips, miniature electronic components, and ultra-fine line printing.

Thread Diameter 

Thread diameter refers to the diameter of the material used to weave the mesh, and is typically measured in micrometers (μm) or millimeters (mm). Its size directly determines the thickness of the screen print, the open area percentage, and the mesh size, making it one of the key parameters affecting ink transfer rate and print quality. In printing, screens with thicker thread diameters are more prone to clogging, resulting in poor ink transfer. Therefore, different mesh counts require matching thread diameters.

What Is the Best Screen Angle for Screen Printing？

1. 0 degrees Vertical: Rarely used, thick lines, large solid areas, prone to moiré patterns
2. 22.5 degrees: Less common, for special halftone dots or avoiding pattern interference
3. 30 degrees: Common standard solution, used in specific halftone dot structures
4. 45 degrees: Most commonly used standard angle, versatile for all applications
5. 55-60 degrees: Occasionally used for special halftones or specific substrates 

Approximately 75% of the industry employs 45 degrees.

Why Is 45° Mesh the Most Commonly Used?

1. Less prone to moiré patterns
2. The 45-degree mesh pattern features a diamond arrangement, ideal for fine dots and lines.
3. 45-degree angled arrangement ensures more uniform ink coverage.
4. 45-degree tension ensures even distribution, delivering consistent print quality. The mesh fabric is durable and resistant to tearing.

Why Does Liyantian Choose a 45° Screen Angle for Printing Outdoor Stickers?

1. Diamond-shaped mesh openings, evenly and stably arranged
2. Liyantian’s UV resistant ink from Japan. This naturally drying ink dries extremely quickly during printing and relies heavily on uniform screen mesh, with 45 degrees being the optimal angle.
3. All stickers ,vehicle decals,warning labels,holographic stickers,helmet stickers printed by Liyantian feature high-precision CMYK gradient colors or intricate patterns and text. Therefore, they must be applied at a 45-degree angle to prevent moiré patterns.
4. The printed materials produced by Liyantian Printing are completely free of burrs.  Achieving this requires not only using high-mesh screens and fine thread diameters, but also a 45-degree screen angle. 

Selection and Applications of Different Screen Tension Levels

 Screen tension is one of the key factors affecting screen printing quality, measured in Newtons per centimeter (N/cm). Different mesh materials and printing applications require distinct tension levels. For instance: nylon mesh typically requires approximately 8-12 N/cm, while stainless steel mesh necessitates 16-20 N/cm. Higher tension is not always preferable. Excessive tension weakens the mesh’s rebound force, making it brittle and prone to tearing. Conversely, insufficient tension causes the mesh to become flaccid, lacking rebound force, and susceptible to stretching and deformation, resulting in blurred prints. 

What is Emulsion and How does it work?

Photosensitive emulsion is a photosensitive material that undergoes a chemical or physical reaction when exposed to light of a specific wavelength (also called exposure), forming a durable film on the screen mesh. It comes in two types: single-component and two-component. Through processes such as applying the photosensitive emulsion, exposure, and development, it can accurately transfer patterns or text onto the screen mesh.

Cleaning and Preparation Before Applying Photo Emulsion 

Before applying photosensitive emulsion to the screen, ensure the screen is free of dust, contaminants, grease, and other substances. These can cause pinholes, sand holes, and broken lines in the image. Therefore, clean the screen with a cleaning agent before applying the emulsion.

Photo Emulsion Coating Methods 

There are various methods for coating photosensitive emulsion onto a screen, with the most common being the squeegee method or the rotary method. Here, we will focus on the squeegee method.

Scoop Coating Method

Select a scoop coater basis on file and stenciling ,the coating edge must be curved,with the edge slightly convex along its length. This ensures the scoop coater with photosensitive emulsion touch mesh, it will not damage the screen while evenly coating the emulsion, guaranteeing consistent thickness of the applied emulsion layer.

How to Coat Photo Emulsion Using the Scoop Coating Method?

1. First, please clean and air-dry the stretched mesh frame or old frame. Position it vertically at an 80-90 degree angle. Pour 6-7 layers of emulsion into the scoop coater , push the coating edge to touch the mesh.
2. Tilt the front edge of the scoop coater to make sure the photosensitive emulsion can touch the screen mesh.
3. Maintain a 70-80 degree angle and move the scoop coater upwards at a constant speed to within 1 cm of the top. Then, flatten the scoop coater and pause.  Next, reverse the direction of the screen frame and repeat the process using the same method. The screen frame needs to be coated 3-4 times on both sides. After each coating, it needs to be thoroughly dried.  Drying can be done naturally at high temperatures, but in low temperatures or humid weather, a heat gun should be used. Using an oven is ideal if available
4. Once the screen frame is dry, exposure must be completed promptly. Avoid dust accumulation during drying, as this can cause pinholes. Therefore, the drying process must be conducted in a dust-free environment.

Screen Printing Exposure

Screen printing exposure is divided into two main steps: exposure and developing.

How to expose a screen using an exposure machine:

1. Open the exposure machine’s top cover.
2. Apply alcohol to a white cloth and clean the exposure glass .
3. Place the film onto the exposure glass,fix it with transparent tape.Position the screen frame face-up on the glass, keep the same area with the film.
4. Close the rubber blanket frame.
5. Check the vacuum and exposure times based on the print content and requirements.
6. Turn on the power switch and set the vacuum and exposure times as required. The exposure unit will automatically perform vacuum processing to seal the film and screen tightly together, creating a vacuum. After the secondary vacuum cycle completes, exposure processing will automatically commence.
7. After finishing exposure, the light source will automatically shut off. Wait until the pressure gauge reading returns to zero before opening the top cover.
8. Remove the screen frame, take off the film, and proceed to the next step: developing.

How to manually develop the screen?

1. Place the exposed screens into the sink.
2. Fill a bucket with water, put the high-pressure water gun hose into the bucket, then adjust the water pressure.
3. Adjust the spray distance between the high pressure water gun and screen.
4. Use a high-pressure water gun to spray the unexposed areas for a few minutes. The unexposed photosensitive film will swell and be washed away by the high-pressure water.
5. Inspect whether all image areas on the screen frame are completely hollowed out.
6. Set aside to air dry naturally, or use a heat gun for drying, or if available, place in a drying oven for drying.

Screen Touch-Up

The developed and dried screen mesh needs to be inspected again to ensure there are no open mesh apertures in the areas that are not supposed to be printed. If there are any, they can be sealed with photosensitive emulsion or transparent tape.  Failure to seal them will result in ink smudges, ink dots, etc.  Also, check if the open mesh apertures in the areas to be printed are open. If they are not, use a toothpick to open them to prevent white spots during printing.

How to silk screen printing

Install the repaired screen frame onto the screen printing machine‘s frame. Adjust the screen frame’s position according to the silk screen printing machine‘s flat surface size and  positions. To keep the non printing area clean, screen mesh can be reused, or to prevent ink leakage that could damage the printing table or printed sheets, must cover the non-printing areas of the screen frame with transparent adhesive tape.

Then select a squeegee blade based on the graphic and screen frame size.Make sure the blade edge is free of defects,and insert the blade with the inferior edge into the squeegee handle. Please pay attention to not hurt the blade edge during install,and ensure the blade is the same position and height within the handle. So they will have some pressure for the whole blade,the same ink thick coming from the opening mesh.Adjust the blade’s hardness (10-25mm) or softness (25-30mm) by altering the length of the blade protruding from the handle.

Select the appropriate screen printing ink based on the graphic requirements. Typically, prepare a 700ml plastic cup, use an ink spatula to take out ink from the ink tank, then add some thinner. Mix it thoroughly with the ink spatula. Pour the mixture into the sealed printing area. Place a test substrate on the platform. Turn on the printing machine to move the squeegee from one side to another. Inspect the printed quality is good or not , if there are any blocked mesh areas and the graphic positioning is right or not. Check every detail through the printing test. Once all details are confirmed, prepare the required substrates.

The process requires preparing an anti-static tool or device.  Any silk screen printing materials must be treated with an anti-static application or dust removal before printing, then put the material on the printing table position for printing.The printed sheets should be placed on a drying rack for natural drying.  Please pay attention to checking the quality all the time during printing, to ensure there are no ink smudges or missed areas, guaranteeing quality, reducing costs, and improving efficiency.

Printed sheets should be placed on the drying rack for approximately half an hour to one hour. Afterward, remove them for quality inspection and proceed to the next step. It is one way screen printing,once finished printing, remember to return excess ink to the ink bucket or designated ink container, and thoroughly clean the screen frame with screen cleaning solution.