What is screen printing?
We have already discussed about some printing techniques that includes offset and digital printing. Now, we are going to have some discussion about screen printing. A versatile process that is used to ornament small and moderate packaging, labels, graphics, garments, and other products is known as Screen printing or Serigraphy. Serigraphy is supposed to use a range of ink types in order to print on a paper, rigid and flexible sign materials, fabrics, garments, metals, plastics, films, glass, ceramics, and 3d objects.
In order to print original art, reproductions, posters, decals, indoor and outdoor fabrics, wallcoverings, electronic circuits, bottles, tubes, labels, glassware, dishes, and many 3d items, this process of Serigraphy is being widely used. Furthermore, it is also used to print the membrane switch control panels employed frequently in industrial, electronic, and consumer devices.
How does it function?
At the point when a squeegee pushes a glue-like ink through the openings in a working screen on the head of a print substrate, the ink is just kept in regions in which the work openings are not obstructed by solidified emulsion. Each ink shading in a structure requires its own screen. Factors that influence the cycle to incorporate the sort and consistency of the ink, the kind of emulsion used to conceal the screen, the piece of the screen work, the edge and hardness of the squeegee cutting edge, and the weight and speed of each stroke of squeegee over the work.
Types of presses
The steps that include in the process of the press operator are, loading each screen and physically pulling the squeegee across the screen. In manual press, the press operator is supposed to conduct all these steps.
Automatic or semi-automatic presses
This type of presses fuses various degrees of computerization for higher-speed printing. For instance, the squeegee might be precisely controlled at explicit speeds and weights. Or on the other hand, the items being adorned are naturally moved to start with one ink station then onto the next.
On a carousel press, the printing beds pivot around a focal center point. Distinctive ink shading is applied at each step in the revolution.
In an in-line press, the items which are supposed to print, move from one print station to the next in a straight line. Such types of presses are used for large-format graphics.
A rotary press constitutes a screen that is wrapped around a cylinder. This cylinder covers the ink feed system and the squeegee blade. The ink is supposed to be applied as the fabric or wallcovering material and is transported beneath each cylinder.
Screen printing jobs require a large amount of labor, specifically for multi-color jobs. There are some steps involved in creating each screen as follows:
- Film positive
It is a solid black ink on a clean, semi-rigid clear film. In order to use wide-format inkjet printers for this process, specialized software and inkjet-printable films are to be used.
All the areas of design that will be printed in a particular shade of ink are supposed to be covered by the black ink. When an emulsion-coated screen is exposed to UV light, the opacity of the inks on the film keeps the desired areas of the screen open. Enlistment marks are inkjet imprinted on the film outside the edges of the design to guarantee the structure will be appropriately adjusted on the screen for precise printing.
A photosensitive chemical that hardens when exposed to UV light is called an emulsion. At the point when UV light goes through the clear areas of the film positive, emulsion ties to the work and blocks of cement. The solidified emulsion keeps ink from moving through the screen during printing.
The screen must be degreased prior to applying the emulsion with cleaning agents to eradicate oils, dust, and dirt that might keep the emulsion from fully attached to the screen. The screens are dried in a dark room after a thin layer of emulsion is applied to the screen where the emulsion won’t be affected by UV light.
In this step, the film positive is taped to the screen and pre-registered. In this way, the registration marks on the film align with registration marks on a template for the item to be adorned.
The emulsion-coated screens are exposed to controlled amounts of light in a dark room. The time of exposure depends on the types of inks and exposing systems being used. In a washout booth, the film positives are untapped from the screens and the uncured emulsion is washed away with water. At this stage, the main openings that ought to be obvious on the screen are the regions through which the squeegee will apply the ink.
Once in awhile, pinholes on the screen must be fixed. Or on the other hand, a hardener can be included to keep the emulsion on the screen from separating during longer print runs.
Screen printing inks
There is a wide variety of water-based, solvent, UV curable inks that can be used in screen printing. To print electronics, conductive inks are to be used. The sort of ink chosen depends on the performance requirements of the ornamented items. For instance, screen-printed crystal and dishes must have the option to withstand commercial dishwashers. Perpetual decals on truck armadas or modern gear may need to last at the least 10 years. Fine content imprinted on plastic cylinders for shampoos and creams should not rub off when the cylinder is filled, dispatched, shelved, and bought.
Article of clothing decorators uses plastisol, water-based, or release inks relying upon how they need the article of clothing to look and feel.
Following are some types of screen printing inks:
Plastisol inks are well-known for they are thick, long-lasting, and easy to mix. This ink stays on the screen without drying out because it needs heat to dry.
Water-based ink absorbs into the clothes or garments being adorned, so the garment does not get hard or stiff from the areas where the ink has been applied.
Last but not the least, it removes the color of the fabric where it is applied and replaces it with pigment in the ink.
There are some special-effect inks that are capable of adding dimensional textures, metallic effects, neon colors, or glitter to the garment or piece of cloth.
Screen-printing inks are formulated to stick to many substrates without the use of pretreatments. Substrates that can be screen-printed are as follows:
- Anodized aluminum
- Coated and uncoated cardstock
- Coated metal
- Coated and uncoated paper
- Fiber drums
- Pressure-sensitive vinyl
- Stainless steel
- Static-cling films
- Top-coated polyester
- Treated polyethylene banner materials
- Uncoated cardstock
- Rigid vinyl
- Vinyl decals
Textile screen-printing inks can decorate cotton, cotton/poly blends, acetates, linen, polyester, and lycra blends, and more.
Screen-printing inks must be completely relieved otherwise they won’t adhere appropriately when the printed article is exposed to scraped spots, water, or synthetic compounds. Many screen-printing shops use frameworks in which printed things are shipped on a transport line through a drying chamber. Flash-curing units can be utilized to partially dry one shade of ink before the following shade is applied.
On the off chance that a screen for a particular activity won’t be expected to future reprints, the screen can be recovered or reclaimed by removing the inks and emulsions.
Trends in technology
To lessen expenses and lift efficiency, gadgets have been developed to robotize labor-intensive processes, for instance, screen covering, enlistment, exposure, flushing, and recovering.
Computer-to-screen (CTS) system
Takes out the need to make film positives. CTS gadgets print light-blocking, water-based dark inkjet inks legitimately from a PC record onto a dried emulsion-covered screen. CTS frameworks have gotten more solid, more affordable, and quicker and empower screen-printing shops to decrease work costs while improving print quality and proficiency.
Hybrid screen-printing system
Hybrid screen-printing frameworks consolidate the flexibility of screen printing with the full-shading capacities of inkjet printing. Articles of clothing decorators can apply a white under base layer of screen printing inks to a wide scope of materials, at that point carefully print four-shading pictures on the head of the under the base. The last layer of screen-printing inks can add surfaces or sparkle to make one of a kind structures that immediate to-piece of clothing inkjet printing frameworks can’t yet coordinate.
Utilizing LED lighting frameworks to dry inks, uncover screens, and fix emulsions lessen vitality utilization and the measure of warmth that is produced. UV-LED screen printing inks are mainstream for enlivening warmth touchy movies and plastics utilized in bundling just as containers and barrel-shaped items.