Tips To Improve Screen Printing Quality

Tips To Improve Screen Printing Quality

Ink Quality: The consistency of ink is a critical factor in the quality of screen printing. Inks can be classified as stiff or loose depending on their consistency. Some printers try to adjust the squeegee angle and pressure to compensate for the consistency of ink. This is likely to make the screen printing process much more difficult and if the process is manual, can even lead to carpel tunnel syndrome or sore joints.

The correct way to modify the way an ink prints is by using two products known as soft hand clear or extender base and curable reducer. The soft hand clear is used to adjust the pigmentation in the ink. In addition to adjusting the percentage of pigment in the ink, the soft hand clear also makes the ink more creamy and easier to screen print. The soft hand clear ink requires less squeegee pressure than regular ink and hence improves screen printing quality.

Curable reducer changes the adhesive quality of the ink and can be used anywhere from 2-4% to 10% depending on its texture. The curable reducer allows the ink to shear easily and thus print better.

Thus it is important to modify the inks as required so that you not only screen print easier and faster but also save ink and get better registration.

Screens: The rule of thumb with screens and meshes is that the tighter they are, the better the quality of output. The benefits of a tight mesh include a decreased likelihood of the mesh moving out of registration during printing and lesser chances of one color bleeding into another.

Tight screens also offer lower resistance when pulling the squeegee thereby reducing labor and cutting the ink cleanly.

A tight mesh also deposits the ink evenly onto the substrate. A soft mesh may have deposits of ink towards the edges thus printing with more ink in the center and less towards the corners. The uneven deposit of ink results in lowered printing quality.

Squeegee: It is vital that the blade of the squeegee is straight and sharp. The squeegee should be sharpened every day if need be to allow for even spreading of the ink.

Press: To get good quality screen printing, the platen must never move during printing. Even if you do everything else right and the platen shifts, the quality of the print will suffer. Also the color arm must not deflect when it in or out of the registration gate.

Curing: You cannot substitute the amount of time that the ink is cured for by increasing the heat. Sometimes inks need to be cured at lower heat for longer time for the ink to fuse with the fabric and get a full cure.

Thus, keep these tips in mind when screen printing to ensure high quality screen printing.

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Types of Sticker Printing

Types of Sticker Printing

Sticker printing has evolved greatly over the past several decades. While a black marker and white paper were once the tools of the trade, today's stickers are available in wide variety of stocks as well as a wide variety of color options.

Screen-printing is the oldest, but the most common technique of sticker printing. As the name implies, the process utilized silk, although today synthetic screens are now used. Screen-printing is the most basic form of printing stickers and is typically limited to very small amounts.

For screen-printing, ultra-violet cured pigment colors are used and the desired image is cut out onto a stencil. The stencil is then placed on the sticker stock. The screen is then laid over the top and ink poured on to the screen and pressed into place using a squeegee. If more than one color is required, the process must be done for each color and only after the last has dried. The process must only be completed once for one-color items.

Letterpress, also known as relief printing, is another form of printing where the image is taken from a raised surface. Letterpress printing is best understood if you think of it as something with ink being pressed down onto the sticker stock. Letterpress printing is used on simple projects that typically only require one color.

Flexography is a much quicker form of printing stickers and allows larger quantities to be produced. This method utilizes reverse master image transfer and is used most commonly in commercial label printing. This method was originally designed to allow for constant contact with the material being printed on. Flexography uses a master print that makes contact with the sticker stock and then leaves a print from the contact of being rolled over it. Flexography is fast becoming the most popular way to print stickers that come on rolls. This process is environmentally cleaner as well as being faster.

Offset printing involves transferring an image from a plate cylinder or rubber cylinder. Although offset printing uses an additional step, it allows you a lot of flexibility in terms of color options. Offset printing provides excellent color results. Offset printing and lithograph printing area often utilized together, as they can provide vivid colors and effects when combined.

The most common type of printing is 4-color process color that utilizes 4 ink colors to create the effect of full color photographs. The four colors are cyan, magenta, yellow and black.

Digital printing is the most advanced form of printing. Digital printing provides you the ability to make changes to the image until just before it is printed. Because the print is a reproduction of the digital image, this technique of printing also allows for color changes on the fly. The inks that are used in digital printing sit on top of the sticker stock rather than being absorbed into it.

Digital printing is one of the most common technologies used in producing personal, commercial and small business products. The biggest advantage to digital printing is that you don't have to have a master file and you can make adjustments to the image as necessary. However, digital printing is usually limited to quantities below 500.

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Printing Industry Overview: Screen Printing

Screen Printing

Many factors such as composition, size and form, angle, pressure, and speed of the blade (squeegee) determine the quality of the impression made by the squeegee. At one time most blades were made from rubber which, however, is prone to wear and edge nicks and has a tendency to warp and distort. While blades continue to be made from rubbers such as neoprene, most are now made from polyurethane which can produce as many as 25,000 impressions without significant degradation of the image.

If the item was printed on a manual or automatic screen press the printed product will be placed on a conveyor belt which carries the item into the drying oven or through the UV curing system. Rotary screen presses feed the material through the drying or curing system automatically. Air drying of certain inks, though rare in the industry, is still sometimes utilized.

The rate of screen printing production was once dictated by the drying rate of the screen print inks. Do to improvements and innovations the production rate has greatly increased. Some specific innovations which affected the production rate and has also increased screen press popularity include:

Development of automatic presses versus hand operated presses which have comparatively slow production times
Improved drying systems which significantly improves production rate
Development and improvement of U.V. curable ink technologies
Development of the rotary screen press which allows continuous operation of the press. This is one of the more recent technology developments

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Screen Printing Inks

Screen Printing

UV Curable

UV curable inks consist of liquid prepolymers, monomers, and initiators which upon being exposed to large doses of U.V. Radiation instantly polymerize the vehicle to a dry, tough thermosetting resin. They also require less energy, overall, to dry or "cure" compared to gas or electric driers.

The down side of UV inks is they can cost as much as three times that of regular inks and must be handled differently than conventional inks due to safety issues. Additionally, solvents are required for clean-up which results in some VOC emissions.

Plastisol Inks

Plastisol inks (both solvent and water based) are used in textile screen printing.

Solvent Inks & Water Inks

Solvent and water based screen printing inks are formulated with primarily solvent or water. The solvent evaporates and results in VOC emissions. Water based inks, though they contain significantly less, may still emit VOC’s from small amounts of solvent and other additives blended into the ink. The liquid waste material may also be considered hazardous waste.

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