Litho printing

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Debbie-Anderson-GMN
By Debbie Anderson | Jul 27, 2018
Example of lithographic printing at GMN

Lithographic printing, an offset printing technique, is based on the basic principle that oil and water do not mix. It is a process in which ink is transferred from a photographic plate to a rubber blanket, which then presses the image onto the printing surface. Allowing for extremely tight tolerances and consistently high-quality images, GMN’s sheet-fed lithographic process is frequently utilized for printing graphic overlays and labels.

While lithographic printing is often performed on standard substrates such as paper and vinyl, GMN walks the unbeaten path by predominantly using materials including polycarbonate, polyester, and aluminum. Lithographic printing at GMN utilizes UV-cured inks. GMN also offers custom color matching services to help customers achieve their exact specifications and uphold brand consistency. To formulate a custom color, the different colored inks are meticulously weighed, poured over a flat glass surface in carefully measured proportions, and mixed together using a putty knife. With projects requiring custom color matches, a small sample sheet is first tested on a machine called the orange proofer. This counter-top machine is simply a condensed version of the actual printing press, that allows GMN to test the color and make necessary alterations before the final production run.

The first step in lithographic printing is creating the artwork on a photographic plate through a chemical process. Similar to the process of developing photographs, lithographic printing also requires the creation of a “negative” and a “positive” image. First, a thin aluminum plate is coated with a hydrophobic material so that it attracts oil (ink) and repels water. The plate is then selectively exposed to light, thereby curing the hydrophobic coating only in areas comprising the artwork. Finally, the coating from the remaining areas is chemically stripped off and the plate is ready for use.

The lithographic printing press consists of a series of rollers laid next to each other. The foremost roller transfers water, placed in a tray beneath it, to the photographic plate. The ink is manually applied to the second roller with a putty knife, which then wets out to the entire cylindrical surface as the roller spins and transfers the ink to the plate. The photographic plate, carrying the artwork, is wrapped around the next roller in the series. Given the immiscibility of ink and water, the ink adheres only to the artwork on the photographic plate, while the water adheres only to the remaining background.

On the other side of the photographic plate are two other rollers called the blanket roller and the impression roller respectively. The blanket roller simply acts as a medium to transfer the artwork from the plate to the substrate. When printing, a stack of printing sheets is placed on the top tray of the machine. A gripper grabs one sheet at a time and wraps it around the impression roller. The artwork on the photographic plate is imprinted on the rubber blanket roller, which in turn transfers it to the substrate on the impression roller. Then, the ink is cured by exposing the printed sheet to UV light. The process is repeated for every unique color in the image.

Ideal for high-volume manufacturing, a lithographic printer can run from 3,000 to 6,000 impressions per hour, with the largest sheet size being 18”x24”. It can produce detailed and intricate artworks with half-tones, gradients, or a four-color process (a four-color process uses a CMYK color module to create four separate dotted patterns, which when printed on top of each other, yield the required color). However, lithographic printing comes with its own limitations. It can only accommodate substrates with thickness ranging from 0.003” to 0.020”. The printing system is not compatible with metallic or conductive inks. Also, the ink used is very transparent, and typically requires extra layers of printing for opacity.

As multiple factors go into consideration before selecting a suitable printing technique, GMN works closely with each customer to understand the project needs and requirements to determine the best printing solution for every unique application. To learn more about our other printing technologies, visit our blog on GMN’s printing capabilities.

By Josh Dunahoe | Aug 28, 2017
Twister T6 aluminum nameplate by GMN

Keirton Inc., a Canada-based company, is a leader in specialty crop harvesting solutions and product engineering. Following a rewarding relationship in the past, they reached out to GM Nameplate (GMN) for another project. This time it was a nameplate for their latest small-capacity trimmer called the Twister T6.

Keirton’s main requirement was that the T6 nameplate should speak the same design language as their existing products. Since this new portable trimmer was primarily designed for the countertops at home, Keirton wanted the nameplate to be slender, sturdy and easy to clean. Keeping these requirements and final product application in mind, an aluminum embossed nameplate emerged as the clear winner.

Aluminum nameplates are lightweight, durable, and scratch-resistant and open up an entire world of textures and finishes. The Twister T6 nameplate was set on a black background with a hint of gradient green on top. Although the color gradation was extremely fine, the most demanding task was to hit the precise shade of green. It took rounds of color development and testing to finally hit the bull’s eye. Thanks to GMN’s decades of experience with brand identity products, our color experts truly understand the significance of a perfect color match and leave no stone unturned to achieve it.

Once the colors were approved, GMN cruised through the production process. First, a thin aluminum sheet was covered with a primer and then litho-printed (also known as off-set printing) with black ink. Halftones were then used to produce the gradient green. Halftones are a pattern of tiny dots, squares or any other shape that gradually fade out, ultimately giving the impression of gradation. Even the slightest change in the size, shape and spacing of the pattern can affect the final outcome, making it extremely tricky to achieve a specific color. If you zoom in on a T6 nameplate, you can decipher the use of halftones by spotting the small dots.

The words ‘Twister’ and the rectangular block of gradient green were embossed in-house to accentuate the details and add texture to the nameplate. Eventually, the entire sheet was blanketed with varnish to hold the inks in place and prevent them from chipping or cracking. A cross hatch test (also called paint adhesion test) to inspect the adherence of the ink to the substrate was conducted and positively concluded.

As a custom-manufacturer of nameplates, GMN brings together a blend of expertise, quality and manufacturing capabilities. From domed to electroformed nameplates, the possibilities of shapes, sizes, materials, finishes and textures are endless. When it comes to nameplates at GMN, you are only limited by your imagination.

To learn more about the different types of nameplates, check out our capabilities page here

By Sandy Dick | Jul 11, 2017
CONMED membrane switch assembly

CONMED, a global medical technology company, came to GM Nameplate (GMN) in need of a membrane switch for the control panel of their surgical generator. With diverse capabilities and decades of experience working with the medical industry, GMN was able to provide not only each component of the membrane switch, but the complete, value-added assembly of the part as well.

The graphic overlay was printed using a combination of screen and litho printing and included multiple display windows and LED indicators. The overlay’s background colors were screen printed to achieve a high opacity, which helped to prevent light bleed from the illuminated LEDs. Litho printing was used to apply fine details and halftone patterns to the part. A halftone dot pattern was printed on top of the background to create a gradient effect on the keys and along the top of the overlay. Creating a halftone pattern that achieved the customer’s desired aesthetic proved to be challenging, but the ideal look was reached after several trials of testing various pattern constructions (altering dot size and space between the dots). GMN also printed the membrane circuit that goes behind the overlay and connects to the LEDs and switches.

Another challenge faced during this project was choosing the correct snap domes for the different-sized keys to create a good tactile feel. The difficulty stemmed from the unusual shapes of the keys and various sizes of domes. As a consistent layer across the entire part, the spacer interacts simultaneously with every dome and affects each dome size differently. Therefore, GMN had to carefully review the stack-up to include a spacer layer with the optimal thickness to give every dome size enough room to provide a crisp tactile feel.

A variety of layers were required in the stack-up in order to ensure that the part would function properly. ESD shielding was placed under the circuit connector to protect from static discharge and an aluminum subpanel was added to support the otherwise flexible structure. A foam gasket surrounded the outside of the panel to seal the area from outside moisture and fluids. Finally, due to a concern of the closeness to the electrical components beneath the panel, an insulating layer was added to the backside of the subpanel to prevent the electrical components from shorting out against this metal layer.

From early development through full-scale production, GMN worked closely with the customer to develop this product and provide design considerations for part manufacturability. As a product used in the operating room, GMN held multiple pilot runs to ensure the part functioned as intended and met the customer’s standards. 

CONMED surgical generator with GMN's membrane switch assembly.

Anna Minzel, GMN
By Anna Minzel | Aug 24, 2016
A Fluke laser radiation label using litho and screen printing

Each printing process has its own advantages and disadvantages. Because of these differences, multiple printing processes can be used for the same part. This Fluke radiation label uses two different printing capabilities – litho and screen printing.

Litho, or offset printing, is often used for very fine text because with screen printing, fine text may become distorted or blurry. During screen printing, the paint is forced through a screen onto the material, leaving more room for error on fine print. In lithographic printing, the ink is transferred from a stone or metal plate to the correct image areas using the repellent properties of water and ink. Lithographic printing for fine text creates a clear, consistent text.

For this part, lithographic printing was used for the fine print and screen printing was used for the colors. The opaque ink colors allowed for backlighting capabilities. During the screen printing process for the colors, the white was not placed over the red color to ensure the red color could be backlit.

Tight registration is essential for small parts because correctly lining up the label can be a challenge when there is little room for error. For more accurate registration, registration holes were used. These holes tell the machine where the part is and where to aim. Without tight registration, the green color around the embossed button would be off-centered and the transparent red section would be distorted. The tight registration allows for a more accurate label.

At GMN, we provide offset, flexo, screen, and digital printing. Find out more about our printing capabilities by reading our printing capabilities blog series.