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A pad printer is a highly practical and versatile piece of printing technology, capable of printing a flat image onto a vast array of products. Simply put, pad printers use rubber-molded pads to transfer two-dimensional images onto three-dimensional objects. Whether a surface (or substrate) is concave, cylindrical, textured, or even highly sensitive, a pad printer can be tailor made to fit nearly any application. Pad printing first became popular after WWII, when watchmakers began printing on curved watch faces. The introduction of the pad printer opened up all sorts of possibilities, as designers and engineers discovered that previously un-printable objects were now printable. Pad printing became a well established printing method, quickly making its way into the medical and automotive industries, as well as appliances, electronics, and countless others. All pad printers include three main parts: the image plate (called a cliché), ink, and rubber-molded pads. But, while the basics are fairly straightforward, not all pad printers are alike. Each of the three main parts present opportunities to optimize a pad printer for your specific application.

Image plates used in pad printing contain the etched image of what will be transferred onto the substrate in ink. The two main types of cliché or plate material are steel and polymer. Polymer plates are easy to use and best suited for short to medium production runs. Steel plates are the preferred material for longer runs: long life thin steel is best for medium to long runs, and thicker steel is recommended for very long production runs. ​ Another category of image plates is the laser plate. Laser plates are made of silver aluminum or other laser-able material. Plates that are laser etched offer long performance life and exceptional precision. Laser plates can also be etched on both sides and either end.

The type of ink used in pad printing will depend greatly on its compatibility with your substrate’s material. For example, pad printing on candy will require food-grade ink, and medical applications may require medical grade ink. Aside from those types of customizations, ink is formulated for the best adhesion to the substrate material, be it glass, aluminum, or various types of plastic. Overall, most inks will fall into one of two categories: solvent based (cured with time and/or heat) or UV based (cured quickly with UV light).

Printing pads are molded of silicone rubber, and depending on the application, will vary in size, shape, and hardness (durometer). The silicone rubber pad can adapt to the substrate’s shape, and the variations in durometer allow for endless optimizations, from printing fine detail on delicate electronics to large images on uneven material.

Since the late 1960s, transfer pad printing has been a popular decorative process, but it hasn’t always been the easiest. Since its inception, the pad printing process has undergone several revolutionary changes, but none are as important as the award winning Diversified Printing Techniques “Green Pad Printing System.” In full, this system includes the Green Cup, Green Plate, G-printer, UV ink, and a direct computer-to-plate laser-engraving machine (KCTP). The G-Cup utilizes a liner that acts as an ink reservoir. This green technology offers a simple advantage: it promotes quick changeovers by reducing cleanup and minimizing the need for cleaning solvents and rags, while greatly enhancing performance. Additionally, the G-Cup liner can be fitted with a lid to reduce ink waste! Construction of the G-Cup body includes several small but strong magnets evenly spaced around the outer parameter of the ink cup body just inside the doctor ring. This design stimulates ink flow by leaving the center of the cup free from obstruction. Doctoring performance on all cliché materials (thin and thick) is optimized by providing a strong and even clamping force. This even force eliminates the problem associated with scraping out ink from the image that is typically associated with center magnets. The plastic liner fits securely within the cup body and effectively protects the O-ring and magnets from ink and their respective solvents. Doctor rings are available in steel and ceramic and are mounted securely via the O-ring to the outer diameter of the ink cup body. Removal of the doctor ring and liner is easily handled through the use of a change out tool. The G-ink cup is indeed a game changer. Please contact your local sales representative to learn more about how this technology can help you.

Advantages:

Superior resolution and fine detail

Can be used on nearly any material

Reliable on a wide variety of surfaces: flat, round, concave, or uneven

Suitable for print on mechanically sensitive and/or delicate surfaces

Limitations:

​Can be more challenging to automate due to diversity of products that can be run on one machine (although Diversified Printing Technologies continually stays on top of latest developments in customization, automation, and robotics)

More expensive than screen printing (but strategic automation ultimately results in measurable cost reduction)

Diversified Printing Techniques specializes in the design, construction and support of standard and automated product decorating solutions. Not all solutions are simple; some require the creative application of auxiliary technologies. Our staff of experts is adept at providing results that are innovative, value based and efficient. We were recently approached by a customer that specializes in various forms of product decoration. They have a long and successful history of providing pad printed products on a contractual basis and had just landed a high volume contract. Although they have an ample supply of standard printers, the application required a custom solution. This need was based on two factors; the before mentioned high volume and the various part configurations consisting of 4 part colors, 7 artworks and 2 ink colors. It was deemed essential that no cross contamination occur. The system had to be capable of identifying and distinguishing between the matrix of part configurations. The customer had one additional request. Since they were not molding the part and were receiving them already boxed, they wanted the ability to scan the box label and download this information into the printing system. This “preset” of information would be the content used by the printing system to confirm that it was processing the correct part color, artwork and ink color. This would allow the customer to run the parts through the system and load them back into the original box with the proper label. Upon identifying the requirements DPT designed a system utilizing two Kent Alien 100 pad printers mounted and interfaced to an 8-station electromechanical dial index table with 8 ea 2 up holding fixtures. Unique to the solution was the addition of a vision inspection system with a scanner at the operator load station. The vision inspection system included two sets of cameras, one for identifying the substrate color and the other for identifying the artwork, ink color and image placement. The sequence of operation included the operator first scanning the label on the box to “preset” the parameters for the vision inspection system. The sequence of operation proceeded in the following order; manual load of two parts, vision inspection to verify part color, printing the left hand part in the two up fixture with the first Alien 100, printing the right hand part in the two up fixture with the second Alien 100, visual inspection of both parts for the correct artwork, ink color and image placement and a automatic unload with a pneumatically activated pick and place unit onto a curing conveyor.