Electromechanical Drive Benefits
The majority of pad printing machines feature electronically controlled pneumatic drive systems. Because compressed air is one of the most expensive sources of mechanical energy in the industrial setting, it is more energy efficient, and therefore less expensive, to use pad printing machines that feature an electromechanical drive.

While compressed air is a versatile tool, running air compressors uses more energy than any other equipment. Air compressor efficiency is the ratio of energy input to energy output. Many air compressors may be running at efficiencies as low as 10 percent.

Consider the cost of the electricity used to generate the compressed air. The average cost for electricity in the United States in 2009 was $ 0.1002 per kWh1. This example utilizes a Tampoprint Model SIC 90 machine with a compressed air consumption of 2.7 NL (normal liters) per cycle. If the machine is working at an average rate of 1,000 cycles per hour, it will require 2,700 NL (about 950 cubic feet per hour) at 6 bar (90 p.s.i).

Maintaining that pressure at the machine with an oil injected rotary screw compressor would require, on average2, about 15 kW. By comparison, an electromechanically driven machine (such as the Tampoprint Model Hermetic 911) consumes a mere 1 kW in performing the same amount of work.

If the air delivery system was 100-percent efficient, and cost was calculated using the average industrial cost of electricity, the electromechanical machine would save $2,024.00 per year. If the air delivery system is only 25-percent efficient, the electromechanical machine becomes $ 3,650.00 less expensive to operate annually.

Increasing Compressed Air Delivery System Efficiency
If switching to electromechanical machines is not an immediate option, a lot can be done to increase the efficiency of the compressed air delivery system. Four aspects of compressed air systems are crucial to efficiency:

Storage tank. Choose a storage tank that can accommodate the needs of the system and prevent pressure from dropping below the minimum. This is especially important when there is peak demand in production, such as when running continuously and when running several machines off the same compressor. The common response to machine malfunctions due to a decrease in air pressure is simply to increase the system pressure. The energy wasted by increasing the system pressure could be saved by increasing the size of the storage tank or by installing smaller accumulating tanks near the pad printers themselves.

Air delivery system layout. Delivery lines that are too long, too narrow and have too many sharp turns are inefficient because they result in significant pressure loss. The solution is to place the compressor and/or storage tank closer to the pad printers, use larger diameter delivery lines and avoid sharp turns and loops whenever possible.

Air intake temperature. Cooler air requires far less energy to compress than does warmer air. Reducing the temperature of intake air by moving the compressor air intake outside (in cooler climates) or using an intake air chiller can substantially reduce the amount of energy required for compression.

Maintenance. Maintenance can have the most significant impact on efficiency. The number one source of energy loss in a compressed air delivery system is leakage. Although leaks often are very small, significant amounts of air can be lost. The graph on page 28 illustrates the amount of air lost through different orifice sizes.

Finally, it is important to include the replacement of compressed air delivery system filtration media in a preventive maintenance program.

Laser Engraved Clichés
Laser technology is rapidly replacing the cliché etching and engraving processes of the past. As a result, it is no longer necessary to handle and dispose of the hazardous chemicals necessary to coat, develop and etch steel and photopolymer clichés.

For example, in order to etch a steel cliché the steel must first be coated with a lacquer-based photo-resist. After exposure, the unexposed resist is removed in a developing process. After developing, a second “spot” application of photo-resist is applied as a “touch-up” to non-image areas. Etching is accomplished by running the cliché through a carefully controlled bath of ferric chloride, or in some cases acid. Finally, the photo-resist is removed with acetone.

Photopolymer clichés may be developed in distilled water or denatured ethyl alcohol; however, as is true with steel clichés, it is still recommended that an ortho-chromatic film be utilized as the carrier for the image being exposed. While the developer is commonly recycled to remove silver halides, there are still environmental considerations for disposal.

Aside from the inherent liabilities involved in working with these chemicals and the amount of ventilation and personal protection required to keep employees safe, one also must contend with costs associated with recycling and/or disposal.

CO2 and YAG Lasers
Relatively new to pad printing, CO2 and YAG lasers can engrave exposed photopolymer, hardened and un-hardened steel, aluminum oxide, ceramic and numerous proprietary cliché materials. Laser systems take a graphic image directly from a computer-based graphics program such as Adobe Illustrator or CorelDraw, convert it using proprietary RIP (routing information protocol) software and engrave it directly into the cliché surface. The only by-product generated is fumes, which are filtered out before the air is returned to the operating environment.

While the capital investment required to obtain a properly designed laser for cliché etching may seem sizeable, it is easily justified by the amount of money that is saved on labor alone, not to mention the costs associated with shipping, handling and disposal of the chemistry required to etch or engrave the “old way”.

UV Curable Inks
UV pad printing inks have unique rheology requirements. During the pad printing cycle, the ink must be able to rapidly change/increase viscosity in order to be efficiently transferred. Conventional solvent-based pad printing inks contain 60 to 70- percent solvent. It is the evaporation of the solvent that allows the ink to rapidly change viscosity for efficient transfer. UV inks, by comparison, contain about 30-percent solvent. This reduced solvent content means lower VOC (volatile organic compound) emissions, which is better for the environment.

UV inks also have an indefinite pot life, meaning that the unused ink does not have to be discarded once pot life has expired, as is the case with conventional two-component (ink + hardener) pad printing inks.

UV curing equipment requires approximately 20 percent of the energy required to run a heat (IR) tunnel4; therefore, electricity, or natural gas (assuming you’re using a gas dryer), is saved. UV curing equipment also requires less floor space and less time, so the building doesn’t have to be as large and more work can be accomplished in less time, which translates to lower overall utility costs.

While UV inks are not yet ready to replace conventional solvent-based pad printing inks in all applications, they are still worth considering, especially if working with highly automated systems and clear or lighter colored substrates.

Companies that truly wish to remain competitive in today’s global economy realize the importance of actively seeking out and implementing “greener” manufacturing solutions. Hopefully this article will serve to initiate discussion as to how pad printing operations in the United States and beyond can be fine-tuned in an effort to create a better environment for future generations.

References

¹ U.S. Energy Information Administration, Electric Power Monthly. January, 2010.

² Don’t Err with Compressed Air, David M. McCulloch, Chemical Processing, 2008.

³ Energy Efficiency in Air Compressors, N.C. Division of Pollution Prevention and Environmental Assistance, January 2004.

⁴ UV Curing comes to Pad Printing. UVEXS Corporation, www.uvexs.com.

John Kaverman is national sales manager for Tampoprint International Corporation. He holds a degree in printing from Ferris State University and has over twenty years of plastics decorating experience in capacities including production, process and applications engineering, sales and management. He may be reached via email at [email protected]. For information on Tampoprint products, visit www.tampoprintusa.com.