The concept of computer-to-plate (CTP) is not new in
the printing industry and is now used on a daily basis in the offset and
flexography industries. The screen printing marketplace also has seen
substantial growth in the use of direct-to-screen systems; however, in the pad
printing arena, the concept and equipment for CTP are still very new (although
are coming on extremely strong). With recent machine developments and
improvements, laser plate engraving systems are beginning to take a significant
hold in this area, and the market appears to be ready for a total conversion
over the next couple of years.
CTP systems, as they apply to pad printing, enable the
user to take a digital graphic file and by means of a laser, make high quality
pad printing plates (clichés) without the use of film, exposure systems,
or chemicals. Advancements to the process, increased efficiency, direct
cost savings, and superior imprint quality have produced such dramatic
improvements over other existing technologies that those who have seen the
results become instant converts.
Over the past few years, advancements to the overall
CTP process have produced highly effective results. Among these results
are the following benefits:
print quality – laser graphics are first generation so there is no loss
of resolution. Plates made using film are second generation.
making is totally repeatable – plates can be made the same every time.
can be made with “combination etching” - halftones for bold areas
and open etch for fine graphics.
ink lay down – laser-engraved plates have a straight walled etching and
more precise inkwell than polymer, thin, or thick steel plates.
In addition, because the CTP process requires less
consumable materials, CTP users are able to enjoy a number of cost saving
plate usage – double-sided laser plates can accommodate up to four
plate costs are similar to polymer clichés.
film costs – image-setter or laser film.
chemical costs – fixer, developer, and plate toner cartridges.
supply shipping costs and hazardous material removal.
maintenance contracts on processing equipment.
Finally, as far as a savings in time and efficiency
are concerned, computer-to-plate systems offer a number of benefits that
directly affect the bottom line:
plate throughput – it takes 3-5 minutes to etch a laser plate (10 minutes
for steel) versus approximately 15 minutes for a polymer plate.
bad plates – complete image and depth control give consistent plates
machine downtime due to improperly made or damaged plates.
• Etch thin steel or thick steel in-house instead of
hazardous waste stream.
There is much to know about the CTP technology that is
available today and when making a decision on the purchase of CTP equipment,
one should be knowledgeable in a few areas that are key to the evaluation
process: laser type, software capability, and system features.
To date, there have been three styles of lasers used
to make pad printing plates: diode-pumped YAG, Ytterbium fiber laser (YAG
wavelength), and CO2. The primary differences between these units are the
maintenance required, the spot size, and ability to ablate (etch) various
The diode-pumped YAG has a diode bar that heats up and can warp after about
10,000 hours of use, thereby requiring costly replacement. The fiber
laser has no diode bar and therefore, has no maintenance for up to 70,000 hours
of operation. The CO2 laser also does not require a significant amount of
Size. The wavelength of a YAG laser (1.064 microns) is
exactly ten times smaller than the CO2 wavelength (10.64 microns) and
therefore, has a resulting spot size that is 10 times smaller than a CO2 (in
the same set-up). YAG lasers are able to provide more detailed graphics
than CO2 when both laser types are put into the same machine set-up.
YAG lasers are ideally suited for metals, but their wavelengths are not easily
absorbed by many other materials (wood, acrylic, plastics, fabrics, etc.)
A CO2 laser beam has much more latitude and can be absorbed easily by many
organic materials such as wood, paper, plastics, glass, textiles, and rubber,
but is not easily absorbed by metal.
The capability of the laser
software is a critical element for producing the high quality pad printing
plates that are able to meet today’s demanding quality standards.
When lasers were first introduced to make clichés, they were only able
to engrave plates with straight “open etch”; they were incapable of
engraving bitmap, gradient, halftone, or process images; and they were not able
to handle industry standard software.
Three of the main file formats that are used in the
industry today are .ai (Adobe Illustrator), .dxf (Corel Draw, Autocad,
Flexisign), and .bmp (gradients, process images). It is critical that the
laser software is able to handle the latest revision of all of these standard
file formats so that any laser plate making system can be seamlessly integrated
into the workflow of the target company.
Other critical software parameters that enable the
operator to completely control image depth and appearance for the
“ideal” laser cliché include dot pattern and depth.
The halftone or dot pattern applied to the target image can be programmed in
with hatch parameters. The “hatch” or separation between the
laser lines is applied to the image and can be varied depending on the type of
image. For fine line graphics, a small hatch can be applied; for bold
graphics, a larger hatch will prevent “scooping”; and for difficult
graphics that combine bold and fine lettering, different hatch patterns can be
applied to the same image.
Precise depth control is typically achieved by doing
multiple passes of the same image so that a small amount (.0002-3”
depending on settings) is removed on each successive pass of the laser.
The power and frequency of the laser also can be varied to fine tune the plate
depth to provide the best printing plate for the type of ink, production speed,
Computer-to-plate systems have several available
features to consider:
• Size of system footprint – stand alone or
bench top system
for future expansion
The selling price of the laser systems in the market
today still may be out of reach for some decorating shops that do not produce
many plates, but for some of the larger shops that make many polymer plates or
for those that outsource many of their steel plates, CTP laser systems can be
easily justified. As with any innovation, it is expected that the selling
price of these systems will decrease as the computer-to-plate systems become
simplified and the technology evolves.
Computer-to-plate systems for the pad printing
industry are a natural progression of digital technology and appear to be in a
strong position to become the de facto standard for making pad printing plates
– they provide pad printing plates of superior quality at a lower cost
with faster turnaround. n
Adner is president of Inkcups Now in Danvers, MA. He has been developing
breakthrough equipment and consumable products in the pad printing industry for
more than 17 years. For more information, call Inkcups Now at (978)
646-8980 or visit: www.inkcups.com.