Computer to plate (CTP) technology is used on a daily basis in offset, flexography, and screen-printing workshops. As for pad printing industry, computer to plate equipment – laser plate-etching systems – have been introduced only recently. However, with latest developments, laser-based systems have the potential to conquer pad printing market over the next couple of years.

CTP benefits:

•Laser systems enable the user to convert a digital graphic file to a highest quality etched image in just 1 to 5 minutes.

•Costs of films, chemicals, consumables shipping, exposure units and removal of hazardous materials are eliminated, as are maintenance contracts on processing equipment and costs of outsourcing steel plate making. Double-sided laser-etched plates can accommodate up to four images, which reduces plate usage.

•There are four steps to make a plate: import the graphic file into the system's software, apply the halftone pattern to the image, specify the etch-depth parameter in the laser's operating software, and press start.

•Laser-imaged graphics are first generation so there is no loss of resolution.

•Etch depth and halftone pattern can be accurately fine-tuned to match the type of image you want to print, the viscosity and rheology of the ink used, the speed of the printing machine, and the durometer of the printing pads used. As specifications can be stored on the computer, resulting image quality is completely repeatable.

•Laser-based CTP systems can accommodate operating settings for fine, combination fine/bold, and bold graphics.

•Laser-engraved plates have a straight-walled etching and more precise inkwell than polymer cliches and thin or thick steel plates.

Choosing a CTP system:

1. Laser type

Today, three types of lasers have been used to make pad-printing plates: diode-pumped Yttrium Aluminum Garnet (YAG), Ytterbium fiber laser (YAG wavelength), and CO2. The primary differences between these units are maintenance, spot size, and ability to etch various materials.

Maintenance – The diode-pumped YAG has a diode bar that heats up and can warp after about 10,000 hours of use, requiring costly replacement. The Ytterbium fiber and CO2 lasers have no diode bar so they have no maintenance requirements for up to 70,000 hours of operation.

Spot size – As the wavelength of a YAG laser (1.064 microns) is ten times smaller than the CO2 wavelength (10.64 microns), the former is able to produce more detailed graphics than CO2.

Materials – YAG lasers are ideally suited for metals. A CO2 laser beam is better absorbed by organic materials – wood, paper, plastics, glass, textiles, and rubber.

2. Software

To ensure seamless integration into the workflow of the target company, laser software must be able to import are .ai (Adobe Illustrator), .dxf (CorelDRAW, AutoCad), and .bmp (bitmaps, gradients, process-color images) files.

To achieve halftone or dot pattern, the software must be able to apply different hatches (or separation between the laser lines) to the image. For fine line graphics a small hatch can be applied, for bold graphics a larger hatch will prevent “scooping”.

The power and frequency of the laser must be variable to finely tune the plate depth to provide the best printing plate for the type of ink, production speed and substrate. The target depth of etch in the plate is .001”

3. System features

The CTP systems have several available features to consider:

•Size of system footprint – stand alone or benchtop system

•Vector-tracing software

•Micro-adjust focal distance

•Plate registration systems

•Particulate evacuation systems

•Pre-etch laser pointer

•Availability of auto-load

•Availability of future expansion