Pad Printing Introduction: Types of Clichés

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Steel Clichés | Mid-Run Clichés | Short Run Clichés

 

 

There are basically three types of cliché’s: steel, mid-run, and short-run.


Steel cliché’s

 

Steel clichés are the most durable of the three types, capable of lasting more than one million impressions. They can be anywhere from .250" to .390" thick depending upon manufacturer.

 

 

Mid-run cliché’s


Mid-run cliché’s are made of thin steel. (.026" to .040") Also referred to as "record" cliché’s, mid-run cliché’s can last anywhere from 35,000 to 150,000 impressions, depending upon the application.

Steel and mid-run cliché’s are coated with a photoresist, dried, then imaged by exposure to UV light. After exposure they are developed, touched up, then chemically etched using either nitric acid or ferric chloride. Due to the complex nature of this process, most steel and mid-run cliché’s are made by pad printing equipment manufacturers.

 

 

Short-run cliché’s


Short-run clichés are also referred to as polymer or plastic clichés. Short-run cliché’s are the least expensive, least durable, and easiest to make. Some types of short-run cliché’s are developed in water, while others are developed in an alcohol and water solution. While the alcohol developed short-runs are typically more durable, the durability and image resolution of both water and alcohol developed cliché’s can vary significantly depending upon manufacturer. For example, some water-developed cliché’s last only a few hundred impressions, while high quality alcohol cliché’s can last 20,000 impressions. Ask your supplier which cliché is best for your application.

When mounting any mid-run or short run cliché to a spacer or dummy plate, be sure that there is no debris between the back of the cliché and the spacer plate. Debris the thickness of an eyelash can result in a bump in the cliché which will be shaved off by the ink cup or doctor blade later, possibly rendering the cliché useless.

Etch depths are usually about .00085" to .001" (18-25 microns). After the image is picked up, transferred, and dried, the finished ink film thickness will be about 20% of your etch depth.

Many people reason that in order to compensate for such a thin ink deposit all one needs to do is make the cliché] deeper. Actually, the best way to increase ink film thickness is to multiple print the image, since etch depths in excess of .00115" (or about 40 microns) result in blurry, smeared images and incomplete transfer.

Screened images are necessary in certain applications. Large open areas need to be screened to support the ink cup or doctor blade so that it doesn't dip into the image during the doctoring stroke. The screen exposure is a second exposure which, once developed, results in a fine pattern of dots or "bumps" in the bottom of the etch. In addition to support, these dots help provide resistance to ink flow when the pad compresses to pick the image up, preventing the ink from forming a wave that results in an inconsistent ink film.

 

Rotary Clichés

 

Rotary clichés are often referred to as "drums", since they are cylindrical. These can be solid steel, mid-run or short-run.

 

 

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