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Etch-Depth Consistency on Pad-Printing Plates

(March 2002) posted on Sun Mar 31, 2002

Discover the negative effects of inconsistent etch-depth on plates and learn about considerations for sourcing, storing, and maintaining pad-printing pads.

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By Carol Swift, Peter Kiddell

Inconsistency from plate to plate is the main challenge that confronts pad printers. This inconsistency generally occurs because of a change in the concentration or temperature of the etchant. When either of these parameters change, so will the speed of etching. And when etching speed changes, so does the resulting etch depth. During printing, the effects of incorrect etch depth generally manifest as unexpected color changes, missing image details, excessive ink (if etch depth is too great), and premature ink drying on the plate or pad (when etch depth is insufficient).

If you are using steel plates, I would not recommend supplying your own plate material to the company that handles your etching needs unless you can provide complete etching characteristics for the material. The etching characteristics can vary dramatically based on the crystalline structure of the metal. The larger the crystals, the faster the material will be etched. As a rule, the harder the metal, the smaller the metallic crystals. One way to ensure that the steel plates you received from your etching supplier are correct is to insist on a certificate of conformity to accepted standards for every plate you buy. You'll be surprised how quickly a manufacturer will get it right once you have rejected a plate or two.

For those who use photopolymer plates instead of steel, the depth of etch is equally important. The main difference here is that photopolymer plates are generally processed in house. If this is the case with your operation, you may want to invest in equipment to accurately measure etch depth yourself.

Silicone printing pads

The pad is the defining part of the pad-printing process, yet, it is often treated badly. Shape, hardness, and surface finish determine the pickup and transfer characteristics of each pad, and thus the quality of the pad-printing work.


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