Pad Printing Steel Plates

The Cliché or Steel Plate is the carrier of the print that will be required on the product or component.

Traditionally the plates are generally of thick steel material which is made by a very special process of hardening and etched by chemical milling process. As clichés or plates for pad printing have very high importance hence selection of proper plates or clichés is extremely critical for quality.

Varying types of clichés are used depending on the desired print quality and quantity. The motif is recessed, etched into or washed out of the cliché. In order to assure smooth fitting and printing, the motif should be at a distance of at least 25 mm (1 inch) from the outer edge, and centered on the plate. In the case of long or fine lines, the motif must be at an angle of approx. 5° to 15° to the blade track in order for the doctor blade not to dip too low and scoop out too much ink.

Numerous trials have shown that an etching depth of 30-35 ?m is optimal for pad printing. Since the pad can only transfer a limited quantity of ink, a greater depth is pointless. At an etching depth of 30-35 µm, the pad only picks up an ink film of 12 µm. The rest remains in the depressions of the cliché. Because the ink film consists of approx. 40 % to 60 % thinner, which evaporates during the transfer and drying, the actual thickness of the ink film left on the substrate comes to around 5 µm - 8 µm, in some cases, as little as 2 µm. As an exception to the above statement, very fine fonts are etched at approx. 15 µm, and very large motifs, at approx. 30 µm. For very large surfaces, the dip of the doctor blade can be avoided by additionally copying a fine screen into the motif.