pad basic forms
All pads have a curved (convex)
This is necessary to guarantee a rolling movement (see
rolling characteristics) during the ink pick up and subsequent
application which ensures a good printing image and prevents
the inclusion of air bubbles.
The shape of the pad is usually
determined by the shape of the print image and the geometry
characteristics of the printing part.
The various pad shapes can be classified into four groups:
- Round pads
- Oval pads
- Square pads
- Elongated pads
The shape of the pad also determines
the orientation of the print image in regard to the pad (see
pad contact point) depends on the pad shape. Round, oval
and square pad shapes have a contact point (see print image
Elongated pad shapes have a contact line (see print image
As a rule, the pad should not make the initaial contact in
the middle of the print image because the biggest compression
occurs in this area.
the following rules apply when choosing a pad:
of the pad shape
|The steeper or pointed the shape of the pad,
the harder and bigger the volume, the better the printing result.
||When printing uneven parts, the selection
of the right pad shape and pad hardness (see Shore-A) determines
the quality of the print image and the print speed.
||Certain cliché types require the
use of steeper pad shapes in higher Shore-A areas depending
on the etching depth and / or the halftone.