Claims
- 1. A method of making a printing member for a press with dampening comprising the steps of:
- forming a metal body with an exposed surface of chromium metal having a grained surface structure with capillaries making said surface hydrophilic, and
- heating without contact said surface at selected image points thereon to transform the surface structure to render said surface nonwater-retaining at said image points.
- 2. The method defined in claim 1 and including the step of continuing said heating until molten chromium metal flows to and occupies said capillaries at said image points.
- 3. The method defined in claim 1 including forming said body as a laminate composed of a steel substrate with a chromium surface layer thereon.
- 4. The method defined in claim 1 including the step of forming said body as a flexible sheet which can engage around a print cylinder.
- 5. The method defined in claim 1 including the step of forming said body as a rigid cylinder having a cylindrical surface of chromium metal.
- 6. The method defined in claim 1 including the step of heating said surface by spacing said surface opposite a point electrode and establishing a potential difference between said electrode and said body at said image points so as to produce spark discharges between said electrode and said surface at said image points.
- 7. The method defined in claim 6 including the step of producing said spark discharges by applying momentary voltage pulses image-wise between said electrode and said body so that a multiplicity of image-representing nonwater-retaining spots are formed on the otherwise hydrophilic body surface.
- 8. The method defined in claim 7 and including the step of pulsing said electrode positive relative to said body.
- 9. The method defined in claim 1 including the steps of
- coating said surface with waterless ink after said surface is heated at said selected image points;
- applying dampening liquid to the coated surface to dislodge the ink from said surface except at said image points thereon thereby leaving ink spots at said image points, and
- setting said ink spots.
- 10. The method defined in claim 9 including the steps of
- selecting a radiation curable ink; and
- applying radiation to said ink spots to set same.
- 11. A printing member for a press with dampening comprising
- a metal body with an exposed surface of chromium metal having a grained surface structure with capillaries making said surface hydrophilic, selected image points on said body surface having a non-impacted heat-treated surface structure which renders said surface hydrophobic at said image points.
- 12. The printing member defined in claim 11 wherein said body comprises a laminate composed of a steel plate with a chromium surface layer.
- 13. The printing member defined in claim 11 wherein said body is a flexible member which can extend around a print cylinder.
- 14. The printing member defined in claim 11 wherein said body is a rigid cylinder and said surface is a cylindrical surface of said cylinder.
- 15. The printing member defined in claim 11 and further including a coating of waterless ink covering said transformed surface structure.
- 16. The printing member defined in claim 15 wherein said ink is a radiation curable ink.
RELATED APPLICATION
This application is a division of Ser. No. 234,475, filed Aug. 19, 1988, now U.S. Pat. No. 4,911,075.
US Referenced Citations (4)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0132293 |
Oct 1980 |
JPX |
1480081 |
Jul 1977 |
GBX |
Divisions (1)
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Number |
Date |
Country |
Parent |
234475 |
Aug 1988 |
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