Printer having an aqueous ink drying system that attenuates image quality defects
A printer includes a drying unit that has a vacuum plenum and a drying belt with an exterior surface along which the media is transported through the drying unit. The drying belt has a plurality of holes extending through the drying belt, each hole in the plurality of holes having a diameter that is less than 300 microns. The drying unit further includes a heater configured to heat the media transported through the drying unit and a vacuum blower operably connected to the vacuum plenum. The vacuum blower is configured to generate a negative pressure in the vacuum plenum that holds the media on the exterior surface of the drying belt by the negative pressure acting through the plurality of holes without producing temperature differentials in the media on the belt that result in noticeable image quality defects.
1. A printer comprising:
a marking unit comprising at least one printhead configured to eject aqueous ink onto media moving in a process direction as the media passes the at least one printhead, the at least one printhead defines a maximum printing width in a cross-process direction;
a drying unit comprising:
a vacuum plenum;
a drying belt having an exterior surface over which the media is transported through the drying unit, the drying belt having a width in the cross-process direction that is greater than the maximum printing width in the cross-process direction and the exterior surface of the drying belt has a surface roughness Ra of less than 1 micron, the drying belt has a plurality of holes extending through the drying belt, each hole in the plurality of holes has a diameter that is less than 300 microns;
a heater configured to heat the media transported through the drying unit; and
a vacuum blower operably connected to the vacuum plenum and configured to generate a negative pressure in the vacuum plenum that holds the media on the exterior surface of the drying belt by the negative pressure acting on the media through the plurality of holes.
2. The printer of claim 1 wherein the surface roughness Ra of the exterior surface of the drying belt is approximately 0.5 microns.
3. The printer of claim 2 wherein each hole has a diameter of between 50 microns and 250 microns.
4. The printer of claim 3 wherein the drying belt is formed of polyimide or a polyamide-polyimide composite.
5. The printer of claim 4 wherein the drying belt has a thickness of between approximately 75 microns and approximately 200 microns.
6. The printer of claim 5 wherein the drying belt is uncoated.
7. The printer of claim 6 wherein the drying belt is tensioned to a force of at least 500 N.
8. The printer of claim 7 wherein the polyimide or the polyamide-polyimide composite is interspersed with at least one of an electrically conductive infrared absorbing particulate material and an electrically conductive non-infrared absorbing filler material.
9. The printer of claim 8 wherein the heater is an infrared heater that generates at least 10 kW of infrared energy directed at the exterior surface of the drying belt.
10. A drying unit for a printer comprising:
At least one printhead, the at least one printhead defining a maximum printing width in a cross-process direction;
a vacuum plenum;
a drying belt having an exterior surface over which media sheets are transported through the drying unit, the drying belt having a width in the cross-process direction that is greater than the maximum printing width and the exterior surface of the drying belt has a surface roughness Ra of less than 1 micron, the drying belt has a plurality of holes extending through the drying belt, each hole in the plurality of holes has a diameter that is less than 300 microns;
a heater configured to heat the media transported through the drying unit; and
a vacuum blower operably connected to the vacuum plenum and configured to generate a negative pressure in the vacuum plenum that holds the media on the exterior surface of the drying belt by the negative pressure acting on the media sheets through the plurality of holes.
11. The drying unit of claim 10 wherein each hole has a diameter of between 50 microns and 250 microns.
12. The drying unit of claim 11 wherein the drying belt is formed of polyimide or a polyamide-polyimide composite.
13. The drying unit of claim 12 wherein the drying belt has a thickness of between approximately 75 microns and approximately 200 microns.
14. The drying unit of claim 13 wherein the drying belt is uncoated.
15. The drying unit of claim 14 wherein the drying belt is tensioned to a force of at least 500 N.
16. A method of operating an aqueous ink printer comprising:
moving media in a process direction through a marking unit having at least one printhead configured to eject aqueous ink onto media moving in a process direction as the media passes the at least one printhead, the at least one printhead defining a maximum printing width in a cross-process direction;
ejecting aqueous ink onto the media using the at least one printhead;
transporting the media through a drying unit using a drying belt having a width in the cross-process direction that is greater than the maximum printing width, an exterior surface of the drying belt having a surface roughness Ra of less than 1 micron, and a plurality of holes extending through the drying belt, each hole in the plurality of holes having a diameter of less than 300 microns;
operating a vacuum blower operatively connected to a vacuum plenum to apply a negative pressure through the plurality of holes in the drying belt to retain the media on an exterior surface of the drying belt; and
heating the media with a heater as the media is transported through the drying unit to evaporate water or solvents in the aqueous ink.