Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C1/00—Forme preparation
  • B41C1/006—Forme preparation the relief or intaglio pattern being obtained by abrasive means, e.g. by sandblasting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N3/00—Preparing for use and conserving printing surfaces
  • B41N3/04—Graining or abrasion by mechanical means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B5/00—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor
  • B24B5/02—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor involving centres or chucks for holding work
  • B24B5/04—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor involving centres or chucks for holding work for grinding cylindrical surfaces externally

Definitions

• the invention relates to a grinding method for printing plates in the flexo or high-pressure region according to the preamble of claim 1.
• elastomeric flexographic printing plates are ground for this purpose on cylindrical grinding machines; the removal of the elastomeric material is found here e.g. by means of a grindstone instead.
• a grindstone or a grinding wheel is used. In this way, based on the width of the grindstone or the grinding wheel, a selective removal of the material by grinding.
• the grinding is always carried out after the vulcanization of the mixture of elastomeric material, so this is fully reacted and can be machined removing.
• the grinding can be carried out in one or more operations.
• the disadvantage here is that it is hard, soot-filled elastomeric rubber compounds (black mixtures), for example, EPDM (ethylene-propylene-diene monomer or ethylene-propylene-diene rubber) having a Shore A hardness of about 45 ShA Due to the very highly cross-linked mixture, there are always oscillations in the grinding machine. These vibrations can swell and strengthen and then show up as chatter marks or even vibration marks in the microsection, ie on the surface of the printing plate. This inhomogeneous micrograph is visible in the paint and in the ink transfer and thus represents a quality defect.
• EPDM ethylene-propylene-diene monomer or ethylene-propylene-diene rubber
• the WO 01/87600 A2 relates to a method for producing a printing plate, in particular for flexographic printing.
• a layer of a curable elastomer is applied to a carrier with a cylindrical surface, then cured the elastomer layer on the support to a substantially cylindrical endless printing block blank and optionally ground to a cylindrical peripheral shape or otherwise processed.
• the printing block blank is separated along a line running substantially parallel to the axial direction of the carrier and the printing plate thus produced is removed from the lateral surface of the carrier.
• the printing block blank for example, by grinding an elastomer layer brought to the desired thickness and thereby produced with a flat and smooth surface.
• the object of the present invention is to provide a grinding method of the type described in the introduction with which flexographic or high-pressure molding with both a hard, soot-filled laserable (Shore A hardness of more than about 45 ShA) and a soft ( Shore A hardness of less than about 45 ShA) surface of elastomer material alike with a low tolerance, preferably of about +/- 0.015 mm over the entire width can be ground as economically as possible to a uniform microsection.
• the present invention relates to a grinding method for printing plates in the flexo or high pressure range, preferably by means of a belt or cylindrical grinding machine, wherein the material to be ground is an elastomeric material or an elastomeric material, which is characterized in that the grinding is carried out over a grinding belt or abrasive paper and the abrasive belt or sandpaper moves at a speed at least five times faster than the feed of the material to be ground.
• the grinding of surfaces of the printing plates by means of grindstone or grinding wheel, ie by means of punctual abrasion is common and known. However, this removal is not yet surface, for example by means of an abrasive belt or sandpaper.
• the performance of the grinding process is determined by a number of parameters and constraints that affect the result of the grinding process, essentially the surface finish of the surface to be ground after the grinding process.
• the present invention is based on the finding that a task-appropriate surface finish just by the use of a surface removal in combination with a certain ratio of feed rate of the abrasive belt or abrasive paper or the like to the feed rate of the material to be ground can be achieved.
• the sanding belt or sandpaper is moved at a speed at least five times faster than the feed of the material to be sanded.
• a hard, soot-filled laserable (Shore A hardness of about 45 ShA) and a soft (Shore A hardness of less than about 45 ShA) surface of elastomeric material produces a uniform grinding pattern, which has a low tolerance of preferably about +/- 0.015 mm.
• a uniform homogeneous surface expression with a good ink transfer and a low color build-up on the rubber surface of the printing plate can be achieved.
• the grinding method according to the invention is economical, since at such a speed ratio, the method can be performed relatively quickly. As a result, the cost of inventively ground printing plates can be kept low.
• the speed of the printing material to be ground is at least about 1 m / min, preferably at most about 6 m / min, and the speed of the sanding belt or sandpaper is at least about 10 m / s, i. about 600 m / min.
• the speed of the abrasive belt or paper is at least about 600 times higher than the feed of the material to be ground.
• the speed of the printing material to be ground is about 1 m / min, preferably at most about 6 m / min, and the speed of the sanding belt or sandpaper at least about 20 m / s, ie about 1,200 m / min.
• the speed of the abrasive belt or paper is at least about 1,200 times higher than the feed of the material to be ground.
• the grain size of the abrasive belt or abrasive paper is at least about 240 mesh.
• the grinding width is greater than about 0.5 mm and less than about 20 mm.
• the grinding width also called Nippbach, or contact surface is understood the width in which the abrasive belt or sandpaper is in engagement with the material.
• a roll width of the material to be ground e.g. about 2,000 mm, i. Approximately 2 m, the Nippbach results over the extent of the delivery of abrasive belt or sandpaper to material.
• This nip width multiplied by the roll width gives the contact area.
• the nip width should be greater than about 0.5 mm and less than about 20 mm, preferably equal to or greater than about 1 mm and less than or equal to about 10 mm. The nip width significantly influences the grinding thickness and the surface quality.
• the grinding is performed at an angle adjustment greater than about 0 ° and less than about 40 °.
• angle setting Assuming that the material to be ground is horizontal, then the winding with which the sanding belt or sandpaper dips into the material or leaves the material is significantly determining the surface quality. At the lowest point of the sanding belt or sandpaper then results in the grinding thickness. This angle adjustment may be different for different rubber compounds (hardnesses). An angle of greater than about 0 ° and less than about 40 ° has proved advantageous, preferably greater than about 0 ° and less than about 20 °.
• the task-related grinding results can be further improved with this angle adjustment. It can be generated in this way roughness of less than about 10 ym Rz.
• the back pressure is generated by means of a soft or compressible roller during grinding.
• Compressible grinding rollers have proven to be advantageous in order not to transmit vibrations or excitation frequencies from the grinding machine to the material to be ground. They thus act as a damping element.
• the grinding is carried out with a first step and a second step, wherein the speed of the abrasive belt or abrasive paper in the first step is greater than in the second step, and / or the roughness of the abrasive belt or abrasive paper in the first step is greater than the second step.
• the grinding size or the surface quality is determined in two grinding cycles.
• This is a pre-sanding with a fast Speed and a rough sandpaper of at least about 240 mesh and then a fine sanding (also called final sanding) at a slow speed and fine sandpaper of at least about 600 mesh.
• the pre-grinding and fine grinding process a thickness of at least about 0.02 mm to about 0.1 mm, preferably of at least about 0.5 mm to about 0.1 mm, particularly preferably of at least about 0.8 mm about 0.1 mm.
• the ground surface is polished by a subsequent step.
• Polishing is by a negative grinding angle at which the abrasive paper, as described above, slowly leaves the material to be ground at an angle of less than about 20 °.
• At least 80% of the roll width is ground in one operation.
• the roll width is to be understood as the width of the material to be processed.
• An operation is understood to mean a continuous process in which the sanding belt or abrasive paper engages with the material to be sanded and is machined continuously with a combination of parameters.
• the grinding cylinder is accelerated with the sandpaper to the desired speed, then the material is biased on the impression cylinder and only upon reaching the speed of the grinding cylinder and upon reaching the biasing material on the impression cylinder, the two cylinders are radially moved towards each other until, the abrasive paper with the desired and predetermined depth of engagement with the surface of the material to be ground is engaged.
• the grinding cylinder according to the invention with a speed at least five times higher than the counter-pressure cylinder (recording cylinder) with the printing form to be ground.
• the two cylinders can be moved further toward each other radially until the printing plate is ground down to the desired thickness.
• the speeds of both the grinding cylinder and the counter-pressure cylinder can be changed with the material to be ground, provided that the speed ratio according to the invention is maintained.
• the material is moved out of the engagement of the grinding cylinder again radially, stopped and then removed the printing plate from the impression cylinder.
• the ground printing plate can be polished in the same machine or on another machine.
• the printing plate together with impression cylinder is transferred from the grinding machine in the polishing machine to save a removal of the printing forme from one cylinder and the subsequent mounting on the next cylinder.
• the same machine may be used for grinding by replacing the grinding cylinder with a polishing cylinder or replacing the abrasive paper on the grinding cylinder with a finer tool.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Polishing Bodies And Polishing Tools (AREA)
• Printing Plates And Materials Therefor (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Grinding Of Cylindrical And Plane Surfaces (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=48986106

Family Applications (1)

Country Status (7)

Cited By (1)

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• 2012
  • 2012-09-26 DE DE102012109071.8A patent/DE102012109071A1/de not_active Withdrawn
• 2013
  • 2013-08-12 JP JP2015532347A patent/JP6234464B2/ja active Active
  • 2013-08-12 CN CN201380050394.5A patent/CN104684736A/zh active Pending
  • 2013-08-12 WO PCT/EP2013/066774 patent/WO2014048632A1/de active Application Filing
  • 2013-08-12 EP EP13750016.1A patent/EP2900479B1/de active Active
  • 2013-08-12 HU HUE13750016A patent/HUE031247T2/en unknown
• 2015
  • 2015-03-25 US US14/668,612 patent/US9434149B2/en active Active

Non-Patent Citations (1)

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