Publikationsserver der RWTH Aachen University
Reinigen von Tiefdruckzylindern mit Excimerlaserstrahlung
Abstract
dc:descriptionThe development of a new environmental aware process for the cleaning of rotogravuere cylinders is the subject of this work. Therefore the optimisation, monitoring and automatic control of the process has been acquired for the large-area cleaning of rotogravure cylinders by excimer laser radiation. It has been realized by the design of an autonomous automatic cleaning machine which is available for the industrial use. Basic research concerning the optical characteristics of different printing inks has shown the special qualification of UV-lasers for this ablation process due to the high absorption of thin layers of ink. Further experiments explore the influence of the accumulated fluence, the pulse repetition rate and the meaning of diffent excimer-wavelengths on the ablation result. Experimental results are used to build-up a self-contained cleaning machine especially for the laser cleaning of rotogravure cylinders. Rotogravure cylinders are handled rotating in this machine. Meanwhile the laser beam strikes radial onto the surface of the cylinder and moves in a parallel way to the axis of the cylinder. The optical beam guiding and shaping system is designed as a "flying optic". It includes a reflective beam homogenizer and a zoom objective to enable variation of the beam size. This optical system is meant to be a new development to allow the large-area cleaning of surface layers by excimer laser radiation. The treatment of original rotogravure cylinders in this cleaning machine has shown that a non-destructive and complete cleaning can be realized with cleaning rates between 2,4 and 11,8m²/h, depending on the colour tone and the layer thickness. In reality layer thicknesses are very inhomogeneous so that monitoring and processing control is necessary to reach complete cleaning on the whole surface of the cylinder. Monitoring is realized by an image processing unit including a colour picture evaluation for the identification of remaining ink. Cylinder cleaning is working in two steps. In the first step standard processing parameters are chosen by the control unit. During the treatment with standard parameters the video monitoring is recording the positions, dimensions and intensity of remaining ink. Positions of remaining ink are well directed approached and ablation is executed by adapted parameters within the second step which leads to complete cleaning. Cleaning process works automatically and beside the mouting of the cylinder the control only needs four input values of cylinder data from the operator. Compared to the investment for conventional cleaning technology (including disposal costs for cleaning solvents or abrasives) the costs for the laser cleaning process are competitive. In addition to that this process represents a progress within laser beam cleaning techonolgy and in the domain of material treatment by excimer lasers as a result of the high level of automation, the good quality of cleaning and further potential of development regarding new cleaning applications.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2001
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Birkel, Jörn
- Contributors dc:contributor
-
- Poprawe, Reinhart
Subjects
dc:subject × 7Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger