| The offset press is the most widely used printing machine with high precision, highspeed, and better printing quality in the printing industry. Because the offset presseshave the most complex structure in printing machines and high quality requirements foroffset printing goods, operating the offset press relies heavily on the captain’s long-termexperience accumulation. Therefore, in order to improve the automation and intelligentlevel of offset printing machine, to develop the online printing quality measurement andcontrol system for offset printing machine has become the industry consensus.However, the true offset online printing quality measurement and control system isvery difficult to actualize, facing a lot of technology barriers. This paper deeplyinvestigated the ways to break some technology barriers on offset printingquality online measurement and control technology as follows.1) The types of offset printing quality online measurement and control system wereanalyzed, and the technical characteristics on online measurement and control systemsummarized. The status quo on this research at home and abroad was discussed. So themain contents of the thesis are determined based on defects in the present research.2) The method to remove the illumination effect on chromatic aberration ofscanning image from online print was studied. To improve the performance of algorithm,Retinex algorithm is transformed from the RGB color space to the L*a*b*colorspace, then the method of weighted least squares filter is used to process collectedimage information. From the experimental results, this method is good to removal theenvironmental light effect on scanning image for its obvious color reduction and detailenhancement effect.3) The study on application of Statistical Process Control (SPC) on offset printingquality online measurement and control system was conducted. The SPC onoffset printing quality was analyzed, and the flow chart of software design process wasprovided. And the SPC on the positioning accuracy of color accuracy in multi-coloroffset printing machine was build, and go through with the experimental test.4) A theoretical model and boundary conditions based on elastic hydrodynamiclubrication theory was built. Then the model was solved numerically by using the multigrid method, to discuss the impact on the printing press ink transfer in different pressing conditions. By analyzing the ink thickness in outlet zone under the common effect ofload and speed, the universal characteristic curve of offset press and the concept ofideal load range were obtained，which are significance guide to design and operateoffset press.5) In order to perfect and refine the offset ink transfer mechanism based on elastichydrodynamic lubrication theory, the following works was done: Using the method ofnumerical calculation, effect on offset ink transfer mechanism was researched by inkviscosity, ink temperature, offset blanket viscoelastic behavior and non-Newtonianfluids ink respectively.6) Experiments were carried out to study the offset ink transfer mechanism: theexperiments on offset blanket viscoelasticity and the experiments on offset printing inktransfer. The creep function of offset blanket was obtained by the first experiment. Andthe second experiment was used to verify and evaluate our theoretical results.The main innovations of the dissertation are as follows:1) A improved algorithm based on color constancy algorithm was presented.From the experimental results, the improved algorithm for the printing to remove the environmental light effects is effective.2) The application method of SPC on offset printing quality online measurementand control system was proposed. The experiment proves that the method is effective.3) A method to study the offset ink precise transfer rule in offset press wasproposed based on elastic hydrodynamic lubrication theory and usage the multigrid method to get the numerical solution.4) The universal characteristic curve of offset press was presented, which clarifiedthe puzzle that has confused the offset printing machine designers and the operatorsfrom the theory.5) The concept of ideal load range on offset press was obtained，which hasimportant significance to the design and guide the printing machine control, operation.The concept is expected to significantly reduce the control difficulty on offsetprinting machine.6) The theoretical formula of the offset blanket creep function and the experimentalmethod to get the offset blanket creep function were proposed. |
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