Sheet-fed Offset Printing Research Articles

Influence of selected sheet-fed offset printing conditions on primary mottling

Influence of selected sheet-fed offset printing conditions on primary mottling

Comparative analysis of print contrast of hybrid modulated digitally modulated screening on different grades of paper

Information technology and Innovation has transformed our life; the same is true for printing. Screening technology has developed and become highly advanced during past few decades. The aim of this research is to identify the significant difference in print contrast between hybrid modulated (XM) digitally modulated (DM) screening on different grades of paper printed by sheet-fed offset printing process. Samples sheets are printed with same solid ink density to make valid comparison. Around 150 sheets are printed to achieve target solid ink density value (+ 0.05) during printing. After the density values are attained in accordance with standard SID values, next 50 sample sheets are printed, measured and evaluated.Information Technology and Innovation has transformed our life and same is true for printing also. Screening Technology has developed and become highly advanced during past few decades. The aim of this research is to identify the significant difference in print contrast between Hybrid Modulated (XM) & Digitally Modulated (DM) Screening on different grades of paper printed by sheet-fed offset printing process. Samples sheets are printed with same solid ink density to make valid comparison. During printing, around 150 sheets are printed to achieve target Solid Ink Density value (+ 0.05). After the density values are attained in accordance with standard SID values, next 50 sample sheets are printed, measured and evaluated.

Comparative study of delta e of hybrid modulated and digitally modulated screening on different grades of paper

Screening technology has become highly advanced during past few decades. This research emphasizes on the use of hybrid modulated(XMS) and digitally modulated screening (DMS) on different grades of paper for evaluating quality parameter. The purpose of thisresearch is to determine the significant differences that exist in measurable print attribute Delta E at 25%, 50% and 75% tint printed bymulticolor sheet-fed offset printing process using XM and DM screening. The experiment is conducted using FOGRA39/ PSO standard.The master of 44.5×29.5 cm output is prepared by incorporating quality measuring parameters and printed in KCMY color sequenceon different paper types by RYOBI 524HX Sheet fed offset process using XM and DM screening technologies. During test, around 150sheets were printed to achieve target Solid Ink density value (+ 0.05). Once the density values were achieved according to standard SIDvalues, next 50 sheets were printed, measured and evaluated. Delta E is used to determine the color difference perceived by humaneye. The color values are specified in the Lab color space. To achieve quality in printing the grey component must be adjusted so thatchromatic CMY values are matched with achromatic in print (grey balance correction).

Comparative Colour Gamut Analysis Of Piezoelectric Inkjet (PIJ) And Sheet-Fed Offset Prinitng Technologies

This paper presents a comprehensive comparative analysis of the colour gamut achieved by Piezoelectric Inkjet (PIJ) and Sheet-Fed Offset printing technologies. The colour gamut, a crucial aspect of print quality, is a measure of the range of colours a printing process can reproduce. Both PIJ and Sheet-Fed Offset printing are widely employed in various industries, including graphic arts and commercial printing. The research methodology involves the characterization of the colour gamut of PIJ and Sheet-Fed Offset printing through empirical experiments and spectral measurements. A diverse set of colour targets is used to assess the gamut volume, including standard colorimetric tests such as colour gamut volume measurements. The study also considers factors such as substrate type, ink formulations, and printing conditions to provide a comprehensive understanding of the gamut limitations and advantages of each technology. Results reveal the strengths and weaknesses of both printing methods in terms of colour reproduction, highlighting areas where one technology may outperform the other. Insights gained from this comparative analysis can inform decision-making processes for print industry professionals, helping them choose the most suitable printing technology based on specific project requirements and desired colour outcomes. Ultimately, this research contributes valuable knowledge to the ongoing discourse on print technology selection, aiding in the optimization of colour reproduction processes for diverse applications ranging from high-quality graphics to commercial printing.

A Study on the Assessment of Quality of Printed Sheets in Offset Sheet-Fed Printing

The quality parameters of printed sheets should be controlled constantly during the sheet-fed offset printing process. This allows the detection of any problems in the initial stages of the printing process. The final control of the quality of printing sheets will eliminate error products before delivering to the costumers. The results of this control should be analyzed continuously. The total quality management (TQM) is an effective method in controlling, doing statistics, and assessing the errors in the offset printing process. Simultaneously, this method delivers the main errors frequently occurred in the printing process. This paper presents the possibility of using some tools of the TQM method such as Pareto chart, Ishikawa diagram, and 5xWhy to analyze and assess the quality of printing sheets in sheet-fed offset printing. The studied results show that the two main errors of the printed sheets are hickeys (occupied 29 %) and low density (occupied 17%). Moreover, the causes of hickey error are analyzed and shown in this paper.

STUDY OF WETTING ON THE NON-IMAGE AREA OF OFFSET PRINTING PLATES BY AN ALTERNATIVE ISO-PROPYL ALCOHOL-FREE FOUNTAIN SOLUTION

In this study, an alternative aqueous isopropyl alcohol-free fountain solution for sheet-fed offset printing is prepared comprising 5 w/w% McIlvaine's buffer system for pH control, 0.3 w/w% Polysorbate 80 as a surfactant, 1 w/w% magnesium nitrate hexahydrate as a conductivity agent and 10 w/w% ethylene glycol mono-butyl ether as an additional wetting agent. The percentages of each composition are w/w% of active and then adjusted to 100 w/w% by adding distilled water. The contact angles of the obtained fountain solution on non-image areas of three common offset printing plates: CTP plate of Kodak, CTP plate of Huaguang Graphic Co. Ltd (China), and CTP plate of Mylan Printing Media Co. Ltd (Vietnam), range from 10° to 20°.The surface tension, conductivity, pH and viscosity were found to be 30.5 mN/m, 1.45 mS/cm, 4.8, and 1.05 x 10-2 g/cm.s, respectively. In comparison to the commercial fountain solution (KF – Trade Mark (China) containing isopropyl alcohol (IPA), the obtained fountain solution shows similar wettability on the non-image area of the offset printing plate whilst having similar physico-chemical parameters. The results indicate that ethylene glycol mono-butyl ether could be a potential substitute for IPA in fountain solution in offset printing, and the obtained fountain solution displays suitable properties for the offset printing process.

Dermatite de Contato Alérgica à Colofónia em operador de impressões gráficas- Caso Clínico

INTRODUCTION Colophony is a complex mixture of over one hundred compounds, resulting from the distillation of oleoresin, obtained from plants belonging to Pinaceae (mainly Pinus genus). The main allergens are the rosin oxidation products (unmodified and modified), as well as some of the new resin acids synthesized during their modification. It has numerous domestic or industrial applications, and exposure to these compounds is practically universal. We report a case of an occupational allergic contact dermatitis to colophony. CASE REPORT A 41-year-old caucasian male, graphic print operator for twenty one years, was referred to the Dermatology Department of Hospital de Braga, due to erythematodesquamative lesions, located on the back and lateral side of the hands, with aggravation during the professional activity. His personal history was negative for allergic rhinitis, asthma and allergy to particular foods or drugs. These lesions have evolved chronically for about ten years, yielding to the topical application of corticosteroids. In the workplace, he is responsible to makes ready and operates sheet-fed offset printing press, that is, calibrates the equipment, fills ink and dampening solution fountains, examines printed copy for ink density and makes adjustments, sometimes without the proper use of personal protective equipment. The patient reported improvement of symptomatology with prolonged withdrawal from the workplace. After resolution of symptoms, patch tests were carried out with the baseline standard Portuguese Contact Dermatitis Research Group series and a rubber series. A positive reaction was achieved to colophony (++) and abietic acid (++) at 72 and 96 hours. After checking the safety data sheets of printing inks and direct contact with their manufacturer, it was possible to confirm the presence of rosin derivatives. Later, the pathology was assumed as an Occupational Disease. DISCUSSION/CONCLUSION In printing ink industry, colophony and its derivatives are mainly used as colour carrier of the ink and to increase its adhesion to paper. In this worker, it was assumed a causal relationship between the exposure to the colophony present in the printing inks and the diagnosed of contact dermatitis. In this case, the implementation of collective protective measures as well as the use of personal protective equipment at work, its necessary to protect the user against health or the safety risk. It includes items such as nitrile gloves, protective clothing, a particle mask or respirator and the use of safety goggles. It is necessary to be aware of this etiology so that, in these workers, an early diagnosis can be made with the recommendation of appropriate protective measures.

The influence of micro and macro porosity of paper on wet repellence mottling in offset printing

Fountain solution induced mottling in offset printing manifests as non-homogenous printing area with optical variation has several influencing factors. One mechanism is that the fountain solution from the previous printing unit has no time to absorb into the coating before ink transfer or the ink cannot emulsify the water and stays on top of the ink surface as an additional hydrophilic layer. In paper coating development, the paper chemistry influences the surface chemistry features of the ink-paper coating interaction and can cause water repellency. Porosity and the absorbing capacity of paper and its coating is of great importance to avoid press related problems. In this paper, we have examined paper substrates which were reported to cause wet repellence mottling and tested their porosity ratio of micro and macro pores and their water/ink absorption properties. The micro macro porosity was determined by using easy and low-cost proprietary technique for the porosity ratio determination. We have measured ink stabilization values, penetration dynamics, wet repellence mottling and micro and macro porosity on paper samples printed with laboratory sheet-fed offset printing. We have found that the lower number of macropores and non-optimal micro and macropore distribution influenced the occurrence of water induced wet repellence and lowered the optical homogeneity of the samples.

Software for Quantitative Estimation of Coefficients of Ink Transfer on the Printed Substrate in Offset Printing

In the framework of standardizing the process of offset printing, one of the most important tasks is the correct selection of the printing system components, taking into account the features of their interaction and behavior in the printing process. The program allows to calculate the transfer of ink on the printed material between the contacting cylindrical surfaces of the sheet-fed offset printing apparatus with the boundaries deformation. A distinctive feature of this software product is the modeling of the liquid flow having free boundaries and causing deformation of solid boundaries when flowing between the walls of two cylinders.

Influence of Ink Viscosity Level on Tone Value Increase in Sheet-Fed Offset Printing

Purpose - Dot gain is caused by ink spreading around halftone dots. Several factors can contribute to the increase in halftone dot area. As printing pressure can squeeze the ink out of its dot shape causing gain, ink viscosity is a contributing factor with coated papers, higher viscosity inks can resist the pressure better than lowest viscosity ink. Halftone dots can also be surrounded by a small circumference of ink. Each halftone dot has a microscopic relief, and ink will fall off the edge before being eliminated entirely by the fountain solution in the case of sheet-fed offset printing. The lithographic inks behavior necessitates viscosity measurement over the full range of shear rates that inks can encounter in use, this range is very wide since very low shear rates are encountered in removing ink from the can and in the ink duct, whereas exceedingly high rates of shear exist in the roller nips of fast running presses. The aim of this research is to determine the influence of the different ink viscosity levels on tone value increase of final prints in sheet-fed offset printing. Design/Methodology/Approach - Three different ink viscosity levels were used with each inking system on each printing unit, to examine tone value increase (dot gain) for sheet-fed offset printing process, measured on matte-coated paper prints. The analysis of tone values results in order to determine their dependency on ink viscosity level and which viscosity level generates the best print reproduction for the tone values. Findings - Applied ink viscosity levels influenced tone value, as well as that there was no clear trends of how print quality degrades or improve with the same ink viscosity change for tone value. Obtained mechanical dot gain values on the plates show that all tone values are reproduced correctly, without bigger increases. Taking into account ISO 12647-2:2004 standard, and reference TVI values for the prints, the most appropriate TVI values were achieved by using different ink viscosity levels for different inks, low ink viscosity level produced the best TVI values for magenta ink, normal ink viscosity level showed as a best option for cyan and yellow inks, while high ink viscosity level generated the best results for black ink.

INFLUENCE OF PRINTING MICROCLIMATE PARAMETERS ON ISOPROPYL ALCOHOL EMISSION

The concentrations of isopropyl alcohol were monitored during the working time (8 hours) in three different printing plants (two sheet-fed offset and one digital) in Novi Sad, Serbia, using portable gas chromatograph. The concentration levels were below the recommended limits by the U.S. National Institute for Occupational Safety and Health. Unequal presence of isopropyl alcohol in printing plants involved a multiple linear regression analysis of microclimate parameters using program ORIGIN 5.0. The results of multiple linear regression confirmed that the microclimate conditions in the digital printing plant generate the lowest values of isopropyl alcohol concentrations due to the installed ventilation fans in comparison with other two sheet-fed offset printing plants. Multiple regression models can be evaluated to predict the values for total isopropyl alcohol concentrations due to the humidity, temperature and light intensity.

Statistical Consideration of Uncertainties in Bolted Joints of the Drive Train of Sheet-Fed Offset Printing Presses

This paper outlines a design process for the bolted joints of the drive train of sheet-fed offset printing presses incorporating statistical data and methods. Sheet-fed offset printing presses are driven by a continuous geared drive train along the length of the press. The bolted joints of the drive train connecting the gears to the cylinders of the press are subjected to high loads, especially during emergency stops. A nonlinear mechanical model of a printing press implemented in Matlab/Simulink is presented which is used to calculate the occurring loads. Measurements of linear and nonlinear system response are presented to support the quality of the mechanical model. The bolted joints between the main drive train gears and cylinders are designed according to current standards. Statistical information based on experimental data is considered during the application of the standardized method. Using the Monte Carlo technique, a more exact description of the joint’s strength is made possible. In this way, the maximum tolerable load for the screw connection is 16% higher than the same result from a standard worst-case calculation.

Life cycle assessment for printed newspapers in Northwestern Mexico

This paper aims to present the relevant results of a Life Cycle Assessment (LCA) study conducted on printed matter under a sheet-fed offset printing process by a company located in northwestern Mexico. Different scenarios were simulated in order to support decisions related to the improvement of environmental performance along the production processes. The study design was based on the European Platform on Life Cycle Assessment (EPLCA), which is in line with the ISO 14040 and 14044:2006 standards on LCA. The scope of the study was cradle-to-gate, with emphasis on the production of printed matter. The method chosen for the impact assessment was Impact 2002+ with a combined midpoint–damage approach. The results of the study showed that the major contributors to adverse effects were, primarily electricity consumption followed by paper consumption during the printing operation, as well as consumption of ink to a small degree. As for the plate-making operation along with the generation of secondary products, the result was negative. This is essentially due to involvement of recyclable materials, thus contributing to the prevention of raw material extraction. The smallest impact was observed from processes involving cleaning products and LP gas. The main issues of concern stemming from the results are electricity consumption and printing – both activities dominate almost all the midpoint categories. Generation of secondary products also had a relative environmental impact along the supply chain. Cleaning agents and LP gas did not have a significant impact on the final results of the process.

Studies on Treatment of Waste Fountain Solution from Sheet-Fed Offset Printing

This article explores treatment method of waste fountain solution from sheet-fed offset printing. First calcium chlorate is used to have a oxidation treatment for the waste water, then it is dealt with composite coagulants polyaluminium chloride (PAC) and cation polyacrylamide (CPAM) under different pH value. The results show that quality of the waste fountain solution could reach the national second-grade standard of sewage comprehensive discharge through the above treatment (GB 8978--1996) when treating with 0.7 g/L calcium hypochlorite and then sinking with PAC 4.0 g/L, CPAM 75.0 mg/L under the pH value of 8.0 for about 10 minutes. With the optimum treatment conditions removal rates of COD, ammonia nitrogen, phosphate and hexavalent chromium are above 90%, 94%, near to 98% and above 99% respectively.

In-line monitoring of the conversion in UV-cured printed layers by NIR spectroscopy in an offset printing press

In this study, it was demonstrated that the conversion in printed layers of UV-cured printing inks and varnishes can be determined in-line in a printing press by NIR reflection spectroscopy supported by chemometric methods. Layers were printed with a thickness of ∼1.2 g m−2 for a printing ink and ∼2.8 g m−2 for a printing varnish. Quantitative analysis of the spectral data was carried out with calibration models based on the partial least squares (PLS) algorithm. In-line monitoring tests were performed at a large-scale sheet-fed offset printing press in order to evaluate the predicting performance of the calibration models under process conditions. Different conversions in the layers were induced by variation of the irradiation dose. The predicting errors were 4.5% for the ink and 4.0% for the varnish. The printing speed was found to have no significant influence on the precision of the measurements.

A Framework for Optimised Design of Serrations on a Printing Gripper.

Serrations on a printing gripper, significant for ensuring the register accuracy in sheet-fed offset printing machines, have to sustain severe contact stresses. Poorly designed serrations can have an adverse effect on its life and performance. However, literature on the design of serrations on a gripper is scarce. In this study, using analytical solutions, we have developed an optimization framework that can help to quickly arrive at design solutions to maximize the durability and performance of a serrated printing gripper. Although the analysis is done in the context of printing grippers, it provides a methodology for development of design optimization frameworks for similar grippers.

Impact of local variation in coating structure on uniformity in print gloss

Point-to-point variation in the gloss of a print has been reported to be one of the most visually disturbing aspects of a printed paper. This work sought to determine the effect of pigment and binder content on the coating structure, surface properties, and print gloss variations occurring in a printed offset paper. The results from a pilot coating and full-scale sheet-fed offset printing trial are reported, with special emphasis on uniformity in print gloss. The effect of calendering and print impression also was considered. Uniformity in print was analyzed in terms of print gloss variation (PGV) in the heavily inked areas. Calendering and point-to-point variation in coating porosity had a significant effect on PGV. The observed nonuniformity in print is discussed in terms of local variations in coating porosity and local variation in coating micro-roughness. Under the conditions investigated, uniformity in surface porosity decreased with increasing latex content, but increased with clay content.

An Investigation of the Problem of Ink Peeling in Sheet-fed Offset Printing on Gloss-coated Paper

An Investigation of the Problem of Ink Peeling in Sheet-fed Offset Printing on Gloss-coated Paper

Trends of Sheet-fed Offset Presses: On-demand Technology and Power-saving UV

Trends of Sheet-fed Offset Presses: On-demand Technology and Power-saving UV

Influence of topcoat pigment particle size distribution on tail-edge pick resistance in sheet-fed offset printing

This paper describes ground calcium carbonate pigment particle size distribution and its influence on the tail-edge picking of pilot-coated paper as determined in full-scale sheet-fed offset printing. A tailor-made method was developed using a modified printing plate and high-tack inks to assess surface strength in terms of edge picking. In addition to the type, fineness, and particle size distribution of the ground calcium carbonate pigment, we also evaluated the solids content of the coating color, binder level, clay usage, and calendering. The printing test method provided differentiation relative to the investigated parameters, and it was possible to correlate these results with laboratory test data on ink-coating interaction and mercury intrusion porosimetry. Maximizing the solids content of the formulation to some extent compensated for the loss of pick resistance that followed binder reduction. Other laboratory tests showed poor correlation with the observed degree of edge picking.