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1

Relationship in between compression of the rollers and contact area width and the clamp force

Jurkiewicz A., Pyryev Y.

Challenges of Modern Technology

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2013

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Vol. 4, no. 2

31--36

EN

In an offset printing machine the rollers (ink unit) and the cylinders (printing unit) are in contact in a lot of places. The contact surfaces comprise a metal surface and a rubber surface. As appears from findings based on the professional literature and experience of people working in printing houses the issue of contact between ink rollers and printing cylinders in an offset printing machine is of great importance. It has impact on the quality of printouts (generation of printouts errors), consumption of energy, time of making the printing machine ready for operation, wear of the machine’s components and related consumables like ink, dampening solution, paper, ink rollers, plate. During the theoretical studies, the equations were derived to show how the rollers compression depends on the contact area width and clamping force. The equations involve Young’s modulus and Poisson’s ratio of rollers’ materials. The difference between these equations and the so far existing equations has resulted from changing the place of applying the clamping force and involving Poisson’s ratio. The paper includes the comparison of the aforesaid new equations and those known from the literature. Moreover, the relationship in between the contact area width and the compression of metal roller and rubber-covered roller was subject to experimental attempts aimed at verification of the equation presented. In order to measure the rollers compression a clock sensor was used, and for measurement of the contact area width – a device called Roller Nip Control. The results of these measurements are presented in this paper and are compared with the results obtained from the equation derived in the course of theoretical studies using the analytical method.

2

Printouts' Quality Depending on Too Small Pressure of a Blanket Cylinder Against an Impression Cylinder and a Plate Cylinder in Offset Machine

Jurkiewicz A., Pyryev Y., Kowalczyk J.

Challenges of Modern Technology

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2013

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Vol. 4, no. 4

12--17

EN

It has been written in many books that correct setting of clamp in a printing offset machine has impact on wear of consumables and machine elements, and quality of printouts. However there has been no clear recipe to do that. In our article we present research on effect of too small pressure between a blanket cylinder against a plate cylinder and an impression cylinder. The challenge was to find method for gaining results of printing with different clamp but with the same printing conditions. During printing, especially when the printing machine stops and starts, a balance between ink and dampening solution is changing. To obtain the same printing conditions with different clamp on the blanket cylinder under blanket, there were fixed underlay sheets with the same thickness and width but different length. To reduce influence of variable thickness of glue the underlay sheets was glued to each other only on the one edge. We printed on two kind of papers: coated and uncoated. The amount of ink transported on paper was adjusted by changing rotation of the ink fountain roller. The spectrophotometer was used to measure optical density. The tone value increase was computed with Murray-Davies equation. While the tone value increase and optical density are very important printoutÂ parameters, our research shows how change of pressure changes printing quality. Our results also help to understand behavior of ink under pressure. Depending on paper and clamp ink could penetrate into the paper or spreads on the paper surface.

3

Analysis of pressure force between two cylinders

Jurkiewicz A., Pyryev Y.

Challenges of Modern Technology

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2012

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Vol. 3, no. 1

10--14

EN

Cylinders are very important elements in an offset printing machine because after being supplied with ink they transfer a printing image on paper. A type of setting as regards the stress between cylinders affects quality of printouts as well as rate of wear and tear of operating materials and machine’s elements. It is of great importance to provide for accurate calculation of stress force between two cylinders because this allows for setting an adequate contact zone width and cylinders indentation. In the printing unit of the offset machine there occurs contact between a metal cylinder and cylinder with fixed rubber blanket. The said blanket is composed of some layers, where one of them is a compressible layer. Therefore, the problem is not of trivial nature, as the blanket is made of a non-linear material.

4

Problems regarding stress between offset printing rollers

Jurkiewicz A., Pyryev Y.

Challenges of Modern Technology

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2011

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Vol. 2, no. 2

27--30

EN

At present, companies show particular care about quality and profit which are inherent with costs. An in adequately set stress between the printing rollers may significantly worsen the quality and increase costs of printing. Until now, a contact between rollers used to be set by a printer, where it was based on his experience. A width of the surface contact was measured or a distance between the form plate or the rubber to the bearer rings (rings made of hardened metal) was calculated. This paper includes a presentation regarding an attempt to solve the contact-related problems by way of mathematical methods.

5

Analysis of vibration of printing unit of offset printing press

Krzyżkowski J., Pyryev Y.

Challenges of Modern Technology

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2011

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Vol. 2, no. 2

31--34

EN

There are several causes of vibration of off set printing presses. Major are cyclic work of feeders and deliveries, gaps with mechanisms for fixing plate and blanket in cylinders of printing pair and inappropriate stress between those cylinders. All mentioned above causes increased exploitation of bearings, gears driving cylinders and other parts of the printing press. The consequences of vibration are also breaking of paper web and such artefacts as doubling and streaking on the prints. In this paper printing pair cylinders of lithographic printing press are described as a two-degree of freedom model. Solution of a system of differential equations, which describes this model shows influence of vibration of printing unit cylinders on the fluctuation of the ink film thickness on the prints (magnitude of streaking phenomenon).