MATERIAL DEVELOPMENTS FOR CIGARETTE PRINTING DIES

Pryor have provided Cigarette printing dies in high quality steels since the early 1960's. Traditionally O1/BO1 tool steel and BD3 tool steel have been used in the manufacture of dies.

BD3 tool steel has predominantly been used for dies that are to work with abrasive inks such as Gold. However, due its hardwearing nature, dies manufactured from this material are more difficult to machine and hence have always attracted a premium price over the more traditional O1/BO1 material.

It is important to understand that the most critical properties of a printing die are not only the quality of the inscription itself, but also the dynamic accuracy of the die blank. This last feature being critical, as it ensures accuracy around the die to provide consistent ink pick up as well as accurate running on today's high speed machines.

Our traditional tool steels are 'through' heat treated, in other words it attains the same hardness throughout the die blank. To achieve this the temperature of the steel has to be elevated to a temperature where micro-structural changes occur, this typically being within the range of 800 - 1000°C. These micro-structural changes cause the material to expand, altering the internal stresses, and then contract when the die is quenched. This means that some limited distortion will occur. However, through the selection of the most suitable material specifications, careful stress relieving before heat treatment and the use of a tightly controlled heat treatment process, these distortions are kept to a minimum.

As part of our commitment to innovation and product development Pryor, have over the last few years tested and evaluated printing dies manufactured from Nitriding (case hardened) steel.

Case hardening, is a process whereby only the surface of the printing die is hardened, as opposed to the conventional method where the whole die blank is hardened.

The advantages to our customers of using Nitriding steel for printing dies, is that a hard wearing durable printing die is still achieved, but with enhanced resistance to abrasive inks, better dimensional stability and better machinability than than BD3, enabling a lower price than a an equivalent BD3 die to be offered.

Nitriding is a specialised form of heat treatment, with the aim of the nitiriding process being to create a very hard surface for maximum wear resistance, whilst maintaining near perfect character integrity, as the engraved inscription does not move during the heat treatment process. This means that the process lends itself readily to extremely fine engraved products, where accuracy of inscription on the finished product is paramount.

The Nitriding process

The nitriding process requires steels to contain large amounts of Nitride formers - in the case of printing dies these are Chromium and Molybdenum- in order to form a shallow, but very hard surface layer.

The process is gas nitriding, whereby nitrogen is introduced into the surface layer of the die by holding in contact with a nitrogen rich gas at a temperature of 500°C for between 8 - 10 hours. This process produces a layer of iron nitrogen compounds, with nitrogen diffusing from this layer into the underlying steel to produce alloy nitrides, and by reaction with the carbon in the steel, carbonitrides. It is due to the low temperature of this process that there is minimal distortion of the inscription.

Dies in this material can be provided for:-

  • 2 Up (Station) - Molins Mk8, Hauni Garrant 4, Sigma, Decoufle Loga and Sasib.

  • 4 Up (Station) - Molins Mk9 and Mk8D, Hauni Protos 80/90, 6000, 7000, 8000,
    Decoufle Loga 2, Loga 3D, Passim

  • 8 Up (Station) - GD121, Hauni Protos 2

For further information or to discuss your needs in depth contact:

    David Smith
    Tel 00 44 (0)114 278 2223
    E-Mail d.smith@pryormarking.com
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