Summary

Dummy plates, i.e. non-printing aluminium plates that are used on the parts of the plate cylinder not carrying any printing ink. Today, they account for up to one quarter of overall plate costs, and this share is expected to increase with the more widespread use of colour printing, especially on rotary presses designed for two-sided, four-colour printing. Therefore it is worthwhile to consider ways to achieve a more efficient use of dummy plates. It is with this objective that IFRA and NATS commissioned the Institute for Printing Technology of the Technical University Chemnitz-Zwickau to carry out a research project in early 1992. The proposal put forward by the scientists in Chemnitz, elaborated after many systematic tests and investigations, recommends that the thickness of the dummy plates should be reduced from 0.3 to 0.2 mm. The thinner plate can be locked-up more tightly and is subjected to less strain, therefore giving it a longer useful life. In practice, after repeated re-locking of the dummy plates, useful lives of up to 6 million cylinder revolutions were achieved. If the economies of high-grade aluminium obtained by reducing the plate thickness are calculated in terms of the global consumption, this will produce the impressive total of 1600 tonnes per annum, corresponding to an additional saving of 50 million kWh electrical energy. If the savings achieved by the repeated use of the dummy plates are included in the calculation, the total will be 4500 tonnes per annum, or 150 million kWh respectively - not taking into account the possible economies in the "wipe-on" plates market.