All printers and print engineers understand how hot foil presses index hot foil. The principles of cold foil indexing are exactly the same which is to say the press needs to be off impression to be able to stop the foil and on impression where foil is applied. The electronics and software control of the system needs to allow a registered response to the changes in impression position. Together these controls allow accurate cold foil indexing as seen in the DGM Foildex system.
It has always been recognised that the most expensive part of cold foil application is the cold foil itself and the larger companies have each introduced their version of cold foil indexing, including Heidelberg, manroland and DGM to minimise this cost. The actual costs savings are job related but comparing to a past generation systems which use the equivalent of the circumference of the blanket cylinder for each sheet that passes irrespective of the amount of foil applied the Foildex system can reduce foil usage by up to 80% thereby saving 80% of the material cost. Further savings are made by the increase in productivity gained by less frequent foil roll changes. The production of less waste also has a positive environmental aspect on an already fully recyclable product.
The point of cold foil application is the enhancement of the printed substrate and to achieve this the perfect laydown of the cold foil is necessary. This is achieved by the precise and variable control of the foil tension. Variable control is absolutely necessary to maintain an even tension between, for instance, several narrow rolls against a single narrow roll against a single wide roll as each require a different torque to drive. A smooth foil laydown is essential for good overprinting, reduction of dust, reduction of piling and improvement in reflectability, which is what the printer’s customer is looking for – at the right price.