User's instructions for the relief press VPLMR-80x100
Moveable under platen and manually driven hydraulic pump
The image above shows a section of a part of the VPLMR-80x100. These instructions are only intended for use of the platens which is almost the same as the use of the SVP-35.
This press is fitted with a manually driven hydraulic pump. If the lever of this pump is moved up- and downwards (relief valve closed) the top platen will move downwards. This happes relatively quickly, because pump displaces a large volume of oil at a low pressure. As soon as the platen touches the forme, the pressure in the system increases and the pump will switch automatically to the high pressure mode (700 bar). In this mode the vertical movement of the top platen is very slow. As soon as the print has been made, the relief valve is opened and the top platen moves upwards. The vertcal movement is limited to approximately 14 cm. In order to increase work speed, it is advisable to stop the vertical movement after a few cm's. For this purpose two threaded bars are fitted next to the hydraulic cylinder. These bars can be adjusted in height and serve as a stop for the vertical movement of the top platen.
Almost anything can be used as a printing forme; composed lead characters, woodcut, lino-cut, cliché, etc.
The paper is laid down on the inked forme. On top of that a PVC plate of approx. 5mm thick is placed, and on top of that a layer of felt. On the image a steel edge is shown, fixed with screws on the lower platen. These edges are normally not provided by Polymetaal. These edges come in handy if a forme has to be locked in. (woodcuts + typography, etc.). We can supply them on demand.
No forme is perfectly plane. If you make a print of such a form it shows that some parts received the ink more than other parts. The felt compensates for small deviations in the forme. The felt however may never touch the paper directly because it can lead to a transfer of the ink to the paper from lower parts in the forme. In order to avoid this from happening a layer of 5mm thick PVC is placed between the paper and the felt. PVC is flexible enough to adapt to deviations in the forme, but is avoids at the same time that the paper touched the hollows in the forme.