9 Vacuum extruding press
The modeling material is now fed in the vacuum extruding press. The press is pouring out an endless cord of blanks and is eliminating even the last bubbles of air from the mass.
10 Cutting wire
The endless cord is then cut into individual tile blanks by a razor-sharp wire.
11 Revolving press
A conveyor system is supplying the unfinished tiles to a revolving press that is forming the final shape of the tile. The tile blanks are formed there under high pressure. In addition, the press is placed under DC current to ensure that the blank will come off the mould more easily. High-performance presses are forming 3,000 roofing tiles every hour.
The moulds to be worked with are made of various gypsum casting compounds in the factory-owned mould casting houses. The advanatge of the gypsum moulds consists in the fact that they are able to absorb eliminated water in the course of the pressing and thus to form a water film between the mould and the tile blank.
As enormous forces and friction act upon these moulds, they must be replaced several times a day.