Roll press frame

Tile is manufactured in several ways. In each method, a continuous sheet is formed gauge refinement and planishing are carried out in subsequent calendering steps. Stresses that could lead to poor dimensional stability are avoided. The efforts to prevent stresses are governed by formulation, stock and roll temperatures, conveyor speeds, etc. After the final calendering, a resin—polymer—wax finish is applied to the surface of the sheet which is then buffed before it moves to the punch press. Frame scrap and tile rejected because of defects are returned to the mixers and recycled. 

Figure 274(a) depicts the drive system which was already part of the earliest machines (see Figure 225). More recent machines, instead of powering shaft (3) by transmission belts, apply a motor (5) with a torque-limiting clutch, a gear reducer (4), and a flexible coupling to drive gear shaft (3) mounted in or on the roller press frame. The gear on shaft (3) transmits torque to the coupled gears (2) on the roll shafts between two roller bodies (1).

Pressing Time, pressure and temperature Manual (clamps) roll or platen press. Cold or hot pressing Frames, autoclaves... 

All operations take place simultaneously in different stations. Sixteen stations were commonly used in earlier machines with outputs between 500 and 1000 TPM and tablet diameters up to 15 mm. Presses with outputs orders of magnitude greater than the above are now widely available. The dies are filled as they pass beneath a stationary feed frame, which may be fitted with paddles to aid material transfer. The die cavities are completely filled and excess ejected prior to compression. Compression involves the movement of both punches between compression rolls, in contrast to single station operations where only the upper punch effects compression. Ejection occurs as both punches are moved away from the die on cam tracks until the tablet is completely clear of the die, at which point it hits the edge of the feed frame and is knocked off the press. Tooling pressure may be exerted hydraulically, rather than through the use of mechanical camming actions, as is the case with machines produced by Courtoy. 

Procedure. Specimen Fabrication. The reinforcements were mixed into the polystyrene melt on a Farrell two-roll mill at 320°F. It was necessary to dry the asbestos fibers for 24 hr at 250°F prior to mixing to ensure the breakup of bundle aggregates. The milling/fluxing time was held to 8 min for all samples. The sheets obtained in milling were cut, crossplied, and compression molded in an open frame on a Wabash press. After they reached the platen temperature the material was held at 330 °F and 2000 psi for 6 min. The frame was then transferred to a cold press, and the sample was cooled under the same pressure. The test specimens were cut from ys-inch thick plates prepared in the foregoing manner. 

It is very important to achieve stiffness of the frames to maintain relative roll positioning (gap between the rollers), even at the highest separation (pressing)... 

Figure 265. Photograph of a roller press with hinged frame in the field, opened for roll removal/maintenance. (Courtesy of Koppern/Berzelius, Hattingen, FRG.) Note that the uneven wear on the roller (concave shape of working surface) is a reason for the need to exchange or, respectively, remachine the pressing tools...

So far, all machines that were presented used the mill shaft design in which the roller shafts are supported on both sides by bearings that are mounted in a frame. Another, relatively new design of roller presses uses cantilevered shafts and rolls. 

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