Mechanical appliance on a positive-locking die casting machine to adjust the mold height.
All positive-locking locking systems require mold height adjustment (construction height of the entire die casting mold parallel to the shot axis) to created the exact required mold locking force when the mold is closed. For this reason, the entire locking mechanism needs to be adjustable in its position along the shot axis. In modern machinery, the mold height is adjusted through its own drive working evenly on all four columns.
In general, two construction types proved to be effective where the mold height is either adjusted using a sprocket of using a worm shaft.
In case of mold height adjustment using a sprocket (Fig. 1), the tie bar nuts are used as adjusting nuts driven by a sprocket. The sprocket always remains in contact adjusting all four tie bar nuts at the same time and mechanically locking them. An execution example of mold height adjustment using a sprocket is illustrated in Fig. 2.
In case of mold height adjustment using a worm shaft, tie bar nuts have the form of worm gears (Fig. 3, Bühler AG). In most cases, two worms are on the same wave remaining in contact with two of the four tie bar nuts. Both worm shafts can be connected through a chain or a bevel drive. These worm gears perform the column gear and the shot plate guiding (joint shield), the machine component where the toggle lever system is highed.
Modern mold height adjustments of this type have a hydromotor drive including distance measuring systems end mechanical end position cut-offs as schematically displayed in Fig. 4 (Bühler AG). The mold height distance measuring occurs through pulse counting at the control limit switch. The cam plate drive by the hydraulic engine serves as pulse generator.
An execution example of mold height adjustment using a worm shaft is illustrated in Fig. 5. The detail image of the chain drive and the worm shaft including tie bar nuts are shown in Fig. 6 (Bühler AG).