Jolt Machine - Molding Machine and Its Operation

In the jolting method, the flask is first filled with the molding sand and then the table supporting the flask is mechanically raised and dropped in succession. Due to the sudden change in inertia at the end of each fall, the sand gets packed and rammed. The action of raising and sudden dropping the table is called "jolting".

The principle of jolt molding machine in which the table 1, with the platen and flask 3 , filled with molding sand , is raised to 30 to 80 mm at short intervals by plunger 8 when the compressed air is admitted through the hose 9 and the channel 10. The air is next released through the opening 11 and the table drops down suddenly and strikes the guiding cylinder 12 at its bottom. This sudden action causes the sand to pack evenly around the pattern. Springs 13 are used to cushion the table blows and thus reduce noise and prevent destruction of the mechanism and the foundation.

The draw back in this method is that sand is rammed hardest at the parting plane and around the pattern remains the less dense in the top. This necessitates hand ramming of the mold at the back after the jolting action is completed. These machines are preferred for horizontal surfaces.

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