A RAM press is a mechanical device used to mold ceramic items using two-piece molds pressed together by a manually-, hydraulically-, or pneumatically-powered mechanism. The device consists of a static table mounted below the moving powered press. The molds used are in two parts, with the negative half of the mold typically being mounted on the static table and the positive portion on the press. A charge of de-aired clay is placed in the negative half of the mold and the press activated. The press then pushes the positive mold section into the clay, forcing it to fill the negative half, thereby developing an interior shape dictated by the positive mold, and an exterior shape that mirrors the negative mold.
The RAM press has been used to mold ceramic items from tableware to tiles since the mid-1940s. Invented by Ohio State University ceramic engineering graduates Keith Blackburn and Richard Steele, the RAM press utilizes a pressed two-part mold system. A negative female mold half is fixed on the lower table, or stage, part of the press. A positive male mold is attached to the moving upper part of the press, which is moved vertically by a ram powered by compressed gas or oil or by a manually-operated mechanism. Index pins and holes in the two mold halves ensure correct alignment during pressing.
When the RAM press is ready for a duty cycle, a suitably-sized piece of de-aired clay is placed in the female portion of the mold. The press is then cycled, forcing the male half of the mold into the hollow formed by the female mold. This action forces the clay to take the form of cavity between the male and female molds, thereby forming the semi-finished ceramic part. When the cycle is finished, the press and male mold is raised and excess material trimmed from the part, which is then removed from the RAM press.
The quality of the two halves of the mold dictate how much finishing is required after the part is removed from the press. Surface imperfections can be cut from the surface of the part or removed using a wet sponge depending on their severity. Once the part is finished, it may then be decorated, glazed, and finally fired. The RAM press can be used to produce complex shapes in a variety of sizes. Press cycle rates depend on a number of factors, with the average being 1,500 cycles in an eight-hour shift.
