Mechanical extraction operations are generally similar to pretreatment workshops. Like pretreatment, many oil presses are fixed in the same building for pressing. In the crushing plant, oil seeds are subjected to extremely high heat and pressure to mechanically press the oil out of the oil-containing cells. Typical pressing processes include steaming, pressing, cooling and finishing of cakes, and filtration of oil.

As with most processes, the operations and layout of almost every plant are different. What follows is a general press operation. The reader is advised that there are many variations in this system design. In this general operation, the pressed kernels from the rolling mill enter the vertical stirred layered steaming and frying pan, where they are heated to denature the protein. After steaming and frying, the hot kernels enter the mechanical press, where they are pressed The enhanced mechanical pressure removes about 60% of the oil (nearly 90% of the oil can be obtained for full pressing operation). The cake passes through the end baffle, where high friction is exerted. The cake is baked and pressed, and is often very hard. The squeezed oil flows out through the drain bar of the press. After pressing, the cake is crushed and cooled, and the pre-pressed cake is usually sent to the solvent leaching workshop for final oil removal. If solvent leaching is not economically feasible, a higher proportion of oil must be squeezed out in the press shop (the so-called full press operation), and the cake is then used directly as animal feed. Since the material is subjected to high heat during operation, urease inactivation and protein denaturation naturally occur, making the product suitable for feeding purposes. The oil from a mechanical pressing operation usually contains a large amount of fines, which enter a screened storage tank and are subsequently removed in a blade or plate and frame filter press. This is done before the crude oil is sent to the refinery. Machine-pressed oil can be of higher quality than solvent-extracted oil because there are fewer oil-soluble impurities (such as phospholipids, etc.). In fact some pressed oils (such as olive oil or evening primrose oil) are suitable for direct use without further processing. The collected powder is generally recycled and sent back to the press.