The cold press oil machine is based on Pascal's law, which imposes a certain pressure on one of the pistons in the hydraulic system and must produce the same pressure increase on the other piston. The pressure is equal to the applied pressure divided by the area of force. If the area of the second piston is 5 times the area of the first piston, the pressure F2 acting on the second piston will increase to 5 times the pressure F1 on the first piston. The phenomenon can be used in oil extraction.
When the cold press oil machine presses oil, after the oil enters the horizontal hydraulic press, as the piston slowly advances, the pressure gradually increases, the oilseeds are continuously squeezed, and the oil seeds directly contact each other generate pressure. The plastic deformation of the oilseed material, the liquid grease is slowly extruded.
The remaining material after oil extraction is no longer a loose body, but a plastic body called a oil cake. In the press, since the temperature does not change much, the nutrients in the oil and fat are less damaged, and the protein is not denatured, so that the obtained oil and cake have high quality. This is because the horizontal hydraulic press adopts slow pressure and pressure during the preparation of grease, which can ensure that the heat generated during the pressing process can not be accumulated, the temperature rise is small, and the pressing process can keep the cold press cold. Therefore, the oil obtained by pressing is far higher than the national standard in terms of acid value, peroxide value and color.
The cold press oil machine has no protein damage during the pressing process, so the oil cake has high value and wide application range.

The design of the cold press oil machine is based on experience and less consideration of the pressing characteristics of the oil.
Shandong Leader Machinery's research on oil press characteristics mainly focuses on hardness and brittleness, oil moisture content, permeability and rheological properties, and obtained related patents.

(1) Hardness and brittleness.
Shandong Leader Machinery uses the cylindrical probe to compress the sample by placing the peanut kernel, rapeseed, flaxseed and perilla seed in the center of the TAXTPLUS physical property tester platform to obtain the hardness and brittleness of the sample.

The order of hardness and brittleness of the four oils is linseed > peanut kernel > rapeseed > perilla seed, which is determined by their basic components. Hardness and brittleness make it easier to establish pressure during pressing, which means that the same horizontal hydraulic press equipment is used in production. Under the same process conditions, the residual oil rate of rapeseed and perilla seed pressed cake should be higher than flaxseed. And the residual oil rate of the peanut kernel press cake. Similarly, if you want to reduce the residual oil rate of rapeseed and perilla seed pressed cake, you must increase the press pressure or reduce the thickness of the cake. This is a prerequisite for the precise design of the horizontal hydraulic press.

(2) Moisture content.
The Shandong Leader Machinery study found that as the moisture content of the material decreases, the residual oil rate of the pressed cake will also decrease. However, for perilla seeds and peanut kernels, when the water content of rapeseed and flaxseed is less than 3%, the residual oil rate of the pressed cake increases with the decrease of moisture content. This is because the moisture in the pressed oil is too low, and it is difficult to form the pressed oil.

(3) Permeability.
Based on the objective fact that the porosity changes with the crush stress during the actual pressing process, Shandong Leader Machinery established an exponential relationship between the permeability and the effective stress. Based on the fluid-solid coupling theory, the deformable rapeseed cake and rapeseed cake were established. Three-dimensional single-phase percolation differential equations. Youyan [7] established a one-dimensional percolation differential equation for deformable sesame and peanut and solved the analytical solution of one-dimensional constant coupling seepage problem according to fluid-solid coupling theory.

(4) Rheological properties.
Based on the creep test of sesame and peanut, Shandong Leader Machinery established a linear viscoelastic model of sesame and peanut using model theory. Based on the creep test of sesame and peanut, the artificial neural network method was used to establish the nonlinear rheological property recognition model of sesame and peanut. The recognition results show that the artificial neural network model can better simulate the nonlinearity of sesame and peanut. Rheological properties. The equilibrium compression time of sesame and peanut was determined using a creep curve that identified the simulation.
Shandong Leader Machinery used a combination of model theory and empirical model to establish a nonlinear viscoelastic-plastic constitutive model of rapeseed and rapeseed, and used the modified simulated annealing calculation method to invert the model parameters. The results show that the nonlinear viscoelastic constitutive model can better simulate the rheological properties of rapeseed and rapeseed.

Shandong Leader Machinery's research on oil properties provides a basis for the refinement of horizontal hydraulic presses, as well as the direction of increasing oil yield and making full use of limited oil resources. The study of these oil press characteristics was applied to the design of horizontal hydraulic presses.