In my journey through the field of hydraulic machinery, I have gained valuable insights into the working principle and classification of hydraulic machines. These machines operate based on Pascal’s law, which states that pressure applied to a confined fluid is transmitted equally in all directions, allowing for efficient force transmission. Understanding this fundamental principle is essential for anyone working with hydraulic systems. Additionally, I have explored the various classifications of hydraulic machines, each designed for specific applications in industries ranging from construction to manufacturing. In this article, I will share my findings on the working principle and classification of hydraulic machines, offering a clearer perspective on their functionality and uses.

●Hydraulic Machine Working Principle and Classification:

⒈Working Principle:

The basic working principle of the hydraulic press machine is the Pascal principle. It utilizes the pressure energy of the liquid, relies on static pressure to deform the workpiece, or presses the material.

As shown in the figure, two chambers with plungers or pistons filled with working fluid are connected by pipes. When the force acting on the small plunger is F1, an upward force F2 will be generated on the large plunger to force the deformation of the workpiece. And: 

F2 = F1 * A2 / A1. A1, A2 are the working area of the small plunger and the large plunger, respectively.

⒉Classification:

Classified by working medium:The working medium of the hydraulic machine is liquid. There are two main types. The emulsion is generally called a hydraulic press, and the oil is called a hydraulic press.

①Hydraulic press–Emulsifier is cheap, does not burn, and is not easy to pollute the work site. Therefore, the hydraulic machine with large fuel consumption and hot processing is mostly hydraulic press.

②Hydraulic press—In terms of anti-corrosion, anti-rust and lubrication properties, oil is superior to emulsion. However, the cost of oil is high and it is also easy to pollute the workplace.

●Characteristics and Application of Hydraulic ;ress:

⒈Advantage

①Easy to get maximum pressure.

②It is easy to get the maximum working stroke and can exert full pressure at any position of the stroke, which is suitable for occasions requiring a large working stroke.

③Easy to get a large work space.

④The pressure and speed can be easily adjusted steplessly in a wide range, and the pressure can be maintained for a long time in a certain stroke according to the process requirements. In addition, it also facilitates speed regulation and prevents overload.

⑤Designed, manufactured, operated and maintained for easy remote control and automation.

⒉Shortcomings:

①High precision requirements for hydraulic components. The structure is more complicated, and the adjustment and maintenance of the machine is more difficult.

②High-pressure liquids are easy to leak, which not only pollutes the working environment, but also wastes pressure oil, and there is a danger of fire in hot-processing places.

③The efficiency is low, and the movement speed is slow, which reduces the productivity. For the fast small press machine, it is not as simple and flexible as the crank press.

⒊Main Application Fields of Hydraulic Press:

①Stamping and drawing forming process of thin metal sheets. Mainly in the automotive, home appliance industry, the processing of metal cover parts.

②Pressure forming of metal mechanical parts. It mainly includes compression molding, extrusion of metal profiles, hot and cold die forging, and free forging.

③Press forming of non-metallic materials, such as SMC forming, automotive interior thermoforming, rubber products, and the like.

③Hot pressing of wood products. Such as plant fiber board. Hot pressing of profiles.

⑤Other apps. Such as press-fit, correction, plastic sealing, imprinting and other processes.