Hydraulic system planning

1. Introduction
Fundamentally, hydraulic pressure is the transfer of force and energy through the static pressure of fluids. In the market, hydraulic systems are parallel with mechanical systems, electrical systems and pneumatic systems, and there is some competition. Hydraulic systems have many comparative advantages as well as some disadvantages.
Advantages of hydraulic system:
- Can transmit large forces in a small space;

- High energy density;

- Energy storage capacity;

- Infinite changes in the amount of exercise, such as speed, force and torque;

- Easy to implement force monitoring;

- Fast commutation due to small component mass (inertia);

- Quick operational response;

- Smooth movement (low vibration and noise);

- Wide transmission ratio;

- Easy conversion from rotation to linear motion and vice versa;

- Large design freedom in layout space;

- The drive input and output can be physically isolated through a line or hose;

- Automatic control of various forms of motion can be achieved through pilot valves and electrical signals;

- Easy to use standard components and submodules;

- Overload protection;

- Hydraulic Components can minimize wear between parts with the help of operating media;

- Long service life;

- Energy recovery capability;

Disadvantages of hydraulic system:
- Loss of pressure and flow between lines and control components due to fluid friction;

- Fluid viscosity is sensitive to changes in temperature and pressure;

- There is a risk of disclosure;

- Hydraulic fluids are compressible

The basic structure of the hydraulic system and energy flow is illustrated below.

Hydrostatic driven devices that can be driven by electric motors or internal combustion engines. Thus, mechanical energy (torque, speed) is converted into hydraulic energy (flow, pressure difference). The hydraulic control unit can adjust the pressure, direction and flow rate to distribute energy to each hydraulic actuator. Hydraulic actuators convert hydraulic energy back into mechanical energy.
Depending on the output needs of the driving device, it can be rotating motion, linear motion or swing. In addition, the system also has pipes, filters, heat exchangers, accumulators and so on.

2. Planning procedures
To build a perfect hydraulic system, the most important prerequisite is to adopt systematic procedures in the hydraulic system planning and execution process. The flowchart shown in the previous figure shows the basic steps of the planning process.
picture
3. Description of flow chart
According to the hydraulic system planning flow chart above, before looking for a practical solution to the problem, there are a lot of ideas, ideas (such as the experience of the planning engineer) that need to be properly considered and reflected in the project process. This requires careful organization, otherwise both the functionality of the installed equipment and the economics of the project may be discounted.
The motivation for planning and designing hydraulic systems can start from the following sources:
- Demand for sales
- Customer questions and inquiries
- The advanced nature of the competitors
- Market Analysis
- Trend Study
- My own idea
- Patents

3.1 Tasks and forms
An important starting point for successful hydraulic system planning is to clearly and thoroughly define and describe the task.
The first step in the planning process is to collect all the data and reorganize it in a clear, easy-to-use way. It is a good practice to prepare a standardized list of questions that are project-specific and can add additional items as needed.
This list of questions frames the planning process. May include the following:
Motion timing, including the force or torque required for each motion, as well as the necessary dynamic response and natural frequency.
Load timing, such as when there is a load interval (when there is no flow or pressure requirement, or only pressure and no flow requirement). This practice is particularly beneficial for optimizing designs, such as considering accumulators for hydraulic systems.
For the motion timing, it is usually difficult to describe in plain words, or the description is incomplete and unclear. Especially in complex systems, where there are many actuators and several movements overlap, it will be more difficult to describe.
Charts, however, can provide users and manufacturers with a common, simple, and clear means of communication. For ease of understanding, annotations can also be inserted into the diagram.
The following figure takes the injection molding machine as an example, giving a motion-time icon, representing each movement action. The ram quickly moves to the position of the injection cavity, slows down, and pressurizes the injection part with a certain force, and the pressure rises in accordance with the set sequence. After reaching the set pressure, the forward movement stops, but the pressure should be kept for a certain time. After curing, the ram is backed back to the initial point for pressure relief. After that, a fixed time is required for demoulding, and then a new injection cycle is entered.