Pressure Switch Diagram

2024-09-29 by Cherry

Introduction

As an important metal forming equipment in modern 

industrial production, the stability, and accuracy 

of the die-casting machine's operation is crucial 

to produce high-quality castings. 

The pressure switch diagram plays a key role in the 

control system of the die-casting machine. It can monitor

and control the pressure changes in the die-casting 

process in real time to ensure the die-casting machine's 

normal operation and the castings' quality. 

This article will explore the application of pressure

switch diagram in the die-casting machine in-depth, 

including its working principle, functional characteristics,

specific application in different links of the die-casting

machine, and its important significance to die-casting 

production.

Basic principles and composition of the pressure 

switch diagram

The working principle of the pressure switch

The pressure switch is an automatic control device that

controls the on and off of the circuit according to the

pressure change. It is used to monitor and adjust the 

pressure in the system. When the pressure reaches the set

value, the switch triggers the corresponding control 

signal to start or stop the operation of the equipment. 

It usually contains an elastic element, such as a spring

or a diaphragm, which will cause deformation when the 

pressure acts on the elastic element. As the pressure 

changes, the degree of deformation of the elastic component

will also change accordingly. 

When the pressure reaches the set threshold, the deformation

of the elastic element triggers a mechanical or electronic 

switch action, thereby realizing the on-off switching of

the circuit. In the die-casting machine, the pressure 

switch controls the operation and stop of related equipment

by monitoring the pressure changes in the hydraulic system.

The basic principle of the pressure switch can be summarized

as follows:

1. Pressure sensing: The pressure switch senses the pressure 

changes in the system through the internal sensor.

2. Signal processing: When the pressure reaches the set threshold,

the sensor transmits the signal to the control system.

3. Execution control: The control system performs corresponding

operations based on the received signal, such as starting 

or shutting down the pump or valve of the die-casting machine.

This automated control makes the die-casting process more 

precise and reduces the possibility of human intervention.

Constituent elements of the pressure switch diagram

The pressure switch diagram is mainly composed of pressure

sensors, signal processing circuits, comparators, and 

output circuits. The pressure sensor is responsible for 

real-time detection of the pressure in the hydraulic system

and converting the pressure signal into an electrical signal. 

The signal-processing circuit amplifies and filters the 

electrical signal output by the sensor to improve the quality

and stability of the signal. 

The comparator compares the processed pressure signal with

the preset pressure threshold and outputs the corresponding 

control signal when the pressure exceeds or falls below the 

threshold. The output circuit drives the relevant actuators,

such as relays, solenoid valves, etc., according to the 

output signal of the comparator to realize the control of 

the die-casting machine equipment.

Functional characteristics of pressure switch diagram in

die-casting machine

1. Accurate pressure monitoring and control

The pressure switch diagram can monitor the pressure 

changes in the hydraulic system of the die-casting machine

in real time and accurately. By presetting a suitable 

pressure threshold, it can be ensured that the pressure

in the die-casting process is always kept within the 

specified range. 

This is crucial to ensure the quality and dimensional 

accuracy of the casting. For example, during the injection

process, the injection pressure needs to be accurately

controlled to ensure that the molten metal can fill the 

mold cavity and will not cause mold damage or defects

such as a flash on the casting due to excessive pressure.

The precise control function of the pressure switch diagram 

can effectively achieve this goal and improve the qualified 

rate of castings.

2. Fast response and stability

During the working process of the die-casting machine, the 

pressure changes very quickly, especially in the injection 

and pressure-holding stages. The pressure switch diagram has 

the characteristics of fast response can detect the pressure

change in time, and quickly outputs the control signal so

that the related equipment of the die-casting machine can 

make timely adjustments. 

At the same time, it also has good stability, can maintain 

accurate pressure monitoring and control during long-term

working processes, and is not affected by external interference

and system fluctuations. This provides a reliable guarantee

for continuous and stable operation of the die-casting 

machine.

3. Multiple pressure control modes

The pressure switch diagram usually supports multiple pressure

control modes to meet the needs of different working links

of the die-casting machine. For example, it can realize the 

constant pressure control mode, that is, keep the pressure 

constant throughout the die-casting process; it can also realize

the variable pressure control mode, according to the requirements

of the die-casting process, and set different pressure values 

at different stages. 

This flexible pressure control mode enables the die-casting 

machine to adapt to various complex casting production processes

and improves the versatility and adaptability of the die-casting

machine.

4. Fault diagnosis and alarm function

The pressure switch diagram also has fault diagnosis and alarm

functions. When the pressure in the hydraulic system changes 

abnormally, such as too high or too low pressure, too large

pressure fluctuations, etc., it can detect and send an alarm

signal in time to remind the operator to check and deal with

it. At the same time, by analyzing the pressure change trend, 

the cause and location of the fault can be preliminarily 

determined, providing effective reference information for 

maintenance personnel, shortening troubleshooting time, 

reducing equipment downtime, and improving production 

efficiency.

Application of pressure switch diagram in different 

links of die-casting machine

1. Application in mold closing process

During the mold-closing process of the die-casting machine, it

is necessary to provide sufficient mold closing force to 

ensure the tight closure of the mold and prevent metal liquid 

leakage. The pressure switch diagram monitors the pressure of

the mold closing hydraulic system and controls the action 

of the mold-closing cylinder to ensure that the mold-closing 

force reaches the set value. 

When the mold closing force is insufficient, the pressure 

switch will send a signal to prompt the hydraulic system to

increase the pressure until the mold closing force meets 

the requirements. Conversely, when the mold closing force

is too large, it will be adjusted in time to avoid damage

to the mold and equipment. This ensures that the mold can

maintain a good sealing state during each die-casting

process, providing a basic guarantee of the quality of the 

casting.

2. Application in the injection process

The injection process is the core link of the die-casting machine,

and the control of pressure directly affects the molding 

quality of the casting. The pressure switch diagram plays a vital

role in the injection process. It monitors and controls the

pressure of the injection cylinder in real-time according to 

the preset injection pressure curve. At the beginning of 

injection, a lower pressure is required to push the molten 

metal to fill the runner. 

As the molten metal gradually approaches the mold cavity, 

the pressure gradually increases to ensure that the molten metal

can fill the cavity at a sufficient speed and pressure to

avoid defects such as pores and looseness. During the 

pressure-holding stage, the pressure switch diagram 

continues to maintain a certain pressure to compensate for the

shrinkage of the molten metal during the cooling process and

prevent shrinkage holes and shrinkage problems in the casting. 

Through precise pressure control, the pressure

switch diagram can ensure the smooth progress of the injection 

process and produce high-quality castings.

3. Application in the pressure-holding process

The pressure-holding process is to maintain a certain pressure for 

some time after the molten metal fills the mold cavity. The purpose

is to compensate for the volume shrinkage of the molten metal 

during the cooling and solidification process and ensure the 

dimensional accuracy and internal quality of the casting. The 

pressure switch diagram strictly controls the size and time of 

the pressure holding pressure during the pressure holding process.

It presents a reasonable pressure holding pressure and time 

according to factors such as the material, shape, and size of

the casting. During the pressure holding period, the pressure 

changes are monitored in real-time. Once the pressure drops below

the set value, the hydraulic system will be started in time to 

supplement the pressure to maintain a stable pressure-holding 

state. 

After the pressure holding is completed, the pressure 

switch diagram controls the hydraulic system to release the 

pressure and prepare for the mold opening. Accurate pressure

holding control is one of the keys to obtaining high-quality 

castings, and the pressure switch diagram plays an indispensable

role in this process.

4. Application in the demolding process

The demolding process is the link of removing the molded casting 

from the mold. During the demolding process, appropriate demolding

force is required to ensure that the casting can be smoothly 

separated from the mold without causing damage to the casting and 

the mold. The pressure switch diagram monitors the pressure of the

demolding hydraulic system and controls the action of the demolding

cylinder to achieve precise control of the demolding force. 

When the demolding force is too large, it may cause deformation or 

damage to the casting; when the demolding force is too small, the

casting may not be de-molded smoothly. The application of the 

pressure switch diagram can ensure that the demolding force is 

within the appropriate range, and improve the success rate of demolding

and the quality integrity of the casting.

When designing the pressure switch system of a die-casting machine,

multiple factors need to be considered:

1. Select the appropriate pressure range

According to the working characteristics of the die-casting machine,

select the appropriate pressure range to ensure that the switch 

can accurately respond to pressure changes.

2. High temperature and corrosion resistance

Due to the presence of high temperature and molten metal in the 

die-casting process, the material and structure of the pressure 

switch must have high temperature and corrosion resistance to 

ensure long-term stable operation.

3. Sensitivity and response time

The sensitivity and response time of the switch directly affects 

the safety and efficiency of the die-casting process. When designing,

it is necessary to ensure that it has high sensitivity and fast

response capabilities.

Installation and debugging of the pressure switch diagram

1. Selection of installation position

The installation position of the pressure switch on the die-casting

machine should be determined according to the layout of the

hydraulic system and the requirements of pressure monitoring.

Generally speaking, a position that can accurately reflect the

changes in system pressure should be selected in the hydraulic

pipeline, usually installed at key locations such as the oil 

pump outlet, the injection cylinder inlet, and the mold closing

cylinder inlet. 

At the same time, the convenience of installation and the operability

of maintenance should be taken into account to ensure that the

pressure switch is easy to install, disassemble, and debug.

During the installation process, it is also necessary to avoid 

the pressure switch from being affected by external mechanical 

damage, vibration, high temperature, and other factors to ensure

its normal operation and measurement accuracy.

2. Debugging steps and methods

After the installation is completed, the pressure switch 

diagram needs to be debugged to ensure that it can accurately

monitor and control the pressure. The debugging steps are 

as follows:

1. Pressure sensor calibration: First, use a standard pressure 

source to calibrate the pressure sensor to ensure that there 

is an accurate correspondence between the electrical signal

output by the sensor and the actual pressure value. During

the calibration process, follow the instructions of the 

pressure sensor to adjust the calibration parameters so that 

the output error of the sensor under different pressures is 

controlled within the allowable range.

2. Set the pressure threshold: According to the process requirements

and operation manual of the die-casting machine set the 

pressure threshold of each working link. These thresholds should

be reasonably determined based on factors such as the material,

shape, size of the casting, and the performance parameters of

the die-casting machine. 

For example, the mold closing pressure threshold, the injection

starting pressure threshold, the injection peak pressure threshold,

the holding pressure threshold, etc. When setting the threshold,

full consideration should be given to the safe operation of 

the equipment and the guarantee of the casting quality, and

a certain adjustment margin should also be left so that fine-tuning

can be performed as needed in actual production.

3. Functional test: After completing the pressure threshold 

setting, perform the functional test of the pressure switch 

diagram. Start the die-casting machine, and simulate each working 

link, and observe the response of the pressure switch diagram 

under different pressures. Check whether the pressure switch 

can accurately output the control signal when the pressure 

reaches the set threshold and drives the relevant equipment to

act.

At the same time, check whether the pressure display 

is accurate and whether the error with the actual pressure 

value is within the allowable range. During the functional 

test, pay attention to recording various data and abnormal 

conditions for timely analysis and processing.

4. System joint debugging: After the pressure switch diagram

is tested separately and the function is normal, the entire

control system of the die-casting machine is jointly debugged.

The pressure switch diagram is tested for coordinated work 

with other parts such as the clamping mechanism, injection 

mechanism, hydraulic system, and electrical control system 

to ensure that the pressure switch diagram can work seamlessly

with other equipment during the actual operation of the 

die-casting machine to achieve precise control of the die-casting

process. 

During the joint debugging process, the various performance

indicators of the die-casting machine should be fully tested,

such as clamping force, injection speed, casting quality, etc.,

and the parameters and settings of the pressure switch diagram

should be further adjusted according to the test results 

to achieve the best working state.

Precautions

During the installation and debugging of the pressure switch 

diagram, the following matters should also be noted:

1. Reliability of electrical connection: Ensure that the electrical

connection between the pressure switch and the control system

is firm and reliable to avoid problems such as poor contact

and short circuit. Use wires and connectors that meet the 

specification requirements, and perform wiring and wiring by 

the electrical installation specifications.

2. Waterproof and dustproof measures: Since the working environment

of the die-casting machine is usually harsh, there are oil 

stains, dust, and moisture. Therefore, effective waterproofing and

dustproof measures should be taken to protect the pressure 

switch and related equipment from pollution and damage. 

The pressure switch can be protected by sealants, protective 

covers, etc. to ensure that it can still work normally in

harsh environments.

3. Safe operation: During the debugging process, the safety 

operating procedures must be strictly followed to prevent 

equipment damage or casualties caused by misoperation. 

When debugging the hydraulic system, pay attention to 

releasing the pressure to avoid danger caused by high-pressure

oil spraying.

At the same time, ensure that the debugging personnel 

have relevant professional knowledge and skills

and are familiar with the working principle and operation 

method of the die-casting machine and the pressure switch 

diagram.

Maintenance and care of the pressure switch diagram

1. Regular inspection and cleaning

In order to ensure the normal operation of the pressure 

switch diagram, it is necessary to inspect and clean it 

regularly. The inspection content includes whether the 

appearance of the pressure sensor is damaged, whether the 

connection line is loose, whether the plug is in good 

contact, etc. 

At the same time, the surface of the pressure sensor 

and the pressure switch should be cleaned regularly

to remove impurities such as oil, dust, etc. to ensure

the accuracy of pressure detection. You can use a clean

soft cloth or a special cleaning agent for cleaning, but 

be careful to avoid using highly corrosive chemicals to 

avoid damaging the equipment.

2. Calibration and verification

The accuracy of the pressure sensor will drift over time 

and the use environment, so it is necessary to calibrate

and verify it regularly. The calibration cycle is generally

determined according to the frequency of use and accuracy

requirements of the equipment, usually once every six 

months to one year. 

During the calibration process, use a standard pressure

source and a high-precision measuring instrument, and

operate according to the prescribed calibration method

to ensure that the output error of the pressure sensor 

is within the allowable range. If the accuracy of the

pressure sensor is found to exceed the standard, it

should be adjusted or replaced in time.

Troubleshooting and repair

When the pressure switch diagram fails, it should be checked

and repaired in time. Common faults include inaccurate 

pressure display, inoperative pressure switch, abnormal 

control signal, etc. For these faults, you can follow the 

steps below to troubleshoot:

1. Check the power supply: First check whether the power 

supply of the pressure switch diagram is normal, including

whether the voltage is stable and whether the power cord 

is well connected. If there is a problem with the power supply,

it may cause the equipment to not work properly or abnormal 

signals to appear.

2. Check the pressure sensor: Remove the pressure sensor from

the hydraulic system and use a multimeter or other tools 

to detect whether its resistance value, the output electrical 

signal, and other parameters are normal. If the pressure 

sensor is damaged, a new sensor should be replaced in time.

3. Check the signal processing circuit and comparator: 

Check the signal processing circuit and comparator to 

see if there are any problems such as component damage

and loose solder joints. If a fault is found, the 

corresponding circuit board should be repaired or replaced.

4. Check the connection line and plug: Check whether the

connection line between the pressure switch diagram and

other equipment is open, short, or poorly contacted, 

especially the plug and socket. Replug the connection 

line to ensure a reliable connection.

5. Check the mechanical parts: For the mechanical parts 

of the pressure switch, such as springs, diaphragms, etc., 

check whether there is deformation, damage, or jamming. 

If there is a problem with the mechanical parts, they 

need to be repaired or replaced.

When troubleshooting and repairing, be sure to record the

fault phenomenon, troubleshooting process and repair 

results for future reference and experience summary. At

the same time, for some complex faults, if you cannot 

solve them yourself, you should contact a professional

maintenance personnel for repair in time to avoid 

further damage to the equipment due to misoperation.

Spare parts management

To ensure the timely repair and replacement of 

the pressure switch diagram, a spare parts management 

system needs to be established. According to the model 

and specifications of the equipment, reserve a certain 

number of commonly used spare parts, such as pressure sensors,

signal processing circuit boards, relays, etc. 

At the same time, spare parts should be classified as managed,

well marked, and recorded to ensure the quality and availability

of spare parts. Spare parts should be inspected and maintained 

regularly to prevent them from being damaged or failing due to

long-term storage. When replacing spare parts, pay attention to 

selecting spare parts of the same model and specification as

the original equipment to ensure compatibility

and stability of the equipment.

Case analysis of pressure switch diagram application

1. Case 1: Improving the quality of castings

During the production process, a die-casting company 

found that some castings had quality problems such as 

internal pores and shrinkage holes, which seriously affected

the product's pass rate and performance. After a comprehensive

analysis of the die-casting process and equipment, it was 

found that this was caused by unstable pressure control 

during the injection process. 

The company introduced a pressure switch diagram control

system to monitor and accurately control the injection 

pressure in real-time. By adjusting the parameters of the 

pressure switch, the injection pressure changes according

to the preset curve, ensuring that the pressure of the molten

metal during the filling of the cavity and the pressure-holding

process is always kept within a reasonable range. 

After a period of operation, defects such as pores and shrinkage

holes inside the castings were significantly reduced, the 

product qualification rate was greatly improved, 

and the mechanical properties of the castings were also 

significantly improved.

2. Case 2: Optimizing production efficiency

During the production process, another die-casting 

company found that the die-casting machine had a long

mold closing time, which affected the overall production

efficiency. Through inspection and analysis of the mold

closing the hydraulic system, it was found that the mold 

closing pressure control was inaccurate, resulting in 

multiple pressure adjustments during the mold closing 

process to achieve the appropriate mold closing force. 

The company installed a pressure switch diagram and optimized 

the mold closing pressure threshold. By accurately controlling 

the mold closing pressure, the mold closing process is smoother,

reducing the mold closing time and the number of adjustments.

In addition, the fault diagnosis function of the pressure switch

diagram can also timely detect potential problems in the mold 

closing system, performing maintenance and processing in advance, 

and avoid downtime caused by equipment failure. After the 

improvement, the production efficiency of the die-casting machine

has been significantly improved, bringing considerable economic

benefits to the company.

Conclusion

As an important part of the die-casting machine control system,

the pressure switch diagram plays a vital role in the operation

of the die-casting machine and the casting production process. 

It ensures the stability and accuracy of the pressure in each 

working link of the die-casting machine through precise pressure 

monitoring and control, rapid response, multiple pressure control

modes, fault diagnosis, and alarm functions, thereby ensuring the

quality, dimensional accuracy, and production efficiency of the 

castings.

In practical applications, according to the specific situation

of the die-casting machine, the pressure switch diagram should

be reasonably selected and installed, debugged, and maintained

correctly to give full play to its advantages. 

With the continuous advancement of science and technology 

and the continuous development of die-casting technology, 

the technology of pressure switch diagrams will continue to 

innovate and improve, providing stronger support for the 

development of the die-casting machine industry. 

It is hoped that this article's detailed introduction 

to the application of pressure switch diagrams in die-casting 

machines can provide useful reference and reference for relevant

practitioners, and promote the continuous advancement of 

die-casting machine technology and the high-quality development

of the industry.

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