Question 1

Technical Scheme of Vacuum Precision Control in Lunar Soil Environment Ground Simulation Test Device

Accepted Answer

Abstract: In the lunar exploration project, it is necessary to collect lunar soil samples in the vacuum environment of the lunar surface. It is necessary to establish a ground test device to simulate the vacuum thermal environment of the lunar surface to test the performance of the sample in vacuum thermal environment. Therefore, the degree of vacuum is required and it can achieve precise control. In this article, a technical scheme for accurate vacuum control using FC series proportional flow control valve is proposed for the ground simulation test device of vacuum thermal environment.

1. Question
In the lunar exploration project, it is necessary to collect lunar soil samples in the vacuum environment of the lunar surface. Therefore, a ground test device needs to be established to simulate the vacuum thermal environment of the lunar surface to test the performance of sample in the vacuum thermal environment, and accurate vacuum control is required to reach precise control. Due to the particularity of the lunar soil, vacuum control in current lunar soil ground model test device still needs to solve the following problems:
(1) Lunar soil and simulated lunar soil samples are generally powdery particles, so the pumping rate in the initial time should be strictly controlled to avoid dust generation.
(2) The current vacuum measurement and control also uses a Pirani vacuum gauge, which makes the matching control system unable to reach precise control of the vacuum, resulting in poor repeatability of the test results.
(3) The lunar soil ground simulation test device is generally small in size, and it has always been difficult to achieve precise control within a wide range of vacuum degrees. The fluctuation of vacuum degree is large, which is also one of the reasons for the poor repeatability of test results. Aiming at the above problems existing in the lunar soil ground model test device, this article focuses on corresponding technical solutions and introduces the detailed implementation process.

2. Technical Scheme
The overall structure of vacuum density control system of lunar soil environment ground simulation test equipment is shown in Figure 1. The whole system mainly includes a vacuum gauge, two proportional flow control valve, a PID controller and a vacuum pump. In order to do the precise control of the full range of vacuum degree, three capacitance vacuum gauges are generally required, and the measurement accuracy of vacuum gauge is 0.25%. In order to match the measurement accuracy of capacitance vacuum gauge, the controller adopts a high-precision PID controller with 24-bit A/D and 16-bit D/A, and the independent dual-channel facilitates the gas flow adjustment and control of the upstream proportional flow control valve and downstream proportional flow control valve control. The precise control of vacuum degree uses dynamic control mode, that is, the downstream proportional flow control valve is adjusted under low vacuum conditions, and the upstream proportional flow control valve is adjusted under high vacuum conditions. This is a typical forward and reverse control method, which can effectively ensure the control accuracy of vacuum degree. In conclusion, with this proven accurate vacuum control scheme, a control accuracy of better than 1% vacuum over the full scale range can be achieved.

For further information on different models of proportional flow control valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm

Question 2

Precision Vacuum Control to Reduce Solvent Loss in Evaporation and Concentration Process

Accepted Answer

Abstract: Aiming at the problems of precision vacuum control to reduce solvent loss in evaporation and concentration process, this article focuses on vacuum evaporation techniques, including the precise control method of vacuum degree, the simultaneous control method of vacuum degree and temperature, and the use of strong resistance of the corrosive electronic valve acts as a vacuum regulator.

1. Question
In the process of solvent extraction, the vacuum evaporation and concentration process is generally used. Since the solvent often has good volatility, the solvent is prone to loss during the vacuum extraction process, and sometimes the loss can reach 5~8%. Therefore, in order to solve the loss of solvent in the evaporation and concentration process, the following problems need to be solved:
(1) The precise control problem of vacuum degree, such as fixed-point control and program control, which is the key to reducing solvent loss.
(2) Simultaneous control problem of vacuum degree and temperature. This is because different vacuum degrees determine the boiling point of the solution. Through coordinated control of vacuum degree and temperature at the same time, the yield of the solvent can be greatly improved.
(3) In the vacuum evaporation and concentration process, many solvents and solutions are often corrosive to a certain extent, which requires the vacuum regulating valve to have good corrosion resistance. In order to solve the requirement of reducing solvent loss in the evaporation and concentration process, this article proposes a solution for precise control of vacuum degree, including the use of electronic flow control valve with strong corrosion resistance as vacuum degree control valves.

2. Solution
For the precise control of vacuum degree and temperature in the evaporation and concentration process, the overall structure of control system is shown in Figure 1.

(Figure 1 Schematic diagram of the vacuum degree and temperature control system structure of the evaporation and concentration process)

The basic principle of precise vacuum control is the dynamic control method, that is, according to the control set value and the measured value of vacuum gauge, the intake flow and exhaust flow of vacuum container are adjusted respectively, so that the flow in and out can reach a dynamic balance. If automatic control is required, PID control algorithms and corresponding controllers are required.

As shown in Figure 1, the accurate control proposal for vacuum degree control in this article adopts a dynamic control method, using an electronic flow control valve to adjust the intake flow, using an electronic ball valve or an electronic needle valve to adjust the exhaust flow, and the vacuum pump is used as a vacuum source. The automatic control of vacuum degree adopts PID controller.

In order to reach the temperature control function at the same time, this scheme adopts a dual-channel PID controller, one channel is used to control the vacuum degree, and another channel is used to control the temperature. This dual-channel PID controller is shown in Figure 2. This PID control has 24-bit A/D and 16D/A, with 47 input signal forms (thermocouple, thermal resistance, DC voltage), and can be connected to various vacuum and temperature sensors for measurement, display and control. It also has 2 independent measurement control channels, two-wire RS485, standard MODBUS RTU communication protocol.

(Figure 2 VPC2021 series dual-channel PID controller)

(Figure 3 FC series electronic needle valve)

In order to reach high-precision adjustment in the vacuum degree control process, an electronic needle valve with fine adjustment by a numerically controlled stepping motor is used, as shown in Figure 3. The hysteresis of this FC series proportional needle valves is much smaller than that of solenoid valves, and has a high-speed response within 1 second, especially the use of fluorine rubber (FKM) sealing technology, which makes the valve have superior corrosion resistance. Equipped with a stepper motor drive circuit module with the numerical control proportional needle valve, it provides the required power supply (24VDC) and control signal (0~10VDC) for the numerical control needle valve, and can also provide direct control of RS485 serial communication.

For larger-diameter air-extraction pipelines, a miniature proportional needle valve is used in this scheme, as shown in Figure 3. This series of proportional needle valve is a small electronic valve. The valve opening can be adjusted continuously according to the change of control signal (0~10VDC). The fastest opening and closing time is less than 7 seconds, and the opening and closing time can also reach less than 1 second. The integrated design of the valve and the valve body reduces external volume and is low in price. It is often installed between the sealed container and the vacuum pump to adjust pumping rate.

In short, through the solution described in this article, the vacuum degree control accuracy in the evaporation and concentration process can reach 1%, and the corresponding temperature control can also be carried out. The vacuum regulating valve has super corrosion resistance, which can effectively reduce the loss of solvent concentration during the vacuum evaporation process.

Question 3

Proposal for Vacuum Precision Control in Low Pressure Carburizing (LPC) Process

Accepted Answer

Abstract: In order to meet the requirements of precise control of vacuum degree in low-pressure carburizing process (vacuum carburizing), corresponding solutions are proposed in this article, including adding a gas mixing tank for permeate gas mixing, using upstream and downstream dynamic vacuum level control methods and vacuum degree by coordinating the control method with the temperature, the rapid and precise control of the vacuum degree and temperature in the infiltration process can be reached.

1. Question
Low-pressure carburizing, also known as vacuum carburizing, is a process in which a carburizing medium is passed into a high-temperature furnace for rapid carburizing under a low-pressure vacuum state. The vacuum carburizing process can be divided into one-stage type, pulse type and swing type. Among them, the degree of vacuum, temperature and carburizing time will change according to the specific requirement, especially the degree of vacuum will change drastically with the temperature change. Therefore, in the vacuum carburizing process, the following problems need to be solved in terms of vacuum degree control:

(1) The problem of fast and accurate control of vacuum degree, such as fixed-point control, program control and fast pulse control, requires the vacuum control system to have high response speed and control accuracy. Especially to achieve precise control in the full range of vacuum, it is necessary to use different vacuum sensors and corresponding upstream and downstream control modes according to different ranges.

(2) Simultaneous control problem of vacuum degree and temperature. The carburizing is carried out in a high temperature environment, requiring simultaneous control of vacuum degree and temperature.
In order to meet the requirements of precise control of vacuum degree in low-pressure carburizing process, this article focuses on a solution for precise control of vacuum degree, and adopts dual-channel PID control to reach synchronous temperature control.

2. Solution
The overall structure of the vacuum degree and temperature control system in the low pressure carburizing process is shown in Figure 1.

Figure 1 Schematic diagram of the structure of vacuum degree and temperature control system in low pressure carburizing process

The basic principle of precise control of vacuum degree is the dynamic control method, that is, according to the control set value and the measured value of vacuum gauge, the air intake flow and exhaust flow of the carburizing chamber are adjusted respectively, so that the flow in and out can reach a dynamic balance. If automatic control is required, PID control algorithms and corresponding controllers are required.

As shown in Figure 1, the precision control solution for vacuum degree proposed in this article adopts a dynamic control method, using an electronic needle valve to adjust the air intake flow, using an electronic ball valve or an electronic needle valve to adjust the exhaust flow, and the vacuum pump is used as a vacuum source. The automatic control of vacuum degree adopts PID controller.

For different low pressure carburizing processes, the control range of the vacuum degree is 1Pa~100kPa. Therefore, in the specific process, different dynamic control modes need to be adopted for the control in different vacuum degree ranges. For the vacuum degree control in the high vacuum range of 1Pa~1kPa, the upstream control mode of fixed exhaust flow and adjustable intake flow is adopted; for the vacuum degree control in the low vacuum range of 1kPa~100kPa, fixed intake flow and adjustable exhaust downstream control mode of the flow.

As shown in Figure 1, in order to reach the adjustment and control of air intake flow, a gas mixing tank is added to the intake end of carburizing chamber, and a gas mass flow meter is used to distribute various permeated gases into the gas mixing tank. The gas flows through the electronic needle valve for flow regulation and control.

In order to reach the temperature control function at the same time, this scheme adopts a dual-channel PID controller, one channel is used to control the vacuum degree, and the other channel is used to control the temperature. This dual-channel PID controller is shown in Figure 2. This PID control has 24-bit A/D and 16-bit D/A, with 47 input signal forms (thermocouple, thermal resistance, DC voltage), and can be connected to various vacuum and temperature sensors for measurement, display and control of 2 independent measurement control channels, two-wire RS485, standard MODBUS RTU communication protocol.

Figure 2 VPC2021 series dual-channel PID controller

Figure 3 FC series electronic needle valve

Figure 4 LCV-DS series electronic ball valve

In order to reach high-precision adjustment in the vacuum degree control process, an electronic needle valve with fine adjustment by a numerically controlled stepping motor is used, as shown in Figure 3. The hysteresis of FC series of needle valves is much smaller than that of solenoid valves, and has a high-speed response within 1 second, especially the use of fluorine rubber (FKM) sealing technology, which makes the valve have superior corrosion resistance. Equipped with a stepper motor drive circuit module with the numerical control electronic needle valve, it provides the required power supply (24VDC) and control signal (0~10VDC) for the numerical control needle valve, and can also provide direct control of RS485 serial communication.

For the larger diameter of the suction pipeline, this scheme uses a miniature electronic ball valve, as shown in Figure 4. This series of electronic ball valve is a small electronic valve. The valve opening can be adjusted continuously according to the change of the control signal (0~10VDC). The fastest opening and closing time is less than 7 seconds, and the opening and closing time can also reach less than 1 second. The integrated design of the valve and the valve body reduces the external volume and is low in price. It is often installed between the sealed container and the vacuum pump to adjust the pumping rate.

In conclusion, through the solution described in this article, the vacuum degree control accuracy in the low pressure carburizing process can reach 1% in the full scale range, and the corresponding temperature control can also be carried out.

Question 4

Ultra-Low Loss Single-Mode Optical Fiber Fused Taper Production by Accurate Vacuum Level Control Adsorption Fixture

Accepted Answer

Abstract: In the fiber fused taper system of fusion method, the fiber coupling with minimal loss corresponds to the optimal vacuum degree for adsorbing and fixing the optical fiber. Therefore, it is necessary to precisely control the adsorption vacuum degree and find the optimal vacuum degree value. In this article, focusing on the stable batch production of fiber fused taper system with minimal loss, an improvement scheme of vacuum system using FC series proportional flow control valve is proposed, which can reach precise control of vacuum degree.

1. Question
In the process of making optical fiber couplers and optical fiber cones in the optical fiber taper system, two or more optical fibers are generally positioned and clamped on the optical table by means of vacuum adsorption and special fixtures, and the two or more optical fibers are fixed in a certain way. A plurality of bare fibers are rotated and moved closer to the axis, heated and melted by a hydrogen-oxygen flame or a laser, and stretched to both sides at a certain speed, and finally a special waveguide structure in the form of a double cone is formed in the heating zone.

The current optical fiber taper technology is difficult to produce optical fiber couplers stably with a loss of less than 0.1 in batches, which is mainly due to the fact that optical fibers are fixed too tightly by vacuum adsorption. Some literatures reported that the vacuum system for adsorption and fixation fixture was improved, and the corresponding fiber couplers were fabricated under a series of different adsorption and fixation vacuum degrees, and it was proved that coupling loss in the entire vacuum degree range has a minimum area, When the vacuum degree is 120mBar, the minimum loss is 0.05dB, as shown in Figure 1.

As you can see from the results in Figure 1, it is not that the higher the vacuum degree, the better vacuum degree would be. The higher the vacuum degree, the tighter the fiber is fixed, and the coupling loss will be larger. It can be seen that in order to obtain an ultra-low loss fiber coupling device, it is necessary to precisely control the vacuum degree of the vacuum adsorption device.

In this article, according to the requirements for precise control of vacuum degree in the process of fabricating ultra-low loss optical fiber coupling devices by fiber taper method, a technical scheme of vacuum control system and corresponding supporting contents are proposed to reach precise and rapid control of vacuum degree.

Fig.1 Coupling loss under different vacuum pressures

2. Technical Scheme
In order to reach the precise control of adsorption vacuum degree in the left and right stretching fixtures, a vacuum tank is added to the original vacuum system. As long as the vacuum pressure in the vacuum tank is controlled, the adsorption vacuum degree of the left and right stretching fixtures can be controlled which shown in figure 2.

The vacuum degree control system shown in Figure 2 mainly includes an electronic needle valve, a vacuum gauge, a PID controller and a vacuum pump. The precise control of the vacuum degree adopts the dynamic control method, that is, according to the comparison between the measured value of the vacuum gauge and the set value, the PID controller adjusts the intake air flow and the exhaust air flow at the same time to quickly achieve dynamic balance and control the vacuum degree to the set value. , the control accuracy can reach ±1%.

In conclusion, through precise control of vacuum degree, stable mass production of ultra-low-loss fiber-coupled devices can be reached.

Figure 2 Schematic diagram of the vacuum degree control system of the fiber taper machine

Question 5

Proportional Flow Control Valve

Accepted Answer

These are some of our proportional flow control valve applications:
1. Torque control
2. Vacuum generator
3. Gas control
4. Gas blending
5. Cooling

We have been offering various models of proportional flow control valve that can be used to control the flow rate of gas, liquid, oil. Customers often uses our valves to replace solenoid valves, where our FC series could act as on/off control and at the same time control the flow rate. We have succesfully replaced Clippard (SCPV), and Burkert flow control valve.

Advantage:

Compact
Low cost
High sensitive
Analog / Digital signal
Easy-control
Full scale linearity flow rate control
control up to 20 L/min of water flow (customisable)

We hope you have enjoyed reading the article. Please remember to visit our product page.

Question 6

Electronic Flow Valve

Accepted Answer

What is an Electronic Flow Valve?

An Electronic Flow Valve is a device that is able to control the flow rate of fluid (liquid and gas) with electronic signal. Ideally, the output flow rate is linearly proportional to input signal. Depend on the type of medial it is regulating, when it’s air, it is called electronic flow regulator, electronic air flow control valve, electronic pneumatic flow control valve; and when the media is water, it’s called electronic water flow control valve, digital flow control valve, digital flow controller, or proportional needle valve for both types.

There are different types of working principle, and in this article we will be introducing you the proportional needle valve type driven by a stepper motor powered linear actuator. We will firstly introduce you what type of electronic flow valve we offer, followed by the working principle and with what is the main advantage of KaoLu’s proportional needle valve, and then conclude with what you should think about before purchasing an electronic flow valve.

What type of Electronic Flow Valve does KaoLu offer?

KaoLu offers 5 types of digital flow control valve. One advantage is that it can control both gas and liquid. Please click on the photo link below for further information

FC20 : Flow rate up to 45 L/min of nitrogen gas @ 6 bar or 750 mL/min of water @ 6 bar
FC120: Flow rate up to 200 L/min of nitrogen gas @ 6 bar or 3.5 L/min of water @ 6 bar
FC300: Flow rate up to 450 L/min of nitrogen gas @ 6 bar or 8 L/min of water @ 6 bar
FC1000: Flow rate up to 650 L/min of nitrogen gas @ 5 bar or 12 L/min of water @ 5 bar
FC2000: Flow rate up to 2000 L/min of nitrogen gas @ 5 bar or 30 L/min of water @ 5 bar

Please refer to our youtube channel for some of the interesting applications:

What is working principle of an Electronic Flow Regulator?

There are different types of Electronic Flow Regulator. Here we will be explaining the type that utilizes a linear stepper motor actuator and proportional needle valve.

So, what is the advantage of KaoLu’s electronic air flow control valve or electronic water flow control valve?

Our parameters tells all the story. With FC series electronic flow valve, we are able to withstand 7 bar of perpendicular operating pressure, with a resolution as high as 20 mL/min of air, repeatability of 0.1% F.S, and 0.1% of linearity. This is due to the motor we used, the extremely low tolerance of mechanical parts, the fine thread needle we used which is extremely difficult to reproduce by others, and the control system we designed.

What should you consider when purchasing an electronic flow regulator?

You should consider 3 main factors ( we called CPR)

Compatibility: Medium, flow range, compatibility with the valve material, and operating pressure
Performance: Resolution, starting flow point, and linearity
Control system

It is important to understand whether the media you used falls into the flow range of the operating valve. As each media has different density so the flow range would be different from the nominal flow range. Next is whether the media used is compatible with the wet material and whether you would also need the body to be special material. The operating pressure is another caveat, where if you simply needs flow control, sometimes it would not be a very important factor.

Next is the performance, with some applications that needs fine control and adjustment between steps, such as laser cutting, the resolution dictated by the control logic and motor performance plays an important role here. Furthermore, as the motion system requires to overcome initial inertia, the start flow point is should be considered.

Then comes the control system where the you should check what type of control system do suppliers offer? Here we provide an external driver that has a cable connected to the control valve. The great advantage that we offer is that should you want to operate the valve from distant away from the site, we offer RS485 modbus where you could control the valve up to half a mile away from the valve.

We hope you have enjoyed reading the article, understand about stepper motor driver electronic flow control valve, understand about our products, and finally help you with selecting the right valve.

We hope you have enjoyed reading the article. Please remember to visit our product page.