Control method of the hottest foaming extrusion

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Foaming extrusion control method

a comprehensive control method connects the various components of modern foaming extrusion systems. The changes at the beginning and end of the whole system are mainly carried out in an automated, repeatable and user-friendly manner

the typical raw material formula for foaming extrusion consists of up to eight components, which must be processed under limited conditions. Equipment manufacturers face the challenges of technology development and production control methods to ensure the repeatability of semi-finished foaming products

this paper focuses on the foam extrusion line device (model: ze/ke; shown in Figure 1) of two series extruders arranged in a coaxial manner

Figure 1. Schematic diagram of series system for foaming extrusion (ze/ke)

this paper focuses on the foaming extrusion production line device of two series extruders arranged in a coaxial manner (model: ze/ke; shown in Figure 1)

◆ a co rotating double screw rod extruder (ZE) for long-time cleaning in strong alkali solution is used to melt polymer and introduce foaming agent

◆ a single screw extruder cooling extruder (KE) is used to cool the melt containing foaming agent

melt extruder

twin screw extruder feeds polymer raw materials through weight measurement unit (weight loss feeder), which determines the production capacity of the system. With the help of the high-pressure pump, the physical foaming agent in liquid form is introduced into the hopper

twin screw extruder carries out "hungry feed". The speed of twin screw can be changed within a certain range. The relationship between polymer output [kg/h] and screw speed [rpm] is defined as characteristic output:

in the production of fixed output, it is mainly based on the existing high-capacity material system, optimize the electrode structure, and improve the load of active materials; Using new material system to improve the working voltage of battery; Optimizing the new material system, the reduction of screw speed can increase the characteristic output. There is also a minimum speed value, under which the feed capacity of the extruder is no longer sufficient. If the maximum characteristic output mspec and Ze are exceeded, the feed section is filled. Increasing the screw speed can reduce the characteristic output. Usually, this will cause the melt temperature to rise and shorten the buffer length. Since the buffer section is critical to provide sealing and prevent the reverse flow of foaming agent during processing, there is also a low limit on the characteristic output. Screw speed cannot be increased to any value

cooling extruder

the characteristic output of single screw extruder (KE) can also be tested in a similar way for melt extruder (ZE):

here, the characteristic output can also be changed within the current range, thus having a certain impact on the melt temperature and the pressure strength of the whole system

with the help of characteristic output, the control of extruder speed can be related to the output of polymer. The rated change of output will automatically lead to the change of screw speed

the typical raw material formula for foaming extrusion consists of up to eight components: pure polymer, recycling and additives for pore size control, color masterbatch and flame retardant. The amount of materials contained is expressed by their percentage. For example, for component 1:

the synthesis of all polymer raw materials is usually 100%

the absolute output of each component in [kg/h] is calculated by correlating with the total output of the polymer. In order to ensure the accurate proportion between materials, all components are fed by weight

similarly, the characteristic amount of foaming agent is also specified by the percentage related to the total output of polymer

The absolute value of the amount of foaming agent added is also calculated by correlating the total output of the polymer, and is set as a selection point in the control part of the metering pump. The measurement of flow velocity is based on the Coriolis force principle

the total output of a series foaming production line is calculated by the sum of the addition of polymer and foaming agent, that is, foaming agent is included in the total addition

for some foaming products (XPS foam board), up to three foaming agents are added to the polymer. The foaming agent is directly injected into the polymer melt, that is, into the hopper of the twin-screw extruder

for the stable quality of finished products, maintaining stable processing parameters is critical. In addition to temperature control, this also means in particular the proportion of polymer components, foaming agent and the characteristic output of the extruder

based on its percentage content, the control of foaming agent can also be related to the output of compounds that reduce the relative error of the experimental formula value. This also means that the absolute flow velocity of foaming agent changes with the change of total output

master each proportion of polymer material and foaming agent, and the formula can be clearly determined. Knowing the polymer output, the proportion of all materials and the characteristic output of these two extruders means that the necessary parameters of an operation step are defined

typical changes in operating points, such as changes in output or at the beginning and end of the entire production line, can now be automated within a certain range. At the beginning of the desired output of the production line, click the mouse on the monitor of a central control platform to initialize (as shown in Figure 2)

with the help of ramp function, the speed at a position that you want to change can be pre selected. It is defined as the change of [min] polymer output [kg/h]:

based on the above connection, the change of parameters can be achieved (1, 2, 5)

all sequences are therefore repeatable. The operator can focus on observing the product quality and adjusting the speed of the production line. Any necessary temperature changes for each section are transmitted to the machine either by manual input or through previously stored programs

all machine parameters are continuously recorded and stored, and can be graphically displayed in the form of a trend chart. Using these diagrams, we often keep the clean and sanitary images of experimental machines and computers, and the processing behavior over time can be observed and analyzed. In this way, the parameter change at the desired operation point can also be well monitored by the operator

with appropriate control methods, the operation points of the foaming extrusion line can be set repeatedly and in a simple way. The method of dynamic adjustment of each group that was usually used in the past can be omitted. When production changes, operator errors can be significantly reduced

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