An apparatus and method for extrusion molding of large cross-section foamed plastic products

Abstract

The present application relates to the technical field of plastic extrusion equipment, and discloses an extrusion molding device and method for large-section foamed plastic products. The extrusion molding device for large-section foamed plastic products comprises an extruder main body, a molding die head arranged on the extruder main body, and a guiding and correcting mechanism arranged at the extrusion end of the molding die head. The guiding and correcting mechanism comprises a profile measurement unit, a correcting execution unit, a force sensing unit, and a control unit. The profile measurement unit is used for non-contact measurement of the spatial position and profile data of the foamed blank extruded from the molding die head. The present application is provided with a guiding and correcting mechanism, which measures the spatial position and profile of the foamed blank in real time, calculates the deviation from the reference line, and then calculates the target resultant force vector required for correction and decomposes it to each independently driven guide piece, so as to restore and maintain the correct posture of the blank, effectively solving the problems of manual adjustment lag and root cause management difficulty.

Description

Technical Field

[0001] This invention relates to the field of plastic extrusion equipment technology, and more specifically, to an extrusion molding apparatus and method for large-section foamed plastic products. Background Technology

[0002] In the field of plastic extrusion molding, the production of large-section foamed plastic products (such as dock fender piles and large floating bodies) has always faced significant challenges. After being extruded from the die, the foamed preform, which is in a high-temperature and soft state, is prone to sagging, bending, or twisting deformation before entering the molding die due to factors such as its own weight, uneven extrusion speed of the molding die, differences in internal foaming pressure, and fluctuations in traction force.

[0003] Currently, common solutions mainly rely on manual observation and experience-based intervention, such as adjusting the forming die head bolts or adjusting the traction machine speed. However, these methods still have certain limitations: although the die head bolts can be finely adjusted locally, their adjustment range and precision are very limited in the production of large-section products. Frequent manual intervention is not only time-consuming but also disrupts the continuity and stability of the production process. On the other hand, adjusting the downstream traction speed to correct deviations is problematic because the traction system has large mechanical inertia and slow response. The adjustment process involves the entire system and is cumbersome, making it unable to effectively cope with instantaneous changes in the blank shape.

[0004] Therefore, given the current difficulties in adjusting at the source and the inefficiency of manual adjustment, there is an urgent need for an intelligent extrusion molding device with real-time perception, autonomous decision-making, and precise execution capabilities to achieve proactive, continuous, and stable control of the billet morphology at the die exit stage. Summary of the Invention

[0005] The purpose of this invention is to provide an extrusion molding apparatus and method for large-section foamed plastic products to solve the aforementioned technical problems.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0007] The present invention provides an extrusion molding apparatus for large cross-section foamed plastic products, comprising: an extruder body, a molding die head disposed on the extruder body, and a guide and correction mechanism disposed at the extrusion end of the molding die head;

[0008] The guidance and correction mechanism includes:

[0009] A contour measurement unit is used for non-contact measurement of the spatial position and contour data of foamed preforms extruded from a self-forming die.

[0010] The correction execution unit includes a base and at least three guide members arranged circumferentially on the base along the foamed blank. Each guide member is connected to an independent electric drive member, which can drive the guide member to apply an independent, vector-controllable guiding contact force to the foamed blank.

[0011] A force sensing unit, which is mounted on the guide member, is used to detect the actual guiding contact force applied by the guide member to the foamed blank.

[0012] The control unit is connected to the contour measurement unit, the correction execution unit, and the force sensing unit via signals, and is configured as follows:

[0013] Receive real-time contour and position data of the foamed preform from the contour measurement unit;

[0014] Based on real-time data, the spatial position deviation of the center axis of the foamed blank relative to the preset baseline is calculated.

[0015] Based on the spatial position deviation, calculate the target resultant force vector acting on the foamed blank required to correct the deviation;

[0016] The target resultant force vector is decomposed into target component forces assigned to each guide component;

[0017] It receives actual guide contact force data from the force sensing unit and controls the action of each electric drive component so that the actual guide contact force applied by each guide component approaches the target component force it is allocated to.

[0018] Preferably, the contour measurement unit is a laser contour sensor, which is used to scan the cross-section of the foamed blank to obtain its two-dimensional contour point cloud data.

[0019] Preferably, the guide includes a swing arm hinged to the base and a contact portion mounted on the free end of the swing arm.

[0020] Preferably, the contact portion is a rotatable guide wheel, and the outer periphery of the guide wheel is covered with a flexible material layer with a low coefficient of friction.

[0021] Preferably, the electric drive component is a servo motor that drives the swing arm to swing about its hinge axis.

[0022] Preferably, the correction execution unit further includes a linear driver for driving the base to move parallel to the extrusion direction of the foamed preform.

[0023] Preferably, the force sensing unit is a pressure sensor located between the swing arm and the contact portion.

[0024] Preferably, the control unit includes a control method that combines outer ring position control and inner ring pressure control; the outer ring position control calculates the target resultant force vector based on the spatial position deviation; the inner ring pressure control ensures that each guide component is accurately applied with the target component force.

[0025] Preferably, the control unit is further configured to:

[0026] Record and analyze historical data trends of spatial position deviation and force application of each guide component;

[0027] Based on historical data trends, identify and warn of systemic process defects that cause directional bending of foamed preforms.

[0028] A method for guiding and correcting the alignment of an extrusion molding apparatus includes the following steps:

[0029] Step S100: Measure the spatial position and contour of the foamed preform using the contour measurement unit;

[0030] Step S200: The control unit calculates the spatial position deviation of the center axis of the foamed blank based on the measurement data;

[0031] Step S300: Based on the spatial position deviation, the control unit calculates the target resultant force vector acting on the foamed blank required to correct the deviation;

[0032] Step S400: The control unit decomposes the target resultant force vector into target component forces assigned to each guide component;

[0033] Step S500: The control unit acquires the actual guiding contact force of each guide element detected by the force sensing unit;

[0034] Step S600: The control unit controls the action of each electric drive component so that the actual guiding contact force applied by each guide component to the foamed blank approaches the target component force it is allocated.

[0035] The beneficial effects of this invention are as follows:

[0036] This invention features an intelligent guiding and correction mechanism comprised of a contour measurement unit, a correction execution unit, a force sensing unit, and a control unit. It measures the spatial position and contour of the foamed blank in real time, calculates its deviation from the baseline, and then calculates the target resultant force vector required for correction, decomposing it to each independently driven guide component. Finally, through force closed-loop control, it precisely applies the guiding contact force, restoring the blank to its correct posture. This represents a leap from passive limiting to active and precise correction, effectively solving the problems of lag in manual adjustment and difficulty in addressing root causes. While retaining the basic functions of traditional guides, it significantly improves product straightness, production continuity, and quality consistency. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of an extrusion molding device for large-section foamed plastic products according to the present invention;

[0038] Figure 2 This is a schematic diagram of the structure between the forming die and the guiding and correcting mechanism in an extrusion molding device for a large cross-section foamed plastic product according to the present invention.

[0039] Figure 3 This is a schematic diagram of the guiding and correcting mechanism in an extrusion molding device for a large cross-section foamed plastic product according to the present invention.

[0040] Figure 4 This is a block diagram showing the relationship between the units in the guiding and correcting mechanism of an extrusion molding device for large-section foamed plastic products according to the present invention.

[0041] Figure 5 This is a flowchart of a guiding and correction method for an extrusion molding apparatus according to the present invention.

[0042] In the figure: 10, Extruder body; 20, Forming die head; 30, Guide and correction mechanism; 301, Base; 302, Laser profile sensor; 303, Swing arm; 304, Guide wheel; 305, Flexible material layer; 306, Servo motor; 307, Linear actuator; 308, Pressure sensor. Detailed Implementation

[0043] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0044] Please refer to the following: Figures 1 to 2 An extrusion molding apparatus for large-section foamed plastic products includes: an extruder body 10, a molding die 20 disposed on the extruder body 10, and a guide and correction mechanism 30 disposed at the extrusion end of the molding die 20; the material is plasticized and extruded through the extruder body 10, and a foamed preform with the required cross-sectional shape is formed through the molding die 20. Then, it is straightened by the guide and correction mechanism 30, cooled and shaped by an external shaping device, and pulled by a traction machine to finally obtain the finished product.

[0045] like Figures 2 to 4As shown, the core of this invention lies in the guiding and correcting mechanism 30, which includes a contour measurement unit, a correction execution unit, a force sensing unit, and a control unit. The contour measurement unit employs a two-dimensional laser contour sensor 302, mounted directly opposite the foamed blank, for real-time scanning and acquisition of the complete cross-sectional contour point cloud data of the blank.

[0046] The correction unit includes an annular base 301 on which four guide members are evenly arranged circumferentially. Each guide member includes a swing arm 303 connected to the base 301 via a hinge shaft. A guide wheel 304 is located at the free end of the swing arm 303. The outer circumference of the guide wheel 304 is covered with a flexible polytetrafluoroethylene (PTFE) material layer 305 to reduce friction and protect the surface of the blank. Furthermore, each guide member is connected to an independent electric drive unit, which is a servo motor 306. Its drive end is connected to the swing arm 303, enabling the swing arm 303 to precisely swing around its hinge shaft, thereby changing the contact point and contact force between the guide wheel 304 and the foamed blank.

[0047] In addition, the base 301 of the correction execution unit can also be mounted via a linear slide rail and driven by a linear actuator 307. The linear actuator 307 can be a servo electric cylinder, which can move the entire guide correction mechanism 30 in a direction parallel to the movement of the billet. When the control system detects that the billet has a continuous and large range of deviation, it can coordinate with the linear actuator 307 to move the entire mechanism for coarse adjustment, while coordinating with the fine adjustment of each guide component to expand the correction range and improve the system adaptability.

[0048] The force sensing unit uses a miniature thin-film pressure sensor 308, which is embedded between the mounting base of the swing arm 303 and the guide wheel 304. It is used to directly measure the actual guiding contact force applied by the guide wheel 304 to the foamed blank and send the measurement data to the control unit in real time.

[0049] The control unit is an industrial controller with data processing and logic operation capabilities, such as a programmable logic controller (PLC), an industrial computer (IPC), or an embedded control system. It is connected to the contour measurement unit, the correction execution unit, and the force sensing unit, respectively. It is used to receive signals from the laser contour sensor 302 and the pressure sensor 308 and control the electric drive components.

[0050] In addition, the control unit also has data recording and analysis functions. It continuously records position deviation data and force data of each guide component over a period of time. By analyzing the trends of these data (for example, if it is found that a leftward correction force needs to be continuously applied to keep the product straight), the system can determine that there may be systemic process defects such as "slow material output on the right side of the die head" or "excessive cooling on the left side", and issue a warning to the operator on the human-machine interface, prompting them to perform equipment maintenance or optimize process parameters.

[0051] It should be noted that, as the core intelligent correction function of this invention, a dual-loop closed-loop control algorithm of "outer loop position control - inner loop pressure control" is configured in the control unit, and the specific process is as follows:

[0052] 1. Outer loop position control (calculate the target resultant force vector). The core of this loop is to convert the detected geometric deviation into the mechanical quantity that needs to be applied.

[0053] a. Calculation of position deviation:

[0054] The control unit receives two-dimensional contour point cloud data sent by the contour measurement unit. By performing centroid calculation or ellipse fitting on this data, the coordinates P of the center point of the current cross-section of the foamed billet can be determined in real time. actual (x, y), the preset ideal baseline usually coincides with the extrusion centerline, and the coordinates of its cross-section center point are P. target (0,0), then the spatial position deviation vector ΔP is:

[0055]

[0056] b. Calculation of the target resultant force vector:

[0057] The control unit takes the position deviation ΔP as input and, through a proportional-derivative (PD) controller, calculates the target resultant force vector F that needs to be applied to the foamed preform to eliminate this deviation. target The calculation follows the formula:

[0058]

[0059] in, K is a two-dimensional vector representing the resultant force to be applied in the horizontal (X) and vertical (Y) directions; p It is a proportional gain matrix, usually a diagonal matrix, whose elements K p-x and K p-y K determines the strength of the system's response to position deviation; d It is the differential gain matrix, also a diagonal matrix, whose element K d-x and K d-yUsed to suppress system oscillations and improve stability, d(ΔP) / dt is the rate of change of position deviation (i.e., velocity deviation), providing a lead correction effect; Kp and Kd are gain matrices that take into account the system stiffness and damping characteristics, and their dimensions realize the mapping from position / velocity to force. The values ​​of both are generally determined experimentally, with Kp ranging from 0.8 to 1.2 N / mm and Kd ranging from 0.2 to 0.5 N•s / mm.

[0060] 2. Force vector decomposition (assigning target force components), this step decomposes the target resultant force F. target Intelligent allocation to each guide component.

[0061] a. Establishing a geometric model:

[0062] The control unit presets the position of the contact point of each guide relative to the ideal blank center. For the i-th guide, its position vector is denoted as P. i The unit normal vector pointing to the center of the billet at this point is denoted as n. i The unit normal vector n i That is, the direction in which the guide component can apply force.

[0063] b. Allocate target force:

[0064] The goal is to make the resultant force F target It is decomposed into a series of component forces f along their respective normal directions. i (i.e., the target force component), this is a vector decomposition problem. In a system with at least three non-collinear guides, this problem has a solution. The control unit completes the decomposition by solving the following optimization problem or system of linear equations:

[0065]

[0066] For i=1 to N (N is the number of guide components); at the same time, constraints must be met, such as f i ≥ 0 (the guide component can only be pushed, not pulled); a specific implementation method is to solve for the normal vector n i The target force vector F is obtained by constructing a system of linear equations or an optimization problem. For example, for a system with symmetrically arranged guides, this process can be simplified to trigonometric function calculations through force / moment balance equations.

[0067] 3. Inner loop pressure control (tracking target force component).

[0068] This circuit ensures that each guide component can accurately output its assigned target force component.

[0069] a. Calculation of force deviation:

[0070] For the i-th guide member, the control unit reads the actual guide contact force f from the corresponding force sensing unit. actual-i and its target component f i By comparison, the force deviation is obtained:

[0071]

[0072] b. Driver instruction generation:

[0073] The control unit will control the force deviation e i As input, a proportional-integral (PI) controller generates a command signal to drive the electric actuator, calculated using the following formula:

[0074]

[0075] Among them, u i It is the control signal (such as torque command or position increment command) sent to the i-th servo motor, Kp f It is the proportional gain of the force control loop, Ki f It is the integral gain of the force control loop, used to eliminate steady-state errors and ensure that the actual force accurately tracks the target force, ∫e i dt is the integral of the force deviation.

[0076] Please refer to the following: Figure 5 The working process of the guiding and correction mechanism provided by the present invention is as follows:

[0077] Step 1: The real-time profile of the billet is acquired by the laser profile sensor 302. The control unit receives the profile data and starts to calculate the instantaneous position of the central axis of the billet. It then compares the position with the preset ideal center line to obtain the spatial position deviation (ΔX, ΔY).

[0078] Step 2 (Outer Loop Position Control): Based on the position deviation, the control unit uses a PID algorithm to calculate the resultant force vector F (including magnitude and direction) required to "push" the billet back to the correct position.

[0079] Step 3: Based on the real-time spatial position of the four guide components, the control unit decomposes the resultant force F into four target component forces (F1, F2, F3, F4) distributed to the four guide wheels 304 using a force vector decomposition algorithm.

[0080] Step 4 (Inner Loop Pressure Control): The control unit sends commands to the four servo motors 306 to adjust the angle of each swing arm 303. At the same time, it reads the feedback values ​​of the four pressure sensors 308 in real time. For each guide, the system compares its target component force (such as F1) with the actual force fed back by the pressure sensor 308. The torque and position of the servo motor 306 are finely adjusted by the second PID controller to ensure that the actual applied force accurately tracks the target component force.

[0081] Through the aforementioned closed-loop control, the system can dynamically and flexibly keep the foamed preform on the ideal path at all times, achieving automatic deviation correction of the extruded preform. Compared with the prior art, this invention has the following advantages:

[0082] First, the present invention constructs a closed-loop automatic control system through the collaborative work of the contour measurement unit, the force sensing unit and the control unit. It can sense the shape changes of the billet in real time and instantly complete the fully automated correction from "detection" to "decision" to "execution", reducing the dependence on the operator's experience and solving the inherent drawbacks of slow and inefficient manual adjustment.

[0083] Second, the intelligent guiding and correction mechanism 30 of the present invention acts independently in the key area between the die head outlet and the shaping die inlet. Its response speed is much faster than the "cumbersome" process of adjusting the traction system, and its control precision and range far exceed the ability of manually adjusting the die lip bolts. As a high-frequency and precise "online corrector", it effectively fills the gap in existing control methods.

[0084] Third, the present invention achieves fully automatic correction, eliminating the need for frequent machine stops for manual adjustment due to billet shape issues, thus ensuring stable and continuous production. At the same time, precise vector force control ensures that each billet enters the shaping mold in the best posture, thereby significantly reducing the scrap rate and improving the consistency of product size and shape.

[0085] Fourth, the present invention achieves precise closed-loop control of the guiding contact force through the force sensing unit, making the correction process "flexible" for the soft foamed blank, avoiding secondary quality problems such as damage to the cell structure, surface depression or uneven density caused by excessive local pressure, and protecting the core mechanical properties and appearance of the product while effectively correcting the deviation.

[0086] Fifth, the guide correction mechanism 30 designed in this invention is an improvement on the traditional guide mechanism. While retaining the basic limit function, it is endowed with the ability to perceive, make decisions and execute, thus realizing the transformation from "fixed limit" to "adaptive dynamic posture adjustment". This makes the invention compatible with existing production lines and completely surpasses and replaces the traditional guide mechanism in terms of function.

[0087] The embodiments of the present invention have been described above, but the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention, all of which are within the protection scope of the present invention.

Claims

1. An apparatus for extrusion molding of large cross-section foamed plastic products, characterized in that, The application relates to a guiding and rectifying mechanism for a foaming blank extruded from a molding die of an extruder, which comprises an extruder body, a molding die arranged on the extruder body and the guiding and rectifying mechanism arranged at the extruding end of the molding die. The guiding and rectifying mechanism comprises: a profile measuring unit for non-contact measurement of the spatial position and profile data of the foaming blank extruded from the molding die; a rectifying execution unit comprising a base and at least three guiding members arranged on the base in a circumferential direction of the foaming blank, each of the guiding members being connected with an independent electric drive member, and the electric drive member being capable of driving the guiding member to apply an independent and vector-controllable guiding contact force to the foaming blank; a force sensing unit arranged on the guiding member for detecting the actual guiding contact force applied by the guiding member to the foaming blank; a control unit connected with the profile measuring unit, the rectifying execution unit and the force sensing unit, and configured to: wherein Kp is a proportional gain matrix and Kd is a differential gain matrix; Receive real-time contour and position data of the foamed preform from the contour measurement unit, and determine the coordinates P of the center point of the current cross-section of the foamed preform. actual (x, y), and calculate its coordinates P relative to the center point of the preset baseline. target The spatial position deviation vector ΔP is (0,0). The control mode of combining outer ring position control and inner ring pressure control is adopted: in the outer ring position control, the position deviation ΔP is taken as the input, and the target force vector F applied on the foaming blank for eliminating the deviation is calculated through the PD controller target , and the calculation formula is: ； so that the actual guiding contact force applied by each guiding member approaches the target component force allocated to the guiding member. The target resultant force vector F target is decomposed into target components f i assigned to the individual guides, the decomposition logic being: ； where n i is the unit normal vector pointing to the center of the blank at the i-th guide contact point and satisfies the constraint condition f i ≥ 0; In inner loop pressure control, actual guiding contact force data f from the force sensing unit is received actual-i , a force deviation is calculated: ； and generates an instruction signal u for driving the electric drive member through a PI controller i The calculation formula is: ； The profile measuring unit is a laser profile sensor for scanning the cross section of the foaming blank to obtain two-dimensional profile point cloud data of the foaming blank.

2. An apparatus for extrusion molding of a large cross-section foamed plastic product according to claim 1, wherein The guiding member comprises a swing arm hinged to the base and a contact part mounted at the free end of the swing arm.

3. An apparatus for extrusion molding of a large cross-section foamed plastic product according to claim 1, wherein The contact part is a rotatable guiding wheel, and the outer periphery of the guiding wheel is covered with a flexible material layer with a low friction coefficient.

4. An apparatus for extrusion molding of a large cross-section foamed plastic product according to claim 3, wherein The electric drive member is a servo motor for driving the swing arm to swing around the hinge shaft.

5. An apparatus for extrusion molding of a large cross-section foamed plastic product according to claim 3, wherein The rectifying execution unit further comprises a linear drive for driving the base to move along a direction parallel to the extruding direction of the foaming blank.

6. An apparatus for extrusion molding of large cross-section foamed plastic articles according to claim 1, characterized in that, The force sensing unit is a pressure sensor arranged between the swing arm and the contact part.

7. An apparatus for extrusion molding of a large cross-section foamed plastic product according to claim 3, wherein The control unit comprises an outer ring position control and an inner ring pressure control, the outer ring position control calculates a target resultant force vector according to the spatial position deviation, and the inner ring pressure control ensures that each guiding member accurately applies the target component force.

8. The apparatus for extrusion molding of a large cross-section foamed plastic product according to claim 1, wherein The control unit is further configured to:

9. The apparatus for extrusion molding of a large cross-section foamed plastic product according to claim 1, wherein record and analyze the historical data trend of the spatial position deviation and the force applying condition of each guiding member; judge and warn the systematic process defects causing the directional bending of the foaming blank based on the historical data trend. The application further discloses an operation method of the guiding and rectifying mechanism, which comprises the following steps:

10. A method for guiding and correcting deviation of an extrusion molding device, applied to the extrusion molding device of a large-section foamed plastic product according to any one of claims 1-9, characterized in that, Step S100: measuring the spatial position and profile of the foaming blank by the profile measuring unit; Step S200: calculating the spatial position deviation of the central axis of the foaming blank by the control unit based on the measurement data; Step S300: calculating the target resultant force vector acting on the foaming blank required for rectifying the deviation based on the spatial position deviation by the control unit; Step S400: decomposing the target resultant force vector into target component forces allocated to each guiding member by the control unit; Step S500: obtaining the actual guiding contact forces of each guiding member detected by the force sensing unit by the control unit; Step S600: controlling the actions of each electric drive member by the control unit so that the actual guiding contact forces applied by each guiding member to the foaming blank approach the target component forces allocated to the guiding member. ​

Images