Extruder and control method thereof

Abstract

To prevent or suppress deterioration of appearance quality of an extruded product.SOLUTION: An extrusion apparatus includes: a cylinder through which a material is introduced and conveyed; an agitation part for agitating the material introduced into the cylinder; a detection part to detect a temperature of the cylinder; a heat source to heat the cylinder; and a control part that controls an output of the heat source according to the temperature detected by the detection part. The control part controls the output of the heat source so that a temperature range does not exceed a pressure threshold, which is the pressure applied to the material when it is extruded from the cylinder and is also a threshold for distinguishing an appearance quality.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an extruder and a method for controlling the same. [Background technology]

[0002] There are known extruders that perform extrusion or injection molding of thermoplastic resins, etc. For example, there is a screw-type extruder in which a material such as thermoplastic resin supplied into a cylinder is stirred and extruded by a rotating part such as a screw, and sent to a die (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-109351 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, in the extrusion molding process, a resin molten in an extruder is extruded through a die and coated onto a core wire or molded into a tube shape or the like.

[0005] In addition, it was said that in the extrusion molding process, the quality of the product's appearance was determined (influenced) by the state of the resin in the die during extrusion and the manufacturing conditions.

[0006] In order to address this issue, various improvement proposals have been made to optimize manufacturing conditions. However, there is a problem in that it is difficult to balance the quality of the product appearance with other product properties, such as tensile strength and outer diameter.

[0007] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0008] In one embodiment, the extruder comprises: a cylinder into which the material is introduced and conveyed; a stirring unit that stirs the material introduced into the cylinder; a detection unit that detects the temperature of the cylinder; a heat source for heating the cylinder; a control unit that controls an output of the heat source in accordance with the temperature detected by the detection unit, The control unit controls the output of the heat source so that the temperature range does not exceed the pressure threshold, which is the pressure applied to the material when it is extruded from the cylinder to the outside and is a threshold for distinguishing between good and bad appearance quality. [Effects of the Invention]

[0009] According to one embodiment, deterioration in the appearance quality of an extrusion-molded product can be prevented or suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating an extrusion device according to an embodiment. [Figure 2] FIG. 2 is a block diagram illustrating the electrical configuration of the extrusion device according to the embodiment. [Figure 3] FIG. 2 is a cross-sectional view illustrating the internal configuration of a screw extruder. [Figure 4] 1 is a data table showing the results of an experiment conducted by the present inventors regarding the appearance quality of a resin product manufactured through an extrusion molding process using the extrusion device of the present disclosure. [Figure 5] FIG. 10 is a characteristic diagram showing the relationship between the resin pressure value at the cylinder outlet and the quality of the product appearance, based on the results of experiments conducted by the present inventors. [Figure 6] 10 is a flowchart showing an example of control content by a control unit. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment will be described in detail below with reference to the drawings. In all drawings used to explain the embodiment, the same reference numerals are used to designate components and devices having the same or substantially the same functions, and repeated description thereof will be omitted.

[0012] <Extrusion equipment> Fig. 1 is a schematic diagram showing an extrusion device according to one embodiment. The extrusion device 1 shown in Fig. 1 shows a part of an extrusion molding device or system that extrudes a resin material (hereinafter also simply referred to as "material") 800 around an electric wire 700 to produce a long tubular covering member (sheath) and produces a cable 900 as a final product. Hereinafter, the terms "conveying direction" and "extrusion direction" refer to the direction in which the material 800 is conveyed or extruded, unless otherwise specified.

[0013] This extrusion device 1 includes an extruder 2 that introduces material 800 into a conveying path 210 (see Figure 3) and extrudes the introduced material 800 downstream while stirring and heating it, a crosshead 3 (see Figure 1) that is provided downstream of the extruder 2 in the conveying direction, and a water tank 5 that forms part of a cooling device 200 (see Figure 2) for cooling the manufactured cable 900.

[0014] Fig. 2 is a block diagram for explaining the electrical configuration of the extrusion device of this embodiment. Although not shown in Fig. 1, the extrusion device 1 includes, as elements thereof, a take-up device 300 for taking up a product (cable 900 in this example), a cutting device 400 for cutting the product, and the like (see Fig. 2 for each). Of these, the take-up device 300 is disposed downstream of the water tank 5 in the conveying direction. The cutting device 400 is disposed downstream of the take-up device 300 in the conveying direction. Note that the take-up device 300 and the cutting device 400 have known configurations, and therefore detailed description thereof will be omitted. The electrical configuration of the extruder 2 will be described later.

[0015] <Extruder> Fig. 3 is a partial cross-sectional view illustrating the internal structure of the extruder 2. Referring to Figs. 1 and 3, the extruder 2 includes a tubular cylinder 21 provided with a conveying path 210, a screw 22 axially rotatably provided within the conveying path 210 of the cylinder 21, and a hopper 23 disposed upstream of the cylinder 21 in the conveying direction. Hereinafter, the extruder may be referred to as a screw extruder to clearly distinguish it from the extrusion device 1, etc.

[0016] <Cylinder and screw> The cylinder 21 is also called a "barrel" and serves to supply the material 800 (e.g., pellet-shaped resin) placed in the hopper 23 into the conveying path 210, compress and heat the supplied material 800, and convey it in the extrusion direction.

[0017] Although not shown in Fig. 3, the cylinder 21 is equipped with a detection unit 120 (see Fig. 2) such as a temperature sensor or a pressure gauge to detect the conditions (temperature, pressure, etc.) inside the conveying path 210. The cylinder 21 also has a heater 140 (see Fig. 2) as a heat source for heating the material 800 inside the conveying path 210. A cylinder equipped with such a heat source is also called a "heating cylinder."

[0018] The screw 22 in the cylinder 21 rotates in a predetermined direction to agitate and compress the supplied material 800 and transport it by pushing it out to the outlet side (right side in FIG. 3) of the transport path 210. The screw 22 rotates in a predetermined direction (the direction in which the material 800 is pushed out) by transmitting the driving force of a motor (located on the left side in FIG. 3), which is an element of the screw driving unit 130 shown in FIG. 2.

[0019] The main function of the conveying path 210 of the cylinder 21 changes for each region along the conveying direction (extrusion direction) depending on the configuration of the screw 22 and the arrangement of the heater 140. That is, as shown in Fig. 3, the main function of the conveying path 210 of the cylinder 21 changes from the upstream side in the conveying direction (extrusion direction) to a supply section, a compression section, and a metering section (discharge amount adjustment section). The differences in functions along the conveying path 210 of the cylinder are well known, and therefore a detailed description thereof will be omitted.

[0020] <Crosshead 3> The crosshead 3 is connected to the outlet side of the cylinder 21 (the right side in FIG. 3, the front side in FIG. 1). In practice, the crosshead 3 is connected to the cylinder 21 via a connecting member called a "neck" (not shown), so that a conveying path (not shown) formed in the head communicates with the conveying path 210 of the cylinder 21. A die 4 is provided downstream of the conveying path in the crosshead 3 to define (shape) the outer shape of the product (a sheath in this example).

[0021] The crosshead 3 introduces the molten material 800 sent from the cylinder 21 through the neck, and advances the introduced material 800 in a direction intersecting the extrusion direction (for example, approximately perpendicular), and passes it through the downstream die 4, thereby shaping the material 800 into a long tubular shape.

[0022] 1, the entrance of the conveying path of the crosshead 3 extends not only on the side where it is connected to the cylinder 21 described above (toward the back in FIG. 1, in other words, the first entrance), but also to the left in FIG. 1 as a second entrance. In this embodiment, the electric wire 700 is inserted from the second entrance of the crosshead 3, and a sheath is formed around the electric wire 700 through the die 4, thereby producing a cable 900 as a final product.

[0023] <Outline of operations during the production of resin extrusion products> An outline of the operation of the extrusion device 1 when manufacturing the cable 900 will now be described.

[0024] First, a material 800 having a predetermined shape (pellets in this example) is introduced into the hopper 23 of the extruder 2. The introduced resin falls by gravity and is introduced into the cylinder 21. The introduced resin is melted in the cylinder 21 and stirred and mixed by the rotating screw 22. The mixed resin (molten material 800) is transported in the extrusion direction indicated by the arrow in FIG. 3 according to the shape of the screw 22, then introduced into the crosshead 3, shaped by the die 4, and drawn out as a sheath. In parallel with this operation, an electric wire (a conductor coated with an insulator) 700 passing through the crosshead 3 is covered with the molten material 800 (sheath) in the crosshead 3, passes through the die 4, and is drawn out from the crosshead 3 as a cable 900 (final product). The cable 900 is cooled in the water tank 5, drawn out by the take-up device 300, and cut to a predetermined length by the cutting device 400.

[0025] <Electrical configuration> The electrical configuration of the extrusion device 1 will be described with reference to FIG.

[0026] As shown in FIG. 2, the extrusion device 1 includes a control unit 100 that controls the entire extrusion device 1, an operation display unit 110 connected to the control unit 100, a detection unit 120, a screw drive unit 130, a heater 140, a recording medium 150, a cooling unit 200, a take-up unit 300, and a cutting unit 400.

[0027] The control unit 100 includes hardware such as a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), RAM (Random Access Memory) that serves as the working area for the processor, and ROM (Read-Only memory) that stores programs that are read and executed by the processor.

[0028] The control unit 100 has the function of controlling the entire extrusion device 1 by outputting control signals to each component of the extrusion device 1. In this embodiment, the control unit 100 also has characteristic functions such as reading out a table T (described later) and setting the extruder 2 based on the read out table T.

[0029] The operation display unit 110 is, for example, a display with a touch panel, and displays various setting screens and accepts operation inputs from the user.

[0030] The detection unit 120 includes various sensors such as a pressure sensor and a temperature sensor. Among these, a plurality of temperature sensors are arranged inside the cylinder 21, and are also arranged in the neck, crosshead 3, and die 4 described above. The pressure sensor is arranged, for example, near the outlet of the cylinder 21.

[0031] The screw driving unit 130 includes a motor for rotating the screw 22, a driving circuit for driving the motor, and the like.

[0032] The heaters 140 are heat sources such as ceramic heaters, and several heaters 140 are arranged at predetermined positions on the cylinder 21 and also on the crosshead 3.

[0033] The recording medium 150 is a medium for storing various data read by the control unit 100, and various data storage media such as a HDD or a flash memory can be used. The recording medium 150 also stores a table T read by the control unit 100. Details of the table T will be described later.

[0034] <Issues in extrusion equipment and extrusion molding> As mentioned above, various improvement proposals have been made to maintain or improve the quality of product appearance. For example, there have been proposals to improve product characteristics by optimizing temperature conditions such as the cylinder temperature and the crosshead temperature.

[0035] On the other hand, it seems that there has not been a perspective (approach) to clarify the most favorable manufacturing conditions during extrusion molding by focusing only on the "appearance" of the product. One reason for this is that it is difficult to balance the appearance of a product manufactured by extrusion molding with other properties of the product (such as the tensile strength and outer diameter of the product), and there is a tendency for the latter properties such as outer diameter to be given more importance.

[0036] From another perspective, in the above-mentioned extrusion device or system, in order to control the appearance of the product manufactured by extrusion molding (cable 900 in the above example), the pressure value (hereinafter also referred to as "extrusion parameter") used to extrude the resin from die 4 was adjusted based on the intuition and experience of the operator.

[0037] More specifically, it has been empirically known that the above-mentioned extrusion parameters are important values that determine the quality of the product. However, the extrusion parameters are also related to other factors (manufacturing conditions) that affect the product quality, such as the temperature of each part of the extrusion device, the linear speed (the speed at which the material is conveyed or taken up, hereinafter also referred to as the "take-up speed"), and the type of material, and therefore it has been thought that it is difficult to determine uniform values.

[0038] Furthermore, it has been said that the appearance quality of a product is dominated by the shear stress generated within the die 4 during extrusion. Here, the shear stress is calculated from the viscosity and shear rate of the resin. Viscosity is a function of temperature, and generally, the higher the temperature, the lower the viscosity. On the other hand, the shear rate is determined by the extrusion force of the screw 22 and the take-up force of the take-up device 300. However, since the latter, i.e., the take-up force, is usually stronger, the shear rate is closely related to the take-up speed of the take-up device 300.

[0039] As a result of extensive research and various experiments into the above problem, the inventors have discovered that the following phenomenon occurs: In other words, in the extrusion device 1 configured as described above, the pressure applied to the molten resin or other material 800 (hereinafter sometimes referred to as "molten resin") in the flow path (conveyance path) leading to delivery to the die 4 increases excessively, which deteriorates the appearance quality of the resin product molded by the die 4.

[0040] In particular, we have found that if the pressure exerted on the molten resin at (or near) the outlet of the cylinder 21 immediately before the neck in the extruder 2 becomes excessively high, the appearance quality of the resin product extruded and molded from the die 4 deteriorates significantly.

[0041] It was also found that the appearance quality of the extrusion-molded product is not closely related to the line speed (the speed at which the product is pulled out by the take-up device 300), and that a faster line speed may be more advantageous depending on the conditions.

[0042] 4 is a data table showing the results of an experiment conducted by the present inventors on the appearance quality of resin products manufactured through an extrusion molding process using the extrusion apparatus of the present disclosure. The present inventors conducted an experiment to inspect the appearance quality of products actually manufactured by using the linear speed (m / min), i.e., the product withdrawal speed by the take-up device 300 and the rotation speed (rpm) of the screw 22, as variables, and also appropriately changing the set temperatures of each zone in the extrusion apparatus 1. The appearance quality inspection was performed by an experienced person who visually judged the appearance to be good or bad (passing product "O" or failing product "X").

[0043] In addition, in each experiment, the inventors used the temperature of each region within the cylinder, the viscosity of the resin near the outlet of the cylinder 21 ("C5" in the data table), which will be described later, and the amount of resin discharged as parameters (input variables) to determine the pressure applied to the resin at the outlet of the cylinder 21 using a simulator, and considered the correlation between each value, etc.

[0044] <Common conditions for Experiments 1-29> Common conditions for each experiment are explained below. In each of Experiments 1 to 29, the inner diameter of the die 4 was 2.4 (mm), and the material 800 was TPU (Thermoplastic Polyurethane), which is used for electrical wires and cables in automobiles.

[0045] In the table, C1 to C5 represent positions and temperatures along the conveying direction of the cylinder 21. Specifically, along the conveying direction of the cylinder 21 (the extrusion direction in FIG. 3), C1 represents the temperature at the most upstream position (near the hopper 23), followed by C2, C3, and C4, in that order, on the downstream side, and C5 represents the temperature at the most downstream position (near the outlet). C1 to C5 are spaced at approximately equal intervals.

[0046] Here, the temperatures (°C) of C1 to C5 in the table can be measured by a temperature sensor in the cylinder 21, but since listing exact measured values would make the table difficult to understand, the temperatures listed are approximate measured values or set values. Similarly, the temperatures shown in N, H, and D in the table are approximate measured values or set values in the passages (transport paths for material 800, etc.) of the neck, crosshead 3, and die 4, respectively.

[0047] Hereinafter, C(1 to 5), N, H, and D in the table may be referred to as "area C1" or "position C1" for convenience.

[0048] As shown in the table, in each of the experiments (1 to 29), the temperatures of the regions C1 and C2 in the cylinder 21 were approximately 130°C and approximately 180°C, respectively. In addition, throughout the experiments 1 to 29, the temperatures of the neck (N), crosshead (H), and die (D) were each 235°C.

[0049] Of the above, regions C1 and C2 of cylinder 21 are not provided with heater 140 and are therefore difficult to regulate the temperature in. In contrast, regions C3, C4, and C5 of cylinder 21 are each provided with both heater 140 and a temperature sensor, making temperature regulation possible (easy).

[0050] In addition, both a heater 140 and a temperature sensor are provided inside the crosshead 3, and the temperature of the neck (N) and die (D) can be adjusted by this heater 140, but in these experiments (1 to 29), the set temperature was fixed (235°C) as described above.

[0051] In actual experiments (1 to 29), the product (cable 900) was manufactured when the temperature of each region (C1 to D) in the table in the extrusion device 1 reached a stable state near the set value.

[0052] Furthermore, in Experiments 1 to 29, the appearance quality of the actually manufactured cable 900 was judged (distinguished) by visual inspection by an experienced person as to whether it was acceptable (passed) or unaccepted (rejected). Furthermore, the "resin pressure" (pressure value (MPa) applied to the resin extruded from the outlet of cylinder 21; the same applies below) in each experiment was calculated using a computer equipped with software for performing thermal fluid analysis simulations.

[0053] Specifically, this software can calculate the above resin pressure by inputting the following parameters (1) to (3): (1) Temperature of each area of the cylinder 21 (five areas C1 to C5) (2) Viscosity of resin when extruded from extruder 2 (cylinder 21) (3) Amount of resin extruded from the outlet of extruder 2 (cylinder 21)

[0054] Note that the above parameters (2) and (3) are not directly shown in the table of Fig. 4. Of these, the viscosity of the resin (2) is a function of temperature (in this example, the temperature of region C5 near the outlet of cylinder 21), and since the viscosity of resin generally decreases as the temperature increases, it is determined by the temperature of region C5 of cylinder 21.

[0055] The resin discharge amount (3) is a function of the linear velocity, and the faster the linear velocity, the greater the discharge amount. Furthermore, the larger the diameter (mm) of the die 4, the greater the resin discharge amount.

[0056] For this reason, the inventors input the temperature (actually measured or set value) at each position (C1 to C5) of the cylinder 21 as parameter (1), calculated the value of parameter (2) from the set temperature of region C5 of the cylinder 21 and input it, calculated the value of parameter (3) from the diameter of the die 4 (2.4 mm in this example) and the set value of the linear speed of the take-up device 300 and input it into the computer, and calculated the resin pressure value to be applied to the material 800 (molten resin) extruded from the outlet of the cylinder 21.

[0057] <About variables> Next, the variables, that is, the conditions that are set to different values depending on the experiment, will be described.

[0058] As shown in the table in Figure 4, in experiments 1 to 10, the temperature conditions (temperatures in areas C1 to D in °C) were the same, the rotation speed (rpm) of the screw 22 was set to a fixed value (15 rpm), and the linear speed (take-up speed (m / min) by the take-up device 300; the same applies below) was set to 10, 12, ... 30 (m / min) in increments of 2 (m / min) for each experiment.

[0059] Similarly, in Experiments 11 to 16, the temperature conditions (temperatures in regions C1 to CD in °C) were the same as in Experiments 1 to 10, the rotation speed (rpm) of the screw 22 was set to a fixed value of 12.5 (rpm), which was slightly slower, and the linear speed was set to 18, 20, and 28 (m / min) in increments of 2 (m / min) for each experiment.

[0060] In addition, in Experiments 17 to 19, the temperature conditions (temperatures in regions C1 to D in °C) were the same as in Experiments 1 to 16, the rotation speed (rpm) of the screw 22 was set to an even slower fixed value of 10 (rpm), and the linear speed was set to 18, 20, and 22 (m / min) for each experiment, increasing in increments of 2 (m / min). Experiment 20, an additional experiment, will be described later.

[0061] On the other hand, in Experiments 21 to 29 as comparative examples, the temperatures of regions C3, C4, and C5 of cylinder 21 were each set to a low value of 200°C, and the other conditions were the same or similar to those of Experiments 3 to 7 or Experiment 11 (see the table in Figure 4 as appropriate).

[0062] More specifically, Experiments 21, 22, 23, 24, and 25 were conducted under the same conditions as Experiments 3, 4, 5, 6, and 6, respectively, except for the temperature conditions downstream of the cylinder 21. On the other hand, in Experiments 26 to 29, based on the results of Experiments 21 to 25, experiments were conducted to examine the possibility that the appearance quality of the product could be improved (○) by changing the combination of linear speed and rotation speed.

[0063] Furthermore, since the appearance quality of the products in the above comparative examples (Experiments 21 to 29) was all unacceptable (×), an additional experiment (Experiment 20) was conducted under the same conditions as Experiment 19 except for the temperature conditions in order to investigate the lower limit of the temperature (in other words, the upper limit of the viscosity) of regions C3, C4, and C5 of cylinder 21.

[0064] <Experimental Results> The results of the above-mentioned Experiments 1 to 29 will be explained below by dividing them into experimental groups in which the rotation speed (rpm) of the screw 22 was kept constant.

[0065] <Results of Experiments 1 to 10> In Experiments 1 to 10, in which the rotation speed (rpm) of the screw 22 was set to 15 rpm, the appearance quality of all products was acceptable (○). In addition, the resin pressure (MPa) at the outlet of the cylinder 21 had little correlation with the linear speed, and rather, there was a tendency for the resin pressure (MPa) to be higher in Experiments 1 to 3, in which the linear speed was slower.

[0066] <Results of Experiments 11-16> In Experiments 11 to 16, in which the rotation speed (rpm) of the screw 22 was set to 12.5 rpm, the appearance quality of all products was acceptable (◯). Similarly, it was confirmed that the resin pressure (MPa) at the outlet of the cylinder 21 has little correlation with the linear velocity.

[0067] <Results of Experiments 17-19> In Experiments 17 to 19, in which the rotation speed (rpm) of the screw 22 was further slowed to 10.5 rpm, the appearance quality of all products was acceptable (○). Similarly, it was found that the resin pressure (MPa) at the outlet of the cylinder 21 had little correlation with the linear speed, and that the resin pressure actually decreased when the linear speed was increased to 20 to 22 (m / min).

[0068] <Results of Experiments 21-25> In Experiments 21 to 25 as comparative examples, the appearance quality of all products was unacceptable (×). In addition, the resin pressure (MPa) at the outlet of the cylinder 21 was a high value (approximately 31 to 43 MPa) that was clearly distinguishable from the above-mentioned Experimental Examples 1 to 19.

[0069] <Results of Experiments 26-29> In Experiments 26, 27, 28, and 29, which were comparative examples, the temperature conditions were the same as in Experiments 21 to 25, i.e., the temperature downstream of the cylinder 21 was set to 200°C, and the rotation speed of the screw 22 was set to 12.5 rpm, the same as in Experiments 11 to 16, where the resin pressure was relatively low. Meanwhile, the linear speed was set to 12 to 18 m / min, the same as in Experiments 2 to 6. However, in Experiments 26 to 29, the appearance quality of all the products was unacceptable (×). Furthermore, the resin pressure (MPa) at the outlet of the cylinder 21 was high (approximately 30 to 36 MPa), clearly distinguishable from the above-mentioned Experiments 1 to 19.

[0070] <Results of additional experiment (Experiment 20)> Based on the results of the comparative examples (Experiments 21 to 29), in Experiment 20, the linear velocity and rotational speed of cylinder 21 were set to the same as in Experiment 19, and the set temperatures of regions C3, C4, and C5 of cylinder 21 were gradually lowered to investigate the lower limit temperature at which the appearance quality of the manufactured product was judged to be pass (○). As a result, it was found that the appearance quality of the product could be maintained even when the set temperatures of regions C3 to C5 of cylinder 21 were lowered to 225°C. In this case, the resin pressure (MPa) at the outlet of cylinder 21 showed a value close to that of Experimental Example 18 described above (see Figure 4 where appropriate).

[0071] Next, the inventors created a characteristic diagram as shown in Fig. 5 to confirm the relationship between the resin pressure (MPa) obtained in the above-mentioned Experiments 1 to 29 and the quality of appearance (good or bad). As a result, it was confirmed that the resin pressure (MPa) at the outlet of the cylinder 21 has a threshold value that distinguishes the quality of appearance (good or bad). In this example, it can be seen that the threshold value (pressure threshold) is in the range of approximately 27 to 29 MPa.

[0072] For ease of understanding, the horizontal axis in the table (characteristic graph) shown in Figure 5 is linear velocity (m / min), but as another example, the horizontal axis may be the rotation speed (rpm) of the screw 22, and it will be understood that the above-mentioned pressure threshold value remains unchanged in this case as well. As described above, the inventors conducted experiments and studies to clarify more preferable manufacturing conditions during extrusion molding, focusing only on the appearance (quality of appearance) of the product manufactured by the extrusion molding process, and discovered that there exists a pressure threshold as described above.

[0073] This "pressure threshold" is the pressure value applied to the material 800 when the material 800 passes through the outlet of the cylinder 21, and is a threshold value that determines whether the appearance quality of the product formed in the downstream die 4 is good or bad depending on this pressure. Specifically, if the pressure applied to the molten resin passing through the outlet of the cylinder 21 exceeds the threshold value (upper limit), the appearance quality of the product formed in the die 4 will deteriorate to a level that can be discerned by human vision.

[0074] In the experiments conducted by the inventors, it was not possible to verify the effect on appearance quality when the pressure applied to the molten resin is low. Referring to Figures 4 and 5, when the resin pressure is lower than a certain value, the appearance quality is good (◯), so in this experimental example, the "pressure threshold" can also be rephrased as the "upper pressure limit."

[0075] It was also found that the "pressure threshold" is not an exact numerical value as in the case of, for example, a phase change, but has a certain degree of width (range). From another perspective, this also means that, as shown by the results of the additional experiment (Experiment 20) described above, the temperature (in other words, viscosity) of the material 800 can be given some degree of width when the material 800 is conveyed downstream, including to the outlet of the cylinder 21.

[0076] Further experimentation also revealed that the "pressure threshold" can vary depending on the type of material being extruded.

[0077] Additionally, it was found that the "pressure threshold" has little correlation with the speed at which the material is extruded (i.e., the linear velocity or material conveying speed).

[0078] In view of the technical significance of the "pressure threshold" described above, it is conceivable to configure the extrusion device or system of the present disclosure as follows. That is, a pressure measurement unit such as a high-performance pressure sensor or pressure gauge is provided at the outlet of the cylinder 21, and an on-off valve is provided to adjust this pressure. Then, while the device is in operation, the measurement results (measured pressure values) of the pressure measurement unit are input to a control unit such as a processor for automatic monitoring, and if there is a risk that the pressure applied to the molten resin will exceed the threshold (upper limit), the control unit opens the on-off valve to control the pressure applied to the molten resin so that it does not exceed the pressure threshold.

[0079] On the other hand, with the above-mentioned configuration, it is not necessarily easy to fine-tune the pressure applied to the molten resin, and the opening operation of the on-off valve may significantly reduce the pressure applied to the molten resin, which may result in other problems such as making it impossible to perform extrusion molding itself.

[0080] Furthermore, even if an on-off valve capable of fine-tuning the pressure is used, there will be a need to modify existing equipment or add additional components, which will pose a cost issue. In other words, from the perspective of minimizing additional costs, it is desirable to have a configuration that requires as few changes as possible to existing equipment.

[0081] In light of the above-mentioned background, the present inventors propose the following method and configuration.

[0082] (Process 1) As a preparatory step, an experiment (hereinafter sometimes referred to as a "preliminary experiment") is carried out to manufacture a test sample of an extrusion molded product, as described above in the explanation of FIG.

[0083] Here, based on the temperature conditions of the downstream region including the outlet portion inside the cylinder 21 (C3, C4, C5 in this example) and the results of the appearance quality of the manufactured test product being good or bad (○ ×), the pressure (resin pressure) applied to the material at the outlet portion inside the cylinder 21 (C5 in this example) is calculated in the experiment in which the appearance quality was good (○) under the lowest temperature conditions, and this pressure value is set as the "pressure threshold value."

[0084] Ideally, this preliminary experiment should be performed for each material that will actually be used. However, if the components of the materials are similar, the pressure threshold values are likely to be similar, so the number of preliminary experiments can be reduced.

[0085] (Process 2) To enable automatic processing by the control unit 100, the experimental results of step 1, in this case the pressure threshold value and the temperature conditions of the downstream areas (C3, C4, C5) including the corresponding outlet portion in the cylinder 21, are registered in table T. This table T is created with a table name (ID, etc.) assigned for each material actually used, and it is advisable to store the table T in a database on a recording medium 150 such as a hard disk drive or RAM, as shown in FIG.

[0086] (Step 3) When the apparatus is put into operation (before the start of operation), the control unit 100 selectively reads out Table T corresponding to the material that will actually be used from the recording medium 150. This step 3 can be performed by, for example, an input operation using a user interface such as the operation display unit 110 described above in FIG. 2. In response to this input operation, the control unit 100 selects the corresponding Table T from the recording medium and reads out the numerical values registered in that Table T (the pressure threshold value and the temperature condition of the corresponding cylinder 21).

[0087] (Step 4) Next, immediately before the device starts operating, the control unit 100 sets upper and lower limit temperatures for each part of the device (in this example, each area where the temperature sensor and heater 140 are located) according to the values read from the table T. Of these, the set lower limit temperature corresponds to the pressure threshold value described above.

[0088] (Step 5) After the device starts operating, the control unit 100 drives the heater 140 and each unit, and determines whether the path (each of the above-mentioned areas) along which the material 800 is conveyed is within the set temperature range. If the control unit 100 determines that all areas are within the set temperature range, it determines that the resin pressure (MPa) applied to the material 800 at the outlet of the cylinder 21 is appropriate, and repeats this determination while maintaining the output of the heater 140.

[0089] On the other hand, when it is determined that there is an area that is outside the set temperature range, the control unit 100 determines that the pressure applied to the material in that area is not appropriate, and controls the output of the heater 140 depending on the deviation mode (whether the upper limit or lower limit is exceeded). Details of this control will be described later in the explanation of the flowchart.

[0090] As described above, the device of the present disclosure controls the output of the heater 140 using a pressure threshold, which is the pressure applied to the material 800 when the material 800 is extruded from the cylinder 21 to the outside and is a threshold for distinguishing between good and bad appearance quality, and can maintain or improve the appearance quality of the extrusion-molded product.

[0091] Furthermore, by using the above-mentioned method, it is possible to minimize changes to existing equipment (i.e., cost increases), suppress a decrease in yield, and maintain high quality of the extrusion molded products produced. Furthermore, when control is performed based on the above-mentioned pressure threshold, the linear speed can be changed to any speed (see Figure 5 as appropriate), further increasing productivity.

[0092] 6 is a flowchart showing a specific example of the control performed by the control unit on the heater, etc. Hereinafter, the content and procedure of the control performed by the control unit 100 of the extruder 2 will be described mainly with reference to FIG.

[0093] In step S1 (setting stage) before the extrusion device 1 (hereinafter sometimes simply referred to as "this device") starts operating, the control unit 100 selects (determines) a table T corresponding to the material to be used during operation from among multiple tables T (T1, T2, ... Tn) stored in the recording medium 150, in accordance with the settings specified by the user. Then, the control unit 100 reads out the numerical values registered in the selected (determined) table T.

[0094] As a specific example, the control unit 100 displays a setting screen on the display of the operation display unit 110 prompting the user to select the type of material 800 to be used in this device, selects table T corresponding to the type of material 800 selected by the user's touch operation, and reads out the numerical value.

[0095] In the next step S2, the control unit 100 determines a pressure threshold value based on the read numerical value. The determined pressure threshold value is stored in the RAM of the control unit 100 or the like.

[0096] More specifically, if the pressure threshold value is recorded in the table T itself, the control unit 100 determines the recorded value as the pressure threshold value.

[0097] On the other hand, when the pressure threshold value itself is not written (specified) in table T as in the above-described FIG. 4 or FIG. 5, control unit 100 determines the pressure threshold value based on the numerical value read from table T.

[0098] In one specific example, when table T has a data structure similar to that of the table described above in FIG. 4, the control unit 100 can determine the maximum resin pressure (MPa) at which the appearance is good (◯) as the pressure threshold. Alternatively, the control unit 100 may calculate a value between the maximum resin pressure (MPa) at which the appearance is good (◯) and the minimum resin pressure (MPa) at which the appearance is poor (×) (e.g., the average of both values), and determine this calculated value as the pressure threshold. Alternatively, when the initial value of the linear speed of the take-up device 300 is determined, the control unit 100 may determine the maximum resin pressure (MPa) at which the appearance is good (◯) under that linear speed condition (e.g., 24 MPa for a linear speed of 20 m / min) as the pressure threshold.

[0099] In step S3 after the pressure threshold is determined as described above, the control unit 100 sets a temperature range for mass production of products in a predetermined region of the cylinder 21 during operation of the apparatus. In this embodiment, the control unit 100 sets the temperature range for temperatures (hereinafter also referred to as cylinder temperatures) in three regions C3, C4, and C5 where heaters are located, among the passage (conveyance path) within the cylinder 21 through which the material 800 is conveyed.

[0100] In one non-limiting example, the control unit 100 sets the lower limit temperature to 225°C for each of the regions C3, C4, and C5 of the cylinder 21. Optionally, the control unit 100 may set upper limit temperature values for the regions C3, C4, and C5 of the cylinder 21. These upper limit values may be set to a predetermined temperature (e.g., a temperature around 235°C) that is higher than the melting temperature of the material 800 used.

[0101] As described above, temperature sensors are also arranged in other regions of the cylinder 21 (C1 and C2 in this example), but these other regions are not provided with heaters 140. For this reason, the control unit 100 does not set the cylinder temperature for these other regions (in other words, does not determine or set a temperature range according to the type of material 800).

[0102] In step S4, the control unit 100 starts the operation of the present apparatus. That is, the motor of the screw driving unit 130 starts to drive, causing the screw 22 in the cylinder 21 to rotate, and the material 800 is mixed (mixed) and conveyed. In addition, each heater 140 (heat source) is turned on, heating of each corresponding region of the cylinder 21 begins, and the temperature of the cylinder 21 is measured by the corresponding temperature sensor of the detection unit 120. Furthermore, the take-up device 300 and the cutting device 400 start operating at an appropriate timing.

[0103] In step S5, the control unit 100 accepts a change in the linear speed, i.e., the take-up speed by the take-up device 300. Here, when the control unit 100 receives an instruction to increase the linear speed by, for example, a user's operation input via the operation display unit 110 described above, it outputs a command to that effect to the take-up device 300.

[0104] At this time, the control unit 100 may refer to the registered information (various values related to the pressure threshold) in the table T and, in response to the change in the linear velocity, appropriately change the previously determined (set) pressure threshold and the temperature ranges (lower and upper limits) of the regions C3, C4, and C5 of the cylinder 21. Furthermore, in response to the change in the linear velocity, the control unit 100 may also perform a process of appropriately adjusting the rotation speed of the motor of the screw driving unit 130 (increasing or decreasing the rotation speed).

[0105] In step S6, the control unit 100 determines, based on the measurement values of each temperature sensor of the detection unit 120, whether any of the regions C3, C4, and C5 of the cylinder 21 is at risk of the cylinder temperature dropping below the set value (lower limit value).

[0106] Here, if the control unit 100 determines that there is no region where the pressure may fall below the lower limit (step S6: No), it determines that the pressure extruding the material 800 at the outlet of the cylinder 21 is good (does not exceed the pressure threshold). In this case, the control unit 100 returns to step S5 and repeats the processes of steps S5 and S6 described above. Therefore, while this process is being repeated, it is possible to change the linear velocity, thereby increasing productivity or adjusting the production volume.

[0107] On the other hand, if the control unit 100 determines that there is an area where the cylinder temperature may fall below the set lower limit value (step S6: Yes), it determines that the pressure pushing out the material 800 at the outlet side of the cylinder 21 may exceed the pressure threshold, and proceeds to step S7.

[0108] In step S7, the control unit 100 performs a process to increase the output of the heater 140 (the heat source closest to that region) corresponding to the region where the cylinder temperature is likely to fall below the set lower limit. By performing such output control of the heater 140 (heat source) (temperature control downstream of the cylinder 21), the pressure for extruding the material 800 at the outlet of the cylinder 21 can be kept at a constant value below the pressure threshold, thereby maintaining the appearance quality of the manufactured product.

[0109] In the following step S8, the control unit 100 determines whether any of the regions C3, C4, and C5 in the cylinder 21 has reached the upper limit of the cylinder temperature (for example, 235° C.).

[0110] If the control unit 100 determines that no region has reached the upper limit (e.g., 235°C) (step S8: No), it repeats the determination in step S8. On the other hand, if the control unit 100 determines that any of the regions C3, C4, and C5 in the cylinder 21 has reached the upper limit (step S8: Yes), it proceeds to step S9.

[0111] In step S9, the control unit 100 performs processing to reduce the output of the heater 140 (heat source) corresponding to the region where the upper limit has been reached, and then the process proceeds to step S10.

[0112] In step S10, the control unit 100 monitors a user instruction from the operation display unit 110, for example, and determines whether or not to terminate the operation of the present apparatus.

[0113] Here, if the control unit 100 determines not to terminate the operation of the device (step S10: No), the control unit 100 returns to step S5 and repeats the processes of steps S5 to S10 described above.

[0114] On the other hand, if the control unit 100 determines that the operation of this device should be terminated (step S10: Yes), it sends an instruction to that effect to the take-up device 300, cutting device 400, etc., and turns off the heater 140 and screw drive unit 130 to terminate operation.

[0115] Thus, according to the extruder (screw extruder) 2 and extrusion device 1 of this embodiment, the pressure for extruding the material 800 at the outlet side of the cylinder 21 is kept within a range below the pressure threshold, thereby maintaining or improving the appearance quality of the manufactured product (in this example, an electric wire cable).

[0116] Furthermore, according to the extrusion device 1 that performs the above-described series of controls, the linear speed can be changed during operation, so in addition to the above-described effects, productivity can be improved or productivity can be adjusted according to the supply status of the material 800.

[0117] Furthermore, according to the extrusion device 1 that performs the above-described series of controls, the pressure for extruding the material 800 at the outlet side of the cylinder 21 can be kept within a range below the pressure threshold while the output of the heater 140 can be reduced, thereby achieving energy savings.

[0118] In this way, the extruder 2 and extrusion device 1 of the present disclosure are configured to control the output of the corresponding heater 140 (heat source) so that the pressure applied to the material 800 at the outlet of the flow path (conveyance route) in the cylinder 21 is within a temperature range that does not exceed a pressure threshold. Such an extrusion device 1 ensures a high level of appearance quality for the extrusion molded product produced, and has various advantages such as improved productivity and energy savings.

[0119] In the above-described embodiment, it is assumed that a table T is created in which values related to the pressure threshold (i.e., the pressure threshold itself or various numerical values from which the pressure threshold can be calculated) are registered for each material 800 used and stored in the recording medium 150, but this is not limited to this.

[0120] As another example, multiple sets of values relating to the material 800 to be used and the corresponding pressure thresholds may be registered in one table T, and the table T may be stored in the recording medium 150 or saved in the memory of the control unit 100 for use.

[0121] The material 800 molded by the extrusion device 1 of this embodiment is typically, but not limited to, a thermoplastic resin such as polypropylene (PP), polyphenylene sulfide (PPS), acrylic resin, polyester resin, or urethane resin. The material 800 molded by the extrusion device 1 may be any material that satisfies the above-mentioned pressure threshold, i.e., the pressure applied to the material when it is extruded from the cylinder 21 and that distinguishes between good and bad appearance quality.

[0122] Although the above description is based on the premise that cable 900 is manufactured, the present invention is not limited to this. Furthermore, the shape, size, etc. of the product manufactured by extrusion molding using extrusion device 1 are arbitrary.

[0123] The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention. [Explanation of symbols]

[0124] 1. Extrusion equipment 2. Extruder 3 Crosshead 4 Die 5. Aquarium 21 cylinders 22 Screw (mixing section) 23 Hopper 100 control section 110 Operation display section 120 Detection unit (temperature sensor) 130 Screw drive unit (mixing unit) 140 Heater (heat source) 150 Recording Media 200 Cooling device 210 Conveyor path 300 Take-off device 400 cutting equipment 800 materials 900 Cables (Products) T-table

Claims

1. a cylinder into which the material is introduced and conveyed; a stirring unit that stirs the material introduced into the cylinder; a detection unit that detects the temperature of the cylinder; a heat source for heating the cylinder; a control unit that controls an output of the heat source in accordance with the temperature detected by the detection unit, The control unit controls the output of the heat source so that the temperature range does not exceed a pressure threshold, which is a pressure applied to the material when the material is extruded from the cylinder to the outside and is a threshold for distinguishing between good and bad appearance quality.

1. An extruder comprising: the control unit reads out a table in which pressure values applied to the material when the material is extruded from the cylinder to the outside are registered in correspondence with whether the appearance quality is good or bad, calculates the pressure threshold value using each pressure value that results in good appearance quality, and controls the output of the heat source so that the calculated pressure threshold value is not exceeded. Extruder.

2. A cylinder into which material is introduced and conveyed; a stirring unit that stirs the material introduced into the cylinder; a detection unit that detects the temperature of the cylinder; a heat source for heating the cylinder; a control unit that controls an output of the heat source in accordance with the temperature detected by the detection unit, The control unit controls the output of the heat source so that the temperature range does not exceed a pressure threshold, which is a pressure applied to the material when the material is extruded from the cylinder to the outside and is a threshold for distinguishing between good and bad appearance quality.

1. An extruder comprising: The control unit reads out a table in which a pressure value applied to the material when the material is extruded from the cylinder to the outside, a temperature on the downstream side of the cylinder along the extrusion direction, and whether the appearance quality is good or bad are registered in correspondence with each other, and sets a temperature range on the outlet side of the cylinder along the extrusion direction so as not to exceed the pressure threshold, and controls the output of each of the heat sources provided downstream along the extrusion direction. Extruder.

3. An extruder that conveys a material introduced into a cylinder while heating it with a heat source and extrudes it out of the cylinder to manufacture a product, controlling the output of the heat source so that the temperature range does not exceed a pressure threshold, which is a pressure applied to the material when the material is extruded outward from the cylinder and is a threshold for distinguishing between good and bad appearance quality; 1. A method for controlling an extruder, comprising: a table in which pressure values applied to the material when the material is extruded from the cylinder to the outside and whether the appearance quality is good or bad are registered in correspondence with each other is read out, the pressure threshold is calculated using each pressure value that indicates good appearance quality, and the output of the heat source is controlled so that the calculated pressure threshold is not exceeded; How to control the extruder.

4. An extruder that conveys a material introduced into a cylinder while heating it with a heat source and extrudes it out of the cylinder to manufacture a product, controlling the output of the heat source so that the temperature range does not exceed a pressure threshold, which is a pressure applied to the material when the material is extruded outward from the cylinder and is a threshold for distinguishing between good and bad appearance quality; 1. A method for controlling an extruder, comprising: a table in which a pressure value applied to the material when the material is extruded from the cylinder to the outside, a temperature on the downstream side of the cylinder along the extrusion direction, and whether the appearance quality is good or bad are registered in correspondence with each other, and a temperature range on the outlet side of the cylinder along the extrusion direction is set so that the pressure threshold is not exceeded, and the output of each of the heat sources provided downstream along the extrusion direction is controlled; How to control the extruder.

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