JPH11334885A - Material supply amount control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To feed a material by a constant amount without measuring the material feeding amount in the replacement of the material by readjusting the rotating speed of a screw on the basis of the weight of a molded product after the replacement of the material, and adding the rotating speed of the screw to the material replacement actual results data with the present material replacement conditions. SOLUTION: The material replacement actual results data 14a indicating the screw rotating speed adjustment amount in the replacement of the material by the last replacement is stored in a memory 14 of a line control computer 7. Whether the weight of a product 15b is within the tolerance or not is judged by an examination device 6 after a specific time from the replacement of the material. When the weight of the product 15b is out of the tolerance, the rotating speed of a screw feeder 2 is readjusted, the weight of the product 15b is measured again, and this process is repeated until the weight of the product 15b becomes within the tolerance. When the weight of the product 15b becomes within the tolerance, the adjustment amount of the present screw rotating speed is added to the material replacement actual results data 14b with the present material replacement conditions to be stored, and the control of the material supply amount is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a raw material supply amount when a powder raw material is used in an extrusion molding system used for molding a pipe or the like. More specifically, the present invention relates to a method for controlling a raw material supply amount for maintaining a constant raw material supply amount before and after switching when a raw material is changed between raw materials having different bulk specific gravities.

[0002]

2. Description of the Related Art In an extrusion molding system used for molding a pipe or the like, a screw feeder is used relatively frequently as a device for quantitatively supplying a powder raw material. However, when the raw material is changed while the screw rotation speed of the screw feeder is kept constant, the actual raw material supply amount fluctuates when the bulk specific gravity differs between raw materials of different lots. Due to this variation, characteristics such as viscosity required in the molding process cannot be obtained and predetermined processing cannot be performed,
There is a problem that the quality of the molded article is deteriorated.

In order to solve such a problem, Japanese Patent Application Laid-Open No.
There is a method disclosed in JP-A-43900. In this method, first, every time the number of times the raw material is supplied reaches a predetermined value, the total weight of the hopper storing the powder raw material and the powder raw material stored in the hopper is measured, and this measured value is measured. And the difference from the previous measurement value are calculated to determine the raw material supply amount of the hopper. Next, an amount of raw material equal to this raw material supply amount is charged into the hopper. At this time, if the obtained raw material supply amount is larger than the preset reference amount, the raw material supply amount is reduced by adjusting the powder raw material flow rate adjusting means, and the obtained raw material supply amount is set to the predetermined reference amount. If it is less than the above, the control is performed such that the powder raw material flow rate adjusting means is adjusted to increase the raw material supply amount, and the raw material supply amount is controlled to be constant.

[0004]

When the raw material is to be changed, the raw material A that has been charged before the raw material change is performed.
However, a measure for removing the raw material A adhered to the inner wall of the hopper or the like is required in order to prevent the raw material A from adhering to the product manufactured using the raw material B supplied after the raw material replacement.
As an example of this measure, there are a knocker that applies a vibration to the hopper to remove the raw material A attached to the inner wall by the impact thereof, and an air purge that blows air to the inner wall to remove the raw material A attached to the inner wall by wind pressure.

However, the above-mentioned Japanese Patent Application Laid-Open No.
In the control method disclosed in Japanese Patent Publication No. 00, the total weight of the hopper and the raw material in the hopper is measured. However, when vibration is applied to the hopper by the knocker, a measurement error occurs due to the vibration. Can not. Further, in order to measure the total weight of the hopper and the raw material, it is necessary to provide the hopper separately from other members, so that a gap is generated between the hopper and the other members. Therefore, when the raw material A is removed by using the air purge, the raw material blows out from the gap, so that the air purge cannot be used. In other words, when the above-described control method is used, since the work of removing the raw material A adhered to the inner wall of the hopper by the knocker or the air purge cannot be performed, when the raw material A having a different bulk specific gravity is changed to the raw material B, the raw material B is used. Since the raw material A is mixed, there is a problem that the accurate weight (raw material supply amount) of the raw material B cannot be measured.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is possible to maintain a constant amount of raw material without measuring the raw material supply amount when the raw material is changed between raw materials having different bulk specific gravities. It is an object to provide a supply amount control method.

[0007]

The raw material supply amount control method of the present invention is a method for controlling the supply amount by using a screw feeder while supplying a powdery raw material and performing extrusion molding. This is a method of controlling the amount of raw material supplied when performing raw material change, wherein the raw material change actual data indicating the screw rotation speed adjustment amount at the time of the previous raw material change includes a raw material change performed under the same conditions as the current raw material change. Determine whether or not the raw material replacement performance data is included, if not included, according to the change in the bulk specific gravity of the raw material, adjust the screw rotation speed of the screw feeder, if included, the raw material The screw rotation speed of the screw feeder is adjusted based on the replacement performance data, and the screw rotation speed is readjusted based on the weight of the molded product formed after switching the raw materials. The Liu rotational speed, is intended to be added to the raw materials sorting performance data with this time of raw materials sorting conditions.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a raw material supply amount control method according to the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram showing an example of an extrusion molding system for implementing a method for controlling a raw material supply amount according to the present invention.

The extrusion molding system shown in FIG. 1 comprises a hopper 1 for storing a powder raw material, a screw feeder 2 provided below a raw material supply port 1a of the hopper 1, and a raw material supplied via the screw feeder 2. Extruder 3 for extruding while kneading, and extruded kneaded material (for example, synthetic resin)
A mold 4 for molding the product into a predetermined shape, a cutting machine 5 for cutting a molded product 15a continuously formed through the mold 4 and processing it into a product 15b, And a line control computer 7 for controlling the line of the extrusion molding system.

The upper part of the hopper 1 is provided with a plurality of raw material inlets, and each raw material inlet is provided with a valve for selecting a raw material to be charged. In the example shown in FIG. 1, two raw material inlets 1b and 1c are provided, and a first valve 10a is provided on the raw material inlet 1b.
A second valve 10b is provided at the material inlet 1c. The first valve 10a is connected to a first raw material transport pipe 11a connected to a raw material storage unit (not shown) for raw material A, and the second valve 10b is connected to a raw material storage tube for raw material B. Raw material transport pipe 11b connected to a section (not shown)
Is connected. Therefore, when the first valve 10a is opened, the raw material A can be charged, and when the second valve 10b is opened, the raw material B can be charged. A leveler 12 for detecting the presence or absence of the raw material in the hopper 1 is provided on the inner wall of the hopper 1, and a detection result of the leveler 12 is output to the line control computer 7. In addition, in FIG.
In order to more clearly illustrate 2, the hopper 1 is shown in a sectional view.

The screw feeder 2 is housed in a screw feeder case 13 so that the raw material does not scatter around.
Is provided with one opening at each of the upper part and the lower part. The opening provided at the upper part is connected to the raw material supply port 1a of the hopper 1, and the opening provided at the lower part is connected to the raw material inlet of the extruder 3. The amount of the raw material supplied from the hopper 1 to the extruder 3 is determined by the number of rotations of the screw of the screw feeder 2. That is, if the rotation of the screw feeder 2 is increased to increase the number of rotations of the screw, the amount of raw material supplied can be increased. If the rotation of the screw feeder 2 is reduced to reduce the number of rotations of the screw, the amount of supplied raw material can be reduced. In FIG. 1, a sectional view of the screw feeder case 13 is shown to more clearly illustrate the screw feeder 2.

The memory 14 of the line control computer 7 records raw material change actual data 14a indicating the screw rotation speed adjustment amount at the time of the previous raw material change. The raw material replacement result data 14a is composed of, for example, information on the screw rotation speed adjustment amount at the time of the previous raw material replacement, conditions at the time of raw material replacement, and the like.

Next, a method of controlling the amount of raw material supplied in the extrusion molding system shown in FIG. 1 will be described.

FIG. 2 is a flow chart showing an example of a procedure when the raw material A is changed to the raw material B by performing the raw material supply amount control method of the present invention.

First, when an instruction to start material replacement is input to the line control computer 7 (S1), the material replacement performance data 14a recorded in the memory 14 of the line control computer 7 is searched (S2). It is determined whether or not the replacement performance data 14a includes data on material replacement performed under conditions that match the current material replacement condition (S3).

If the information is not included (S
3 is NO), the fact that the information is not included in the raw material replacement result data 14a is displayed on the display device of the line control computer 7, and the worker in charge of this display confirms that the raw material A The adjustment amount of the screw rotation speed of the screw feeder is input using the input device of the line control computer 7 in consideration of the difference in the bulk specific gravity of the raw material between the raw material B and the raw material B (S4).

If the information is included (S3
If the determination result is YES), only the data relating to the material change performed under the conditions that match the current material change condition is extracted from the material change actual data 14a, and the optimum value of the screw rotation speed adjustment amount is automatically determined. It is determined by calculation (S5).

Subsequently, the first valve 10a is closed with the screw feeder 2 kept rotating (S6), and the charging of the raw material A into the hopper 1 is stopped. In this state, it is determined whether or not the raw material A remains in the hopper 1 based on the raw material detection result output from the leveler 12 (S7). This determination is repeated at regular intervals while the raw material A remains in the hopper 1 (when the determination result in S7 is YES).

Next, when it is determined that the raw material A does not remain in the hopper 1 (when the determination result in S7 is YES),
The raw material A adhering to the inner wall of the hopper 1 is removed by air purging (S8). In the present embodiment, air purge is used as a method of removing the raw material A attached to the inner wall of the hopper 1. However, the raw material A may be removed by another method, for example, by applying vibration to the hopper 1 by a knocker. You may.

After the completion of the air purge, the second valve 10b
Is opened, and the raw material B is charged into the hopper 1 (S9). At the same time, the screw rotation speed of the screw feeder 2 is adjusted according to the input of the operator (S4) or the screw rotation speed adjustment amount determined by the automatic calculation (S5) (S10).

Next, it is determined whether or not the product processed by the cutting machine 5 has been switched to a product manufactured using the raw material B (S11). In the present embodiment, the product is
The switching from the one manufactured using the raw material A to the one manufactured using the raw material B is determined based on a preset time. However, the criterion for the determination is not limited to this. For example, if a change occurs in the color or gloss of the product due to the raw material, add a mechanism to detect this change, and based on the detection result of this mechanism,
Switching of the raw materials may be determined.

Next, after the lapse of the predetermined time (S1)
After the determination result of step 1 changes from NO to YES), the weight of the product is measured by the inspection device 6, and it is determined whether or not the weight of the product is within a permissible range (S12).

If the weight of the product is not within the allowable range (NO in S12), the screw speed of the screw feeder is readjusted (S13), and the weight of the product is measured again. It is determined whether the weight of the product is within a tolerance (S12). This readjustment of the screw rotation speed is repeated until the weight of the product becomes a value within an allowable range.

When the weight of the product falls within the allowable range (when the result of the determination in S12 is YES), the adjustment amount of the current screw rotation speed is changed together with the current material replacement condition. It is additionally recorded in the performance data (S14),
The control of the raw material supply amount ends.

[0026]

Next, an embodiment of the raw material supply amount control method of the present invention will be described with reference to FIGS. In this embodiment, the ambient temperature of the extrusion molding system is 25.
The case where the raw material α is switched to the raw material β when the temperature is ° C will be described.

First, when an instruction to start material replacement is input to the line control computer 7 (S1), the material replacement performance data 14a recorded in the memory 14 of the line control computer 7 is searched (S2). It is determined whether or not the replacement performance data 14a includes data on material replacement performed under conditions that match the current material replacement condition (S3).

Table 1 shows an example of the raw material change result data 14a recorded in the memory 14 of the line control computer 7.

[0029]

[Table 1]

Table 1 shows, as raw material change actual data, raw materials before the raw material change (expressed as "previous raw materials" in the table) and raw materials after the raw material change (in the table, " And the data on the ambient temperature of the extrusion system and the screw speed adjustment. More specifically, the raw material replacement performance data includes four raw material replacement conditions and a screw rotation speed adjustment amount under these conditions. At the time of the first raw material change, the raw material α is switched to the raw material β when the ambient temperature is 25 ° C., the adjustment amount of the screw rotation speed is set to +10 rpm, and at the time of the second raw material change, the raw material β is used at the ambient temperature 23 ° C. α, the screw rotation speed adjustment amount is set to −8 rpm, and at the time of the third raw material change, the raw material α is switched to the raw material β at an ambient temperature of 25 ° C., and the screw rotation speed adjustment amount is set to +8 rpm. At the time of the fourth raw material change, the raw material β is switched to the raw material α at an ambient temperature of 21 ° C., and the screw rotation speed adjustment amount is set to −6 rpm. When the screw rotation speed adjustment amount is a negative value, the screw rotation speed is decreased, and when the screw rotation speed adjustment amount is a positive value, the screw rotation speed is increased. The ambient temperature of the extrusion molding system is measured by a thermometer 1 provided around the hopper 1.
The signal indicating the measured temperature is input to the line control computer 7. In the present embodiment, as a search item when extracting only data that matches the current material change condition, the material before the material change, the material after the material change, and the ambient temperature of the extrusion molding system are included. Although employed, the search items are not limited to this, and may be any condition that can affect the characteristics of the product, such as season and humidity. When extracting data, all conditions may be used as search items, or only some conditions may be used.

Referring to Table 1, the conditions at the time of the second and third material replacement match the conditions of the current material replacement (the determination result at S3 is YES). Therefore, only the data related to the second and third raw material changes are extracted from the raw material change actual data shown in Table 1, and the extracted raw material change actual data is created as shown in Table 2. Further, the optimum value of the screw rotation speed adjustment amount is determined by automatic calculation based on the raw material change result data after the extraction (S4). In the present embodiment, an average value of a plurality of adjustment amounts of the screw rotational speed under the same condition is determined by an automatic calculation and is set as an optimum value. That is, referring to Table 2, the screw rotation speed adjustment amount at the time of the second raw material change is +10 rpm, and the screw rotation speed adjustment amount at the third raw material change is +8 rpm.
Therefore, +9 rpm is set as the optimum value of the screw rotation speed adjustment amount.

[0032]

[Table 2]

In this embodiment, the average value of the plurality of adjustment amounts of the screw rotation speed under the same condition is set as the optimum value.
The automatic calculation method is not limited to the average calculation, and for example, an average value obtained by excluding the maximum value and the minimum value among a plurality of screw rotation speed adjustment amounts under the same condition may be obtained as the optimum value.

Subsequently, the first valve 10a is closed with the screw feeder 2 kept rotating (S6), and the charging of the raw material α into the hopper 1 is stopped. In this state, it is determined whether or not the raw material α remains in the hopper 1 based on the raw material detection result output from the leveler 12 (S7). Next, when it is determined that the raw material α does not remain in the hopper 1 (when the determination result in S7 is YES), the raw material α attached to the inner wall of the hopper 1 is removed by air purging (S8). After the completion of the air purge, the second valve 10b is opened, and the raw material β is charged into the hopper 1 (S9). at the same time,
The screw rotation speed of the screw feeder 2 is increased by 9 rpm according to the screw rotation speed adjustment amount determined by the automatic calculation (S5) (S10).

Next, after the product processed by the cutting machine 5 is switched to a product manufactured using the raw material β (S1).
(After the determination result of No. 1 changes from NO to YES), the weight of the product is measured by the inspection device 6, and it is determined whether or not the weight of the product is within an allowable range (S12). The screw rotation speed of the screw feeder is readjusted (S13). The readjustment of the screw rotation speed is repeated until the weight of the product becomes a value within an allowable range. In this embodiment, since the measured weight of the product is smaller than the allowable range in the determination in S12 (the determination result in S12 is NO), the screw rotation speed is further increased by 3 rpm (S13). Assume that the weight of the product is measured again, and as a result, the weight of the product becomes a value within the allowable range (the determination result in S12 is YES). Accordingly, the adjustment amount of the screw rotation speed in this case is +12 rpm as the sum of +9 rpm obtained by the automatic calculation and +3 rpm at the time of readjustment.

Then, the current screw rotation speed adjustment amount (ie, +12 rpm) is changed along with the current raw material change condition (ie, the raw material α is switched to the raw material β when the ambient temperature of the extrusion molding system is 25 ° C.). The additional recording is performed on the performance data (S14), and the control of the raw material supply amount ends. Table 3 shows an example of the raw material change result data after the additional recording.

[0037]

[Table 3]

Next, when the ambient temperature is 25 ° C., the raw material α
When the raw material change is performed under the condition that the raw material is switched to the raw material β, there are three screw rotation speed adjustment amounts under the same condition in the raw material change actual data shown in Table 3, and +10 rpm and +8 rpm
m and +12 rpm, the automatic calculation (S
By performing 4), the first screw rotation speed adjustment amount is +10
rpm.

In the present embodiment, the final adjustment amount of the screw rotation speed after the readjustment is determined by the adjustment amount of the screw rotation speed as a result of the automatic calculation (or input by the worker) adopted in step S10. Although the sum is the sum with the screw rotation speed adjustment amount at the time of adjustment, for example, a procedure of multiplying each by an arbitrary coefficient and summing them may be used.

According to the raw material supply amount control method of the present invention, the number of raw material change actual data used in performing the automatic calculation increases each time the number of raw material change is repeated.
The adjustment of the screw rotation speed at 10 can be performed more accurately. Therefore, it is not necessary to perform readjustment later in step S13, so that the time required for controlling the supply amount of the raw material at the time of replacing the raw material can be reduced, and the occurrence of defective products due to the replacement of the raw material can be reduced.

Here, the screw rotation speed is adjusted by the raw material supply amount control method of the present invention, that is, the screw rotation speed is adjusted based on the conditions for changing the raw material, and if necessary, readjustment is performed after the weight measurement (hereinafter, referred to as “the adjustment”). The change in the weight of the product in the case of “feed forward control” is compared with the change in the weight of the product in the case where the screw rotation speed is adjusted only after the weight measurement. FIG. 3 shows a change in the weight of the product when the screw rotation speed is adjusted according to the raw material supply amount control method of the present invention, and FIG. 4 shows the screw feeder screw even when the previous raw material is switched to the next raw material. The number of rotations shows the change in the weight of the product when the number of rotations of the screw was adjusted after the weight measurement without adjusting the number of rotations of the previous raw material. In FIGS. 3 and 4, the vertical axis indicates the number of rotations of the screw and the weight of the product, the horizontal axis indicates time, and “t1” indicates the time when the raw material change is started (step S2 in FIG. 2 was executed). ), “T2” indicates a case in which the rotation speed of the screw is adjusted according to the automatic calculation or the input of the operator (when step S10 in FIG. 2 is executed), and “t3” indicates a screw in accordance with the result of the weight measurement. (When step S13 in FIG. 2 is executed), and “W” indicates the allowable range of the weight of the product. The solid line indicates the number of rotations of the screw, and the black circle indicates the measurement result of the weight of the product.

As shown in FIG. 4, when the feedforward control is not performed, the weight of the product greatly fluctuates due to the difference in the bulk specific gravity of the raw materials, and the outline arrow T in FIG.
At the timing indicated by, there is a high possibility that a trouble due to a fluctuation in the discharge of the extruder, for example, a trouble such as a kneaded material being cut due to excessive take-off, will occur. On the other hand, as shown in FIG. 3, when the feedforward control is performed, the material is switched and the number of rotations of the screw is adjusted according to the automatic calculation or the input of the worker (step S10 in FIG. 2 is executed). The variation in the weight of the product is small, and the above-described trouble can be prevented.

[0043]

As described above, according to the present invention,
Fluctuations in the weight of the product due to the difference in bulk specific gravity between the previous raw material and the next raw material can be reduced, and the occurrence of trouble during the manufacturing process can be prevented. Further, since the number of raw material change actual data used when performing the automatic calculation increases each time the number of times of raw material change is increased, the screw rotation speed performed in accordance with the raw material change actual data can be adjusted more accurately. Therefore, it is not necessary to readjust the number of rotations of the screw later, so that the time required for controlling the supply amount of the raw material at the time of replacing the raw material can be reduced, and the occurrence of defective products accompanying the replacement of the raw material can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of an extrusion molding system for implementing a raw material supply amount control method of the present invention. .

FIG. 2 is a flowchart illustrating an example of a procedure in a case where a raw material change is performed by performing the raw material supply amount control method of the present invention.

FIG. 3 is a graph showing a change in weight of a product when a screw rotation speed is adjusted according to a raw material supply amount control method of the present invention.

FIG. 4 is a graph showing a change in the weight of the product when the screw rotation speed is adjusted only after the weight measurement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hopper 2 Screw feeder 3 Extruder 4 Die 5 Cutting machine 6 Inspection device 7 Line control computer

Claims (1)

[Claims] 1. A method for controlling a raw material supply amount when exchanging a raw material between raw materials having different bulk specific gravities when supplying and extruding a powder raw material while controlling a supply amount using a screw feeder. It is determined whether or not the raw material change actual data indicating the screw rotation speed adjustment amount at the time of the previous raw material change includes the raw material change actual data related to the raw material change performed under the same conditions as the current raw material change If not included, according to the change in the bulk specific gravity of the raw material,
Adjust the screw rotation speed of the screw feeder, if included, based on the raw material replacement performance data,
Adjust the screw rotation speed of the screw feeder, readjust the screw rotation speed based on the weight of the molded product after switching the raw materials, and add this screw rotation speed to the raw material change actual data together with the current raw material change conditions A method for controlling a raw material supply amount.