JP2008290298A - Cleaning method of injection molding apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method of an injection molding apparatus by which remaining resin tailings can be lessened, cleaning time and cost can be reduced and a machine working rate can be improved at a low cost, in cleaning of the injection molding apparatus. <P>SOLUTION: In the cleaning method of the thermoplastic resin injection molding apparatus having an extruder which comprises a heating cylinder having a nozzle at its top end and a screw that is inserted in the heating cylinder so as to be able to advance and retreat, ultrasonic vibrators are respectively attached to a nozzle part of the heating cylinder, a heating cylinder main body part and the screw. After injection molding of the thermoplastic resin is performed by using the injection molding apparatus, a purging material is supplied into the extruder, ultrasonic wave is applied from the ultrasonic vibrator to the extruder either or both of before purging the remaining resin by extruding the purging material and during purging. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  This proposal clearly describes an efficient cleaning method for an injection molding apparatus cleaning method used in the field of thermoplastic resin molding. By using the method of the present invention, it is possible to reduce the residual resin residue in the cleaning of the injection molding apparatus, reduce the time and cost required for cleaning, and improve the machine operating rate at low cost.

  An injection molding apparatus for thermoplastic resin is generally provided in connection with an extruder having a heating cylinder having a nozzle at the tip, a screw inserted in the heating cylinder so as to be able to advance and retreat, and a nozzle at the tip of the extruder. A desired thermoplastic resin is put into an extruder, the resin is melted and kneaded in the extruder, transferred to the tip side, and extruded from a nozzle into the cavity of the molding die. It is structured to inject and produce a molded product. In the injection molding of a thermoplastic resin using this injection molding apparatus, when replacing the resin to be used, it is necessary to perform cleaning in order to remove the residual resin in the extruder.

Conventionally, with regard to a method for cleaning an extruder of an injection molding apparatus, for example, a cleaning apparatus disclosed in Patent Document 1 has been proposed.
In Patent Document 1, in a screw cleaning apparatus that removes resin dirt adhered to the screw surface of a resin molding machine, an anode electrode is provided in a cleaning tank having a dimension capable of accommodating at least the helical screw portion of the screw, and A chuck for gripping the rear end of the screw is provided near the periphery of the opening of the cleaning tank, and the power supply for electrolysis is connected to the anode electrode and the cathode electrode while the chuck is electrically connected to the cathode electrode. A screw disposed in a cleaning tank filled with a cleaning liquid in a posture held by the chuck is configured to electrolytically clean the screw surface by power supply to each electrode by the electrolysis power supply unit. A screw cleaning device for a resin molding machine is disclosed.
JP 2002-144374 A

  However, the conventional technique disclosed in Patent Document 1 has a problem that the screw has to be removed from the molding machine main body during ultrasonic cleaning of the screw, resulting in an increase in work man-hours and a reduction in operating rate. Further, only the screw body is cleaned, and the cleaning method for the inside of the injection nozzle where the resin residue is most likely to remain and the inner wall of the cylinder is not clearly described.

  The present invention has been made in view of the above circumstances, and is a method that can reduce the amount of resin residue remaining in cleaning of an injection molding device, reduce the time and cost required for cleaning, and improve the machine operating rate at low cost. For the purpose of provision.

In order to achieve the above object, the present invention provides a method for cleaning an injection molding apparatus for a thermoplastic resin having a heating cylinder having a nozzle at its tip and an extruder having a screw inserted into the heating cylinder so as to advance and retreat. ,
Ultrasonic vibrators are attached to the nozzle part of the heating cylinder, the heating cylinder body part, and the screw, respectively, and after injection molding of thermoplastic resin using this injection molding device, the purge material is supplied to the extruder. A method for cleaning an injection molding apparatus is characterized in that ultrasonic waves are applied from an ultrasonic vibrator to an extruder before or during purging of a residual resin by extruding a purge material. To do.

  In the cleaning method of the injection molding apparatus of the present invention, it is preferable that two or more ultrasonic transducers are attached to the nozzle portion.

  According to the present invention, it is possible to reduce the residual resin residue in cleaning the injection molding apparatus, reduce the time and cost required for cleaning, and improve the machine operation rate at low cost.

  In general, when an injection molding apparatus is used, there is a so-called “material change” operation. For example, the thermoplastic resin materials used include various plastic materials including polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), acrylonitrile-butadiene-styrene copolymer (ABS), and their molecular weight. It is known that the material characteristics differ depending on the difference in distribution and crystallinity. Furthermore, it is known that the material characteristics differ depending on the presence or absence and addition amount of additives such as a colorant, a stabilizer, and an antioxidant. Therefore, it is known that the conditions for injection molding (for example, temperature and pressure) are performed under conditions optimal for these material characteristics. Moreover, even if the same material is used, it is well known that there are variations in the characteristic values depending on the production lot, and even when external conditions such as temperature and humidity when processing with an injection molding device change, it is optimal for injection molding. It is known that conditions change.

  As described above, when manufacturing a molded product with an injection molding device, it is a matter of course that there is a lot variation even if the same material is used. It is obvious to do. The present invention proposes a cleaning method for an injection molding apparatus that can shorten the working time and improve the operating rate of the apparatus by efficiently performing the “material change” operation.

  Generally, when changing the material of an injection molding apparatus, it is necessary to completely scrape off the first resin (resin residue) remaining on the inner side of the nozzle and the inner wall of the heating cylinder. Otherwise, it will be mixed when the next material is thrown in, and as a molded product, foreign matter is mixed and it is a defective product. As a method for removing the resin residue, a method for removing the resin residue by injecting a purge material at a high pressure is known. However, this method has a problem that a large amount of purge material and a lot of time are required when a large amount of residual resin residue is left, resulting in a high cost and a reduction in machine operation rate.

  The present invention proposes a cleaning method for an injection molding apparatus that reduces residual resin residue, reduces the amount of purge material used and purge time, and improves the machine operating rate at low cost.

  1 and 2 are cross-sectional views illustrating a method for cleaning a resin residue by purging in a conventional injection molding machine. In these drawings, reference numeral 1 is an extruder of an injection molding apparatus, 2 is a heating cylinder, 3 is a nozzle portion, 4 is a screw, 5 is a resin extrusion port, 6 is a resin residue (residual resin), and 7 is a purge material. . The extruder 1 is configured to include a heating cylinder 2 having a nozzle portion 3 having a resin extrusion port opened at the tip, and a screw 4 inserted into the heating cylinder 2 so as to be able to advance and retract.

FIG. 1 shows a state immediately before purging in a “material change” operation, and a resin residue made of a resin used before material change is formed on the inner surface of the heating cylinder 2, the inner surface of the nozzle portion 3 and the outer surface of the screw of the extruder 1. 6 remains.
FIG. 2 shows a state in which the resin residue 6 remaining on each surface is purged by the purge material 7 by the purge.

  When changing the material, as shown in FIG. 1, in order to clean the resin residue 6 of the previously used resin remaining on the inner surface of the heating cylinder 2 of the extruder 1, the inner surface of the nozzle portion 3 and the outer surface of the screw by purging, As shown in FIG. 1, the purge material 7 is put into the extruder 1, and the resin residue 6 is purged by extruding it at a high pressure. As shown in FIG. 2, the remaining resin residue 6 is scraped off by the purge material 7 and is extruded from the resin extrusion port 5 together with the purge material 7.

  However, in order to actually remove these resin wastes 6 completely, it is necessary to repeat such a purge operation many times, so a large amount of purge material 7 is required in proportion to the number of times, and the cost is reduced. In addition to being bulky, there is a problem that a lot of time is required for cleaning because the purge must be performed a plurality of times.

The present invention provides a cleaning method in an injection molding apparatus equipped with the extruder 10 shown in FIG. 3 in order to greatly increase the efficiency of this purge.
An extruder 10 shown in FIG. 3 includes a heating cylinder 2 having a nozzle portion 3 having a resin extrusion port opened at a tip thereof, and a screw 4 that is inserted into the heating cylinder 2 so as to be able to advance and retract. The ultrasonic vibrator 11 is attached to each of the nozzle part 3, the main body part of the heating cylinder 2, and the screw 4.

  The ultrasonic vibrator 11 includes a piezoelectric element such as barium titanate, strontium titanate, or quartz, and a high-frequency power source that applies a high-frequency voltage to the piezoelectric element, and generates ultrasonic waves having a predetermined frequency and output. What is to be used is used, and can be appropriately selected from various commercially available products.

  The number of the ultrasonic transducers 11 arranged in each part is not particularly limited, but it is preferable to arrange two or more ultrasonic transducers 11 for the nozzle unit 3.

  The cleaning method of the injection molding apparatus provided with the extruder 10 shown in FIG. 3 performs the injection molding of the thermoplastic resin using this injection molding apparatus, and then the purge material 7 (for example, nitrogen gas or new The resin used for injection molding), the purge material 7 is extruded, and before or during the purge of the resin residue 6 remaining in the extruder 10, the ultrasonic transducer 11 is used. Is characterized in that ultrasonic waves are applied to the extruder 10.

  In this way, by applying ultrasonic waves from the ultrasonic transducer 11 to the extruder 10 before or during the purge while purging the purge material 7 while extruding, the resin residue 6 is ultrasonically vibrated. Can be easily peeled off from the wall surface, and the purge operation can be completed with a smaller number of times.

  The cleaning method of the present invention can be applied to inline screw type and screw pre-plastic type electric molding machines and hydraulic molding machines. The ultrasonic vibrator 11 can be retrofitted to an arbitrary portion of the extruder 10.

[Example 1]
In the extruder 10 shown in FIG. 3, cleaning was performed by purging at the time of resin change. As the resin material, the resin before the resin change was made by Technopolymer, model number: F1390 ABS resin, and the resin after the resin change was made by Technopolymer, model number: F1150 ABS resin.
Two ultrasonic vibrators 11 were installed in the nozzle portion of the extruder 10, six in the heating cylinder main body, and three in the screw.
At the time of resin change, while applying ultrasonic waves from the ultrasonic vibrator to the extruder 10, the resin after resin change was extruded and purged.

[Comparative Example 1]
According to the technique disclosed in Patent Document 1, the extruder was cleaned at the time of resin change. The extruder used was the same as in Example 1 except that no ultrasonic vibrator was attached, and the combination of resins used was also the same as in Example 1.

[Comparative Example 2]
It is known to “disassemble and clean” when changing the resin of an injection molding apparatus. The cylinder part, the screw part, the nozzle part, etc. were all disassembled, the resin before resin change was cleaned, and the case of reassembly was designated as Comparative Example 2. The extruder used was the same as in Example 1 except that no ultrasonic vibrator was attached, and the combination of resins used was also the same as in Example 1.

  The working time for cleaning each of Example 1 and Comparative Examples 1 and 2 is summarized in Table 1. The “purge time” in Table 1 is the time of purge (in this example, using nitrogen gas) performed to completely remove the resin residue. is there.

  From the result of Table 1, in Example 1 which concerns on this invention, it was able to clean in the working time of 1/4 of the comparative example 1, and 1/6 of the comparative example 2. Therefore, according to this invention, it can contribute to the improvement of a machine operation rate.

  Further, the present inventor has found that resin residue tends to remain particularly on the inner surface of the nozzle portion when changing the resin, and has found a correlation between the number of ultrasonic transducers attached to the nozzle portion and the purge time. This is demonstrated by Examples 2-6 below.

[Example 2]
The number of ultrasonic transducers attached to the nozzle portion was one, and the other configurations were the same as those in Example 1.

[Example 3]
Two ultrasonic transducers attached to the nozzle part were used (same as Example 1).

[Example 4]
The number of ultrasonic transducers attached to the nozzle portion was three, and the other configuration was the same as in Example 1.

[Example 5]
The number of ultrasonic transducers attached to the nozzle portion was four, and the other configuration was the same as in Example 1.

[Example 6]
The number of ultrasonic transducers attached to the nozzle portion was five, and the rest was the same as in Example 1.

  The purge time for each of Examples 2-6 is shown in Table 2. However, this purge time is a relative value when the purge time of Example 1 is 0.3.

  From the results in Table 2, when the number of ultrasonic transducers in the nozzle part is one in Example 2, the purge time becomes long, and the total work time becomes close to that in Comparative Example 1. The merit by the method of the present invention is small. Therefore, it is desirable that the number of ultrasonic transducers in the nozzle portion be at least two.

It is sectional drawing which shows the state just before the purge in the material change operation | work of an extruder. It is sectional drawing which shows the purge state of an extruder. It is sectional drawing which shows an example of the extruder of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Heating cylinder, 3 ... Nozzle part, 4 ... Screw, 5 ... Resin extrusion port, 6 ... Resin waste, 7 ... Purge material, 10 ... Extruder, 11 ... Ultrasonic vibrator.

Claims (2)

In a method for cleaning an injection molding apparatus of a thermoplastic resin having an extruder having a heating cylinder having a nozzle at the tip and a screw inserted in the heating cylinder so as to be able to advance and retreat,
Ultrasonic vibrators are attached to the nozzle part of the heating cylinder, the heating cylinder body part, and the screw, respectively, and after injection molding of thermoplastic resin using this injection molding device, the purge material is supplied to the extruder. A method for cleaning an injection molding apparatus, comprising applying ultrasonic waves from an ultrasonic transducer to an extruder before or during purging of a residual resin by extruding a purge material.   2. The method for cleaning an injection molding apparatus according to claim 1, wherein two or more ultrasonic transducers are attached to the nozzle portion.

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