JP3930467B2 - Injection molding control method - Google Patents

Description

  The present invention relates to an injection molding control method for an injection molding machine.

  As shown in FIG. 4, an injection device of a conventional injection molding machine generally includes a cylinder 106 having a nozzle 108 attached to the tip, a hopper 109 storing resin to be supplied into the cylinder 106, and a cylinder 106. A screw 107 rotatably inserted into the screw, a measuring servo motor 103 for rotating the screw 107 in a measuring step of collecting molten resin at the tip of the screw while kneading the molten resin, and a molten resin stored at the tip of the nozzle 108. A reverse flow prevention ring 110 for preventing the molten resin from flowing back to the screw side at the time of injection, and an encoder 111 for retracting the screw 107 in a suck back process for preventing drooling after completion of the weighing process are provided. Suckback servo motor 105, weighing servomotor 103 and suckback A process controller 101 having a function of controlling the servo motor 105, and a servo amplifier unit 102.

  FIG. 5 shows each process from the injection pressure holding process to the mold opening in a general injection molding process by the injection molding machine having such a configuration.

After the mold is closed and the mold is clamped to finish the injection process and the pressure holding process, a cooling process is performed to solidify the molded product. In general, the cooling step is controlled by a timer with a cooling time T ₁ required for the molded product to be cooled to a temperature at which it is cooled by a mold and does not interfere with removal. The cooling time T ₁ controlled by the timer can be arbitrarily set in the process controller 101. Therefore, there is no specific value, and it is set by the quality of the molded product and the experience value of the molding engineer.

  In order to shorten the cycle, a metering (plasticizing) process and a suck-back process are performed in parallel with the cooling process.

  The metering step is a step of storing a molten resin corresponding to the weight of the molded product at the tip of the nozzle 108. In the measuring step, a signal arbitrarily set by the process controller 101 is transmitted to the measuring servo motor 103 through the servo amplifier unit 102 to rotate the measuring servo motor 103, and this rotational force is applied to the timing belt 104. To the screw 107 that is rotatably inserted into the cylinder 106. When the molten resin is plasticized by the screw 107 that retreats while rotating and is collected at the tip of the nozzle 108 in accordance with the weight of the molded product, it stops by the signal of the encoder 111 and the measuring process is completed.

  The suck back process performed after the metering process is a process for preventing the occurrence of drooling (melted resin leakage from the hole at the tip of the nozzle 108) after the metering process. In this suck back process, the process controller A signal arbitrarily set in 101 is transmitted to the servo motor 105 for suck-back through the servo amplifier section 102, and the screw 107 is slightly moved back without rotating to reduce the resin pressure at the tip of the screw 107. Position holding control is generally performed.

The cooling time T _1, the metering time T ₂ required for the metering process, the relationship between the suck-back time T ₃ required for the suck back step can be molded technician arbitrarily set, each of these times molding techniques Since the user can arbitrarily set, there are cases where the optimum value is not reached. On the other hand, as a method for improving the suckback process, a suckback process control using a suckback delay timer is disclosed (see, for example, Patent Document 1).
JP-A-11-227016

When the suck back process of the conventional injection molding machine is set according to the quality of the molded product and the experience of the molding engineer as described above, generally, the total time of the measuring time T ₂ and the suck back time T ₃ is Actually, the cooling time is set to be shorter than T ₁ . For this reason, for example, when the measurement time T ₂ is shortened by setting the screw rotation speed to a high rotation speed, the suck back process that is started immediately after the measurement process is completed before the cooling process is completed. Become. For example, if the cooling time T ₁ is 20 [sec], the metering time T ₂ at a certain screw speed is 12 [sec], and the suck back time T ₃ is 0.25 [sec], the cooling process is completed. The time, 20 [sec] − (12 [sec] +0.25 [sec]) = 7.75 [sec] is the waiting time T ₄ .

  Further, when the screw is retracted by the suck back process, the pressure of the molten resin that has been kept even in the cylinder becomes higher at the rear of the backflow prevention ring than at the front. This pressure difference before and after the backflow prevention ring causes the molten resin to flow from the back of the backflow prevention ring to the tip side of the nozzle until the injection process is started. Variations in the absolute mass of the molten resin for molded articles stored at the tip were induced.

The relationship between the reverse flow prevention ring pressure across the pressure of the front P _f, when the rear pressure to P _r, that a relationship of P _f> P _r, is ideal suppressing means mass variation However, by performing the suck back process, the relationship of P _f <P _r is satisfied, and the molten resin flows into the tip portion of the nozzle. However, _{if the} cooling process is completed with the relationship of P _f > P _r maintained and the mold opening of the next process is started, the nozzle hole is opened and drooling occurs. This drooling remains as traces on the surface of the molded product as cold slag (a state in which the resin is in contact with the outside air or the mold surface and solidifies), and causes molding defects.

Also, if the molding conditions such as the viscosity and temperature of the molten resin change, the amount of molten resin flowing into the tip also changes. Therefore, the measurement time T ₂ of the measurement process and the suck back time T ₃ of the suck back process are used as the molding conditions. depending but to change required, if you change the time of each of these steps the user, so that the waiting time T ₄ is changed. When the waiting time T ₄ changes, the amount of molten resin flowing into the tip of the nozzle also changes, and settings for preventing this sometimes become complicated.

  As described above, the setting based on the experience of the molding engineer is warped to induce a defect of the molded product, and it may take time to stably manufacture the molded product.

  Moreover, in the method of controlling the suck back process based on the comparison result of the resin pressure in front of the screw disclosed in Patent Document 1 described above, it is necessary to obtain a reference value for comparison in advance. In the production base of production, it can be considered that it takes a considerable amount of time just to obtain the reference value, and it may be difficult to set the reference value. In addition, it is considered that the response in high cycle production may cause problems such as measurement errors and variations of the resin pressure sensor, delay in response of the sensor itself, and cost of the apparatus itself.

  Therefore, the present invention provides an injection molding control method capable of preventing molding weight variation and improving molding accuracy and quality without being affected by a change in time setting required for the weighing process or suck back process. The purpose is to do.

In order to achieve the above object, the injection molding control method of the present invention is configured so that the amount of the molten resin to be injected next is retracted by the screw in the cylinder during the cooling step of cooling and solidifying the molten resin filled in the mold. In an injection molding control method for controlling an injection molding process in which a weighing process for weighing and a suck back process for preventing drooling after the weighing process is performed,
A cooling step starts at t _cs cooling process is completed after the cooling step time T _c elapses from t _ce, sacks carried out from the weighing process starts at t _ws to be cooled process start t _cs simultaneously after the metering process time T _m elapsed step includes terminating the the suck-back end t _se and said cooling step by comparing a completion time of the back step and the suck-back process simultaneously, characterized in that it comprises a.

  Since the injection molding control method of the present invention as described above ends the suck back process simultaneously with the end of the cooling process, there is no waiting time until the cooling process ends after the suck back process ends. For this reason, the time until the next injection process can be shortened by the waiting time. Furthermore, even if the time required for the metering process and suckback process is changed in consideration of the viscosity, temperature, etc. of the molten resin, the time from the end of the suckback process to the next injection process is not affected. Can be constant.

In addition, the injection molding control method of the present invention includes a step of calculating the suck back start time T _w by subtracting the suck back step time T _s from the cooling step time T _c, and a suck back start from the cooling step start time t _cs. after the time T _w, it may include the step of initiating the suck-back step.

  According to the present invention, the time until the next injection process can be shortened and made constant by terminating the suck back process simultaneously with the end of the cooling process. As a result, the amount of molten resin that flows from the back of the screw to the front due to sackback can be made small and constant, so that molding is not affected by changes in the time setting required for the metering process or sackback process. Variations in the weight of the product can be prevented, and the molding accuracy and quality can be improved.

  Next, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 1, the schematic block diagram of the injection apparatus of the injection molding machine which is one Embodiment of this invention is shown.

  The injection device of the injection molding machine includes a cylinder 9 having a nozzle 11 attached to the tip thereof, a hopper 7 that stores a resin to be supplied into the cylinder 9, and a screw 8 that is rotatably inserted into the cylinder 9. In order to move the screw 8 back in the sucking process for preventing drooling after the completion of the metering process, and the measuring servo motor 3 for rotating the screw 8 in the metering process for accumulating the molten resin at the screw tip. A back-back preventing ring 10 for preventing the molten resin from flowing back to the screw side when injecting the molten resin stored at the tip of the nozzle 11; A control unit 14 having a process controller 1, an arithmetic processing unit 12, a cooling time interlocking ON switch 13 and a determination unit 15, and a servo And a pump unit 2.

The process controller 1 of the control unit 14 has a function of controlling the metering servo motor 3 and the suck back servo motor 5, and a suck back start function for starting the suck back process. The arithmetic processing unit 12 has a function of calculating a suck back process time T _s and a suck back start time T _w described later. The cooling time interlocking ON switch 13 is a switch for starting a process of simultaneously terminating the suck back process and the cooling process. The determination unit 15 has a function of determining whether or not the suck back process and the cooling process are completed at the same time.

  Next, an injection molding process by the injection molding machine according to the present embodiment will be described with reference to FIGS.

  FIG. 2 is a cycle process diagram showing one cycle of injection molding by the injection molding machine of this embodiment, and FIG. 3 is a flowchart of an injection molding control method by the injection molding machine of this embodiment.

  As shown in FIG. 2, the injection molding process in the injection molding machine generally includes a mold closing process for closing a mold (not shown), a mold clamping process for clamping the mold, and a nozzle advance for pressing the nozzle 11 against the sprue of the mold. Touching process, an injection process in which the screw 8 in the cylinder 9 is advanced to inject the molten resin accumulated in front of the screw 8 into the mold cavity, and then holding pressure to suppress the generation of bubbles and sink marks For a while, cooling process for cooling and solidifying the molten resin filled in the mold cavity, nozzle retreating process for retreating the nozzle 11 pressed against the sprue of the mold, and solidified molding The mold opening process for opening the mold to remove the product from the mold, the ejector process for extruding the molded product with the protruding pin provided on the mold, the ejecting operation, and the removal of the molded product An intermediate step for ensuring, and a weighing step for measuring the amount of molten resin injected in the next cycle, which is performed during the cooling step, and a suck back step for preventing drooling after the weighing step Are performed in parallel.

  In the case of the above-described shift molding in which the nozzle 11 is moved forward and backward, the injection molding process includes a nozzle forward touch process and a nozzle backward process, but the touch is performed by continuously molding the nozzle 11 while pressing it against the sprue of the mold. In the case of molding, the nozzle forward touch process and the nozzle backward process are omitted in the injection molding process.

  Next, suck back control in the injection molding control method of this embodiment will be described in detail. The terms used in the following description are defined as follows.

The suck back speed V _s is the moving speed of the screw 8 in the suck back process, and the suck back distance X _s is the moving distance of the screw 8 in the suck back process.

The cooling process time _Tc is the time required for the cooling process. The cooling process start time t _cs is the time when the cooling process is started. The time t _ce at the end of the cooling process is the time at which the cooling process ends.

The weighing process time T _m is the time required for the weighing process, and the weighing process start time t _ws is the time when the weighing process is started.

The suck back process time T _s is the time required for the suck back process. The suck back start time _Tw is the time from the start of the cooling process t _cs to the start of the suck back process. The time _tse when the _suckback ends is the time when the _suckback process ends.

The injection process start time tis _{is the} time when the injection process starts.

  The suck back control will be described below.

  First, molding is started on the basis of the normal molding conditions set from the experience values of the molding engineer, and after confirming the stability to the molding conditions, for example, after 20 shots from the start of molding, or a satisfactory molded product is obtained. From the time of molding, the cooling time interlock ON switch 13 of the control unit 14 is turned on (step S1).

Since the cooling time interlock ON switch 13 is turned on, the suck back speed V _s and the suck back distance X _s are measured (step S2). The suck back speed V _s and the suck back distance X _s of the screw 8 are measured and calculated by processing the position pulse of the encoder 6 provided in the suck back servo motor 5 by the servo amplifier unit 2.

The suck back speed V _s and the suck back distance X _s thus obtained and the preset cooling process time T _c are input to the arithmetic processing unit 12 of the control unit 14 (step S3).

Next, the determination unit 15 determines whether or not the cooling process end _tce and the suckback end _tse are equal (step S4). That is, the cooling step starts at t _cs cooling process is completed after the cooling step time T _c elapses from t _ce, rows from the metering process at the start t _ws after metering step time T _m elapsed as the cooling step starts at t _cs simultaneously by comparing the suck-back at the end t _se is the end time of the suck-back step of dividing, the cooling step and the suck-back step a determination is made whether or not to end at the same time.

As a result of the determination, when the cooling process end t _ce is equal to the suck back end t _se and the cooling process and the suck back process end simultaneously, the molding is continued under the current molding conditions (step S7). ).

As a result of the determination, if the cooling process end t _ce is not equal to the suck back end t _se and the cooling process and the suck back process do not end at the same time, the arithmetic processing unit 12 inputs the suck The suck back process time T _s is calculated from the back distance X _s and the suck back speed V _s, and the suck back start time T _w is calculated by subtracting the suck back process time T _s from the cooling process time T _c (step) S5).

Next, the calculated suckback start time _Tw is sent to the suckback process start function in the process controller 1, and is converted into a time from the start of the cooling process t _cs to the start of the _suckback process. Return to (step S6). As a result, the next suck back process is started after the suck back start time _{Tw has} elapsed from the start of the cooling process t _cs . The suck back process is started after the suck back start time _{Tw has} elapsed, so that the cooling process end t _ce and the suck back end t _se become equal, that is, the cooling process and the suck back process end simultaneously. It becomes.

  Hereinafter, processing in the case where the cooling process and the suck-back process are not completed at the same time in the suck-back control of the present embodiment will be described using specific numerical values.

For example, when the suck back speed V _s is 20 [mm / sec], the suck back distance X _s is 5 [mm], and the cooling process time T _c is 20 [sec] is input to the arithmetic processing unit 12 in step S3. To do.

Here, in the molding performed last time, the weighing process is the weighing process time T _m = 12 [sec], and the suck back process continuously performed immediately after the weighing process is the suck back process time T _s . In the case of 25 [sec], t _se = T _m + T _s = 12 [sec] +0.25 [sec] = 12.25 [sec] at the end of suckback. Since the measurement process is started at the measurement process start time t _ws that is the same as the cooling process start time t _cs at which the cooling process is started, in step S4, at the end of suckback t _se = 12.55 [sec]. Unlike the cooling process time T _c = 20 [sec], the determination unit 15 determines that the cooling process and the suck back process do not end simultaneously.

When it is determined that the cooling process and the suckback process do not end at the same time, the arithmetic processing unit 12 performs the suckback in step S5 based on the suckback distance X _s and the suckback speed V _s input in step S2. The process time T _s is calculated as T _s = X _s / V _s = 5 [mm] / 20 [mm / sec] = 0.25 [sec], and the suck back start time T _w is calculated as T _w = Calculation is performed as T _c −T _s = 20 [sec] −0.25 [sec] = 19.75 [sec].

In step S6, the suck back start time T _w = 19.75 [sec] is sent to the suck back process start function in the process controller 1, and the time from the start of the cooling process t _cs to the start of the suck back process. The process returns to step S3. Accordingly, the next suck back process requiring the suck back process time T _s = 0.25 [sec] is started after the suck back start time T _w = 19.75 [sec] from the cooling process start t _cs. Therefore, T _w + T _s = 20 [sec] = T _c , and the cooling process and the suck back process are completed at the same time.

  As described above, the injection molding control method of the present embodiment that simultaneously ends the cooling process and the suck back process can obtain the following functions and effects.

Conventionally, there has been a so-called standby time that waits for the end of the cooling process even though the suck back process has already been completed, but the injection molding control method of the present embodiment simultaneously performs the cooling process and the suck back process. Because it is terminated, there is no waiting time. That is, in the present embodiment, the time from the end of suckback _tse to the start of the next injection process tis _is shortened compared to the conventional case.

Here, the pressure relationship of the front and rear of the backflow prevention ring 10, when pressure P _f of the front of the backflow prevention ring 10 (the nozzle 11 side), the pressure behind (hopper 7 side) was P _r, the suck-back step By doing so, the relationship of P _f <P _r is satisfied and the molten resin flows into the tip portion 11a of the nozzle 11. However, in this embodiment, the molten resin flows from the back of the backflow prevention ring 10 to the front. The time can be shortened by the standby time that has been generated conventionally. Thereby, since the flowing amount of molten resin can be reduced, the dispersion | variation in the mass of the molten resin measured and stored in the front-end | tip part 11a can be reduced.

Furthermore, since the injection molding control method of the present embodiment ends the cooling process and the suck back process at the same time, even if the user changes the molding conditions, the next injection process start time t _is from the tuck back end t _se. The time until can be made constant. Molded if Kaware molding conditions such as the viscosity of the molten resin, the temperature, since changes also the amount flow of molten resin into the distal end portion 11a, the metering process time T _m, the suck-back process time T _s, further cooling step time T _c Although it is necessary to change according to conditions, even if the time of each of these steps is changed, the injection molding control method of the present embodiment does not change the time setting of each step until the next injection step after the cooling step. As long as the time from the end of _suckback t _se to the next injection process start t _is constant, the amount of molten resin flowing into the tip portion 11a can be made constant, and the amount measured at the tip portion 11a is measured. It is possible to reduce the variation in the mass of the molten resin accumulated. That is, the user can set the measurement process time T _m , the suck back process time T _s, and the cooling process time T _c without worrying about variations in the mass of the molten resin.

  Thus, according to the injection molding control method of the present embodiment, the amount of molten resin flowing from the back of the backflow prevention ring 10 due to suck back into the tip portion 11a of the nozzle 11 can be made small and constant. Variation in the weight of the molded product can be reduced.

In the present embodiment, from the cooling step time T _c suck back process time by subtracting the time T _s is calculated as a suck back start time T _w, after suck back start time T _w from the cooling step starts at t _cs, sacks The injection molding control method that ends the cooling process and the suck back process almost simultaneously by starting the back process is shown as an example. However, the control that can end the cooling process and the suck back process almost simultaneously is shown. Anything can be used. For example, in this embodiment, since the cooling process start time t _cs and the weighing process start time t _ws are simultaneous, it is assumed that the suck back process is started after the suck back start time T _w from the weighing process start time t _ws. Also good.

  Next, a description will be given of the results of a comparative study of the weight variation of the molded product molded by one embodiment of the injection molding control method of the present invention and the weight variation of the molded product molded by the conventional injection molding method.

  Table 1 shows the molding conditions, the weight of the molded product, and the results of injection molding in this example. Table 2 shows the molding conditions, the weight of the molded product, and the results of the injection molding of the comparative example performed for comparison.

  As the molten resin, a PP resin having a low melt viscosity (melt index value: 40 [g / 10 min]) is used for both the present example and the comparative example, and a circle with a molded article reference weight of 3 [g] and a diameter of φ15 [mm] is used. A test piece (one piece) was molded by the side gate method. Moreover, J35EL3 (made by Nippon Steel Works) was used for the injection molding machine.

As shown in Table 1, when the weight variation amount of the comparative example is 100%, the weight variation amount according to this example is
(0.133 / 0.403) × 100 = 33.002 [%] (≈33 [%])
It becomes. Thus, in the case of this example, the weight variation relative to the comparative example is
((0.403-0.133) /0.403) × 100
= 66.997 [%] (≈ 67 [%])
It becomes. Thus, in the case of the present Example, the weight variation was able to be improved about 67 [%] with respect to the comparative example. Moreover, the cutting of the molded product gate portion was stable due to the stability of the solidified layer of the nozzle gate portion.

It is a schematic block diagram of the injection device of the injection molding machine which is one Embodiment of this invention. It is a cycle process figure which shows 1 cycle of injection molding by the injection molding machine which is one Embodiment of this invention. It is an example of the flowchart of the injection molding control method of this invention. It is a schematic block diagram of an example of the injection apparatus of the conventional injection molding machine. It is an example of the cycle process figure which shows 1 cycle of the injection molding by the conventional injection molding machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Process controller 2 Servo amplifier part 3 Servo motor for measurement 5 Servo motor for suck back 6 Encoder 7 Hopper 8 Screw 9 Cylinder 10 Backflow prevention ring 11 Nozzle 11a Tip part 12 Arithmetic processing part 13 Cooling time interlock ON switch 14 Control part 15 Judgment Part t _is at the start of injection process T _c cooling process time T _m weighing process time T _s suck back process time T _w suck back start time t _{ce at} cooling process end t _{cs at} cooling process start t _{se at} suck back time t _ws weighing At the start of the process V _s suckback speed X _s suck back distance

Claims (2)

In the cooling step of cooling and solidifying the molten resin filled in the mold, the amount of the molten resin to be injected next is measured by retreating the screw in the cylinder, and the drooling after the measuring step In an injection molding control method for controlling an injection molding process in which a suck back process for preventing occurrence is performed,
Upon cooling process starts (t _cs) cooling step time (T _c) during the cooling process is completed after a lapse and a (t _ce), from the time of the cooling step starts (t _cs) and the simultaneous measuring process at the start (t _ws) step weighing process time (T _m) is compared with the suck-back end (t _se) is the end time of the suck-back process performed after it includes terminating and said suck back step and the cooling step at the same time The injection molding control method characterized by including these. A step of calculating the cooling step time (T _c) from the suck back process time (T _s) time obtained by subtracting the a suck back start time (T _w),
The cooling step starts at a (t _cs) after the suck back start time (T _w), and a step of initiating the suck-back step, injection molding control method according to claim 1.

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