JP2008284793A - Mold heating method and molding apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold heating method which can raise the uniformity of the temperature distribution of a mold of an injection molding machine and to provide a molding apparatus. <P>SOLUTION: The mold heating method comprises includes the steps of arranging two or more plate-type heaters 10a-10h to each side of a rectangular mold 7, arranging two or more temperature sensors 12a-12h for detecting the temperature of each control point A-H of the mold 7, and controlling power supply to of the heaters 10a-10h by employing the average temperature and gradient temperature (temperature difference) based on the detected temperature of the each temperature sensors 12a-12h into a controlled variable. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a molding apparatus such as an injection molding machine and a method for heating a mold used therefor.

  Conventionally, for example, an injection molding machine is used to mold relatively precise precision parts such as an optical lens (see, for example, Patent Document 1).

  Such injection molding machines include a horizontal molding machine that opens and closes by moving a movable mold in a horizontal direction with respect to a fixed mold, and in this horizontal injection molding machine, a molded product is Widely used because it can be automatically dropped and downsized.

  The temperature control of the mold of such a horizontal injection molding machine is performed as follows, for example.

  FIG. 11 is a schematic plan view showing the mold 30 and the heater 31 on the fixed side. FIG. 11 shows the front surface of the mold 30 that forms a cavity (space) (not shown) corresponding to the molded product when the mold is clamped, facing the movable mold.

As shown in FIG. 11, plate-type heaters 31 are provided on each of the four side surfaces of the mold 30 having a rectangular front surface, and one point of the mold 30, for example, a control point near the center surface. The temperature of P is detected, and the temperature is controlled by a temperature controller (not shown) so that the detected temperature becomes a set temperature.
Japanese Patent Laid-Open No. 9-183146

  In a horizontal injection molding machine in which the mold is opened and closed in the horizontal direction, the mold 30 is arranged vertically, that is, the front surface constituting the cavity is perpendicular to the ground. And a temperature difference occurs in the vertical direction of the mold 30.

  As described above, in a one-channel temperature control system that detects the temperature of one control point P and uniformly heats the upper, lower, left, and right side surfaces by a single heater 31 so as to reach a set temperature, the vertical direction Therefore, it is difficult to control the temperature difference to be uniform and control the temperature difference.

  For this reason, particularly when molding optical parts such as lenses, the residual stress of the molded parts due to non-uniform temperature distribution in the mold surface may directly affect the optical characteristics. There is.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a mold heating method and a molding apparatus using the same that can improve the uniformity of temperature distribution. .

  (1) The mold heating method of the present invention is a mold heating method in which the front surface, which is the surface constituting the cavity, is rectangular, and a plurality of plate heaters are arranged on the four side surfaces of the mold. In addition, at each of the four corners of the rectangle, the heaters located on both sides of each vertex are operated as one heater.

  A cavity refers to a space corresponding to a molded product formed inside a mold in a closed state in which the mold according to the present invention and another mold are brought into contact with each other.

  It is preferable that a plurality of cavities are configured to correspond to a plurality of molded products so that a plurality of cavities can be accommodated, and in order to make the flow path uniform, the plurality of cavities are made of molding material. It is preferable to be formed so as to be located on the same circumference from the center of the mold serving as the supply port.

  The heaters located on both sides of each of the four vertices may be constituted by one heater that is bent along the corner and is continuous, or the two heaters located on both sides are used as one heater. You may make it act.

  According to the mold heating method of the present invention, a plurality of heaters are provided on the side surface of the mold to heat the mold. For example, when the mold is heated with a single heater, the mold is not desired. When such a temperature distribution is generated, it is possible to cancel the temperature distribution and heat it so as to be uniform.

  Moreover, at each corner of the rectangular mold, the heaters located on both sides of each vertex act as a single heater, so that, as will be described later, the rectangular mold has an octagonal shape like a corner cut. The temperature distribution can be made, and the temperature distribution is closer to the circumference than the rectangular shape, which is effective when a plurality of cavities are arranged along the same circumference from the center of the mold.

   (2) In one embodiment of the mold heating method of the present invention, at each corner, heaters located on both sides of each apex are bent and continuously along the corner. Each of the side faces is provided with at least one heater in addition to the single heater.

  According to this embodiment, the mold can be heated using four single heaters bent at four corners and at least eight heaters, one heater on each side, for example, a single When an undesired temperature distribution is generated in the mold when the mold is heated by the heater, it is possible to effectively suppress the temperature distribution and heat the mold so as to obtain a uniform temperature distribution. .

   (3) In another embodiment of the method for heating a mold according to the present invention, at least three heaters are provided on each side surface.

  According to this embodiment, at least 12 heaters are provided, and at each of the four corners, two heaters located on both sides of the apex are operated as one heater, so at least eight heaters are used. The mold can be heated. For example, when an undesired temperature distribution is generated in the mold when the mold is heated with a single heater, the temperature distribution is effectively suppressed to a uniform temperature. It is possible to heat to a distribution.

   (4) In another embodiment of the mold heating method of the present invention, the mold is a horizontal mold in which the movable mold moves in the horizontal direction relative to the fixed mold and opens and closes the mold. This is a mold on at least one of the fixed side and the movable side of the injection molding machine.

  In a horizontal injection molding machine, since the mold is arranged perpendicular to the ground, an undesired temperature difference occurs in the vertical direction. According to this embodiment, the temperature difference is reduced by a plurality of plate-type heaters. It can be heated to a uniform temperature by suppressing.

   (5) In one embodiment of the mold heating method of the present invention, the mold is provided with a plurality of temperature sensors corresponding to the plurality of heaters, and a plurality of detected temperatures from the plurality of temperature sensors. The heating by the heater is controlled using the average temperature and the gradient temperature based on the above as control amounts.

  The gradient temperature refers to a temperature gradient, that is, a temperature difference, for example, a temperature difference between two detected temperatures, or a temperature difference between an average temperature and each detected temperature.

  According to this embodiment, instead of individually controlling each heater based on the detected temperature of each corresponding temperature sensor, the average temperature and the gradient temperature based on a plurality of detected temperatures from a plurality of temperature sensors are used as control amounts. Since control is performed, temperature control with high accuracy with reduced interference between the heaters becomes possible.

   (6) A molding apparatus according to the present invention is a molding apparatus that forms a cavity by abutting the opposed front surfaces of a fixed side mold and a movable side mold and filling the cavity with a molding material. In addition, a plurality of plate-type heaters are disposed on the side surfaces of at least one of the fixed-side mold and the movable-side mold, while a plurality of the mold-type heaters detect the temperature of the mold. The temperature sensor is provided, and a temperature controller is provided for controlling energization of each heater based on the temperature detected by each temperature sensor.

  According to the molding apparatus of the present invention, a plurality of heaters and a plurality of temperature sensors are arranged in the mold to control the temperature of the mold. For example, in the temperature control with a single heater and the temperature sensor, the mold is When an undesired temperature distribution occurs, it is possible to control the temperature so that the temperature distribution is suppressed and uniform.

  Thereby, for example, in the molding of an optical component such as a lens, the influence of the residual stress on the optical characteristics can be reduced as much as possible.

   (7) In another embodiment of the molding apparatus of the present invention, the front surface of the mold is rectangular, and at each of the four corners, the heaters located on both sides of each vertex are used as one heater. The energization is controlled by the temperature controller.

  According to this embodiment, at each corner of the rectangular mold, the heaters located on both sides of each vertex act as one heater, so that the corners of the rectangular mold are cut as described later. The octagonal temperature distribution can be obtained, and the temperature distribution is closer to the circumference than the rectangle, and the temperature of multiple cavities arranged along the same circumference from the center of the mold is made uniform. Can be achieved.

  (8) In another embodiment of the molding apparatus of the present invention, the temperature adjuster uses the average temperature based on the plurality of detected temperatures from the temperature sensors and the gradient temperature based on the plurality of detected temperatures as control amounts. The energization of the heater is controlled.

  According to this embodiment, instead of individually controlling each heater based on the detected temperature of each corresponding temperature sensor, the average temperature and the gradient temperature based on a plurality of detected temperatures from a plurality of temperature sensors are used as control amounts. Since control is performed, temperature control with high accuracy with reduced interference between the heaters becomes possible.

  (9) In one embodiment of the molding apparatus of the present invention, with respect to the fixed mold, the movable mold is moved in a horizontal direction to open and close the mold, and the molding material is The cavity is injection filled.

  According to this embodiment, the temperature difference of the mold of the horizontal type injection molding machine in which an undesired temperature difference is generated in the vertical direction can be suppressed and controlled to a uniform temperature.

  According to the present invention, a plurality of heaters are arranged on the side surface of the mold to heat the mold. For example, when the mold is heated with a single heater, an undesirable temperature distribution is generated in the mold. In such a case, it is possible to suppress the temperature distribution and to heat it uniformly.

  In addition, since a plurality of heaters and a plurality of temperature sensors are arranged in the mold to control the temperature of the mold, for example, in the temperature control using a single heater and the temperature sensor, an undesired temperature distribution is present in the mold. In such a case, it is possible to suppress the temperature distribution and control the temperature so as to be uniform, and in particular, in the molding of optical components such as lenses, the optical characteristics due to residual stress can be reduced. The influence can be reduced as much as possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram of an injection molding machine as a molding apparatus according to one embodiment of the present invention.

  The injection molding machine 1 includes a mold 3, a heating cylinder 4 that kneads and melts the material from the hopper 2 and injects the material into the mold 3, and a temperature controller 5 that controls the temperature of the mold 3. .

  The mold 3 includes a fixed mold 7 attached to the fixed platen 6 and a movable mold 9 attached to the movable platen 8.

  The injection molding machine 1 opens and closes the mold 3 by moving the movable mold 9 in the horizontal direction (left and right in the figure) with respect to the fixed mold 7 by a mold clamping device (not shown). In the horizontal injection molding machine, in the clamped state of FIG. 1, a cavity (not shown) corresponding to the molded product is formed between the opposing surfaces of both molds 7 and 9.

  In this embodiment, each of the molds 7 and 9 is provided with a plurality of plate-type heaters 10 and 11 and a plurality of temperature sensors 12 and 13, respectively.

  In FIG. 1, one of the plurality of heaters 10 and 11 and the plurality of temperature sensors 12 and 13 of the molds 7 and 9 is representatively shown.

  The temperature controller 5 is supplied with detected temperatures from the temperature sensors 12 and 13 of the molds 7 and 9, and is controlled by the control output from the temperature controller 5 via the SSR (not shown). The energization of the heaters 10 and 11 is controlled.

  FIG. 2 is a schematic front view showing a mold on one side of FIG. 1, in this example, a mold 7 on the fixed side and a plurality of heaters 10a to 10h, and corresponds to the conventional example of FIG. is there.

  In the mold heating structure of this embodiment, the plate-type heaters 10a to 10h attached to the four side surfaces of the mold 7 having a square front surface are divided into eight, and the heaters at the four corners are provided. Reference numerals 10b, 10d, 10f, and 10h are respectively configured as a single bent heater. Each of the heaters 10a to 10h is attached with a diffusion plate (not shown) made of aluminum or the like interposed between the side surfaces of the mold 7 and the like.

  Further, in the vicinity of the surface of the mold 7, the above-described plurality of temperature sensors 12 a to 12 h that respectively detect the temperatures of the eight control points A to H corresponding to the eight heaters 10 a to 10 h are arranged. ing.

  A recess (not shown) for forming a cavity is formed on the surface of the mold 7, and a plurality of molded products, for example, a plurality of molded products in order to enable a large number of optical components such as lenses. Are formed along the same circumference from the center of the mold 7.

  1 controls the energization of each of the eight heaters 10a to 10h based on the detected temperatures of the temperature sensors 12a to 12h at the control points A to H. In this embodiment, the temperature control system is an eight-channel temperature control system.

  Moreover, in this embodiment, the temperature is not individually controlled for each channel, but the temperature control method already proposed by the present applicant and patented as, for example, Japanese Patent No. 3278807 is used.

  This temperature control method converts a plurality of detected temperatures corresponding to a plurality of control points into, for example, an average temperature of a plurality of detected temperatures and a temperature difference (gradient temperature) based on the plurality of detected temperatures. This is a method of controlling the temperature using the gradient temperature as a control amount (hereinafter also referred to as “gradient temperature control”).

  FIG. 3 is a block diagram showing the configuration of the gradient temperature control in the temperature controller 5 of this embodiment, and is a block diagram corresponding to the fixed mold 7.

  The temperature controller 5 of this embodiment converts the input temperatures PV1 to PV8 from the eight temperature sensors 12a to 12h into one average temperature (average PV) and seven gradient temperatures (gradient PV1 to gradient PV7). Based on the deviation between the mode converter 14 and each temperature (average PV, slope PV1 to slope PV7) from the mode converter 14 and the target temperature (average SP, slope SP1 to slope SP7), operation signals are calculated. The eight PID control units 15 and the operation signals from each PID control unit 15 are distributed so that the influence of the control by each PID control unit 15 on the control by other PID control units 15 is eliminated or reduced. And a pre-compensation unit 16 that gives control outputs MV1 to MV8 to the heaters 10a to 10h.

  The mode conversion unit 14 converts the eight input temperatures PV1 to PV8 into an average temperature (average PV) that is an average value thereof and, for example, a temperature difference (PV1-PV2, PV2-PV3, PV3-PV4) between adjacent input temperatures. ,..., PV7-PV8) are converted into seven gradient temperatures (gradient PV1 to gradient PV7).

  Note that the gradient temperature is not limited to the temperature difference with the adjacent input temperature. For example, the temperature difference between the average temperature (average PV) and each input temperature (PV1-average PV, PV2-average PV, PV3-average). PV, ... PV7-average PV). As described above, by using the temperature difference between each input temperature and the average temperature as the inclined temperature, the temperature of the symmetrical mold 7 can be more uniformly controlled.

  For the target temperature SP, the difference between the target average temperature (average SP), which is the average value of the set temperatures (target temperatures) SP1 to SP8 of the eight control points A to H, for example, the adjacent set temperature (SP1- SP2, SP2-SP3, SP3-SP4,... SP7-SP8) are set as seven target gradient temperatures (gradient SP1 to gradient SP7).

  Each PID control unit 15 performs a PID calculation so as to eliminate the deviation between the input temperature PV and the target temperature SP, and outputs an operation signal (operation amount).

  The pre-compensation unit 16 decomposes an operation signal (operation amount) from the PID control unit 15 and has the same configuration as that disclosed in Patent Document 1 and Japanese Patent Application Laid-Open No. 2002-157001. , Gc is a pre-compensation matrix that is a matrix of the distribution ratio of the pre-compensation unit 16, and the detected temperatures (PV1 to PV8) by the above-described mode converter 14 are gradient temperatures (gradients PV1 to PV7) and average temperatures (average If the matrix to be converted into (PV) is a mode conversion matrix Gm and the transfer function matrix to be controlled is Gp, the pre-compensation matrix Gc can also be obtained as an inverse matrix as follows.

Gc = (Gm · Gp) ⁻¹
When each of the eight control points A to H is individually controlled, a certain control point affects other control points, that is, it is difficult to perform highly accurate temperature control due to interference. In the temperature control, since the average temperature and the gradient temperature based on the detected temperatures of the eight control points A to H are controlled as control amounts, highly accurate temperature control with reduced influence of interference becomes possible.

  Next, test results comparing this embodiment with the above-described conventional example will be described.

  FIG. 4 is a front view showing the arrangement of the test mold and the heater.

  The test mold 17 is a square having a side of 190 mm and is made of stainless steel having a thickness, that is, a side width of 40 mm, and each side has three 100 V 60 W plate heaters 18- 1-18-12 are attached. Further, in correspondence with the conventional one-channel system, a temperature sensor 19 is attached to detect the temperature of the center P ′ of the surface of the mold 17 as a control point, and it corresponds to the eight-channel system of the above-described embodiment. And the temperature sensors 20a-20h which detect the temperature of eight control points A'-H 'along the same periphery, respectively were attached.

  In the one-channel system, all the heaters 18-1 to 18-12 were energized and controlled in the same manner so that the normal PID control, that is, the detected temperature from the temperature sensor 19 became the target temperature.

  On the other hand, the 8-channel system has the above-described gradient temperature control, that is, heaters located on both sides of each apex of the four corners, that is, the heater 18-3, the heater 18-4, and the heater 18-6. The heater 18-7, the heater 18-9 and the heater 18-10, the heater 18-12 and the heater 18-1 act as one heater, respectively, and the 8-channel gradient temperature control is performed.

  In the 1-channel system, the temperatures at the above eight points A ′ to H ′ were measured for evaluation.

  FIG. 5 and FIG. 6 show the temperature rising waveforms at points P ′, A ′ to H ′ from room temperature to 150 ° C. in the 1-channel and 8-channel systems, respectively.

  In the conventional one-channel system of FIG. 5, the temperatures of the points A ′ to H ′ vary even after the temperature rise is completed, whereas in the eight-channel system corresponding to the embodiment, as shown in FIG. Further, it can be seen that the temperatures of the points A ′ to H ′ are uniform, and the temperature variation is suppressed and the temperature distribution is uniform.

  FIG. 7 shows the temperatures of the points A ′ to H ′ at the time of settling, in which the broken line indicates a one-channel system and the solid line indicates an eight-channel system.

  FIG. 7 is a graph in which the temperatures at points A ′ to H ′ at 70 minutes after the completion of the temperature rise are plotted with 140 ° C. as the center. Is higher at the upward points A ′, B ′, and H ′, and it can be seen that the distribution is shifted upward. There is a maximum temperature difference of about 10 ° C., and it is thought that precision molding has a significant impact on the quality of molded products.

  On the other hand, in the 8-channel system corresponding to the embodiment shown by the solid line, the control temperature is not deviated from 1 ° C. to 150 ° C., and the temperature is uniform.

  FIG. 8 and FIG. 9 are diagrams respectively showing changes in temperature difference between the average temperature and the temperatures of the points A ′ to H ′ when the temperature of the 8-channel system and the 1-channel system is raised.

  Here, the differential temperature is a temperature difference between the average temperature of the eight points A ′ to H ′ and the temperature of each point A ′ to H ′, and indicates the temperature uniformity in the mold surface. Yes.

  In the 8-channel system to which the gradient temperature control of FIG. 8 is applied, it can be seen that the temperature difference is within ± 0.5 ° C. except for the temperature variation of about ± 1 ° C. at the time of start-up.

  In this test, a K thermocouple was attached to the surface with aluminum heat-resistant tape as a temperature sensor, and the fine vibration observed on the waveform seems to be an error in this measurement method itself. In the 8-channel control system, it seems that the measurement level is almost uniform.

  On the other hand, in the one-channel system shown in FIG. 9, the temperatures at the points A ′ to H ′ are set at the respective equilibrium temperature differences while being switched up and down. At 70 minutes, a temperature difference of a little less than 10 ° C. occurs.

  The difference in performance from gradient temperature control is close to an order of magnitude. On the way, it is assumed that the waveform is crossed because there is interference between the points and a temperature drift in the vertical direction as the temperature rises.

  Moreover, as a result of confirming the temperature distribution of the mold of the 8-channel system with a thermoviewer, it was confirmed that there was no temperature deviation in the vertical direction.

  FIG. 10 shows the color image showing the temperature distribution of the mold by the thermoviewer in shades.

  As shown in FIG. 10, it can be seen that there is no temperature deviation in the vertical direction.

  In addition, at the four corners of the rectangular mold, the heaters on both sides of the apex act as one common heater, so the octagonal temperature is as if the four corners were cut off. In the rectangular mold, an octagonal temperature distribution closer to the circumference is obtained.

  As is clear from the above test results, in this embodiment, it is possible to control the mold at a uniform temperature as compared with a one-channel system. The influence of the stress on the optical characteristics can be reduced as much as possible.

  In addition, since the heaters on both sides of the apex act as the same heater in each corner of the mold, the rectangular mold can have an octagonal temperature distribution closer to the circumference, and a plurality of A plurality of cavities so as to correspond to the molded product is more effective for equalizing the temperature of each cavity portion arranged on the same circumference from the mold center.

(Other embodiments)
Although the gradient temperature control is applied in the above-described embodiment, as another embodiment of the present invention, for example, the target temperature of each control point of the above-described eight channels is set low on the upper side and high on the lower side, You may make it perform temperature control separately.

  Although applied to the horizontal injection molding machine of the above-mentioned embodiment, it may be applied to a vertical injection molding machine, and may be applied not only to an injection molding machine but also to other molding machines such as a press molding machine. .

  Also, the number of channels is not limited to eight, and any number of channels may be used.

  The present invention is useful for temperature control of a molding apparatus such as an injection molding machine.

It is a schematic block diagram of the injection molding machine which concerns on one embodiment of this invention. It is a front view which shows the metal mold | die and heater of FIG. It is a block diagram of the principal part of the temperature controller of FIG. It is a top view of the metal mold | die for a test. It is a figure which shows the temperature rising waveform of each point by the control system of 1 channel. It is a figure which shows the temperature rising waveform of each point by the control system of 8 channels corresponding to embodiment. It is a figure which shows each point temperature in each control system. It is a figure which shows the change of the temperature difference of the average temperature of 8 points | pieces, and the temperature of each point in the control system of 8 channels corresponding to embodiment. It is a figure which shows the change of the temperature difference of the average temperature of 8 points | pieces, and the temperature of each point in the control system of 1 channel. It is a figure which shows the monochrome image of the thermoviewer which shows the temperature distribution of the metal mold | die surface in the control system of 8 channels corresponding to embodiment. It is a front view which shows the metal mold | die and heater of a prior art example.

Explanation of symbols

1 Injection molding machine 3 Mold 5 Temperature controller 7 Mold (fixed side)
10a to 10h heater 18-1 to 18-12 heater 12a to 12h temperature sensor 20a to 20h temperature sensor

Claims (9)

The front surface which is a surface constituting the cavity is a heating method of a rectangular mold,
A plurality of plate-type heaters are disposed on the four side surfaces of the mold, and the heaters located on both sides of each apex are allowed to act as one heater at each corner of the four rectangles. A method for heating a mold.   In each corner, the heaters located on both sides of each apex are each composed of a single heater that is bent and continuous along the corner, and each side has a heater other than the single heater. The method for heating a mold according to claim 1, wherein at least one heater is provided respectively.   The method for heating a mold according to claim 1, wherein at least three heaters are provided on each side surface.   At least one of the fixed side and the movable side of a horizontal injection molding machine in which the mold moves horizontally with respect to the fixed side mold so that the movable side mold moves in the horizontal direction. It is a metal mold | die, The heating method of the metal mold | die as described in any one of Claims 1-3.   The mold is provided with a plurality of temperature sensors corresponding to the plurality of heaters, and the heating by the heater is controlled using the average temperature and the gradient temperature based on the plurality of detected temperatures from the plurality of temperature sensors as control amounts. The method for heating a mold according to any one of claims 1 to 4. It is a molding apparatus that forms a cavity by forming the cavity by butting the opposed front surfaces of the fixed side mold and the movable side mold, and filling the cavity with a molding material,
At least one of the fixed mold and the movable mold is provided with a plurality of plate heaters on its side surface, and a plurality of temperature sensors for detecting the temperature of the mold. Arrange
A molding apparatus comprising: a temperature controller that controls energization of each heater based on a temperature detected by each temperature sensor.   The molding according to claim 6, wherein the front surface of the mold is rectangular, and at each of the four corners, the heaters located on both sides of each vertex are energized and controlled by the temperature controller as one heater. apparatus.   8. The molding according to claim 6, wherein the temperature controller controls the energization of the heater by using an average temperature based on a plurality of detected temperatures from each of the temperature sensors and a gradient temperature based on the plurality of detected temperatures as control amounts. apparatus.   The mold according to any one of claims 6 to 8, wherein the mold is opened and closed by moving the movable mold in a horizontal direction with respect to the fixed mold, and the molding material is injected and filled into the cavity. The molding apparatus according to Item.