Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/76—Measuring, controlling or regulating
  • B29C45/7626—Measuring, controlling or regulating the ejection or removal of moulded articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
  • B29C2945/76—Measuring, controlling or regulating
  • B29C2945/76003—Measured parameter
  • B29C2945/7604—Temperature
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
  • B29C2945/76—Measuring, controlling or regulating
  • B29C2945/76177—Location of measurement
  • B29C2945/76254—Mould
  • B29C2945/76257—Mould cavity
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
  • B29C2945/76—Measuring, controlling or regulating
  • B29C2945/76494—Controlled parameter
  • B29C2945/76551—Time
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
  • B29C2945/76—Measuring, controlling or regulating
  • B29C2945/76822—Phase or stage of control
  • B29C2945/76896—Ejection

Definitions

• the present invention relates to a molding method of a plastic molding formed by a mold by using plastic as a material.
• the present invention is suitable for improving the accuracy of a long angle lens such as an f9 lens which requires high accuracy and which is used in a scanning optical system of a printer and an image recording device of a copier.
• the ⁇ lens which is mounted in a scanning optical system of a printer and a copier, requires high accuracy.
• Fig. 12 shows the variation of the shapes of the moldings in mass production of the moldings. For every three shots in continuous 30 shots in mass production of the moldings, a longitudinal shape of the f9 lens that passes through the center of the optical axis is measured and an error from a targeted shape is measured, so that a graph of the error forms is created. As shown in Fig. 12, the shapes of the moldings vary between shots due to various factors in a molding process.
• PTL 1 utilizes a temperature at which a molding is removed.
• PTL 1 discloses a molding method in which a temperature of a thermocouple disposed on a mold parting line is detected and when the temperature reaches a
• the mold is opened and the molding is removed.
• the molding is intermittently in close contact with a movable side member of the mold until a moment when the molding is pushed out from the mold by an ejector.
• the molding continuously receives temperature of the mold higher than room temperature from a movable surface of the mold until the mold is opened and the molding is removed.
• the contraction condition of the molding varies according to the received temperature and the shape of the molding is affected, so that PTL 1 and PTL 2 which stabilize the temperature history until the mold is opened are not sufficient to suppress the variation of the shape of the molding. Therefore, there may be a case in which performance evaluation has to be performed on the molded lenses one by one in order to select lenses that satisfy the performance. So, a large amount of labor is consumed to perform the evaluation.
• the present invention is made in view of the background describe above and the present invention reduces the variation of the shape of the molding.
• the present invention provides a manufacturing method of a molding, in which a mold includes a cavity formed by a first die member and a second die member and which includes injecting a resin into the cavity, cooling the resin, thereafter, opening the mold by separating the first die member and the second die member from each other, holding a molding by the first die member, and thereafter, removing the molding from the first die member. After the mold is opened, a temperature of the first die member that holds the molding is measured, and when the temperature of the first die member reaches a predetermined temperature, an operation to remove the molding from the first die member is started.
• a mold of the present invention includes a cavity formed by a first die member and a second die member and the first die member includes a temperature sensor for measuring temperature of the first die member after the mold is opened.
• a mold of the present invention includes a cavity formed by a first die member and a second die member and a member adjacent to the first die member includes a
• temperature sensor for measuring temperature of the first die member after the mold is opened.
• a mold of the present invention includes a cavity formed by a first die member and a second die member and a non-contact temperature sensor for measuring temperature of the first die member after the mold is opened.
• FIGs. 1A and IB are schematic diagrams of an f0 lens .
• FIG. 2 is a schematic diagram of an example of an injection mold for manufacturing a molding of the present invention .
• FIGs. 3A to 3D are schematic diagrams showing an example of a manufacturing method of molding of the present invention.
• Figs. 4A and 4B are diagrams showing variation of temperature of a first die member.
• Fig. 5 is a diagram showing a relationship between temperature and form error of the first die member at
• Fig. 6 is a flowchart from when a value of a temperature sensor is obtained in a molding machine to when ejection is performed.
• Figs. 7A and 7B are diagrams showing a relationship between temperature of the first die member and form error at ejection time.
• Fig. 8 is a diagram showing a second embodiment.
• Fig. 9 is a diagram showing a third embodiment.
• FIGs. 10A and 10B are diagrams showing the third embodiment .
• FIG.. 11 is a diagram showing a fourth embodiment.
• Fig. 12 is a diagram showing molding variation. Description of Embodiments
• FIG. 1A is a diagram of the ⁇ lens as seen from the side.
• Fig. IB is a diagram of the f0 lens as seen from the above.
• the f9 lens has a longitudinal length L, a short side length W, a height H, and two optical surfaces Rl and R2.
• a longitudinal direction is indicated by an arrow 8.
• the f0 lens has high optical sensitivity and requires extremely high accuracy in a resin injection molding process.
• Fig. 2 is a schematic diagram of an example of an injection mold for manufacturing a molding of the present invention.
• reference numeral 22 denotes a molding machine movable side platen
• reference numeral 23 denotes a molding machine fixed side platen
• reference numeral 9 denotes a plasticization unit
• reference numeral 10 denotes a sprue
• reference numeral 11 denotes a runner
• reference numeral 12 denotes a gate.
• Reference numeral 161 denotes a movable side mirror-finish insert member which is a first die member
• reference numeral 162 denotes a fixed side mirror-finish insert member which is a second die member
• reference numeral 261 denotes a movable side die set that fixes the movable side mirror-finish insert member
• reference numeral 262 denotes a fixed side die set that fixes the fixed side mirror-finish insert member.
• Reference numeral 13 denotes a cavity formed by the first die member 161 and the second die member 162.
• Reference numeral 14 denotes a mold temperature adjusting water pipe and reference numeral 15 denotes a mold parting line.
• Reference numeral 17 denotes a temperature sensor such as a
• thermocouple disposed to measure temperature of the movable side mirror-finish insert member and reference numeral 18 denotes a lead wire for inputting a value of the temperature sensor into a molding machine.
• Reference numeral 19 denotes an ejector pin
• reference numeral 20 denotes an ejector plate
• reference numeral 21 denotes a molding machine ejector rod
• reference numeral 24 denotes an automatic molding removal machine (see Fig. 3D) .
• the temperature of the mold is adjusted at a predetermined preset temperature by a temperature adjustment machine connected to the mold temperature adjusting water pipe 14.
• a resin plasticized by the plasticization cylinder 9 is injected into the mold and fills the cavity 13 through the sprue 10, the runner 11, and the gate 12.
• transfer surface of the second die member are transferred to the resin by a pressure from the plasticization cylinder 9 and a lens is formed. Thereafter, the molding in the cavity is cooled until the resin is solidified.
• FIGs. 3A to 3D are schematic diagrams showing an example of the manufacturing method of molding of the present invention.
• Fig. 3A is a diagram showing a state of the mold and the molding when cooling is completed.
• Fig. 3B is a diagram showing a state of the mold and the molding after the mold is opened.
• Fig. 3C is a diagram showing a state of the mold and the molding when the molding is
• Fig. 3D is a diagram showing a state of the mold and the molding when the molding is chucked by the removal machine.
• the molding is cooled until the resin is solidified.
• the parting 15 opens, the mold is divided into a fixed side and a movable side, and the movable side mirror-finish insert member (the first die member) 161 and the fixed side mirror-finish insert member (the second die member) 162 are separated from each other.
• the molding is held in a cavity- formed portion of the movable side mirror-finish insert member (the first die member) 161.
• the molding is kept in close contact with the shape transfer surface of the movable side mirror-finish insert member (the first die member) 161 for a certain time period. Thereafter, as shown in Fig.
• the ejector rod 21 in conjunction with an ejector drive motor of the molding machine slides, so that the ejector plate 20 is pushed out.
• the ejector pin 19 attached to the plate is relatively moved, so that the molding is pushed out from the first die member.
• the molding is gripped by the molding removal machine 24 and thereafter stored in a molding storage room.
• the time period from when the mold is opened to when the molding is separated from the first die member is about 5 to 15 seconds although depending on the timing of the molding removal machine 24.
• Figs. 4A and 4B show an example of temperature change of the first die member.
• the temperature of the first die member is a value measured by a temperature sensor such as a thermocouple disposed in the movable side mirror- finish insert member 161 which is the first die member.
• the temperature sensor such as a thermocouple is disposed near the shape transfer surface of the first die member or the cavity as much as possible. A resin melted at a temperature higher than that of the first die member is injected into the cavity, so that the temperature of the mold member rises temporarily. After a while, the mold member is cooled by temperature adjusting water flowed in the mold temperature adjusting water pipe 14. When the temperature of the mold member reaches near the preset temperature of the
• Fig. 4B is an enlarged diagram of an area enclosed by a dashed line in Fig. 4A and shows an example of a temperature waveform measured by the thermocouple 17 from when the mold is opened. Before the mold is opened, that is, while the mold is being cooled, a parting surface which is a contact surface between the first die member and the second die member is not
• the parting surface which is the contact surface between the first die member and the second die member is exposed to room temperature, so that a large temperature change occurs.
• the waiting time from when the mold is opened to when the molding is ejected from the first die member is about 5 to 15 seconds. Temperature change occurs in the molding during the waiting time, so that the molding is pushed out while a large temperature change occurs.
• the temperature of the first die member that holds the molding is measured after the mold is opened and the molding is removed from the first die member when the temperature reaches a predetermined temperature.
• thermocouple 17 disposed in the first die member is inputted into the molding machine. Then, the ejector drive motor is driven when the temperature reaches a preset timing which is arbitrarily set, so that the ejection temperature is stabilized and the form error of the molding is reduced.
• a sequence shown in Fig. 6 is embedded in the molding machine to form moldings. After the mold is opened, the temperature monitored by the
• thermocouple 17 is inputted into the molding machine, and when the temperature reaches a preset temperature T°C, the ejector drive motor of the molding machine is driven.
• the temperature at which the mold is opened is K°C
• the variation of the shape of the molding is suppressed if the preset temperature T°C is set to any temperature lower than K°C.
• the variation of the temperature at which the molding is ejected can be reduced by sufficiently prolonging the time from when the mold is opened to when the molding is ejected. This is because the mold temperature and the room temperature reach equilibrium and the mold temperature is stabilized. However, if the longer the time from when the mold is opened to when the molding is ejected, the longer the molding cycle and the higher the cost.
• the preset temperature T°C should be set to near the temperature at which the mold is opened as much as possible. It is desired that the molding before ejection is held and cooled in a state in which the molding is perfectly in contact with the shape transfer surface of the first die member. However, if the time period is long in which the surface formed by the shape transfer surface of the second die member is exposed to room temperature, the molding contracts and the molding is peeled from the shape transfer surface of the first die member. If the molding is peeled before ejection, a discontinuous shape called surface cracking is formed from the center to the outside on an optical surface. Therefore it is necessary to eject the molding while the surface cracking does not occur. As a result of study, it is found that the surface cracking hardly occur in a range from the temperature at which the mold is opened to the temperature 1.5°C lower than the temperature at which the mold is opened.
• the timing when the ejector pin is pushed out is when the temperature is lower than K°C that is the temperature at which the mold is opened and higher than or equal to (K-1.5)°C.
• the preset temperature T°C which is arbitrarily set should be set to K > T > ( -1.5) .
• the temperature range (temperature variation) of the preset temperature should be about ⁇ 0.3°C. Thereby, the variation of the shape of the molding is suppressed to about one-third of that of conventional molding. Therefore, poor appearance such as surface cracking does not occur, so that it is possible to mount a plastic molded lens in a product that requires high accuracy .
• Fig. 8 shows an embodiment in which a thermocouple cannot be disposed in the movable side mirror-finish insert member (first die member) 161.
• the temperature of the first die member is a value measured by a thermocouple disposed in a member adjacent to the first die member.
• the temperature of the largest die member for forming a molding which is the movable side mirror-finish insert member (first die member) 161 in the case of an optical element such as an f9 lens, is monitored and the monitored temperature is used as the temperature of the first die member.
• the thermocouple may not be disposed in the die member. In this case, the thermocouple is disposed in a mold die set 261 which is a member adjacent to the first die member and temperature measured by the
• thermocouple is used as the temperature of the first die member, so that the same effect can be obtained.
• thermocouple 25 disposed in the mold die set and which is inputted into the molding machine, reaches a preset temperature, the ejector drive motor of the molding machine is driven and the molding is ejected.
• the thermocouple 25 is disposed near the shape transfer surface of the first die member or the cavity as much as possible.
• Fig. 9 shows an embodiment in which multi-piece molding is performed.
• the mold includes two sets of the first die member and the second die member and the two sets form the cavity 27 and the cavity 28 respectively.
• the thermocouple 29 and the thermocouple 30 are disposed in the two first die members respectively.
• Fig. 10 shows waveforms of the temperature of the cavity 27 measured by the thermocouple 29 and the
• thermocouple 30 temperature of the cavity 28 measured by the thermocouple 30 before and after the mode is opened.
• the temperatures of the cavities may be different from each other. It is considered that this is because ambient temperatures around the mold may be different due to the condition of convection flow or the like.
• both temperatures monitored by the thermocouples 27 and 28 disposed in the first die members are inputted into the molding machine. Then, the average values of the monitored temperatures for each time are calculated, and when the average value reaches a preset temperature, the ejector drive motor of the molding machine is driven and the molding is ejected.
• the third embodiment can be applied to multi-piece molding that uses two or more
• the temperature sensor described in the first, the second, and the third embodiments is a
• thermocouple sensor that senses temperature by contact with a member
• a method in which the temperature of the movable side of the mold is monitored by a non-contact temperature sensor using infrared will be described.
• the temperature of the first die member is a value of the temperature of the first die member and the molding measured by the non-contact temperature sensor.
• Fig. 11 shows the fourth embodiment.
• An infrared temperature sensor 34 is disposed on an upper surface of a molding machine fixed side platen 23, and the first die member and the molding is monitored by the infrared temperature sensor 34 when the mold is opened, so that the temperature of the movable side mold member or the temperature of the molding can be measured from parting direction.
• the monitored temperature is inputted into the molding machine, and when the temperature reaches a preset temperature, the ejector drive motor of the molding machine is driven and the molding is ejected.
• thermocouple need not be disposed in the movable side mold member (the first die member) , so that the present invention can be easily applied to existing molds.
• a molding such as a lens in which the thickness largely varies has different contraction coefficients within the molding, so that an absolute value of warp may be large.
• a temperature difference of preset temperature of the mold set by a temperature adjusting device may be set between a mold temperature adjusting path of a fixed side mold 262 and a mold temperature adjusting path of a movable side mold 261.
• the temperature of the fixed side mold 262 is set to 125°C and the temperature of a medium that adjusts the temperature of the movable side mold 261 is set to 135°C
• the temperature of the fixed side mold is measured by a thermocouple disposed in the fixed side mold and the
• thermocouple disposed in the movable side mold. Then, after the mold is opened, a phenomenon occurs in which the
• the temperature gradient of the movable side mold when the molding is ejected is larger than that in molding in a constant temperature in which the temperature difference between the fixed side mold and the movable side mode is not set. Therefore, due to uncertain factors such as fluctuation of ambient temperature in the molding atmosphere as described above, the temperature at which the molding is pushed out varies more largely.
• the variation of the shape between shots of the moldings pushed out in the state described above is larger than that in the molding in which the fixed side mold and the movable side mold are kept at a constant temperature.
• the temperature at which the molding is pushed out is stabilized by the present invention, so that it is possible to largely reduce the variation of the shape of the molding. Further, the present invention is a very effective means for reducing the
• Continuous molding of f0 lens is performed by using the molding method described in the first embodiment.
• the temperature of the fixed side mold 23 and the movable side mold 22 are set to 120°C and a pressure application of the molding machine is set to 110 Mpa .
• the temperature monitored by the thermocouple 17 reaches 121.3 °C, the ejector drive motor of the molding machine is driven and the molding of the f6 lens is continuously performed.
• the continuous molding is performed, ten moldings are extracted at random from every three shots and the temperature of the first die member when the moldings are ejected and the form errors of the moldings are measured.
• a longitudinal shape of the f9 lens that passes through the center of the optical axis is measured and an error from a targeted shape is measured.
• Fig. 7A shows the measured values.
• the shot numbers are plotted on the horizontal axis.
• the temperatures of the cavity of the first die member and the form errors are plotted on the vertical axis. From the graph of Fig. 7A, it is confirmed that the variation of the temperature at the moment of ejection, that is, at the moment when the ejector pin is pushed out, is within ⁇ 0.3°C. It is also found that the variation of the form error is about 10 ⁇ . and very small.
• Fig. 7B is a table of the amount of variation of the temperature at which ejection is performed (at which the ejector pin is pushed out) and the amount of variation of the form error (the amount of variation of the molding) . It is found that the smaller the variation of the temperature at which ejection is performed, the smaller the variation of the form error of the molding. It is also found that the ejection timing is preferred to be in a variation range of ⁇ 0.3°C to satisfy the performance of the fQ lens.
• the first embodiment shows an example in which the ejector drive motor is driven when the monitored temperature of the thermocouple 17 reaches 121.3°C, here, instead of using temperature, the ejector drive motor is driven after 12 second has elapsed since the mold was opened.
• the continuous molding is performed in the same manner as in the first embodiment except for the process describe above.
• ten moldings are extracted at random from every three shots and the temperature of the first die member when the moldings are ejected and the form errors of the moldings are measured.
• the form error a longitudinal shape of the ⁇ lens that passes through the center of the optical axis is measured and an error from a targeted shape is measured.
• Fig. 5 shows the measured
• the shot numbers are plotted on the horizontal axis.
• the temperatures of the cavity of the first die member and the form errors are plotted on the vertical axis. It is found that the variation of the form error is about 28 urn . It is also found that there is a high correlation between the temperature of the first die member and the form error when the ejection is performed.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)

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Citations (6)

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• 2011
  • 2011-06-30 JP JP2011146511A patent/JP5921099B2/ja not_active Expired - Fee Related
• 2012
  • 2012-06-21 CN CN201280031307.7A patent/CN103648745B/zh not_active Expired - Fee Related
  • 2012-06-21 WO PCT/JP2012/066464 patent/WO2013002297A1/en active Application Filing

Patent Citations (6)

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