JP2639585B2 - Insulation control method for injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dwell control method for an injection molding machine.

[Conventional technology]

In a conventional pressure-holding control method of an injection molding machine, there is a method of detecting a position of an injection stroke and an injection pressure and performing pressure-holding control in accordance with a preset pressure-holding value set based on experience. However, in this method, during injection molding,
It was not possible to cope with changes in molding conditions due to fluctuations in mold temperature and molten resin temperature due to disturbances, and there was a drawback that the quality of molded products varied. As a method for solving this drawback, there is the following dwell control method.

A predetermined section is set in a path of a moving body such as an injection piston and a molten resin that moves at the time of injection molding, a change time in which the moving body moves within the fixed section is detected, and the moving time and a preset time are set. And a method of correcting and controlling the holding pressure preset according to the magnitude of the time difference between the two (hereinafter referred to as “Ti
This is called "me-P control." ).

FIG. 3 conceptually shows an example of the above-mentioned pressure holding control method.

The passage FP in the mold, which is a passage (flow passage) of the molten resin, is the third passage.
As shown in the figure, a sprue portion S, a runner portion R, a gate portion G, and a cavity portion C are provided between the sprue entrance and the cavity end portion. The injection stroke IS includes an injection process IP from the start of injection to switching to pressure holding, and a pressure holding process DP from switching to pressure holding to stroke end.
In the holding pressure process DP, the corrected holding pressure specified by the holding pressure control device DA
The pressure holding device (not shown) maintains P ₀ .

The corrected holding pressure P ₀ corrects a preset holding pressure P _S during the same shot by the following steps.

The channel points f ₁ to runners R, the passage point f ₂ in the cavity C
Are respectively described in advance, and a passage F in the mold is provided between the flow path points f ₁ and f _2.
Let it be a fixed section of P. The pressure sensor A in the flow path point f _1, respectively provided a pressure sensor B in Nagareroshio f _2. After injection starts, it reaches the resin within the flow path point f _1, as shown in FIG. 4, the resin pressure by the pressure sensor A detects, travel time when it reaches the time measurement start P _m1 set in advance Start measuring t _m . Then, to reach the resin within the flow path point f _2, as shown in FIG. 4, the resin pressure by the pressure sensor B detects the movement time when it reaches the time measurement end pressure P _{m @ 2} to a preset t _m Measurement is completed (step 21).

The measured movement time t _m is compared with a preset time t _S (step 22). When moving time t _m is equal to the set time _{t S (t m = t S} ) is the set holding pressure P _S is equal corrected holding pressure P ₀ = P _S a maintained pressure in the pressure-holding step DP (step 2
3). When the moving time t _m is shorter than the set time t _S (t _m <t _S ), the corrected dwell pressure P _{0 which is} smaller than the set dwell pressure P _S by a pressure ΔP _t1 corresponding to the time difference t _S −t _m. = a P _S -ΔP _t1 and maintained pressure in the pressure-holding step DP (step 24). Moving time t _m is longer than the set time _{t S (t m> t S} ) when the set holding pressure P _S relative time difference t _m -t modified holding pressure is increased by the pressure [Delta] P _t2 corresponding to _S P ₀ = P _S + ΔP _t2 is set as the holding pressure in the holding pressure process DP (step 25).

The set section is not limited to a predetermined position between the runner portion R and the cavity portion C, and can be provided at any position of the sprue portion S, the runner portion R, the gate portion G, or the cavity portion (Japanese Patent Laid-Open No. 63-132021). Gazette).

[Problems to be solved by the invention]

The above-mentioned Time-P control corrects and controls a preset holding pressure based on the magnitude of the moving time of the moving body before the pressure holding step. Although the variation in the quality of the molded product during stable molding is improved, However, there is a problem that the quality at the time of starting the molding varies.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and shows an unstable state at the time of molding start-up, that is, a variation in mold temperature due to disturbance, a variation in molten resin viscosity due to a variation in molten resin temperature. Pressure control method in an injection molding machine capable of performing molding without fluctuations in the quality of molded products through stable molding from the start of molding by performing pressure holding control corresponding to subtle variations in molding conditions such as changes in molding The purpose is to provide.

[Means for solving the problem]

In order to achieve the above object, the pressure control method for an injection molding machine according to the present invention can set a fixed section in a path of a moving body that moves during injection molding, and can measure a moving time during which the moving body moves in the fixed section. In advance, the holding pressure of the non-defective product and the moving time of the moving body obtained during molding of the non-defective product are set in advance as the set holding pressure and the setting time, respectively, and the moving time is measured for each shot. By comparing the movement time with the set time and correcting the set holding pressure to the corrected holding pressure in the same shut according to the magnitude of the time difference between the two, the maximum mold internal pressure becomes constant throughout all shots. In the holding pressure control method for an injection molding machine, which controls the holding pressure at a predetermined time, a mold temperature obtained during molding of a non-defective product is set in advance as a set temperature, the mold temperature is detected for each shot, and the mold temperature is detected. By comparing the temperature difference between the two and the set temperature, and by re-correcting the corrected holding pressure to the re-corrected holding pressure within the same shot according to the magnitude, the maximum internal pressure is kept constant throughout all shots. It is characterized in that the holding pressure is controlled to be as follows.

[Action]

In injection molding, it is convenient to determine the quality of a molded product by measuring the size and weight of the molded product, in addition to the determination based on the appearance of the molded product. In the case of a non-defective product, the size and weight are constant, and the variation in the size and weight of the molded product of each shot is small. Therefore, the quality of the molded product from the start of molding to the time of stable molding can be determined by observing variations in the size and weight of the molded product in each shot.

 In addition, as a result of various experiments, the following items were found.

(1) From the start of molding to the stable molding, variations in the mold temperature due to repeated shots and disturbances, changes in the viscosity of the molten resin due to fluctuations in the temperature of the molten resin, changes in the physical properties between raw material lots, etc. The flow state of the molten resin to be injected and filled is affected. As a result, the pressure waveform in the mold, in particular, the value of the maximum mold pressure changes.

(2) When the mold temperature is stable, the value of the maximum mold internal pressure can be made substantially constant by the Time-P control, which has been reduced in the section of the prior art, but the mold temperature is stable. If not, the value of the maximum mold internal pressure fluctuates only with the Time-P control.

As shown in FIG. 2, in the state where the above-mentioned Time-P control was used, as a result of examining the correlation between the mold temperature and the maximum inner pressure,
The correlation coefficient indicating the correlation between the two was 0.871. That is, as the mold temperature decreases, the value of the maximum mold pressure decreases, and as the mold temperature increases, the value of the maximum mold pressure increases.

(3) The value of the maximum resin pressure in the mold also fluctuates depending on the holding pressure at the time of completion of filling, and the larger the holding pressure, the larger the maximum mold internal pressure, and the smaller the holding pressure, the smaller the maximum mold internal pressure.

(4) The maximum internal pressure of the mold after completion of filling can be controlled by controlling the holding pressure.

(5) The size and weight of the molded product are greatly affected by the value of the maximum internal pressure after filling is completed.

(6) In order to reduce fluctuations in the size and weight of the molded product of each shot from the start of molding to the stable molding, the maximum internal pressure of each shot may be kept constant.

The present invention is configured based on the above-mentioned land inspection, and preliminarily sets a holding pressure, a moving time of a moving body and a mold temperature obtained during molding of a non-defective product as a set holding pressure, a setting time and a setting temperature, respectively. Each time, the mold temperature detected for each shot is compared with the set temperature, and the holding pressure corrected by the above Time-P control is increased when the mold temperature is lower than the set temperature, and the mold temperature is higher than the set temperature. If it is also high, re-correct it to make it smaller (hereinafter referred to as “Temp-P control”).
Hold pressure control is performed so that the maximum mold inner pressure is constant for each shot.

〔Example〕

 Embodiments will be described with reference to the drawings.

A temperature sensor T is provided inside the mold M shown in FIG. The injection stroke IS is similar to the injection stroke IS shown in FIG. 3 when the Time-P control described in the section of the prior art is used. It consists of a pressure holding process DP from switching to pressure to the stroke end. In the pressure-holding step DP, the re-correction holding pressure P ₁ to holding pressure control device DA is instructed, so that the unillustrated pressure-holding device is maintained.

Re-correction maintained pressure P ₁ is the steps described below, to re-correct the corrected holding pressure P ₀ by the Time-P control in the same shot.

The holding pressure, the moving time of the moving body, and the mold temperature obtained at the time of molding a non-defective product are set in advance as a set holding pressure, a set time, and a set temperature T _S in a setting device (not shown) in advance. Ti
me-P controlled by obtaining a modified holding pressure P ₀ (step 10).
By the temperature sensor T, it detects the mold temperature T _m of a start of injection time (step 11). A mold temperature T _m, is compared with the set temperature T _S set in advance (step 12). Mold temperature T _m is equal to the set temperature _{T S (T m = T S} ) time, the correction holding pressure P ₀ equal recorrection holding pressure P ₁ = P ₀ and maintained pressure in the dwelling step DP ( Step 13). Mold temperature T _m is higher than set temperature T _S (T _m
> T _S ), the corrected holding pressure P ₁ = P ₀ − which is smaller than the corrected holding pressure P ₀ by the pressure ΔP _T1 corresponding to the temperature difference T _m −T _S.
ΔP _T1 is set as the holding pressure in the holding pressure process DP (step 14). When the mold temperature T _m is lower than the set temperature T _S (T _m <T _S ), the re-hold pressure is increased by a pressure ΔP _T2 corresponding to the temperature difference T _S −T _m with respect to the corrected hold pressure P ₀ . P ₁ = P ₀ + the ΔP _T2 dwelling step DP
(Step 15).

In the above embodiment, detects the mold temperature T _m of a start of injection time, it can be detected at any point during the injection process IP. Further, the temperature sensor T can be provided at an arbitrary position in the mold M.

For reference, the method of the present invention, Ti
Molding is performed by me-P control and open-loop type pressure-holding control using a general proportional solenoid valve, and the weight of the molded product and the maximum mold pressure Pmax are measured for each shot for a while after each rise to a stable state from the start. The results obtained are shown in FIGS. 5 (A) and (B), FIGS. 6 (A) and (B) and FIGS. 7 (A) and (B). 5 (A) and (B) show Time.
6 (A) and (B) using only Time-P control, FIG. 6 (A) and FIG.
FIGS. 1A and 1B show an example using an open-loop type pressure-holding control using a general proportional solenoid valve. In each case, a molding material of general-purpose polystyrene was molded using an open-loop injection molding machine having a clamping force of 150 ton class. In addition, each mold temperature changed almost continuously from 35 ° C. to 50 ° C. at the time of rising by repeating the shots. Using the open-loop type pressure-holding control by a general proportional solenoid valve shown in FIGS.
Compared to those without the -P control and Temp-P control, those using only the Time-P control in FIG. 6 show a significant improvement during stable molding. Time-P shown in FIGS. 6 (A) and (B)
Control using only control and Time-
Compared to those using P control and Temp-P control, the variation of the maximum internal pressure Pmax was 13 kg / cm ² using only Time-P control, and using Time-P control and Temp-P control. It is 4 kg / cm ² , and it is clear that the latter has less variation than the former and stabilizes earlier. In addition, the variation in the weight of the molded article is 0.065 g in the case where only the Time-P control is used, and 0.026 g in the case where the Time-P control and the Temp-P control are used.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects.

Since the set holding pressure is corrected based on the travel time and further corrected based on the mold temperature, the maximum mold pressure in each shot can be kept almost constant regardless of the mold temperature fluctuation. A molded product of stable quality is obtained.
This is particularly effective because the temperature of the mold changes rapidly at the start of molding, but is effective when the temperature of the mold changes due to disturbance even after stable molding has started.

[Brief description of the drawings]

FIG. 1 is an explanatory view conceptually showing an embodiment of a pressure holding control method for an injection molding machine according to the present invention, FIG. 2 is a graph showing a correlation between a mold temperature and a maximum mold internal pressure, and FIG. FIG. 4 is an explanatory view conceptually showing a conventional example of a holding pressure control method of an injection molding machine, and FIG.
FIGS. 5 (A) and (B), FIGS. 6 (A) and 6 (A) show resin pressure waveform diagrams for explaining a method for measuring the movement time t _m in the drawing.
7 (B) and FIGS. 7 (A) and 7 (B) are time series graphs showing the results of measuring the molded article weight and the maximum mold inner pressure for each shot. M ...... die, T ...... temperature sensor, T _m ...... mold temperature, T _S ...... set temperature, P ₀ ...... Modify holding pressure, P ₁ ...... re-fix the coercive pressure, ΔP _T1, ΔP _T2 ... … Pressure corresponding to temperature difference, DA… Pressure control device, IS… Injection stroke, IP… Injection process, DP… Pressure holding process, 10-15… Steps, Pmax… Maximum mold pressure.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Shinichi Ninomiya 1-6-1, Funakoshi Minami, Aki-ku, Hiroshima-shi, Hiroshima Japan Steel Works Co., Ltd. (56) References JP-A-63-132021 Tokiko Sho 57-30658 (JP, B2)

Claims (1)

(57) [Claims] 1. A path (FP) of a moving body that moves during injection molding.
A fixed section (f ₁ , f ₂ ) is set in the area so that the moving time of the moving body in the fixed section (f ₁ , f ₂ ) can be measured, and the non-defective product obtained at the time of molding the non-defective product can be measured. The pressure and the moving time of the moving body are set in advance as a set holding pressure (P _S ) and a set time (t _S ), respectively, and the moving time (t _m ) is measured for each shot, and the moving time (T _m ) is measured. t _m ) is compared with the set time (t _S ), and the set holding pressure (P _S ) is corrected to the corrected holding pressure (P ₀ ) within the same shot according to the magnitude of the time difference between the two. The maximum internal pressure (Pma
In the holding pressure control method of an injection molding machine that controls the holding pressure so that x) is constant throughout all shots, a mold temperature obtained during molding of a good product is set in advance as a set temperature (T _S ). detecting a mold temperature (T _m) for each shot, depending on the magnitude of the temperature difference between them is compared with the mold temperature (T _m) and the set temperature (T _S), in the same shot The corrected holding pressure (P ₀ ) is re-corrected to the corrected holding pressure (P ₁ ) to control the holding pressure such that the maximum internal pressure (Pmax) is constant throughout all shots. Pressure control method of injection molding machine.