JPH0455574B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a molding method for an injection molding machine that can be used for setting molding conditions, etc.

[Conventional technology]

Generally, in the speed control region of the molding process of an injection molding machine, for example, the injection process of an in-line screw type injection molding machine, injection process control is performed by setting the injection speed of the screw (injection plunger) in multiple stages. That is, a plurality of shift points are set in advance in the stroke range of the screw, and different injection speeds are set between each shift point. During molding, the forward position of the screw is detected by a position sensor, and when the speed change point is reached, a control signal is applied to the screw driving device to control switching to a predetermined speed.

By the way, in an injection molding machine, the electric circuit of the control system,
Drive system hydraulic circuit, injection mechanism (screw weight, etc.)
The presence of this causes the required response delay. Therefore, even if the molding conditions are set in advance, the actual operation does not match the set conditions, and there is a problem that the forward position of the screw deviates from the normal position. For this reason, in the past, operators had to rely on their experience and intuition, take into account response delays, and set molding conditions by trial and error while checking the molded product.

[Problem that the invention seeks to solve]

However, with this method of setting molding conditions, it is difficult to find a relationship between the molding conditions and the corresponding molded product, so it is not possible to perform accurate and reliable settings or corrections, and it is also difficult to investigate the cause of molding defects. It is.

Further, the setting work is extremely disadvantageous in terms of time, labor, efficiency, etc., and there are also problems that involve wasted materials and energy consumption.

Furthermore, if the interval between the shift points is short and the speed change is large, the next shift point will be reached before the predetermined speed is reached due to response delay, and the original control will not be performed and the The products were defective, and there were limits to methods that relied on the operator's experience.

Although it is possible to measure how the actual speed affects the setting conditions by connecting various measuring instruments (such as an It is difficult to adopt this method in molding factories that mold a wide variety of molded products because they have no choice but to rely on it.

[Means for solving problems]

The present invention aims to provide a molding method for an injection molding machine that solves the problems existing in the above-mentioned prior art, and is achieved by the molding method shown below.

That is, in the molding method of the injection molding machine according to the present invention, for example, a speed condition having at least one shift point X0 is set in the speed control region of the injection molding machine 1, preliminary injection is performed, and actual measurement data based on this preliminary injection is performed. A response delay is detected from the setting data, and this response delay is equated to a predetermined function consisting of a constant region and a function change region with respect to time, and this predetermined function is used as a delay detection function specific to the injection molding machine.
It is characterized in that it is used for correction of molding conditions, etc. Note that the same process can be performed in the pressure control region as well.

[Effect]

Next, the operation of the present invention will be explained.

The molding method of the injection molding machine according to the present invention performs preliminary injection using a method that can clearly detect response delays before setting the original molding conditions.

Then, the response delay of the injection molding machine 1 is detected through preliminary injection, and the constant region and function change region for time, which is a predetermined function, are made equal to each other, thereby making it easier to handle the response delay. The equivalent response delay is regarded as the inherent delay detection function of the injection molding machine, and is used for correction when setting molding conditions, analysis of defective molded products, etc.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

Fig. 1 is a relational diagram of the screw position versus injection speed showing setting data and actual measurement data of preliminary injection conditions used in the molding method of the injection molding machine according to the present invention, and Fig. 2 is an equivalent delay detection function using the same method. Fig. 3 is an explanatory diagram of a method for equalizing response delay using the same method, and Fig. 4 is a graph of screw position versus injection showing predicted execution data corrected by the same method. The speed relationship diagram, FIG. 5, is a configuration diagram of an injection molding machine suitable for use in the same method.

First, in order to clarify the present invention, the overall schematic configuration of the in-line screw type injection molding machine 1 illustrated in FIG. 5 will be described.

The injection molding machine 1 includes a heating cylinder 4 at the front, into which a screw 2 is inserted and an injection nozzle 3 at the front end. Further, at the rear part, there is an injection cylinder 6 into which a ram 5 connected to the rear end of the screw 2 is inserted, and this ram 5.
It is equipped with an oil motor 7 that rotates.

Next, a description will be given of the configuration of a control thread that can carry out the method of the present invention. First, the rear side oil chamber 5r of the injection cylinder 5 is connected to a hydraulic pressure source 9 via a control device 8 consisting of an electromagnetic proportional flow valve, an electromagnetic proportional pressure valve, an electromagnetic directional switching valve, and the like. This control device 8 is controlled by a sequence controller 10 to which a predetermined setter group is connected. On the other hand, the rear end of the screw 2 is provided with a projection 11 that follows the forward and backward movement of the screw 2,
The position of the moving protrusion 11 is detected by a position sensor 12 using a linear encoder, rotary encoder, potentiometer, or the like. It also includes an arithmetic processing device 14, to which the position sensor 12 is connected via an amplifier 13, and a display device using the sequence controller 10, preliminary injection speed setting device 15, CRT, plasma display, etc. Connect 16.

Next, the molding direction of the injection molding machine according to the present invention will be explained.

First, perform preliminary injection. In preliminary injection, at least one shift point XO is set as shown in FIG. 1, and the preliminary injection conditions for decelerating from speed V ₁ to speed V ₂ around this shift point and set it. Note that the mold is separated from the injection nozzle 3 and injection is performed by blank firing. In this way, when the mold is separated from the injection nozzle 3, versatile basic data can be collected, while when the mold is placed in contact with the injection nozzle 3, data including gold can be collected.

During the preliminary discharge, the forward position of the screw 2 is continuously detected by the position sensor 12, and is also detected as a time variable by the internal timer of the processing unit 14. Then, the detected position data and time data are stored in the memory in the arithmetic processing unit 14, and further, velocity data is obtained by calculation of the position data and time data, and is simultaneously stored in the memory.

The speed of the screw 2 relative to the forward position is as shown in FIG. 1, and the actual measured data is shown as a dotted line due to a predetermined response delay compared to the setting data shown as a solid line.

In this way, after switching to the shift point X0, the speed
There is an inherent response delay determined by the injection molding machine 1 until V ₂ is reached. This response delay is the second
Time L from shift point X0 (t0) to t1 as shown in the diagram
A constant region in which the speed V ₁ before switching is maintained for only a period of time (dead time), and after this time L has elapsed, the speed is gradually decelerated and reaches speed V ₂ after a time T (delay time) has elapsed t1
It can be equivalent to a function consisting of a function change region from to t2.

As a result of experiments using a large number of different speed differences, it was confirmed that these times L and T are constant for each injection molding machine regardless of the speed difference, and can be regarded as delay functions inherent to the injection molding machine. Also,
It was confirmed that there is no practical problem even if the function change region is approximated to the step response of a first-order lag system.

Next, analyze the specific delay function.

Now, if the injection speed t seconds after the time t0 when the injection speed is changed from V ₁ to V ₂ is V(t), then when t<L, V(t)=V ₁ …(1) L≦ When T, it can be expressed as V(t)=V ₁ +(V ₂ −V ₁ )(1−e ^−(tL)/T ) …(2), and the screw position ^t ₀ V(t)dt =∫ ^L ₀ V ₁ dt+∫ ^t _L V(t)dt =V ₁ L+(V ₂ −V ₁ ) {(t−L) −T(1−e ^{−(tL)/ T} )}+V ₁ (t-L) =V ₁ t+(V ₂ -V ₁ ){(t-L) -T(1-e ^-(tL)/T )} ...(3) .

Also, equation (2) is V(t)-V ₁ /V ₂ -V ₁ = 1-e ^-(tL)/T 1-V(t)-V ₁ /V ₂ -V ₁ = e ^{-(tL )/T} 1n [1-V(t)-V ₁ /V ₂ -V ₁ ]=L/T-1/Tt...
(4), and equation (4) can be expressed as shown in Figure 3, where the horizontal axis is time t and the vertical axis is 1n [1-V(t)-V ₁ /V ₂ -V ₁ ]. It represents a straight line with an intercept L/T and a slope -1/T.

Therefore, when a linear regression calculation is performed on t and 1n [1-V(t)-V ₁ /V ₂ -V _{1 ] from the time data, speed data, and speed setting value collected during preliminary injection in the arithmetic processing unit 14} , T and L is found.

Once T and L are determined, the injection speed V(t) after an arbitrary time t seconds can be determined from equation (2), and the screw position X can be obtained by integrating the speed over time using equation (3), so the screw position The injection speed for can be determined by calculation.

Therefore, the processing unit 14 calculates the speed change points X1 to X4 and the injection speeds _V1 to _V3 set by the setter group connected to the sequence controller 10 under the setting conditions used for actual molding as shown in FIG. By reading the data into the program and performing calculations using the above function, expected execution data for the set conditions can be obtained. This can be displayed as a waveform on the display device 16 together with the setting data. These calculations can be performed in the same way every time the settings of the speed change point or injection speed are changed, and the waveform display is also changed accordingly, so the operator can check the optimum molding conditions for the molded product while looking at the waveform display. can be set.

On the other hand, by specifying coordinates from the expected execution data displayed on the display device 16 using a cursor or ten keys, it is possible to specify the screw position and injection speed necessary for molding. As a result, the original injection speed can be obtained at the designated point, and a shift point and injection speed corrected by the unique delay detection function can be set.

Although the embodiments have been described in detail above, the present invention is not limited to these embodiments.
For example, although the equivalent function is expressed as a constant region and a function region of a first-order lag system, if the constant region is extremely short, it may be ignored, or other functions such as a second-order lag system may be used. good. Further, although one shift point is set, more reliable data can be obtained by setting two or more with different conditions if necessary and averaging them. Furthermore, although the injection speed has been described, the unique delay detection function can be detected for the injection pressure in a similar manner, and can be similarly applied to other injection molding machines such as a plunger type. Other detailed configurations, methods, etc. may be modified as desired without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, the molding method of the injection molding machine according to the present invention detects the response delay by performing preliminary injection under predetermined conditions, and this result can be used equivalently to an easy-to-handle function. get an effect like

There is no variation between operators, and it can be used as objective data in the following ways, contributing to high-quality molding and improved work efficiency.

(a) If used to correct conditions when designing molding conditions, accurate and reliable settings can be made, and the setting work can be done easily or quickly.

(b) Since the state of response delay can be easily grasped,
Even if unfeasible molding conditions are set, it can be easily determined, making it easier and more accurate to investigate the cause of defects in molded products.

Preliminary injection without actual molding allows detection of inherent delay conditions, eliminating wasted material and energy loss.

[Brief explanation of the drawing]

Fig. 1: Relationship diagram of screw position vs. injection speed showing setting data and actual measurement data of preliminary injection conditions used in the molding method of the injection molding machine according to the present invention, Fig. 2:
A diagram showing the relationship between time and injection speed showing the delay detection function equivalent by the same method, Figure 3: An explanatory diagram of the method of equalizing the response delay by the same method, Figure 4: FIG. 5 is a diagram showing the relationship between the screw position and the injection speed showing correction of expected execution data; FIG. 5 is a configuration diagram of an injection molding machine suitable for use in the method. In the drawing, 1: injection molding machine, X0: speed change point.

Claims (1)

[Claims] 1 Preliminary injection is performed by setting speed conditions and/or pressure conditions having at least one speed change point and/or pressure change point, and response delay is detected from actual measurement data and set data based on the preliminary injection. At the same time,
A molding method for an injection molding machine, characterized in that the response delay is made equivalent to a predetermined function and used as a delay detection function specific to the injection molding machine. 2. The molding method for an injection molding machine according to claim 1, wherein the predetermined function includes a constant region and a function changing region with respect to time. 3. A molding method for an injection molding machine according to claim 1, wherein molding conditions are corrected using the delay detection function.