JP2598746B2 - Injection pressure setting method of injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for setting an injection pressure of an injection molding machine suitable for using a mold whose mold data is unknown.

[0002]

2. Description of the Related Art Generally, there are cases where mold data is known or unknown for molds used in an injection molding machine. For example, when manufacturing a product, if all manufacturing processes including mold design are provided in-house, mold data such as cavity capacity can be known from a mold drawing or a model. However, in a manufacturing company or the like having only a manufacturing department, when receiving a molding commission, there are cases where only the mold is delivered, and in this case, the mold data is often unknown.

By the way, when the magnitude of the injection pressure is set as a molding condition, if mold data such as a cavity capacity is known, some temporary initial conditions are considered in consideration of molding conditions including a measured value and the like. Although molding can be performed by setting conditions, it is not easy to set the initial conditions when mold data is unknown. For this reason, conventionally, a skilled operator visually inspects the mold cavity and the like, sets the injection pressure (initial conditions) based on intuition and experience, and sets a small measurement value at first to perform molding. The magnitude of the injection pressure has been set by trial and error by repeating molding while gradually increasing the measured value while observing the filling state of the molded article.

[0004]

However, the above-mentioned conventional method has the following problems since it has to rely on the intuition and experience of a skilled operator.

[0005] First, since the operator who performs the setting operation requires considerable skill, the operators who can make the setting are limited. In addition, since setting work is not easy even for a skilled operator, setting time is lengthened,
This leads to a decrease in productivity and an increase in manufacturing cost, and also involves wasteful consumption of resources and energy.

Second, if the injection pressure is excessively set due to a setting error or an improper setting, abnormal pressure may be applied to the inside of the mold, and the mold may be damaged. Also inferior.

The present invention has solved the above-mentioned problems in the prior art. Even an operator having low skill can easily and surely set the injection pressure, greatly shortening the setting time, and improving productivity. It is an object of the present invention to provide a method for setting an injection pressure of an injection molding machine capable of improving the manufacturing cost, reducing resources and energy, preventing mold breakage, and improving safety.

[0008]

According to the injection pressure setting method for an injection molding machine according to the present invention, as an initial condition, at least the injection pressure is set to one pressure value Pd on the low pressure side, and more preferably, the injection speed is set to the high pressure side. By setting the injection start position of the screw at the first speed value Vh to the last retreat position Xb and performing molding, and increasing the injection pressure in response to poor filling of the molded product, the injection pressure for obtaining a good product is obtained. Is obtained by adding or subtracting another molding condition, for example, a correction pressure accompanying a change in the injection speed or the like, to the obtained injection pressure, and setting the obtained injection pressure as the molding condition. And

In this case, the remolding cycle of changing the magnitude of the injection pressure by a preset change amount in accordance with the degree of defective filling of the molded article and re-molding with the changed injection pressure is performed to obtain a good product. It is desirable to repeat until Further, the magnitude of the correction pressure can be set based on the fluctuating pressure due to the override characteristic in the driving unit.

[0010]

According to the injection pressure setting method of the present invention, for example, when setting the injection pressure of an injection molding machine using a mold whose mold data is unknown, first, certain molding conditions are set as initial conditions, That is, at least the injection pressure is set to the first pressure value Pd on the low pressure side, and the injection speed is set to the first speed value Vh on the high speed side.
Molding is performed by setting the screw injection start position to the last retreat position Xb.

Further, by increasing the injection pressure in response to the insufficient filling of the molded article, the magnitude of the injection pressure for obtaining a good product is obtained. In this case, the remolding cycle of changing the magnitude of the injection pressure by a preset change amount in accordance with the degree of defective filling of the molded product and reforming with the changed injection pressure may be repeated until a good product is obtained, Thereby, an injection pressure at which a good product can be formed can be obtained.

On the other hand, a correction pressure accompanying a change in other molding conditions is added to or subtracted from the obtained injection pressure. For example, when the injection speed is changed (decreased), the correction pressure set based on the fluctuation pressure due to the override characteristic in the drive unit is added. The injection speed is set to the first speed value Vh on the high speed side according to the initial condition. However, since the actual averaged injection speed becomes smaller than the first speed value Vh,
Even if the magnitude of the injection pressure for obtaining a molded non-defective product is set as it is according to the initial conditions, the injection speed may become unstable due to the fluctuation pressure based on the override characteristics of the drive unit. Therefore, the injection speed can be stabilized by adding the correction pressure set based on the fluctuation pressure due to the override characteristic. Therefore, the magnitude of the injection pressure obtained by adding (or subtracting) the correction pressure is set as the target molding condition.

[0013]

Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, a schematic configuration of an injection molding machine 1 that can execute an injection pressure setting method according to the present invention will be described with reference to FIG.

The injection molding machine 1 has a machine base 3, and the machine base 3
Is provided with an injection device 4 on one side of the upper surface and a mold 5 with unknown mold data covered with a safety cover 6 on the other side of the upper surface.
Is provided. In this case, the mold 5 is supported by a mold clamping device that does not appear in the drawing, and the injection device 4 is
To move forward and backward. The injection device 4 has an injection nozzle 9 at the tip.
Is provided with a heating cylinder 8 having a hopper 10 at the rear, and a screw is built in the heating cylinder 8. On the other hand, a screw driving device 11 for rotating and moving the screw forward and backward is provided at the rear end of the heating cylinder 8. As the screw driving device 11, an electric driving type using a servomotor and a hydraulic driving type using a hydraulic circuit are known.

On the other hand, in FIG. 8, reference numeral 12 denotes a controller which is built in the machine base 3 and controls the entire injection molding machine 1. Reference numeral 13 denotes an input device (keyboard) attached to the side panel 3p of the machine base 3, which is connected to the controller 12. The input device 13 and the controller 12 have a setting function for setting various conditions, and in particular, in accordance with the present invention, a plurality of ranks corresponding to the degree of the filling failure of the molded article and injection in a direction corresponding to each rank to eliminate the filling failure. A function of setting a plurality of change amounts for changing the magnitude of pressure is provided. For this reason, the input device 13 is provided with selection keys K1, K2, and K3 for selecting the type of the filling failure and the rank for each degree of the filling failure.
, A plurality of change amounts corresponding to each rank for changing the injection pressure in a direction to eliminate the filling failure are set. Further, the controller 12 has a control function of changing the molding conditions according to the change amount corresponding to the selected rank, and a function of setting the molding conditions using the magnitude of the molding conditions when a good product is molded.

In this case, a plurality of ranks corresponding to the degree of defective filling of the molded article and a plurality of change amounts for changing the magnitude of the injection pressure in a direction corresponding to each rank to eliminate the defective filling are as follows:
It is set as follows:

For example, when the filling failure is a short shot, as shown in FIG. 4, the degree of the short shot is classified into three levels of "large", "medium" and "small".
When "Large", the pressure change rate (change amount) is "+ 20%",
When "medium", the pressure change rate is set to "+ 10%", and when "small", the pressure change rate is set to "+ 5%". Note that the ranks are "large", "medium", and "small", but may of course be numerical. In addition, the pressure change rate is used as the change amount because the injection pressure is usually set as a ratio to the maximum pressure. Therefore, for example, if "large" is selected as the degree of the short shot, the pressure change rate "+ 20%" is selected, and 20% is added to the set injection pressure ratio. As described above, the change amount may be set as an absolute amount or a ratio, or may be changed by adding or subtracting or multiplying or dividing the injection pressure.

Similarly, in the case of overfilling, as shown in FIG. 5, the degree of overfilling is classified into three levels of "small", "medium" and "large". When the pressure change rate is “−2%”, when “medium”, the pressure change rate is “−5%”,
When "large", the pressure change rate is set to "-10%". As described above, in any case, the pressure change rate is set so as to increase in accordance with the rank in which the degree of defective filling is large.

On the other hand, 14 is a screw position detector,
For example, in the case of an electric drive type, a rotary encoder that detects the number of rotations of a servomotor can be used, and in the case of a hydraulic drive type, a linear scale that directly detects a screw position can be used. The screw position detector 14 is directly connected to the controller 12, and is also connected to the controller 12 via the speed converter 15. The speed converter 15 has a function of differentiating the position signal from the screw position detector 14 and converting it into a screw speed signal.

An injection pressure detector 16 is, for example, a load cell for detecting the back pressure at the rear end of the screw in the case of the electric drive type, and a hydraulic pressure for detecting the hydraulic pressure of the hydraulic cylinder in the case of the hydraulic drive type. Sensors and the like can be used. Note that 17
Is a display attached to the side panel 3p, which performs various displays and is used as an auxiliary device of the input device 13. The controller 12 is connected to the system computer 18 by an optical communication system (wireless system) or the like.

Next, an overall procedure for setting molding conditions including the injection pressure setting method according to the present invention will be described with reference to FIGS.

FIG. 1 is a flowchart showing a procedure for setting molding conditions (injection pressure). When setting the molding conditions,
The input device 13 and the display 17 are used to input known data relating to a molding material, a specification screw, and the like. Controller 12 has material properties, molding machine performance specifications,
A database relating to basic molding conditions and the like is stored. The controller 12 obtains basic molding conditions such as a temperature-related molding condition and a maximum stroke of the screw based on the input known data and the stored database, and sets them in the controller 12. . The molding conditions relating to the temperature, that is, the heating cylinder temperature and the mold temperature are automatically set based on the type of the molding material.

On the other hand, the selection key Ks on the input device 13
The initial condition setting mode is selected by pressing, and the initial conditions are set (steps 21 and 22). The setting of the initial condition is performed according to the flowchart shown in FIG.

First, as an injection condition, the injection speed is set to the first speed value Vh on the high speed side (step 41). in this case,
The first speed value Vh on the high speed side is higher than the middle point of the set range in the injection molding machine to be used, and preferably a value of 90% or more with respect to the maximum speed is selected. Further, the injection start position of the screw is set to the last retreat position Xb (step 42). In this case, the last retreat position Xb does not mean a complete rear end, but is a concept including an arbitrary rear position at which a sufficient amount of resin can be measured with respect to the volume of the mold 5. Furthermore, the injection pressure is set to the one pressure value Pd on the low pressure side (step 43). In this case, the one pressure value Pd on the low pressure side is lower than the middle point of the set range in the injection molding machine to be used, and is desirably set to a value of 30% or less with respect to the maximum pressure. In addition to the above settings, in the setting of the initial conditions, various molding conditions such as a pressure-holding switching position, a back pressure, a cooling time, and a screw rotation speed are set (step 44).

Further, a set speed Vs and a set time Ts for detecting the injection end position Xf of the screw are set. The set speed Vs is a threshold value for the injection speed V for detecting the end of the filling of the mold 5 with the resin, and can be set to about several m / sec which is almost in a stopped state. The set time Ts is a time for ensuring more reliable filling after the speed becomes equal to or less than the set speed Vs, and can be set to, for example, about several seconds.

Next, the back pressure is turned off (zero), and measurement is performed without back pressure (step 23). At this time, the screw retreats to the last retreat position Xb. Then, by selecting the semi-automatic molding mode, the injection device 4 (the injection nozzle 9) advances (steps 24 and 25). On the other hand, the injection is started by the nozzle touch. That is, the screw advances according to the set initial conditions, and the resin is injected and filled into the mold 5 (step 26). At this time, the controller 12 controls the speed converter 1
The injection speed V at the time of filling obtained from 5 is monitored. Injection speed V
When the resin is being filled in the mold 5, the speed becomes much higher than the set speed Vs. When the filling of the resin is completed, the speed rapidly decreases to become equal to or lower than the set speed Vs. Therefore, the injection speed V is monitored, and when the injection speed V becomes equal to or lower than the set speed Vs, the set time Ts is counted (steps 27 and 2).
8). When the set time Ts has elapsed, the injection end position Xf of the screw is monitored (steps 29 and 3).
0). In this case, by setting the set pressure Ps as the threshold value, the injection pressure P obtained from the injection pressure detector 16 is obtained.
May be monitored. In other words, the injection pressure P is much smaller than the set pressure Ps while the mold 5 is being filled with the resin. However, when the filling of the resin is completed, the injection pressure P rises rapidly and becomes equal to or higher than the set pressure Ps. Therefore, based on the fact that the injection pressure P has reached the set pressure Ps, the screw injection end position Xf can be detected in the same manner as described above.

Next, the injection pressure (molding condition) is changed (step 31). This change processing is to increase the injection pressure (one pressure value Pd) set on the low pressure side as an initial condition to a required level so that it can be finally used for molding conditions. FIG. 3 shows the change processing procedure. Shown in a flowchart.

At this time, first, the back pressure is turned on, weighing is performed with the back pressure applied, the injection device 4 (the injection nozzle 9) is retracted, and the mold 5 is opened (step 5).
1, 52, 53). Then, while judging a defective filling of the taken-out molded article, a necessary data collection, for example, a data collection of a wall thickness, a gate pressure and the like is performed (Step 5).
4). At this time, the cooling time is automatically calculated from the collected data on the thickness and the gate pressure.

On the other hand, the molded product is visually inspected to determine whether or not a defective filling has occurred. If a short shot has occurred due to insufficient filling, a process of increasing the injection pressure is performed (steps 55 and 56). ). That is, the degree of the short shot is determined. For example, if the degree is “large”, the corresponding selection key K1 on the input device 13 may be pressed. In this case, since the injection pressure is set to the low pressure side one pressure value Pd as an initial condition, the one pressure value Pd is set to 20%.
Is set to the injection pressure 20
By adding 20% of pressure change rate to%,
Change the injection pressure to 40%. Then, reshaping is performed by the changed (increased) injection pressure, that is, step 2 shown in FIG.
A re-forming cycle, which is a process of steps 5 to 31 and steps 51 to 54 shown in FIG. 3, is executed (step 57). Then, if a short shot has further occurred in the molded product, a process of increasing the injection pressure is performed again. In this case, for example, if the degree of the short shot is “medium”, the reforming cycle is executed by adding 10% of the pressure change rate to the injection pressure. Since the magnitude of each pressure change rate is different and is set to be large corresponding to the rank with a high degree of defective filling, if the remolding cycle after changing the injection pressure is repeated, the rank to be selected is selected. Gradually becomes smaller, and finally a good product can be obtained (step 5).
8).

On the other hand, when the molded article is visually inspected and a filling failure such as a burr due to overfilling has occurred, a process for reducing the injection pressure is performed (steps 59 and 60). In this case, the degree of overfill is determined and, for example, the degree is “small”.
Then, by pressing the selection key on the input device 13, the controller 12 subtracts 2% of the pressure change rate from the set injection pressure magnitude. Then, reshaping by the changed (reduced) injection pressure, that is, the reshaping cycle is repeated until a good product is obtained (steps 61 and 6).
2).

Therefore, if a good product is finally obtained, the controller 12 takes in the injection end position Xf at that time obtained from the screw position detector 14, and calculates the injection stroke from the obtained injection end position Xf and the last retreat position Xb. Si (= X
b-Xf) is calculated, and the cushion value Sc set in advance is added to obtain the weighing value Md. Then, the measured value Md is used as a molding condition by the controller 12.
Set to.

Further, the molding conditions are determined by using the injection pressure and the injection speed at the time when finally a non-defective product is obtained, and the determined molding conditions are set in the controller 12.

First, the average injection speed Va during the injection stroke Si when a good product is obtained is determined.
The injection speed is set to the first speed value Vh on the high speed side according to the initial condition. However, as shown in FIG. 6, the injection speed V at the time of actual molding is much smaller than this, so that the average injection speed Va is obtained, and the obtained injection speed Va is set in the controller 12 as a molding condition. In this case, the average injection speed Va may be obtained by dividing the injection speeds V sampled every fixed short time by the number of times of sampling, or by obtaining the area of the speed characteristic with respect to the position of the screw 3 and calculating this area. And may be averaged.

On the other hand, the injection pressure is set in accordance with the present invention by adding a correction pressure having a fixed magnitude. The injection speed is set to the first speed value on the high speed side according to the initial condition, and is set after averaging as described above. Therefore, the average injection speed Va becomes smaller than the first speed value Vh for the initial condition. Therefore, in order to stabilize the reduced injection speed Va, a constant override pressure is added to the injection pressure as a correction pressure in consideration of the fluctuation pressure due to the override characteristic F of the proportional pump or the like shown in FIG. Set. In the case of a proportional pump used for a hydraulic drive type, usually, a value of about 10% can be added (step 32).

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.
For example, as an example of using a mold with unknown mold data,
Initially, the injection speed was set to the first speed value on the high speed side, the injection start position of the screw was set to the last retreat position, and the injection pressure was set to the single pressure value on the low pressure side, but if the mold data is known, etc. Other settings may be made. Also, the correction pressure is set based on the override characteristic of the drive unit due to the change of the injection speed, but the correction pressure according to the change of other molding conditions is set and is set by adding or subtracting from the injection pressure. It does not hinder. In addition, it is possible to arbitrarily change the detailed configuration, method, and the like without departing from the gist of the present invention.

[0037]

As described above, according to the injection pressure setting method for the injection molding machine according to the present invention, at least the injection pressure is set to one pressure value on the low pressure side as the initial condition, and the molding is performed.
By increasing the injection pressure in response to poor filling of the molded product, the size of the injection pressure to obtain a good product is determined.
The correction pressure accompanying the change of other molding conditions is added or subtracted from the obtained injection pressure, and the obtained injection pressure is set as the molding condition. Therefore, the following remarkable effects are obtained.

The injection pressure can be easily and reliably set even by an operator with low skill, and the setting time can be significantly reduced, productivity can be improved, manufacturing costs can be reduced, and resources and energy can be saved.

Since setting errors and improper settings are eliminated, it is possible to prevent damage to the mold and improve safety.

An adverse effect on other molding conditions can be prevented. For example, when the other molding conditions are injection speeds, the injection speed can be stabilized.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a procedure for setting an injection pressure by an injection pressure setting method according to the present invention;

FIG. 2 is a flowchart showing a procedure for setting an initial condition according to the injection pressure setting method;

FIG. 3 is a flowchart showing a procedure for changing an injection pressure according to the injection pressure setting method;

FIG. 4 is a principle explanatory diagram for explaining a method of changing an injection pressure by the injection pressure setting method;

FIG. 5 is another principle explanatory view for explaining a method of changing the injection pressure by the injection pressure setting method;

FIG. 6 is a characteristic diagram of an injection speed for explaining the injection pressure setting method;

FIG. 7 is an override characteristic diagram of a pump for explaining the injection pressure setting method;

FIG. 8 is a schematic configuration diagram of an injection molding machine that can execute the injection pressure setting method.

[Explanation of symbols]

 1 Injection molding machine

Claims (5)

(57) [Claims] As an initial condition, molding is performed by setting at least the injection pressure to one pressure value on the low pressure side, and a good product is obtained by increasing the injection pressure in response to a poor filling of the molded article. Injection molding characterized by determining the magnitude of the injection pressure, adding or subtracting a correction pressure accompanying a change in other molding conditions to the determined injection pressure, and setting the obtained injection pressure as a molding condition. Machine injection pressure setting method. 2. The injection molding machine according to claim 1, wherein, as the initial conditions, the injection speed is set to a first speed value on the high-speed side, and the injection start position of the screw is set to the rearmost position. Pressure setting method. 3. A remolding cycle in which the magnitude of the injection pressure is changed by a preset amount in accordance with the degree of defective filling of the molded article, and remolding is performed with the changed injection pressure until a good product is obtained. 2. The method according to claim 1, wherein the step is repeated.
Or an injection pressure setting method for an injection molding machine according to item 2. 4. The method for setting an injection pressure of an injection molding machine according to claim 1, wherein the other molding condition is an injection speed. 5. The method for setting an injection pressure of an injection molding machine according to claim 1, wherein the magnitude of the correction pressure is set based on a fluctuating pressure due to an override characteristic in the drive unit.