JP2649010B2 - Molding 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 molding method for 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 section, there are cases where only a mold is given when a molding commission is received. In this case, the mold data is often unknown.

By the way, when setting a weighing value (a weighing stroke) as a molding condition, if mold data such as a cavity volume is known, a certain temporary weighing value is set as an initial condition and molding is performed. Although it can be performed, it is not easy to set the weighing value when the mold data is unknown. For this reason, conventionally, a skilled operator visually inspects the mold cavity and the like, sets initial conditions such as injection speed and injection pressure based on intuition and experience, and sets a small measurement value at first to perform molding. Then, while gradually increasing the measured value while observing the filling state of the molded article, the molding is repeated to set the measured value by trial and error.

[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 the setting operation cannot be easily performed even by a skilled operator, the setting time is prolonged, the productivity is reduced, and the manufacturing cost is increased. In addition, useless resources and energy are consumed.

Second, if the weighing value is excessively set due to a setting error or 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. By eliminating the necessity of setting a weighing value, it is possible to easily set molding conditions, improve productivity, reduce manufacturing costs, and so on. An object of the present invention is to provide a molding method for an injection molding machine that can save resources and energy, prevent damage to a mold, and improve safety, and can contribute to improvement of molding quality.

[0008]

According to the molding method of the injection molding machine according to the present invention, the screw 2 is moved to the rearmost position X in the injection step.
Inject the resin by moving it forward from b and filling the mold 5 with the resin L
If There was completed, along with to end the injection of a resin remaining state Zm resin L having a predetermined amount ahead of the screw 2 remains, put the screw 2 to the resin remaining state Zm is the weighing process
From the current position to the last retreat position Xb .

In this case, molding is performed in advance by setting the injection speed V to the first speed value Vh on the high-speed side and the injection pressure to the first pressure value Pd on the low-pressure side, and copes with a defective filling of the molded article. Then, the magnitude of the injection pressure is changed until a non-defective product is molded, and the magnitude of the obtained injection pressure and the magnitude of the average injection speed at this time can be used as the molding conditions.
In order to improve the quality of the molded product, a remolding cycle is performed in which the magnitude of the injection pressure is changed by a preset change amount in accordance with the degree of defective filling of the molded product, and remolding is performed with the changed injection pressure. It is desirable to repeat until a good product is formed.

[0010]

According to the molding method of the injection molding machine according to the present invention,
In the weighing step, the screw 2 is uniformly retracted to the last retracted position Xb, so that substantial weighing is not performed. On the other hand, in the injection step, the screw 2 is advanced from the last retreat position Xb to perform injection. In this case, the injection is performed until the filling of the resin L into the mold is completed, and the screw 2 is advanced from the last retreat position Xb. Residual resin remaining state Zm occurs. Therefore, in the measuring step, the screw 2 is retracted from the resin remaining state Zm, and the above-described measurement substantially without measurement is performed up to the last retracted position Xb.
As a result, even if the mold data such as the cavity capacity is unknown, the mold can be molded, and the resin remaining state Z
Since m is generated, the resin L is heated in the heating cylinder for a sufficient time, and the molten resin L is surely injected and filled in the mold, thereby improving the molding quality.

Since a mold whose mold data is unknown is used, the injection pressure and the injection speed, which are molding conditions, can be set as follows as an example.

That is, the injection speed is previously set to the first speed value V on the high speed side.
h, the injection pressure is set to the one pressure value Pd on the low pressure side and molded, and the magnitude of the injection pressure is changed by a preset change amount in accordance with the degree of failure of the molded product, The remolding cycle of remolding with the changed injection pressure is repeated until a good product is obtained. Then, when a non-defective product is molded, the injection pressure and the average injection speed at this time are obtained, and the obtained injection pressure and injection speed are used as molding conditions.

[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 capable of performing a molding 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 the screw 2 is built in the heating cylinder 8 (see FIG. 1). On the other hand, a screw driving device 11 for rotating and moving the screw 3 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. 3, 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. Further, a screw position detector 14 uses, for example, a rotary encoder for detecting the number of rotations of a servo motor in the case of an electric drive type, and a linear scale for directly detecting the screw position in the case of a hydraulic drive type. it can. The screw position detector 14 is directly connected to the controller 12 and the speed converter 1
5 to the controller 12. Speed converter 1
Reference numeral 5 has a function of differentiating the position signal from the screw position detector 14 and converting it into a screw speed signal.

On the other hand, reference numeral 16 denotes an injection pressure detector, for example, a load cell for detecting the back pressure at the rear end of the screw 2 in the case of the electric drive type, and detecting the hydraulic pressure of the hydraulic cylinder in the case of the hydraulic drive type. A hydraulic sensor or the like can be used. In addition, 1
Reference numeral 7 denotes 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, a molding method according to the present invention will be described with reference to FIGS.

First, molding conditions are set prior to molding. FIG. 4 is a flowchart showing a procedure for setting molding conditions.

When setting the molding conditions, the input device 1
3. Further, using the display 17, input known data relating to the molding material, the specification screw, and the like. The controller 12 stores a database relating to material characteristics, molding machine performance specifications, basic molding conditions, and the like. The controller 12 uses the input known data and the stored database to store temperature-related molding conditions, such as the maximum stroke of the screw. Controller 1
Set to 2. 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 31 and 32). 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 51). 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 2 is set to the last retreat position Xb (step 52). 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. Further, the injection pressure is set to the one pressure value Pd on the low pressure side (step 53). 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 54).

Further, a set speed Vs and a set time Ts for detecting the injection end position Xf of the screw 2 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 33). At this time, screw 2 is
As shown in (a), it 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 34, 3).
5). On the other hand, the injection is started by the nozzle touch. That is, the screw 2 advances according to the set initial conditions, and the mold 5 is injected and filled with the resin L (step 36). At this time, the controller 12 monitors the injection speed V at the time of filling obtained from the speed converter 15. The injection speed V is much higher than the set speed Vs when the mold 5 is being filled with the resin L, and rapidly drops to become equal to or lower than the set speed Vs when the filling of the resin L is completed. 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 37 and 38). When the set time Ts has elapsed, the injection end position Xf of the screw 2 shown in FIG. 1B is monitored (step 3).
9, 40).

Next, the injection pressure is changed (step 41). This change processing mainly increases the injection pressure (one pressure value Pd) set on the low pressure side to an appropriate value. FIG. 6 shows a flow chart of the change processing procedure.

At this time, first, the back pressure is turned on, weighing is performed with the back pressure applied, the injection device 4 (injection nozzle 9) is retracted, and the mold 5 is opened (step 6).
1, 62, 63). Then, while judging a defective filling in the taken-out molded article, a necessary data collection, for example, a data collection such as a wall thickness and a gate pressure is performed (Step 6).
4). At this time, the cooling time is automatically calculated from the collected data on the thickness and the gate pressure.

By the way, the input device 13 is provided with selection keys K1, K2, K3 (see FIG. 3) for selecting the type of filling defect and the rank for each filling defect. A plurality of change amounts corresponding to each rank for changing the injection pressure in the direction to be performed are set.

For example, in the case of a short shot, as shown in FIG.
It is classified into three levels of “medium” and “small”. When “large”, the pressure change rate (change amount) is “+ 20%”, and when “medium”, the pressure change rate is “+ 10%”, “ When "small", the pressure change rate is set to "+ 5%". In this case, the ranks are set to “large”, “medium”, and “small”, but of course, they may be converted into numerical values. 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. 8, 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.

Therefore, the molded product is visually inspected, and if a short shot has occurred due to insufficient filling, processing for increasing the injection pressure is performed (steps 65 and 66). 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 one pressure value Pd on the low pressure side as an initial condition, if the one pressure value Pd is set to 20%, the controller 12 sets the pressure change rate to the injection pressure 20%. The injection pressure is changed to 40% by adding 20%. Then, reshaping is performed with the changed (increased) injection pressure, that is, steps 35 to 41 shown in FIG. 4 and steps 61 to 6 shown in FIG.
The remolding cycle, which is the process of step 4, is executed (step 6).
7). Then, if a short shot has further occurred in the molded product, a process of increasing the injection pressure is performed again. That is, if the degree of the short shot is “medium”, similarly, 10% of the pressure change rate is added to the injection pressure, and the reshaping cycle is executed. Since the magnitudes of the respective pressure change rates are different from each other and are set to be large in accordance with the ranks with a high degree of defective filling, selection is made by repeating such a remolding cycle after changing the injection pressure P. The rank gradually decreases, and finally a good product can be obtained (step 6).
8).

On the other hand, when the molded article is visually inspected and a defective filling such as burrs due to overfilling has occurred, processing for reducing the injection pressure is performed (steps 69 and 70). 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 71 and 7).
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.
(Step 42).

Further, molding conditions are obtained by using the injection pressure P and the injection speed V at the time of finally obtaining a good product, and the obtained molding conditions are set in the controller 12. In this case, an average injection speed in the injection stroke Si when a good product is obtained is obtained. The injection speed is set to the first speed value on the high speed side according to the initial conditions. However, since the injection speed V at the time of actual molding is much smaller than this, an average injection speed is obtained, and the obtained injection speed is calculated. The molding conditions are set in the controller 12. In this case, the average injection speed is the injection speed V sampled every fixed short time.
May be divided by the number of times of sampling, or the area of the speed characteristic with respect to the position of the screw 2 may be determined, and this area may be divided by the position and averaged.

On the other hand, the injection pressure is set by adding the correction pressure. 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 is smaller than the first speed value Vh for the initial condition. Therefore, in order to stabilize the reduced injection speed, a constant override pressure is added to the injection pressure as a correction pressure in consideration of a fluctuation pressure based on an override characteristic of a proportional pump or the like. In the case of a proportional pump used for a hydraulic drive type, 10%
The values before and after can be added.

In the embodiment described above, the injection end position X
In detecting the injection speed f, the injection speed V is monitored.
Although the injection end position Xf is detected when is equal to or lower than the set speed Vs, the injection pressure P obtained from the injection pressure detector 16 may be monitored by setting the set pressure Ps as a threshold value. In other words, the injection pressure P is much smaller than the set pressure Ps when the resin 5 is being charged into the mold 5, and rises sharply when the filling of the resin L is completed to reach the set pressure Ps or more. Become. Therefore, based on the fact that the injection pressure P has reached the set pressure Ps, the injection end position Xf can be detected in the same manner as in the above-described embodiment.

Next, the actual molding process using the molding method according to the present invention will be described with reference to FIGS.

First, in the weighing step, the screw 2 is retracted and weighed to the last retracted position Xb as shown in FIG. 1A (steps 21 and 22). In this case, in the weighing step, the screw 2 is uniformly retracted to the last retreat position Xb, so that substantial weighing is not performed. Next, the process proceeds to the injection step. In the injection step, the screw 2 is advanced from the last retreat position Xb to perform injection. At this time, injection is performed until the filling of the resin L into the mold 5 is completed (steps 23 and 2).
4). And when filling is completed, it shifts to the pressure holding process,
A holding pressure is applied to the screw 2 for a preset holding time (step 25). At this time, the switching timing to the pressure holding step can be set in consideration of the injection end position Xf or the injection time of the screw 2 described above. FIG. 1 (b)
As shown in (2), since the screw 2 is advanced from the last retreat position Xb, after the injection is completed, a resin remaining state Zm in which a predetermined amount of the resin L remains in front of the screw 2 occurs.

On the other hand, when the pressure-holding step is completed, the process shifts to the measuring step (step 21). At this time, in the measuring step, the screw 2 is retracted from the above-described resin remaining state Zm, and is measured to the last retracted position Xb. That is, since the screw 2 uniformly retreats to the last retreat position Xb, weighing substantially without weighing is performed as described above.

Therefore, even in the case of the mold 5 whose mold data such as the cavity capacity is unknown, the molding can be easily realized, and the resin residual state Zm occurs, so that sufficient time is required in the heating cylinder. The resin L that has been heated and melted reliably is injected and filled into the mold 5, thereby improving the molding quality.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.
For example, the setting method and conditions of the injection speed and the injection pressure may use other methods than those illustrated. In addition, it is possible to arbitrarily change the detailed configuration, method, and the like without departing from the gist of the present invention.

[0041]

[Effect of the Invention] Thus, the present invention is in the molding process of an injection molding machine including an injection step and the metering step, performed emitted by advancing the screw from the most retracted position in the injection process, the mold
If filling of the resin into the finished, with to end the injection of a resin remaining state in which a predetermined amount of resin in front of the screw remains, the resin remaining the screw in the metering process
By retreating from the position in the state to the last retreat position , the following remarkable effects are obtained.

Since it is not necessary to set the weighing value even if the mold data is unknown, it is possible to easily set the molding conditions, improve the productivity, reduce the manufacturing cost, and save resources and energy. Further, even an operator with low skill level can easily mold.

Since setting errors and improper settings are eliminated, damage to the mold can be prevented and safety can be improved.

Since the resin is sufficiently heated in the heating cylinder and the molten resin is injected and filled into the mold, it is possible to contribute to improvement in molding quality.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a heating cylinder showing a screw position for explaining a molding method of an injection molding machine according to the present invention;

FIG. 2 is a flowchart showing a procedure of the molding method;

FIG. 3 is a configuration diagram of an injection molding machine that performs the molding method,

FIG. 4 is a flowchart showing a procedure for setting molding conditions in the molding method;

FIG. 5 is a flowchart showing a procedure for setting initial conditions in the molding method;

FIG. 6 is a flowchart showing a procedure for changing an injection pressure in the molding method;

FIG. 7 is a principle explanatory view for explaining a method of changing an injection pressure in the molding method;

FIG. 8 is another principle explanatory view for explaining a method of changing the injection pressure in the molding method;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 injection molding machine 2 screw L resin Zm resin remaining state Xb screw retreat position Xf screw injection end position

Claims (4)

(57) [Claims] In a molding method of an injection molding machine including an injection step and a measuring step, in the injection step, a screw is advanced from a last retreat position to perform injection, and filling of a mold with resin is completed.
Then , the injection is terminated in a resin remaining state in which a predetermined amount of resin remains in front of the screw , and in the measuring step, the screw is moved from a position in the resin remaining state.
A molding method for an injection molding machine, comprising retreating to the last retreat position . 2. Molding is performed by setting the injection speed to the first speed value on the high speed side and the injection pressure to the one pressure value on the low pressure side in advance. 2. The molding method for an injection molding machine according to claim 1, wherein the magnitude of the injection pressure is changed until molding is performed, and the magnitude of the obtained injection pressure is used for molding conditions. 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. 3. The molding method for an injection molding machine according to claim 2, wherein the method is repeated until molding is performed. 4. The method according to claim 2, wherein an average injection speed at the time of molding a good product is used as a molding condition.
Or a molding method of an injection molding machine according to 3.