JPS63236618A - Plasticizing control method of molding material in injection molding machine of inclined screw type - Google Patents

Abstract

PURPOSE:To mold stably the molded object excellent in property by correcting at least one of the back pressure acting to an injection screw and the rotating speed of the feeding screw in a raw material feeding device correspondingly to the compared difference so that the actual retreating required time in a divided section coincides with the objective retreating required time therein. CONSTITUTION:An objective retreating required time/retreating speed change ratio operator 44 feeds the signal S8n of objective retreating required time indicating the objective retreating required time Ton to a substraction operator 46 every time when an injection screw 10 reaches the position where measuring stroke is equally divided by N. The compared difference signal S9n indicating the time difference DELTATn between the objective required time Ton and the actual retreating required time Trn in a divided section DELTASn is supplied to a correction value operator 48 from a substraction operator 46. Consequently, the correction value operator 48 corrects at least one of each control signal supplied to an injection screw driving device 26, a hydraulic circuit 28 and a feeding screw driving device 24 so that the actual retreating required time Trn+1 coincides with the objective retreating required time Ton+1 in the next divided section DELTASn+1 of the injection screw 10.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for controlling plasticization in an in-line screw injection molding machine, and in particular, by stabilizing the time required for plasticizing a molding material, it is possible to produce molded products of good quality. This relates to technology for stably molding.

(Prior Art) Conventionally, as one type of injection molding machine, by rotating the injection screw while applying a predetermined back pressure in an injection cylinder to the injection screw fitted in the heating cylinder, A predetermined molding material supplied into the heating cylinder as the feed screw of the raw material supply device rotates is guided to the front of the injection screw while being plasticized, while the molding material guided to the front of the injection screw is caused to retreat. An in-line screw type injection molding machine is known in which the amount of molding material to be injected is measured by regulating the backward stroke of the injection screw.

By the way, in recent years, such in-line screw type injection molding machines have started to plasticize the molding material by rotating the injection screw in order to improve the measurement accuracy of the molding material and to plasticize the molding material to a desired molten state. During the conversion operation, the rotational speed of the injection screw, the back pressure applied to the injection screw by the injection cylinder, and the rotational speed of the feed screw in the raw material supply device are determined in relation to the movement position of the injection screw. Control has come to be performed according to control patterns.

(Problem) However, in the past, the rotational speed of the injection screw, back pressure, and rotational speed of the feed screw during the plasticizing operation of the molding material were simply controlled so that they matched the corresponding control patterns. As a result, variations in the particle size of the molding material supplied from the raw material supply device into the heating cylinder, variations in the biting state of the injection screw into the molding material, or L/L during the plasticizing operation were
Due to the substantial change in D, there is a problem that the time required for plasticizing the molding material and, by extension, the melting temperature of the molding material varies relatively greatly depending on the molding cycle.Especially in precision stable molding to mold precision molded products, the molded product may There was a problem that variations were likely to occur.

(Solution Means) Against this background, the present invention suppresses the above-mentioned variations in the required time for plasticizing in an in-line screw injection molding machine as described above, and solves the problem caused by the dispersion in the required time for plasticizing. This was done in order to provide a plasticization control method that reduces variations in molded products as much as possible, thereby making it possible to stably mold high-quality molded products, and its summary is as follows: However, the rotational speed of the injection screw during the plasticizing operation of the molding material, the back pressure applied to the injection screw by the injection cylinder, and the rotational speed of the feed screw in the raw material supply device are all determined at the time of molding a good product. While controlling according to the control pattern, the retraction stroke of the injection screw is divided into a plurality of sections based on the retraction speed pattern of the injection screw and the required plasticization time during molding of the good product, and for each divided section, In addition to determining the target retraction time for the injection screw, the actual retraction time required for the injection screw to actually retract through each divided section is compared with the target retraction time, and the actual retraction time for the next divided section is determined. The rotational speed of the injection screw is controlled according to the respective control patterns according to the comparative difference so that the time and the target required retreat time match, and the back pressure is applied to the injection screw in the injection cylinder. Further, at least one of the rotational speeds of the feed screw in the raw material supply device is corrected.

(Function/Effect) If the plasticizing operation of the molding material is performed according to this method, the backward stroke (metering stroke) of the injection screw
The actual retraction time required for the injection screw to actually move (retreat) through each divided section accurately matches the target retraction time required for each divided section, and therefore The actual plasticization required to plasticize the molding material, regardless of variations in the particle size of the molding material, variations in the penetration of the injection screw into the molding material, or substantial changes in L/D during the plasticizing operation. The time required for plasticization corresponds with good accuracy to the time required for plasticization when molding a good product.

Therefore, it is possible to effectively reduce variations in molded products due to variations in the time required for plasticization, and even when performing precision and stable molding, it is possible to stably mold molded products of good quality. This makes it possible to do so.

(Example) Hereinafter, in order to clarify the present invention more specifically,
One embodiment thereof will be described in detail based on the drawings.

Here, we will first explain the structure of an injection molding machine that can suitably implement the present invention, and then describe an example of implementing the plasticization control method according to the present invention in the injection molding machine. do.

That is, FIG. 1 shows an example of an injection molding machine in which the present invention can be preferably carried out, in which numeral 10 is an injection screw, and there is a heating screw equipped with a heater (not shown) on the outer periphery. It is fitted into the cylinder 12. A raw material supply device 18 having a structure in which a feed screw 16 is fitted in a feed cylinder 14 is attached to the upper rear end side (right side in the figure) of the heating cylinder 12. The molding material is guided through the feed cylinder 14 as the feed screw 16 rotates, and is supplied into the heating cylinder 12 through the raw material drop hole 22. Note that the feed screw 16 is connected to a feed screw drive device 24 such as an electric servo motor.
It is designed to be rotated by.

On the other hand, at the rear end of the injection screw 10, an injection screw drive device 2 consisting of an electric servo motor, a hydraulic motor, etc.
6 is attached, and this injection screw drive device 2
6 allows the injection screw 10 to be rotated. Further, an injection cylinder 30 driven by a hydraulic circuit 28 is attached to the rear end of the injection screw 10, and the injection cylinder 30 moves the injection screw 10 forward and backward.

Here, as in the conventional case, the injection screw 10 drives the injection screw in a state where the hydraulic pressure, that is, the back pressure t (generated in the injection cylinder 30) acts as a resistance against the backward movement of the injection screw 10. Device 2
6, so that the molding material supplied from the raw material supply device 18 into the heating cylinder 12 is guided to the front of the injection screw 10 while being plasticized. In addition, by restricting the retreat N (retreat stroke S) of the injection screw 10 that is caused to retreat by the molding material guided forward,
The molding material is measured, and after the molding material is measured, the injection screw 10 is inserted into the injection cylinder 3.
0, the plasticized and metered molding material is injected from the nozzle 32 of the heating cylinder 12.

By the way, the injection screw 10 has, as shown in the figure,
A well-known screw position detector 34 consisting of a rack, pinion, etc. is provided, and is used to detect the movement position of the injection screw 10,
That is, the retracted position of the injection screw 10 accompanying the plasticizing operation of the molding material is detected by the screw position detector 34. Then, a screw position signal S1 indicating the retracted position of the injection screw 10 is output from the screw position detector 34, and a screw position signal S1 indicating the retracted position of the injection screw 10 is outputted from the
The signal is supplied to a divided signal generator 38.

The control device 36 controls the backward stroke S (hereinafter referred to as metering stroke S) of the injection screw 10, which is a metering stroke, the rotational speed control patterns of the injection screw 10 and the feed screw 16 during the plasticizing operation of the molding material, or It is equipped with a setting device that sets various conditions for molding, such as back pressure control patterns, and the entire injection molding machine is sequence-controlled according to the various setting conditions set with the setting device. , during the plasticizing operation of the molding material, the injection screw drive device 2
6, hydraulic circuit 28, and feed screw drive device 2
4, an injection screw rotation drive signal S2 according to each control pattern set by the setting device according to the screw position signal S1 from the screw position detector 34, respectively;
A back pressure control signal S3 and a feed screw rotation drive signal S4 are supplied. And here,
Each control signal S2. supplied from the control device 36. S
3 and S4 control the injection screw drive device 26, the hydraulic circuit 28, and the feed screw drive device 24, thereby controlling the rotational speed of the injection screw 10 during the plasticizing operation of the molding material, and the injection screw 1.
The back pressure with respect to
The rotational speed of 0, the back pressure, and the rotational speed of the feed screw 16 are each controlled according to corresponding control patterns set by the setting device of the control device 36.

Further, the control device 36 compares the metering stroke S set by the setting device with the screw position signal S1 supplied from the screw position detector 34, and when the injection screw 10 moves by the metering stroke S, the control device 36 The rotation operation of the molding material is stopped to stop the plasticizing operation of the molding material, and a metering stroke signal S5 representing a metering stroke S is outputted, and this metering stroke signal S5 is transmitted to the N-divided signal generator 38. It is designed to be supplied to

In addition, in the figure, 40 is the output line 41 of each control signal.
This is an amplifier provided on A, 41B and 41C.

Here, the N-divided signal generator 38 to which the metering stroke signal S5 from the control device 36 and the screw position signal S1 from the screw position detector 34 are supplied is configured to divide the metering stroke signal S5 into N equal parts each dividing value. and the screw position signal S1, and each time the injection screw 10 reaches a position where the metering stroke S is divided into N equal parts, an N-divided position arrival signal S6 representing this is outputted, and the N-divided position arrival signal S6 is outputted. The position arrival signal S6 is supplied to an actual required backward time measuring device 42 and a target required backward time/reverse speed change ratio calculator 44.

Then, the actual backward required time measuring device 42 calculates the time interval at which the N-divided position arrival signal S6 from the N-divided signal generator 38 is input, that is, each N-divided section ΔS7 (however, n = l to N; the same applies hereafter) is measured, and each time the N-divided position arrival signal S6 indicating the end of each divided section ΔS7 is input, the actual backward time Tr is measured. Required time Tr,
The actual backward required time signal S7 corresponding to the actual backward movement time signal S7 is supplied to the subtracter 46.

On the other hand, the target retraction time/retraction speed change ratio calculator 44 calculates the target plasticization time T0 measured during molding of a good molded product and the injection screw 10 calculated during molding of the good product. Based on the backward speed pattern, the injection screw 10 performs each divided section Δ of the metering stroke S.
A target required backward time TO7 required for reversing S7 is calculated, and each time an N-divided position arrival signal S6 indicating the end of each divided section ΔS is input, the target required backward time TO7 is calculated. Target retreat time signal S representing
8 is supplied to a subtractor 46. As a result, each time the injection screw 10 passes through each divided section ΔS, the subtracter 46 sends a message to the correction value calculator 48 about the target retraction required time T in that divided section ΔS.
Comparison difference signal S9.O, . represents the time difference ΔT between the actual required backward time Tr7. , is now being supplied.

In addition, this target backward required time/reverse speed change ratio calculator 4
4 is based on the target plasticization time T0 and the retraction speed pattern of the injection screw 10, the target retraction speed (■) of the injection screw 10 in the divided section ΔS7, and the target retraction speed of the injection screw 10 in the next divided section ΔS7.1. Speed vfi. , the backward speed change ratio C, (=V,,I/
V, ), and each time the injection screw 10 passes through each divided section ΔSA, a backward speed change ratio signal 5109 representing the backward speed change ratio C7 is supplied to the correction value calculator 48. .

Note that the target retraction required time/reverse speed change ratio calculator 44 receives a target plasticization time representing the target plasticization time T0 from the target plasticization time setting device 50 that sets the target plasticization time T0 or from the control device 36. A retraction speed pattern setter 52 is configured to be supplied with the required time signal Sll and set the retraction speed pattern of the injection screw 10.
Alternatively, a backward speed pattern signal 312 representing the backward speed pattern of the injection screw 10 is input from the control device 36, and the target backward required time/reverse speed change ratio calculator 44 uses these input signals Sll and Based on S12, the target required backward time To and the reverse speed change ratio c7 are determined.

Comparison difference signal S9 from subtractor 46. , and the correction value calculator 48 to which the target backward time required/reverse speed change ratio signal 510n from the backward speed change ratio calculator 44 is supplied.
A coefficient setter 54 is connected, and this coefficient setter 54
3 is input into the coefficient values corresponding to the injection screw rotational speed control pattern, the back pressure control pattern, and the feed screw rotational speed control pattern set by the control fIff device 36. It has become so. Then, the correction value calculator 48 applies 2°k3 to each coefficient value from the coefficient setter 54, and the comparison difference signal S9. Correction values corresponding to each of the above control patterns are calculated based on the time deviation ΔTI% represented by The correction value signals S13, , S14 . , and S15. , are supplied to the changeover switch mechanism 56, respectively.

Further, the changeover switch mechanism 56 is connected to the correction value calculator 4.
Each correction value signal 313 . .

S14. , S15. and each corresponding output line 41A of the control device 36, depending on the switching setting state.
, 41B, adders 58B provided on 41C
and 58C, or any of them simultaneously.

In other words, the correction value signal S output from the correction value calculator 48
13. , S14. and 515fi are the injection screw drive device 26. Each control signal S2. supplied to the hydraulic circuit 28 and the feed screw drive 24. The values are added to S3 and S4 according to the switching setting state of the changeover switch mechanism 56, so that the injection screw 10 is retracted after the divided section ΔS, . . . in the divided section ΔS7. In .1, the actual required retreat time Tr. 1 and the target retraction required time T07°1. Hydraulic circuit 2
At least one of the control signals supplied to the feed screw drive device 8 and the feed screw drive device 24 is corrected.

Note that the coefficient values corresponding to each control pattern set by the coefficient setter 54 are 2 and k.

is determined empirically based on actual molding operations.

Further, in the correction value calculator 48, each correction value is corrected according to the content of the switching position signal S16 supplied from the changeover switch mechanism 56. That is, the correction value signal (S13fi,
3140. S15. ) is selectively selected by the changeover switch mechanism 56, the correction value signal is selected simultaneously by the changeover switch mechanism 56 so that its value is larger than the magnitude of the time deviation ΔT1. If the number of
Each correction value is corrected accordingly so that its value becomes smaller than the magnitude of the time deviation ΔT7.

Further, the changeover switch mechanism 56 includes a correction value calculator 48.
An off function is provided to cut off all correction value signals supplied from the adder 58.
An inverting amplifier 60 is provided on the line that supplies B.

Next, an example of implementing the plasticization control method according to the present invention in an injection molding machine having such a structure will be described.

That is, in the injection molding machine shown in FIG. 1, when performing an injection molding operation, first, the changeover switch mechanism 56 is
Set to off state. In this state, that is, during the plasticizing operation of the molding material, the injection screw drive device 26. Hydraulic circuit 28 and feed screw drive device 2
4. In other words, the rotational speed of the injection screw 10, the back pressure, and the rotational speed of the feed screw 16 are controlled by each control signal S2.4 output from the control device 36, as in the conventional case. With control based only on S3 and S4,
Perform an injection molding operation. Then, each control pattern when a good molded product is molded by such injection molding operation is determined, and the retraction speed pattern of the injection screw 10 at that time is determined.

At the same time, during molding of a good product, the time required for plasticizing the molding material, that is, the target plasticization time T0, is measured, and each coefficient value to be set in the coefficient setting device 54 is set to: and .

As described above, each control pattern, retreat speed pattern, and target plasticization time T during molding of a non-defective product are performed using the same injection molding operation as the conventional one. and 1° kt for each coefficient value, the injection molding operation is completed with the changeover switch mechanism 56 set to OFF, and the above-mentioned backward speed pattern is
2. To the target plasticization time T0 and each coefficient value. Reverse speed pattern setter 52 corresponding to 3 respectively. This is set using the target plasticization time setting device 50 and the coefficient setting device 54. In addition, when the changeover switch mechanism 56 is set to a position other than the OFF state, that is, at least one of the correction value signals (Si2, 1.5140.Si2, . , 58B, 58
C). In this state and during the plasticizing operation of the molding material, each control signal S2 is generated according to each control pattern obtained during the above-mentioned molding of a non-defective product.
．． Injection molding operation is performed with S3 and S4 output.

In this way, during the plasticizing operation of the molding material,
Each time the injection screw 10 passes through each N-divided section ΔS7 of the metering stroke S, each corresponding correction is sent from the correction value calculator 48 to each adder 58A, 58B, 58C selected by the changeover switch mechanism 56. Value signal S13. ,S1
4. . Control signals (S2, S3 .
S4), and the divided section ΔS
Actual retraction time T of the injection screw 10 at ,,+1
rM+1 is caused by variations in the particle size of the molding material supplied from the raw material supply device 18 into the heating cylinder 12, variations in the biting state of the injection screw 10 into the molding material, or a substantial change in L/D during the plasticizing operation. Regardless, it precisely matches the target required backward travel time TO, . . . l determined for the divided section ΔS all.

In other words, the actual plasticization time T required for plasticizing the molding material
r is the variation in the particle size of the molding material supplied from the raw material supply device 18 into the heating cylinder 12, the variation in the biting state of the injection screw 10 into the molding material, or the substantial change in L/D during the plasticizing operation. Regardless of the time required for plasticization, the required time for plasticization always matches the target time To for molding a good product set by the target time required for plasticization setting unit 50 with high precision. It is possible to effectively suppress variations in the molded product due to variations in (Tr), and it is possible to stably mold a molded product with good quality.

Here, if the backward speed pattern has a constant or approximately constant slope as shown in FIG. 2, the target backward required time/reverse speed change ratio calculator 44, the target backward required time T in each divided section ΔS1 of the metering stroke S is determined as follows, for example.
o7 and the reverse speed change ratio C7 are determined.

That is, if the target retraction speed of the injection screw 10 in the first divided section ΔS of the metering stroke S is Vl and that in the last divided section ΔSH is VN, then the average speed of the injection screw 10 in the metering stroke S is (V
Since it is expressed as 1+VN)/2, assuming that the target plasticization time T0 is expressed by the following formula (1), V can be expressed by the following formula (3).

On the other hand, if the target backward speed in the metering stroke SOn-th divided section ΔS, , is v7, this Vl is as follows (
Since it is expressed as in equation 4), the target required retreat time To++ in the divided section ΔS9 can be expressed as in (5) 2 below.

Therefore, by substituting the above-mentioned equations (2) and (3) into (5)2, the target required retreat time To can be expressed as shown in the following equation (6).

On the other hand, the backward speed change ratio C, (
=V, , /V,) is the speed difference Δ■ between adjacent divided sections
7 is always approximately constant at Δ■, and VI'l+l+vn and Δ
Since (2) is shown by the following formulas (7) to (9), it can be determined according to the following Cl0I formula.

V, 1=V, -(n-1)ΔV ・
... (7) V, , = V, -nΔv (8) In other words, when the backward speed pattern has a constant or almost constant slope as shown in Figure 2, In this case, the constant A expressed by the equation (2) above is input as data for specifying the backward speed pattern in the reverse speed pattern setter 52, and the constant A expressed by the above equation (2) is inputted into the reverse speed pattern setter 52, and the above (6 ) and the α0 equation, it is possible to obtain the target required backward time T07 and backward speed change ratio C7 corresponding to each divided section ΔSfi.

In the correction value calculator 48, for example, when only one of the correction value signals is supplied to the adder (58), the time deviation ΔT7.
For each coefficient set by the coefficient setter 54,
Then, the reverse speed change ratio C7 calculated by the target backward required time/reverse speed change ratio calculator 44 is integrated, and a correction value corresponding to each control pattern is calculated.

Although one embodiment of the present invention has been described in detail above, this is a literal illustration, and it goes without saying that the present invention should not be interpreted as being limited to this specific example.

For example, in the embodiment, the reverse speed pattern setter 52
Although the case where the reverse speed pattern set in 1 has a constant or substantially constant slope has been described, the reverse control pattern may also be set without such a condition.
It is possible to apply the present invention.

Further, in the embodiment, the target plasticization time T is supplied to the target retraction time/reverse speed change ratio calculator 44. Although the case has been described where the reverse speed pattern and the reverse speed pattern are set by the setter 50.52, it is also possible to have them supplied from the control device 36 without setting them using the setter 50.52. In addition, each target backward required time TO7 and backward speed change ratio Cn corresponding to each divided section ΔS7
are sequentially stored in the control device 36 during molding of non-defective products, and these target retraction required time To and retraction speed change ratio C7
It is also possible to read out the subtracter 46 and the correction value calculator 48 as necessary and input it directly from the control device 36.

Furthermore, in the above embodiment, a case has been described in which various data at the time of molding a non-defective product are obtained prior to the injection molding operation, but if such data is obtained in advance, the control device 3
Each control signal 32 outputted from 6. S3. It is also possible to immediately perform a desired injection molding operation by combining the control pattern of S4 and the data into a predetermined program and setting the program in the control device 36.

Further, various calculations in the injection molding machine may be performed by a microcomputer.

In addition, although not listed, various modifications may be made without departing from the spirit of the present invention.

It goes without saying that the present invention can be implemented with modifications, improvements, etc.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an example of an injection molding machine that can suitably implement the plasticization control method according to the present invention.
FIG. 2 is a graph showing an example of a retraction speed pattern of the injection screw. 10: Injection screw 12: Heating cylinder 16: Feed screw 18; Raw material supply device 24: Feed screw drive device 26: Injection screw drive device 28: Hydraulic circuit 30: Injection cylinder 34: Screw position detector 36: Control device 38: N Divided signal generator 42: Actual required backward time measuring device 44: Target required backward time/reverse speed change ratio calculator 46:
Subtractor 48: Correction value calculator 50: Target visualization required time setting device 52: Backward speed pattern setting device

Claims (1)

[Claims] By rotating the injection screw while applying a predetermined back pressure in the injection cylinder to the injection screw fitted in the heating cylinder, the injection screw is rotated according to the rotation of the feed screw of the raw material supply device. A predetermined molding material supplied into the heating cylinder is plasticized and guided in front of the injection screw, while regulating the backward stroke of the injection screw, which is caused to retreat by the molding material guided in front of the injection screw. In an in-line screw type injection molding machine that measures the molding material to be injected, the rotational speed of the injection screw during the plasticizing operation of the molding material and the action on the injection screw in the injection cylinder are controlled. A plasticization control method comprising: controlling the applied back pressure and the rotational speed of the feed screw in the raw material supply device according to a control pattern determined in relation to the movement position of the injection screw, the method comprising: The rotational speed of the injection screw during the plasticizing operation, the back pressure applied to the injection screw by the injection cylinder, and the rotational speed of the feed screw in the raw material supply device are controlled by a control pattern determined at the time of molding a non-defective product. On the other hand, the injection screw's retraction stroke is divided into a plurality of sections based on the retraction speed pattern of the injection screw and the required plasticization time during molding of a good product. In addition to determining the target retraction time, the actual retraction time required for the injection screw to actually retract each divided section is compared with the target retraction time, and the actual retraction time in the next divided section is calculated. The rotational speed of the injection screw is controlled according to each of the control patterns, the back pressure applied to the injection screw in the injection cylinder, and the A method for controlling plasticization in an in-line screw injection molding machine, comprising correcting at least one rotational speed of a feed screw in a raw material supply device.