JPH0455575B2 - - Google Patents

Description

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

(Prior Art) Conventionally, as one type of injection molding machine, by rotating the injection screw while applying a predetermined back pressure with an injection cylinder to the injection screw fitted in the heating cylinder, As the feed screw of the raw material supply device rotates, a predetermined molding material supplied into the heating cylinder is plasticized and guided to the front of the injection screw, while being retracted by the molding material guided to the front of the injection screw. 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.

Incidentally, in recent years, such in-line screw type injection molding machines have been designed to increase the amount of 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 plasticizing 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 were determined in relation to the moving position of the injection screw. Control is increasingly performed according to control patterns.

(Problem) However, in the past, the injection screw rotation speed, back pressure, and feed screw rotation speed during the plasticizing operation of the molding material were simply controlled so that they matched the corresponding control patterns. As a result, there may be 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.
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 widely depending on the molding cycle. There was a problem in that stable molding tends to cause variations in molded products.

(Solution Means) Against this background, the present invention suppresses the above-mentioned variations in the required plasticization time in the above-mentioned in-line screw type injection molding machine, and solves the above-mentioned variations in the required plasticization time. This was done in order to provide a plasticization control method that reduces the resulting variation in molded products as much as possible and enables stable molding of high-quality molded products. This is because 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 each determined during molding of a good product. While controlling according to a control pattern determined 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 a 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 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 each of the control patterns, and the back pressure applied to the injection screw by the injection cylinder is adjusted according to the comparison difference so that the time and the target required retreat time match. pressure,
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 actual amount required for the injection screw to actually move (backward) through each divided section of the backward stroke (metering stroke) of the injection screw will be reduced. The required retraction time accurately matches the target retraction time determined for each divided section, and therefore, it is possible to avoid variations in the particle size of the molding material supplied into the heating cylinder and the state of the injection screw biting into the molding material. Regardless of variations in L/D during the plasticizing operation, the actual plasticizing time required to plasticize the molding material can be determined with good accuracy in the plasticizing time required for molding a good product. They match. 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 produce molded products of good quality. This makes it possible to mold the material.

(Example) Hereinafter, in order to clarify the present invention more specifically, one example 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. .

That is, FIG. 1 shows an example of an injection molding machine in which the present invention can be preferably carried out, in which reference numeral 10 denotes an injection screw, which is equipped with a heater (not shown) on its outer periphery. Cylinder 1
It is fitted in 2. A raw material supply device 18 having a structure in which a feed screw 16 is fitted in the feed cylinder 14 is attached to the upper rear end side (right side in the figure) of the heating cylinder 12. The falling 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. The feed screw 16 is rotated by a feed screw drive device 24 such as an electric servo motor.

On the other hand, an injection screw drive device 26 consisting of an electric servo motor, a hydraulic motor, etc. is attached to the rear end of the injection screw 10, and the injection screw drive device 26 drives the injection screw 1.
0 can be rotated. Further, a hydraulic circuit 2 is provided at the rear end of the injection screw 10.
An injection cylinder 30 driven by a motor 8 is attached, and the injection screw 10 is moved forward and backward by this injection cylinder 30.

Here, as in the conventional case, when the injection screw 10 is retracted, hydraulic pressure, that is, back pressure is generated in the injection cylinder 30, which acts as resistance against the retraction operation.
is rotated by the injection screw drive device 26, whereby the molding material supplied from the raw material supply device 18 into the heating cylinder 12 is plasticized and guided to the front of the injection screw 10. It's starting to get worse. Furthermore, by regulating the amount of retraction (backward stroke S) of the injection screw 10 that is retracted by the molding material guided forward, the molding material can be measured. After metering, the injection screw 10 is pushed forward by the injection cylinder 30, so that the plasticized and metered molding material is injected from the nozzle 32 of the heating cylinder 12.

By the way, as shown in the figure, the injection screw 10 is provided with a known screw position detector 34 consisting of a rack, pinion, etc., which determines the movement position of the injection screw 10, that is, the position of the injection screw 10 as the molding material is plasticized. The retracted position of the injection screw 10 is detected by this screw position detector 34. This screw position detector 34
A screw position signal S1 representing the retracted position of the injection screw 10 is outputted from the screwdriver 10, and is supplied to a control device 36 and an N-divided signal generator 38, which will be described later.

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 rotation speed control pattern of the injection screw 10 and the feed screw 16 during the plasticizing operation of the molding material, or the back stroke. It is equipped with a setting device that sets various conditions for molding such as 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 setting device controls the injection screw drive device 26, the hydraulic circuit 28, and the feed screw drive device 24 in accordance with the screw position signal S1 from the screw position detector 34, respectively. Injection screw rotation drive signal S2, back pressure control signal S3 and feed screw rotation drive signal S according to each set control pattern
4. Here, the injection screw drive device 26, the hydraulic circuit 28, and the feed screw drive device 24 are controlled by the control signals S2, S3, and S4 supplied from the control device 36, so that the injection screw drive device 26, the hydraulic circuit 28, and the feed screw drive device 24 are controlled. Injection screw 1 during plasticizing operation
The rotation speed of the injection screw 10 and the back pressure on the injection screw 10 as well as the rotation speed of the feed screw 16 are controlled, thereby controlling the rotation speed and back pressure of the injection screw 10 during the plasticizing operation of the molding material. The pressure and the rotation speed of the feed screw 16 are respectively 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 injection screw 10 stop the rotation of the
It is designed to stop the plasticizing operation of the molding material, output a metering stroke signal S5 representing the metering stroke S, and supply this metering stroke signal S5 to the N-divided signal generator 38. .

In the figure, 40 is an amplifier provided on the output lines 41A, 41B, and 41C for each of the control signals.

Here, a metering stroke signal S5 from the control device 36 and a screw position signal S1 from the screw position detector 34 are supplied to N.
The split signal generator 38 generates a metering stroke signal S5
is divided into N equal parts and each division value is compared with the screw position signal S1, and the injection screw 10 reaches the metering stroke S.
Each time the vehicle reaches a position divided into N equal parts, it outputs an N-divided position arrival signal S6 representing this, and the N-divided position arrival signal S6 is sent to the actual required backward time measuring device 42 and the target required backward time. /Reverse speed change ratio calculator 44.

The actual backward required time measuring device 42 measures the time interval at which the N-divided position arrival signal S6 from the N-divided signal generator 38 is input, that is, the time interval at which the injection screw 10
is each N divided section ΔS _o of the metering stroke S (however,
n=1 to N; the same applies hereinafter) ₎ is measured, and each time an N-divided position arrival signal S6 indicating the end of each divided section ΔS _o is input, An actual required backward _time signal S7 _o corresponding to the actual required backward time T 0 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 T _p measured during molding of a good molded product and the injection screw 10 similarly determined during molding of the good product. Based on the retraction speed pattern of the injection screw 10
calculates the target required retraction time _Too required for reversing each divided section ΔS _o of the metering stroke S, and an N-divided position arrival signal S6 indicating the end of each divided section ΔS _o is input. Each time, a target required backward time signal _{S8o representing the target required backward time To o is} supplied to the subtracter 46. As a result, each time the injection screw 10 passes through each divided section ΔS _o , the subtracter 46 sends a message to the correction value calculator 48 about the target required retreat time To _o and the actual required retreat time in that divided section ΔS _o . T r _o
A comparison difference signal S9 o representing the time difference ΔT _o with respect to the time difference ΔT _o is supplied.

The target retraction time/retreat speed change ratio calculator 44 calculates the target retraction speed V of the injection screw 10 in the divided section ΔS _o based on the target plasticization time T _p and the retraction speed pattern of the injection screw 10. _o and _the target retreat speed V _{o+1 of} the injection screw 10 in the next divided section ΔS _{o+1 .} Every time the section ΔS _o is passed, a backward speed change ratio signal S10 _o representing the backward speed change ratio C _o is generated.
is supplied to the correction value calculator 48.

Note that the target retraction required time/reverse speed change ratio calculator 44 includes a target plasticization required time setting device 50 or the control device 3 for setting the target plasticization time _Tp .
6, a target plasticizing time signal S11 representing the target plasticizing time T _p is supplied, and a backward speed pattern setting device 52 or a control device 36 sets the backward speed pattern of the injection screw 10. , a backward speed pattern signal S12 representing the backward speed pattern of the injection screw 10 is inputted, and the target backward required time/reverse speed change ratio calculator 44 calculates the backward speed pattern signal S12 based on the input signals S11 and S12. , the target backward travel time To _o and the reverse speed change ratio C _o are determined.

A coefficient setter 54 is connected to the correction value calculator 48 to which the comparison difference signal _S9o from the subtracter 46 and the backward speed change ratio signal S10n from the target backward required time/reverse speed change ratio calculator 44 are supplied. From this coefficient setter 54, the control device 3
Coefficient values k ₁ , k ₂ and k ₃ corresponding to each of the injection screw rotation speed control pattern, back pressure control pattern, and feed screw rotation speed control pattern set in step 6 are input. Then, the correction value calculator 48 calculates the coefficient values k ₁ , k ₂ , k ₃ from the coefficient setter 54, the time deviation ΔT o represented by the comparison difference signal S9 _o , and the time deviation ΔT _o represented by the backward speed change ratio signal S10n. Reverse speed change ratio
Based on C _o , correction values corresponding to each of the above-mentioned control patterns are calculated, and correction value signals S13 _o and S14 _o represent the calculated correction values.
and S15 _o respectively.
It is now being supplied to Further, the changeover switch mechanism 56 receives each correction value signal S13 _o , S14 _o , S15 _o supplied from the correction value calculator 48 .
and corresponding output lines 41A and 41 of the control device 36, respectively, depending on the switching setting state.
Adders 58A, 58B provided on B, 41C
and 58C, or any of them simultaneously.

That is, the correction value signals S13 _o , S14 _o and S15 _o outputted from the correction value calculator 48 are used as control signals S2, S3 and The value is added to 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 _o+ 1 in the divided section ΔS _o+1. Actual retreat time
At least one of the control devices supplied to the injection screw drive device 26, the hydraulic circuit 28, and the feed screw drive device 24 is corrected so that T _o+1 and the target retraction time To _o+1 match. It is becoming more and more common.

Note that the coefficient values k ₁ , k ₂ and k ₃ corresponding to each control pattern set by the coefficient setter 54 are 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. In other words, when the correction value signals S13 _o , S14 _o , S15 _o outputted from the correction value calculator 48 are selectively selected by the changeover switch mechanism 56, the time deviation ΔT _o is so that the value becomes larger, and the more correction value signals are simultaneously selected by the changeover switch mechanism 56, the smaller the value becomes relative to the size of the time deviation ΔT _o . , each correction value is modified.

Furthermore, the changeover switch mechanism 56 is provided with an off function that cuts off all of the correction value signals supplied from the correction value calculator 48, and also has an off function that cuts off all of the correction value signals supplied from the correction value calculator ₄₈ . teeth,
An inverting amplifier 60 is provided.

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

That is, in the injection molding machine shown in FIG.
When performing an injection molding operation, first, the changeover switch mechanism 56 is set to the OFF state. and,
In this state, that is, during the plasticizing operation of the molding material, the injection screw drive device 26, the hydraulic circuit 28
and the feed screw drive device 24, 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 S output from the control device 36 as in the conventional case.
2. Perform the injection molding operation with control based only on S3 and S4. Then, each control pattern when a good molded product is molded by such injection molding operation is determined, and
The backward speed pattern of the injection screw 10 at that time is determined. At the same time, the time required for plasticizing the molding material during molding of the non-defective product, that is, the target plasticization time To, is measured.
Each coefficient value k ₁ to be set in the coefficient setter 54,
Find k ₂ and k ₃ .

As described above, by the same injection molding operation as the conventional one, each control pattern during molding of a good product, the backward speed pattern, the target plasticization time To, and each coefficient value k ₁ ,
Once k ₂ and k ₃ have been determined, changeover switch mechanism 5
6 is set to OFF, the injection molding operation is finished, and the above retraction speed pattern and target plasticization time are set.
To and each coefficient value k ₁ , k ₂ , k ₃ are set by the corresponding backward speed pattern setter 52, target plasticization required time setter 50, and coefficient setter 54, respectively. Further, 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 S13 _o , S14 _o , and S15 _o output from the correction value calculator 48 is set to the corresponding adder 58A, 58 .
Switch to the position where it supplies to B and 58C. Then, in this state and during the plasticizing operation of the molding material, the injection molding operation is performed while outputting the control signals S2, S3, and S4 according to the control patterns obtained during the molding of the non-defective product. Let's do it.

In this way, during the plasticizing operation of the molding material, each adder _58A , 58 selected by the change-over switch mechanism 56 is
Corresponding correction value signals S13 _o , S14 _o , S15 _o are supplied from the correction value calculator 48 to B and 58C, so that the injection screw 10 retracts the next divided section ΔS _o+1. In the case where at least one of the rotational speed and back pressure of the injection screw 10 and the rotational speed of the feed screw 16 is corrected by the correction value signal S2,
The actual retraction time T _o+1 of the injection screw 10 in the divided section ΔS _o+1 is controlled by S3 and S4.
Regardless of variations in the particle size of the molding material supplied within the molding material, variations in the biting state of the injection screw 10 into the molding material, or substantial changes in L/D during the plasticizing operation, the dividing section ΔS _o+1 This accurately matches the target required retreat time To _o+1 calculated for

In other words, the actual plasticization time Tr required for plasticizing the molding material is
Regardless of variations in the particle size of the molding material supplied within the molding material, variations in the biting state of the injection screw 10 into the molding material, or substantial changes in L/D during the plasticizing operation, the target plasticization time setting device Therefore, even when performing precise and stable molding, the molding time due to variations in the plasticization time (Tr) always matches the target plasticization time To for molding a good product set in It is possible to effectively suppress the occurrence of variations in products, and it is possible to stably mold molded products of good quality.

Here, if the backward speed pattern has a constant or approximately constant slope as shown in FIG. Then, for example, the target retraction required time To _o and the retraction speed change ratio _Co in each divided section ΔS _o of the metering stroke S are determined as follows.

That is, the target retraction speed of the injection screw 10 in the first divided section ΔS ₁ of the metering stroke S is
V ₁ and the value in the last divided section ΔS _N is V _N , then the injection screw 1 in the metering stroke S
Since the average speed of 0 is expressed as (V ₁ +V _N )/2, the target plasticization time To is expressed by the following equation (1).

Assuming that To=2S/V ₁ +V _o (1) V _N /V ₁ =A (2), V ₁ can be expressed by the following equation (3).

V ₁ = 2S / To (A + 1) ... (3) On the other hand, if the target backward speed in the nth division ΔS _o of the metering stroke S is V _o , then this
Since V _o is expressed as the following equation (4), the target required retreat time To _o in the divided section ΔS _o is as follows (5)
It can be expressed as follows.

V _o =V ₁ +V _N -V ₁ /N-1(n-1) ...(4) To _o =(N-1)S/N(N-1)V ₁ +N(n-1)(V
_N −V ₁ ) ...(5) Therefore, by substituting equations (2) and (3) above into equation (5) and rearranging, the target required retreat time To _o is as follows (6)
It can be expressed as follows.

To _o = To(A+1)(N-1)/2N[(N-1)+(A
-1) (n-1)]...(6) On the other hand, the backward speed change ratio corresponding to the divided section ΔS _o
For C _o (=V _o+1 /V _o ), the speed difference ΔV _o between adjacent divided sections is always approximately constant, and V _o+1 , V _o and ΔV are expressed by the following equations (7) to (9), respectively. From what is shown below (10)
It can be obtained according to the formula.

V _o = V ₁ − (n-1) ΔV … (7) V _o+1 = V _{1 − n} ΔV … (8) ΔV = V ₁ − V _o / (N-1) = (1-A) / ( N
−1) V ₁ …(9) C _o =V _o+1 /V _o =(N-1)-n(1-A)/(N-1
)-(n-1)(1-A)...(10) In other words, if the backward speed pattern has a constant or almost constant slope as shown in Figure 2, the backward speed pattern In the speed pattern setting device 52, input the constant A expressed by the above formula (2) as data specifying the backward speed pattern, and
By performing calculations such as the above equations (6) and (10) in the target backward time required/reverse speed change ratio calculator 44, the target backward required time To _o and reverse speed change ratio C corresponding to each divided section ΔS _o are calculated. It is possible to find _o .

In addition, in the correction calculator 48, for example, when only one of the correction value signals is supplied to the adder 58, the time deviation ΔT _o detected by the subtracter 46, the coefficient setter 54 Each coefficient set in
k ₁ , k ₂ , k ₃ , and the target backward time required/reverse speed change ratio calculated by the reverse speed change ratio calculator 44
C _o 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 example, and it goes without saying that the present invention should not be construed as being limited to this specific example.

For example, the present invention can be applied to a case where the reverse speed pattern set by the reverse speed pattern setting device 52 does not have a constant or substantially constant slope in the above embodiments. .

Further, in the embodiment described above, the target plasticization required time To and the backward speed pattern supplied to the target backward required time/reverse speed change ratio calculator 44 are set by the setter 5.
Although the case where the values are set at 0 and 52 has been described, it is also possible to have them supplied from the control device 36 without setting them using the setting devices 50 and 52. In addition, each target retraction time To _o and retraction speed change ratio C _o corresponding to each divided section ΔS _o are sequentially stored in the control device 36 during molding of a good product, and these target retraction time To _o and retraction speed change ratio are stored.
It is also possible to read out C _o as necessary and input it directly to the subtracter 46 and the correction value calculator 48 from the control device 36.

Further, in the above embodiment, a case has been described in which various data are obtained during molding of a good product prior to the injection molding operation, but if such data is obtained in advance, each control signal S2 output from the control device 36 may be used. , S3, S4, etc. and their data are set into a predetermined program, and by setting that program in the control device 36, it is also possible to immediately perform the desired injection molding operation. .

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

In addition, various modifications and changes may be made without departing from the spirit of the present invention, although they will not be listed one by one.
Things that can be implemented with modifications, improvements, etc. are:
It goes without saying.

[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, and FIG. 2 is a graph showing an example of the backward speed pattern of the injection screw. be. 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, 3
8: N-divided signal generator, 42: Actual backward required time measuring device, 44: Target backward required time/reverse speed change ratio calculator, 46: Subtractor, 48: Correction value calculator, 5
0: target plasticization time setting device, 52: backward speed pattern setting device, 54: coefficient setting device, 56: changeover switch mechanism, 58A, 58B, 58C: adder.

Claims (1)

[Scope of Claims] 1. By rotating the injection screw while applying a predetermined back pressure with the injection cylinder to the injection screw fitted in the heating cylinder, the rotation of the feed screw of the raw material supply device is controlled. Therefore, the predetermined molding material supplied into the heating cylinder is plasticized and guided to the front of the injection screw, while the injection screw is retreated by the molding material guided to the front of the injection screw. In an in-line screw type injection molding machine that measures the molding material to be injected by regulating the rotational speed of the injection screw during the plasticizing operation of the molding material, the injection cylinder A plasticization control method, wherein the back pressure applied to the screw and the rotational speed of the feed screw in the raw material supply device are controlled according to control patterns determined in relation to the movement position of the injection screw, respectively. , 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 each determined at the time of molding a non-defective product. At the same time, the retraction stroke of the injection screw is divided into a plurality of sections based on the retraction speed pattern of the injection screw during molding of a good product and the required time for plasticization. , calculate the target required time for retraction of the injection screw, compare the actual required time for retraction of the injection screw to actually retract each divided section with the target required time for retraction, and determine the required time for retraction in the next divided section. The rotational speed of the injection screw is controlled according to each of the control patterns, and the injection cylinder is operated on the injection screw according to the comparative difference so that the actual time required for retraction matches the target time required for retraction. 1. A method for controlling plasticization in an in-line screw injection molding machine, comprising correcting at least one of the applied back pressure and the rotational speed of a feed screw in the raw material supply device.