JP3037932B2 - Control method of injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling an injection molding machine, and more particularly to a method for controlling an injection molding machine capable of shortening a cycle.

[0002]

2. Description of the Related Art In a conventional injection molding machine of this kind, a screw in a heating cylinder is advanced by advancing a screw in a heating cylinder after a mold clamping process is completely completed (at the time of completion of retightening). The molten resin was injected and filled into the cavity of the mold, and thereafter, the screw was held at the most advanced position to hold the pressure for a predetermined time. Also, after the end of the pressure-holding process, the screw is rotated, and the resin pellets supplied from the hopper to the rear of the screw are transferred forward while kneading and plasticizing, and the back pressure is controlled accordingly. He was performing a charging process to retract the screw. Also, depending on the charging time and cooling time,
If this time factor allows, the mold opening is started in the middle of the charging process, and the eject mechanism ejects the product in the middle of the mold opening process.
Then, the mold clamping process is started after the completion of the mold opening process and the return process of the eject mechanism. When performing suck-back control to prevent drooling, a suck-back period is set between the end of the charging process and the start of mold opening, during which the screw is forcibly retracted by a small amount. In this case, the suck-back process is performed (when the suck-back is performed, a partially combined operation of the charging process and the mold opening process is not performed).

[0003]

As is well known, in such an in-line screw type injection molding machine, roughly, a driving source for opening and closing a mold, a driving source for charging (for rotating a screw), and a driving source for injection. In many cases, four drive sources, ie, a drive source (for forward and backward movement of the screw) and a drive source for an eject mechanism, are provided, and by selectively controlling the drive of the four drive sources, the above-described steps are executed. Is done.

By the way, in a conventional injection molding machine,
Each of the above-mentioned driving sources is configured such that the operation by another driving source is started after the operation of one driving source is generally finished. Composite operation of eject operation (ejection ejection operation),
Alternatively, the above-described composite operation of the charging operation and the mold opening operation has been conventionally known as a composite operation by two driving sources.

Japanese Utility Model Application Laid-Open No. 62-102616 discloses a drive source for a mold opening / closing mechanism comprising a toggle link mechanism, and a drive source for the mold opening / closing mechanism selectively connected via an electromagnetic clutch or the like. In a toggle-type injection molding machine having an eject mechanism, at a predetermined time after the start of mold opening,
By turning on the electromagnetic clutch, the ejector ejecting stroke is started, and by turning on the electromagnetic clutch during the mold closing stroke, the ejector returning stroke is performed at the same time, and the ejector returning stroke is completed before the die touch. In this manner, it has been known that a combined operation of the mold clamping and the eject return is performed. However, in the technology disclosed in the prior application, since the eject mechanism is driven via the electromagnetic clutch by the drive source for opening and closing the mold, the start of the eject return operation cannot be performed before the start of the mold clamping stroke, For this reason, at the time of the combined operation of the eject return and the mold clamping, there is a possibility that the eject pin or the like hits the fixed mold and is damaged.

As described above, the composite operation of the mold opening operation and the eject ejection operation or the composite operation of the mold clamping operation and the eject return operation has been conventionally known. The entirety of the opening and closing operations) and the entirety of the ejecting operation (ejection ejecting and ejecting return operations) are efficiently combined within the safety range of the mechanism, thereby shortening the molding cycle as much as possible. Has not been considered at all.

[0007] The present invention has been made in view of the above points,
Its purpose is to achieve a compact molding cycle by effectively performing a combined operation of the mold opening / closing operation and the ejecting operation within the safety range of the mechanism, thereby increasing the mass production efficiency. An object of the present invention is to provide a control method for an injection molding machine.

[0008]

According to the present invention, a drive source for a mold opening / closing mechanism (for a mold clamping mechanism) and a drive source for an eject mechanism are independently provided so as to achieve the above object. In the control method of the injection molding machine, in which the eject and the eject can be controlled independently, when the parting surface is opened by a predetermined amount in the middle of the mold opening process, the eject mechanism is ejected and the operation is started, thereby opening the mold and ejecting the eject. A partial composite operation of eject return and mold clamping by detecting that the movable part of the ejector has returned to the safe range in the middle of the return stroke of the eject mechanism and starting the mold clamping stroke. and be executed, eject mechanism, after completion of the ejection projecting stroke, immediately enters the ejection return stroke, mold opening and closing the Eje <br/> transfected return stroke period To, mold opening stroke is complete timing
And the timing at which the mold clamping process starts .

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 relate to one embodiment of the present invention, and FIG. 1 is an explanatory diagram showing an outline of an injection molding machine according to this embodiment.

In FIG. 1, reference numeral 1 denotes a base.
A plurality of tie bars 4 are arranged between the fixed die plate 2 installed above and the support board 3, and a movable die plate 5 is slidably fitted into the tie bars 4. A mold clamping cylinder 6 is fixed to the support board 3, and its piston rod 6a is connected to the movable die plate 5 via a toggle link mechanism 7, and the movable die plate 5 is moved by the forward and backward movement of the piston rod 6a. The fixed die plate 2
To move forward or backward. In addition, 8 is a fixed side mold attached to the fixed die plate 2, and 9 is a movable side mold attached to the movable die plate 5.

Reference numeral 10 denotes a heating cylinder, 11 denotes a screw disposed in the heating cylinder 10 so as to rotate and move forward and backward, 12 denotes a hopper for supplying a resin material, and 13 denotes a motor for driving the screw 11 to rotate. , 14 are injection cylinders (hydraulic cylinders) for controlling the forward and backward movement of the screw 11.

As is known, the resin material supplied from the hopper 12 to the rear end of the screw 11 is transported forward while being kneaded and plasticized by the rotation of the screw 11, and is transferred to the front end of the screw 11. As the fed molten resin is stored, the screw 11 retreats while controlling the back pressure, and when the molten resin stored on the tip side of the screw 11 reaches the amount of one shot,
The rotation of the screw 11 is stopped. Then, at a predetermined injection start timing, the screw 11 is driven forward so that the molten resin is injected into the cavity formed by the two dies 8 and 9 and then the pressure is maintained for a predetermined time. Has become. Thereafter, in a state where the resin injected into the mold is cooled and solidified, the mold is opened and ejected, and a product (molded product) is taken out. Reference numeral 15 denotes an eject mechanism for extruding a product from the movable mold 9 and includes a known eject pin and an appropriate drive source (for example, an air cylinder) for moving the eject pin back and forth.

20 is an injection stroke sensor, 21 is a screw rotation sensor, 22 is an injection pressure sensor, 23 is a mold opening / closing stroke sensor, 24 is an eject stroke sensor attached to the eject mechanism 15, and 25 is a temperature sensor. Measurement information from the sensors 20 to 25 and other sensors (not shown) is transmitted to an arithmetic and control unit described later via an input conversion circuit as needed. In addition,
The temperature sensor 25 is composed of a thermocouple or the like disposed on each part or nozzle of the heating cylinder 10. For convenience of illustration, only one temperature sensor 25 is illustrated, but a plurality of temperature sensors 25 actually exist. .

Numeral 30 denotes an arithmetic and control unit mainly composed of a microcomputer for controlling the entire injection molding machine, 31 denotes a key input device for inputting various commands to the arithmetic and control unit 30, and 32 denotes a processing by the arithmetic and control unit 30. A display device including, for example, a color CRT display for displaying a result, a display pattern for a setting mode created in advance, and the like;
Reference numeral 33 denotes a printer for printing out processing results and the like by the arithmetic and control unit 30.

The arithmetic and control unit 30 includes an input processing unit 3
4, an output processing unit 35, a molding sequence control unit 36, and the like, for controlling the automatic operation and automatic monitoring operation of the injection molding machine, displaying various display modes on the display device 32, or The printer 33 prints out desired data and the like. The arithmetic and control unit 30 is mainly composed of a microcomputer as described above.
Equipped with various I / O interfaces, ROM for storing main programs and fixed data, RAM for reading and writing measurement data and various flags, clock, MPU for overall control, clock and main memory as needed Is backed up by a battery. The arithmetic and control unit 30 controls and executes automatic operation of the injection molding machine based on a program created in advance.

That is, the molding sequence control unit 36 of the arithmetic and control unit 30 fetches the output from each of the above-mentioned sensors from the input processing unit 34 based on the molding process control program and the set condition values created in advance, and refers to them. While controlling the mold opening stroke, the ejecting stroke, the mold closing / tightening stroke, the injection / holding stroke, the charging stroke, and the like, and performing the injection by the control output signal sent from the output processing unit 35 to the driver circuit 37. Controls the drive source of each part of the molding machine.

Next, the operation of the injection molding machine of the present embodiment having the above configuration will be described with reference to FIG. FIG. 2 is an explanatory view showing one example of a molding cycle, and shows an example of a molding cycle for a lightweight and thin-walled molded product in which a cooling process is completed during a charge process.

As shown in FIG. 2, in this embodiment,
After the eject mechanism 15 projects the product, the eject mechanism 15 enters a return stroke (return stroke of an eject pin or the like), and the eject stroke sensor 24 confirms that the eject pin and the like have returned to a preset safety range. At this point, the arithmetic and control unit 30 drives the mold clamping cylinder 6 to start a mold clamping (mold closing) process. That is, to start the mold clamping stroke on the way of ejecting the return stroke, to perform some complex operation of eject return and clamping in period T ₁ of FIG. In the period T _1, as shown in FIG. 3, the movable die to eject pin 15b and the eject plate 15c of the eject mechanism 15 that is being returned in the direction of arrow A by the eject drive source 15a, which is driven by the mold clamping cylinder 6 Although the plate 5 moves forward in the direction of the arrow B in the opposite direction, there is no possibility that the eject pin 15b abuts on the fixed side member after the eject mechanism 15 has retreated to the safe range.

After the return stroke of the eject mechanism 15 is completed, the above-described mold clamping process proceeds, and the movable mold 9 comes into contact with the fixed mold 8 soon. After this, the mold clamping process still proceeds, and the process enters a so-called additional clamping process. In this embodiment, since the toggle link mechanism 7 is used as the mold clamping mechanism, for example, the tightening amount (the moving amount of the movable die plate 5 for the tightening) is 1.2 mm, and the mold clamping mechanism is used. If it is set to have a toggle characteristic of a force of 80 tons, the mold clamping force is increased up to about 73 tons even 0.1 mm before the completion of mold clamping (completion of tightening). The piston rod 6a of the mold clamping cylinder 6 is
It has been confirmed by the inventors' experiments that mm still leaves a stroke. Therefore, in the present embodiment, when a certain amount of mold clamping force is generated just before completion of mold clamping (for example, when 50 to 90% or more of the set mold clamping force is generated).
Then, the arithmetic and control unit 30 drives the injection cylinder 14 to advance the screw 11 to start the injection stroke. That is, to start the injection stroke the end of the clamping stroke, to execute the injection of some complex operations and clamping the period T ₂ of FIG. By doing so,
Before the retightening is completed (the set mold clamping force is reached), the molten resin starts to be injected and filled into the cavity, but a relatively small ejection force is sufficient until the filling is completed (before the pressure-holding stroke). The clamping force does not need to be very strong,
If the tightening is completed before the filling is completed and the pressure-holding process is started, injection and filling can be performed without any trouble, and the quality of the molded product is not adversely affected.

When the pressure-holding process at a predetermined time after the filling of the cavity is completed, the arithmetic and control unit 30 drives the motor 13 to rotate the screw 11 to start the charging process. As a result, the resin raw material (resin pellets) is transferred to the distal end of the screw 11 while being kneaded and plasticized. As the molten resin is stored at the distal end of the screw 11, the screw 11 retreats, and the stored molten resin becomes 1 When the amount of the shot has been reached (at the time of completion of the measurement), the rotation of the screw 11 is stopped, and the charging process is completed.

In this embodiment, immediately after the end of the charge stroke, the arithmetic and control unit 30 immediately retreats the screw 11 by the injection cylinder 14 by a small amount (suck back stroke) and opens the mold by the mold clamping cylinder 6. to initiate and process simultaneously, in period T ₃ in FIG. 2, so as to perform the combined operation of the suck back and mold opening. That is, as shown in FIG. 4, during the period T ₃ , the screw 11 is retracted from the charge completion position P ₁ to P _2, and the pressure of the molten resin 40 stored at the leading end side of the screw 11 is reduced to drool. Is to be prevented. At this time, immediately after the screw 11 starts to retreat, the resin pressure in the above portion is reduced, and even if the mold opening is started at the same time as the start of suckback, the mold opening / closing mechanism by the toggle link mechanism 7 does not open the mold. At the beginning of the stroke, the parting surface PL of the mold is closed by the amount of tightening described above, so that the solidified resin 41 is present in the sprue portion 42, so that the suck back and the mold There is no practical problem even if the composite operation of opening is executed.

After the suck-back process is completed, the mold opening process proceeds. During the mold opening process (at the time when the parting surface PL is opened by a predetermined amount), the arithmetic and control unit 30 operates.
Causes the eject mechanism 15 to protrude the product. Then, the eject mechanism 15 immediately enters the eject return stroke after the end of the product ejection stroke due to the forward movement, during which the mold opening stroke is completed. During the eject return stroke, the mold clamping stroke starts as described above. In this manner, a series of continuous molding cycles is repeated.

As described above, according to this embodiment, since the composite operation is executed during the periods T ₁ , T ₂ , and T ₃ , the actual cycle time can be reduced by about 2 seconds in total, and the mass production efficiency can be reduced. It becomes possible to greatly increase. The T
Needless to say, even if only one of the composite operations in the periods ₁ , ₂ , and ₃ is performed, the cycle can be shortened.

Further, in the present embodiment, the eject return stroke is started immediately after the completion of the eject ejection stroke, and the mold opening stroke is completed and the mold clamping stroke is started during the eject return stroke period. In other words, eject ejection and eject return are continued, and mold opening completion and mold clamping start are performed within a short eject return stroke period, so eject ejection completion from the ejection ejection start The time from completion of mold opening to the start of mold clamping is reduced as much as possible, and the entire mold opening / closing operation and the entire ejecting operation are controlled by a mechanism. The compound operation can be efficiently performed within the safe range of the above, and also in this regard, the molding cycle can be greatly reduced.

[0025]

As described above, according to the present invention, the mold opening / closing operation and the ejecting operation can be efficiently combined in the safe range of the mechanism to shorten the molding cycle. It is possible to provide a method of controlling an injection molding machine which improves the mass production efficiency, improves the yield per hour, and contributes to cost reduction. The value of this kind of in-line screw type injection molding machine is enormous.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an outline of an injection molding machine according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of a molding cycle in the injection molding machine according to one embodiment of the present invention.

FIG. 3 is an explanatory view showing a combined operation of a return operation of an eject mechanism and a mold clamping operation in the injection molding machine according to one embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a suck-back operation in the injection molding machine according to one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 2 fixed die plate 5 movable die plate 6 mold clamping cylinder 7 toggle link mechanism 8 fixed mold 9 movable mold 10 heating cylinder 11 screw 13 motor 14 injection cylinder 15 eject mechanism 30 arithmetic control unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/40-45/44 B29C 45/64-45/70 B29C 45/76-45/82

Claims (1)

(57) [Claims] 1. An injection molding machine in which a drive source for a mold opening / closing mechanism (for a mold clamping mechanism) and a drive source for an eject mechanism are independent from each other, and the mold opening / closing and the eject can be controlled independently. When the parting surface is opened by a predetermined amount in the middle of the opening process, the eject mechanism starts to protrude, and then a part of the combined operation of mold opening and eject protruding, and the eject movable part in the middle of the return process of the eject mechanism Detects the return to the safe range and starts the mold-clamping process, thereby performing an eject return and a partially combined operation of the mold-clamping.The eject mechanism, after completion of the eject-projecting stroke,
Immediately enter the eject return stroke and open / close the mold within the eject return stroke period when the mold opening stroke is completed
And a timing at which a mold clamping process is started .