JPH0446731B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for changing resin in an injection molding machine.

(Prior art) Figure 3 shows a side sectional view of a conventional injection molding machine.
1 is a heating cylinder, 2 is a screw, 3 is a band heater, 4 is a thermocouple, 5 is a nozzle, 6 is a hopper, 7
indicates a thermometer.

Now, the raw material from the hopper 6 falls into the interior 1a of the heating cylinder 1 due to its own weight, and the raw material from the hopper 6 falls into the interior 1a of the heating cylinder 1.
While being kneaded by the rotation, the mixture is sent to the tip 1b of the heating cylinder 1 along the groove. At this time, the raw material is heated by the band heater 3 attached to the outer periphery of the heating cylinder 1, and the frictional heat generated by the kneading action is added to the raw material, causing the temperature to rise from the inside and become molten. As the molten resin is stored in the tip 1b of the screw 2, the reaction force (back pressure) pushes the screw 2 back.

The amount of retraction is sensed by a limit switch (not shown) or the like, and the rotation of the screw 2 is stopped at a set position to determine the amount of injection. After this, the mold (not shown) is closed and the injection process begins.

In this injection process, an injection force is applied to the screw 2 by a hydraulic cylinder (injection cylinder) not shown, and the screw 2 acts as an injection plunger and is injected into the mold from the nozzle 5 at the tip of the heating cylinder 1. Inject molten resin. The band heaters 3 are divided into three to five groups, each group forming a heating zone, and a thermocouple 4 and a thermometer 7 are provided corresponding to each zone.

In recent years, high-mix, low-volume production has progressed in injection molding, and the frequency of changing the type of resin (hereinafter referred to as resin change) has increased. Resin replacement is generally performed by the following method.

(1) Remove all the resin in the hopper 6 using the discharge port 6a.

(2) Remove the resin remaining in the heating cylinder 3 by repeating screw rotation and injection.

(3) Put new resin into the hopper 6 and repeat the screw rotation and injection until the resin is replaced.

By the way, in order to replace the resin that has accumulated and adhered inside the screw and cylinder by plasticizing the new resin, it is necessary that the melt viscosity of the new resin is higher than that of the old resin.

Therefore, in general, it is easy to change from a resin with a low melting point to a resin with a high melting point. This is because a resin with a high melting point naturally has a high melt viscosity at the same temperature.

In injection molding machines, resins with different melting points and molding temperatures are used. Here, the relationship between the melting point or softening temperature of the resin and the molding temperature will be explained with reference to FIG. Generally, crystalline resins have a melting point, but amorphous resins do not have a melting point, so the softening temperature at which the rigidity decreases and deformation occurs is used instead of the melting point. As shown in FIG. 4, the molding temperature is divided into three groups, A, B, and C, in descending order of molding temperature.

First, A is generally a heat-resistant engineering plastic, B is a general-purpose engineering plastic,
C is called a general-purpose resin. Further, the line drawn below each resin name indicates the range of molding temperature with respect to the melting point or softening temperature of each resin on the vertical axis. The lower limit of the molding temperature is the temperature at which the melt viscosity reaches its maximum value at which injection into the mold is possible, and the upper limit is generally the temperature immediately before the resin deteriorates thermally. The melt viscosity of the resin in this range decreases as the temperature increases, but the rate of decrease differs depending on the characteristics of the resin.
In addition, the dotted line drawn diagonally in the center in Figure 4 is
This is the line where melting point or softening temperature = molding temperature.

(Problems to be Solved by the Invention) The resin is changed from heat-resistant engineering plastics of group A, which have a high molding temperature, to general-purpose engineering plastics of group B, which have a low molding temperature, or general-purpose resins of group C, which have a low molding temperature. However, since the melt viscosity of group A resin is always high at the cylinder temperature when changing the resin, the resin of group A that has accumulated and adhered to the screw 2 and heating cylinder 1 is used to plasticize the resin of group B and C.・There were problems such as it could not be removed by repeated injections and it was difficult to replace it with Group B or C resin.

The present invention aims to provide a resin replacement method and apparatus that can solve the above-mentioned conventional problems.

(Means and effects for solving the problem) Therefore, when changing the resin from heat-resistant engineering plastics to general-purpose engineering plastics or general-purpose resins, the present invention provides for glass whose molding temperature range overlaps with the molding temperatures of both resins. After changing the resin to a low-viscosity resin containing fillers such as fibers, the resin is then changed to a general-purpose engineering plastic or a general-purpose resin, and this is the means and action to solve the problem. It is something.

The present invention also provides a hopper for storing heat-resistant engineering plastics and general-purpose engineering plastics or general-purpose resins, a temporary replacement resin storage device for storing low-viscosity resin containing fillers, and a system for switching from heat-resistant engineering plastics to general-purpose engineering plastics or general-purpose resins. edge,
It has a control device that performs temperature control of a heating cylinder corresponding to each resin and sequence control such as supply and stop of each resin, and this is used as a means for solving the problem.

(Embodiments) The present invention will now be described with reference to the embodiments shown in the drawings. FIG. 1 shows an embodiment of the method and apparatus of the present invention. Incidentally, since the members numbered 1 to 6 and 6a in the figure are the same as those shown in FIG. 3, detailed explanation thereof will be omitted here. Next, the differences from FIG. 3 will be explained. Reference numeral 10 denotes a control device that controls each device described below so as to automatically carry out the resin changing method of the present invention. 11 is a temporary replacement resin storage device containing a low viscosity resin containing a filler such as glass fiber; 12 and 13 are resin supply devices consisting of solenoid valves and feed screws that control resin dropping on and off; and 14 is a resin dropping device. It is a hole.

The control device 10 has the configuration shown in FIG. 2, and includes an operation panel 20, a main CPU 21 that sends operation commands to the resin supply devices 12 and 13, and transfers operation commands and data to a temperature control CPU 22 and a screw operation control CPU 23. , interface 2
It consists of 4, 25, and 26.

Next, to explain the operation, for example, after the molding of heat-resistant engineering plastic such as polyetherimide is completed, the resin in the hopper 6 is discharged from the discharge port 6.
Remove from a. Next, as a low-viscosity resin containing a filler such as glass fiber, for example, a high-flow grade polycarbonate mixed with glass fiber (hereinafter referred to as replacement resin) is used, and the replacement resin is stored in the temporary replacement resin storage device 11. put it in.

Next, from the operation panel 20 of the control device 10, the resin change operation time, the screw rotation speed during the resin change operation, the back pressure, the heating cylinder temperature (340 degrees Celsius), and the example of the general-purpose resin that is the target resin for resin change in this example. Set the polyethylene molding temperature (260℃).

Thereafter, polyethylene is put into the hopper 6, and a switch on the operation panel 20 outputs a signal to start the resin change operation. And use this start signal as the main
When the CPU 21 inputs the input, it instructs the temperature control CPU 22 to set the heating cylinder temperature at the time of resin change.

The temperature control CPU 22 compares the temperature detected by the thermocouple 4 with the set temperature (340°C) and controls the band heater 3 so that the temperature of the heating cylinder 1 reaches the set temperature (340°C). Here, the set temperature (340℃) is the molding temperature of polyetherimide,
The molding temperatures of the replacement resins are selected from a range that overlaps with each other.

Next, when the temperature of the heating cylinder 1 reaches the set temperature (340°C), the temperature control CPU 22
A temperature change completion signal is output to the main CPU 21.
The main CPU 21 sends a supply start signal to the resin supply device 13 via the interface 25, and also outputs an operation command to the screw operation control CPU 23.

Next, according to the output, the resin supply device 13 supplies the replacement resin to the heating cylinder 1 through the resin drop hole 14.
Supplied to the interior 1a. At the same time, a screw driving device (not shown) is controlled by a command from the screw operation control CPU 23 to rotate the screw 2,
The injection is repeated.

Although the substituted resin has a lower viscosity than polyetherimide, the glass fibers mixed in it have a high hardness, so it acts similar to an abrasive and removes the high viscosity that adheres and stays inside the screw 2 and heating cylinder 1. Heat-resistant engineering plastics such as polyetherimide can be easily replaced with resin.

When the resin replacement operation time for each pair reaches the resin replacement operation time setting value, the main CPU 21 instructs the screw operation control CPU 23 and the resin supply device 13 to stop the screw operation and the supply of replacement resin. The main CPU 21 also instructs the temperature control CPU 22 to set the polyethylene temperature (260° C.). The temperature of the heating cylinder 1 decreases due to the operation of the temperature control CPU 22.

Next, the temperature of heating cylinder 1 is the set value (260℃)
When the temperature control CPU 22 reaches the main
Outputs a completion signal to the CPU 21. Main CPU2
1 instructs the resin supply device 12 to supply the polyethylene in the hopper 6 to the interior 1a of the heating cylinder 1. At the same time, the main CPU 21 commands the screw operation control CPU 23, and the CPU 23 repeats the rotation and injection of the screw 2.

The high flow grade polycarbonate used as the replacement resin has a low viscosity over the molding temperature, so it can be easily replaced with a general-purpose resin such as polyethylene. This resin change is carried out for a time according to the resin change operation time setting value, and when it is completed, the rotation and injection of the resin supply device 12 and the screw 2 are stopped by a command from the main CPU 21.

In addition, although the above example shows the resin change from polyetherimide to polyethylene, it is possible to change from the heat-resistant engineering plastic of group A shown in FIG. It is also easy to change the resin to a C group general-purpose resin.

Also, unlike the above embodiment, instead of setting the resin change operation time, a level meter (not shown) is provided inside the temporary replacement resin storage device 11 and the hopper 6, and the level meter detects the resin inside the temporary replacement resin storage device 11 and the hopper 6. The resin change control device may stop each resin change operation when the height of the resin decreases to a preset height.

(Effects of the Invention) As described above in detail, according to the present invention, it is possible to easily change the resin from heat-resistant engineering plastic to general-purpose engineering plastic or general-purpose resin. In other words, since the low-viscosity resin used as the replacement resin contains fillers such as glass fibers, heat-resistant engineering plastics can be easily peeled off and discharged, and since the replacement resin has a low viscosity, it can be used as a general-purpose engineering plastic or general-purpose resin. Since the resin can be changed easily, productivity can be improved.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a resin changing device for an injection molding machine showing an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the control device, and FIG. 3 is a side sectional view of a conventional injection molding machine. FIG. 4 is an explanatory diagram showing the relationship between resin melting point or softening temperature and molding temperature. Explanation of main parts of the figure, 10...control device, 11
...Resin storage device for temporary replacement, 12, 13...Resin supply device, 14...Resin drop hole.

Claims (1)

[Claims] 1. When changing the resin from a heat-resistant engineering plastic to a general-purpose engineering plastic or a general-purpose resin, the resin is first changed to a low-viscosity resin containing a filler such as glass fiber whose molding temperature range overlaps with the molding temperature of both resins. 1. A method for changing resin in an injection molding machine, which comprises performing the following steps, and then changing the resin to a general-purpose engineering plastic or a general-purpose resin. 2. A hopper for storing heat-resistant engineering plastics and general-purpose engineering plastics or general-purpose resins, a temporary replacement resin storage device for storing low-viscosity resin containing fillers, and a hopper for storing heat-resistant engineering plastics and general-purpose engineering plastics or general-purpose resins, and a A resin changing device for an injection molding machine, comprising a control device that performs temperature control of a heating cylinder corresponding to the resin and sequence control such as supplying and stopping each resin.