JPH05337946A - Hot-runner color changing method - Google Patents

Abstract

PURPOSE:To shorten time to be taken for changing color safely and reduce the working cost without prolonging bound time of an operator to be taken for operation. CONSTITUTION:A plasticizing device is moved to a plasticizing backward limit position. A first purging is performed under a first color change condition so as to perform color changing of a heating cylinder. A second purging is performed under a second color change condition so as to perform the color changing of the heating cylinder. Next, the plasticizing device is moved to a plasticizing forward limit position so as to confirm a nozzle touching, color change molding is performed under a color change molding condition, and mass molding is performed under a mass molding condition. During the color changing of the heating cylinder, a hot-runner temperature up signal is outputted to a hot-runner controller, the temperature of the hot-runner is raised, and the color, change molding is performed in that state. Accordingly, when the color change molding is to be started, the temperature of the-hot runner is raised sufficiently, so that residual resin can be discharged easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot runner color changing method for an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, a resin which has been heated and melted in a heating cylinder and fluidized is injected into a cavity through a hot runner in the mold, and then cooled and solidified therein, and then the mold. In the injection molding machine that opens the mold to take out the molded product, when changing the color of the resin or the resin itself, change the color or change the resin (hereinafter, simply “color change”).
That. ) Is done.

First, the colored resin melted in the heating cylinder is injected under high pressure, and purging is performed with the next resin or the resin dedicated to purging until the color completely changes. The purging consists of measuring and injection operations, and by repeating the purging, the resin accumulated in the heating cylinder or attached to the screw is removed.

Subsequently, the resin accumulated in the hot runner is completely discharged, and then the inside of the heating cylinder is replaced with the next resin. In this case, the resin in the hot runner is discharged after continuous molding or by breaking the mold to remove the solidified layer. FIG. 2 is a time chart showing a conventional hot runner color changing method by continuous molding.

First, the color of the heating cylinder is changed by purging. The purging is carried out in two stages for the screw main body part and for the screw head and the injection nozzle. For the purging of the screw body part, the measured value is 1 / of the maximum stroke of the screw.
The injection speed and injection pressure should be low for safety reasons. The purging of the screw head and the injection nozzle has a measured value of 5 to 10 [mm],
Increase the injection speed and injection pressure. The molten resin removes the resin adhering to the inner wall of the heating cylinder and the surface of parts such as the screw head and the injection nozzle.

Next, the color of the hot runner is changed by molding. In this case, the resin that adheres to the inner wall of the hot runner and forms the solidified layer is removed. Therefore, the temperature of the manifold, the body, etc., that is, the temperature of the hot runner is raised to the extent that resin burning does not occur, and molding is performed for about 50 to 1000 shots. Then, the temperature of the hot runner is changed to a normal molding temperature and continuous molding is performed to form a solidified layer of the next resin.

FIG. 3 is a time chart showing a conventional hot runner color changing method by removing the solidified layer. in this case,
First, the color of the heating cylinder is changed, and molding is performed for about 5 shots. Then, the temperature of the hot runner is lowered to the heat distortion temperature. Then, the mold plate and the back plate of the mold are split to remove the solidified layer.

Subsequently, the temperature of the hot runner is raised to the molding temperature, the color of the hot runner is changed, the mold is assembled, and then the molding is carried out.

[0009]

However, in the above-mentioned conventional hot runner color changing method, the operator needs to operate the injection molding machine every time each process is executed, and the time required for the operation is restricted. That is, downtime becomes long. Further, since it is difficult to set a program for changing the color of the heating cylinder, not only time loss occurs but also it takes time to remove the resin accumulated in the injection nozzle of the heating cylinder.

Further, since the temperature of the hot runner is manually set, there is a possibility that it may be erroneously set, and it is dangerous that the resin burns. Then, especially in the hot runner color changing method by removing the solidified layer, skill is required for the die splitting work, and the work cost becomes high.
The present invention solves the problems of the conventional hot runner color changing method so that the operator does not have to be restrained for a long time for the operation, the time for changing the color is short, the operation is safe, and the work is stable. It is an object to provide a hot runner color changing method with low cost.

[0011]

Therefore, in the hot runner color changing method of the present invention, the plasticizing device is moved to the plasticizing backward limit position, and the first number of shots is performed the first time by the first color changing condition. The purging is performed to change the color of the heating cylinder, and the purging is performed a second time for the predetermined number of shots under the second color changing condition to change the color of the heating cylinder.

When the color change of the heating cylinder is completed, the plasticizing device is moved to the plasticizing forward limit position to confirm the nozzle touch, and the color change molding is performed for the predetermined number of shots according to the color change molding condition, and the mass production molding condition is set. Mass production molding is performed by the planned number of shots. During the color change of the heating cylinder, a hot runner temperature raising signal is output to the hot runner controller to raise the temperature of the hot runner to a preset temperature, and color change molding is performed in that state.

[0013]

According to the present invention, as described above, the plasticizing device is moved to the plasticizing backward limit position, and the purging is performed the first time by the predetermined number of shots according to the first color changing condition to change the color of the heating cylinder. Then, the heating cylinder is color-changed by performing the second purging by the expected number of shots under the second color-changing condition. Therefore, the resin discharged from the injection nozzle by the purging is dropped as a purge lump.

When the color change of the heating cylinder is completed,
The plasticizer is moved to the plasticization advance limit position, the nozzle touch is confirmed, color change molding is performed for a predetermined number of shots according to the color change molding conditions, and mass production molding is performed for a predetermined number of shots according to the mass production molding conditions. During the color change of the heating cylinder, a hot runner temperature raising signal is output to the hot runner controller to raise the temperature of the hot runner to a preset temperature, and color change molding is performed in that state. Therefore, when the color change molding is started, the temperature of the hot runner has risen sufficiently, and the number of shots of the color change molding can be reduced.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 is a time chart of a hot runner color changing method showing an embodiment of the present invention, FIG. 4 is a sectional view of an injection nozzle used in a conventional hot runner color changing method,
FIG. 5 is a cross-sectional view of an injection nozzle used in the hot runner color changing method of the present invention, and FIG. 6 is a discharge state diagram of purge lumps in the hot runner color changing method of the present invention.

As shown in the figure, the hot runner is color-changed by performing purging twice and color-changing molding once in each cycle, and mass production molding is started after the color-changing molding is performed. Is becoming Therefore, each color change condition in each purging, each color change molding condition in color change molding, mass production molding condition in mass production molding, and the expected number of shots in each process are preset by the setter and stored in the memory. There is.

The memory stores two color change conditions, one color change molding condition, and one mass production molding condition for one color change. For example, when three color changes are performed, 12 The individual conditions are stored and sequentially read out every time the process changes. Therefore, the injection molding machine can automatically perform the first purging, the second purging, the color change molding, and the mass production molding according to the conditions stored in the memory, the set number of shots, and the like. it can.

First, when the fully automatic mode is selected, the plasticizing device is retracted, and the injection nozzle is placed at the plasticizing retract limit position farthest from the fixed platen. The plasticizing device is driven by an electric motor, a hydraulic cylinder or the like to move backward, and a limit switch or the like detects the plasticizing backward limit position, and is stopped. Then, purging is started and the color of the heating cylinder is changed. At this time, air blow is performed in front of the injection nozzle. That is, air is blown to the resin discharged from the injection nozzle by purging, and the resin is forcibly deflected by the air and falls as a purge lump on the chute.

Since the purging is carried out twice and the color changing conditions are made different, the amount of resin discharged can be reduced. When the first purging is completed, the hot runner temperature rising signal is output from the controller of the injection molding machine to the hot runner controller before the second purging is started. Upon receiving the hot runner temperature rising signal, the hot runner controller issues a command to the heating device to heat the hot runner such as the manifold and the body.

During this time, the second purging is being performed, and when the purging of the planned number of shots is completed, the hot runner temperature rising signal is turned off. Subsequently, the color change molding is performed at a high pressure for a predetermined number of shots, and the color change of the hot runner is performed. Therefore, after measuring to the measurement value setting position of the color change molding condition, the plasticizing device moves forward and moves to the plasticization forward limit position, and when the nozzle touch is confirmed, the color change molding is started. In this case, since the temperature inside the hot runner has risen to a temperature sufficient for color change molding, the amount of resin discharged can be reduced. In addition, since the heating of the hot runner is stopped while color change molding is being performed,
The temperature of the hot runner falls naturally to the normal molding temperature.

When the color change molding is performed for a predetermined number of shots, mass production molding is automatically started, and the mass production molding is performed for a predetermined number of shots. When the mass-production molding is completed, the mold clamping device ejects the molded product by the ejector pin and then closes the mold to stand by without generating a mold clamping force. Next, the plasticizing device is automatically retracted and moved to the plasticization retracted limit position to prepare for the next color change.

In this case, at the same time when the first purging is started, the control device commands the liquid color supply device to supply the liquid color for coloring into the heating cylinder. Then, after the second purging and color change molding processes, the mass production molding process is started. During mass production molding, at a predetermined point before the scheduled shot number ends,
The following liquid colors are available. Therefore, the amount of resin discharged during purging can be reduced.

In this embodiment, the case of performing color change for changing the color of the molded article is explained.
It can also be applied to the case of changing the resin for changing the resin itself. Next, the injection nozzle will be described. In FIG. 4, 11 is a heating cylinder, and 12 is an injection nozzle attached to the tip of the heating cylinder 11. The injection nozzle 12 is formed with a tapered and tapered resin flow channel 13 at the center, and a nozzle port 14 is formed at the tip of the resin flow channel 13. The nozzle opening 14 has a constant diameter in the longitudinal direction.

Further, in FIG. 5, 11 is a heating cylinder, and 16 is an injection nozzle attached to the tip of the heating cylinder 11. The injection nozzle 16 has a tapered and tapered resin flow channel 17 formed at the center thereof, and a nozzle port 18 is formed at the tip of the resin flow channel 17. The nozzle opening 18 is tapered unlike the conventional nozzle opening 14 (see FIG. 4), and the diameter is not constant in the longitudinal direction, and the diameter increases toward the tip.

Therefore, it is possible to suppress the resin from staying at the time of purging, and the amount of resin discharged is reduced. Next, the discharge of the purged mass will be described. In FIG. 6, 11 is a heating cylinder, 16 is an injection nozzle, 21 is a fixed platen, and 22 is a plasticizer.
The plasticizing device 22 is located at a plasticizing retracted limit position apart from the fixed platen 21. Reference numeral 23 is an air blow device, and the air blow device 23 has an air discharge port provided in front of and above the injection nozzle 16 at the plasticizing backward limit position of the plasticizing device 22.

Then, purging is performed and the resin is discharged from the injection nozzle 16, but at this time, air is blown from the air discharge port. The resin is deflected downward by the air, and the fixed platen 21 and the sprue bushing 25
Purge lumps 27 fall onto the chute 26 without coming into contact with. A cooling pipe 28 is embedded in the chute 26, and cooling water is supplied to the cooling pipe 28. Therefore, the purge mass 27 that has dropped onto the chute 26 slides on the chute 26 without sticking to the chute 26 and is discharged into the purge receiving box 30.

The present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the present invention, and these are not excluded from the scope of the present invention.

[0028]

As described in detail above, according to the present invention, the plasticizing device is moved to the plasticizing backward limit position and the first purging is performed for the predetermined number of shots under the first color changing condition. The heating cylinder is color-changed, and the heating cylinder is color-changed by performing the second purging by the expected number of shots under the second color-changing condition. Therefore, the resin discharged from the injection nozzle by the purging is dropped as a purge lump.

When the color change of the heating cylinder is completed,
The plasticizer is moved to the plasticization advance limit position, the nozzle touch is confirmed, color change molding is performed for a predetermined number of shots according to the color change molding conditions, and mass production molding is performed for a predetermined number of shots according to the mass production molding conditions. During the color change of the heating cylinder, a hot runner temperature raising signal is output to the hot runner controller to raise the temperature of the hot runner to a preset temperature, and color change molding is performed in that state. Therefore, when the color change molding is started, the temperature of the hot runner has sufficiently risen, and the accumulated resin can be easily discharged. Therefore, the number of shots required for color change molding is reduced, and the amount of resin discharged can be reduced.

Further, since the planned number of shots for each process is set in advance, each process can be performed automatically, and the time for restraining the operator is shortened. further,
Since the temperature inside the hot runner is automatically raised to a preset temperature, the hot runner will not be overheated due to an erroneous setting or the like, and resin burning will not occur.

[Brief description of drawings]

FIG. 1 is a time chart of a hot runner color changing method according to an embodiment of the present invention.

FIG. 2 is a time chart showing a conventional hot runner color changing method by continuous molding.

FIG. 3 is a time chart showing a conventional hot runner color changing method by removing a solidified layer.

FIG. 4 is a sectional view of an injection nozzle used in a conventional hot runner color changing method.

FIG. 5 is a sectional view of an injection nozzle used in the hot runner color changing method of the present invention.

FIG. 6 is a diagram showing the discharge state of purged mass in the hot runner color changing method of the present invention.

[Explanation of symbols]

 11 Heating Cylinder 16 Injection Nozzle 22 Plasticizer 27 Purge Mass

Claims (1)

[Claims] 1. A color changing of a heating cylinder is performed by (a) moving a plasticizing device to a plasticizing backward limit position, and (b) purging a first number of times by a predetermined number of shots according to a first color changing condition. (C) The second color changing condition is used to perform the second purging for the predetermined number of shots to change the color of the heating cylinder, and (d) the plasticizing device is moved to the plasticizing forward limit position to perform the nozzle touch. (E) The color change molding is performed for the expected number of shots according to the color change molding conditions, (f) The mass production is performed for the expected number of shots according to the mass production molding conditions, and (g) During the color change of the heating cylinder. A hot runner color changing method comprising outputting a hot runner temperature raising signal to a hot runner controller to raise the temperature of the hot runner to a preset temperature.