JPH0929806A - In-line screw type injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of metering performance in the metering step in an in-line screw type injection molding machine in which the ratio S/D of the rated maximum injection stroke of a screw to the screw diameter is set to a specific value or more. SOLUTION: In the in-line screw type injection molding machine in which S/D is set to 5 or more, the last part of the external exposed area of a heating cylinder 2 is so managed at the temperature for guaranteeing that the metering velocity of the feed zone of the screw 3 to move resin material forward is not lowered even at the time of the metering step of retreating the screw 3 in the amount to meet the amount of rated maximum injection stroke. It is lower temperature managing area than the other site of the external exposure area of the cylinder 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-line screw type injection molding machine, and more particularly, to a temperature control technique for a heating cylinder in an injection molding machine in which the rated maximum injection stroke of the screw is set to 5 times the screw diameter or more. It is about.

[0002]

2. Description of the Related Art As is well known, in an in-line screw type injection molding machine, a screw in a heating cylinder, which is heated and controlled by a band heater, is rotated during a metering process (kneading / plasticizing / measuring process). As a result, the resin material is transferred to the tip side of the screw while kneading and plasticizing,
As the molten resin accumulates on the tip side of the screw, the screw moves backward while controlling the back pressure by the reaction force from the accumulated resin, and when a predetermined amount of resin is accumulated on the tip side of the screw (the screw is At the time of retreating to the measurement completion position), the screw rotation is stopped. After that, when the injection start timing is reached, the screw is rapidly advanced to inject and fill the mold with the molten resin.

In such an in-line screw type injection molding machine, the rated maximum injection stroke of the screw is generally set to about 3 to 4 times the screw diameter (screw diameter). Hereinafter, the rated maximum injection stroke of the screw is S, the screw diameter (screw diameter) is D, and the ratio between the rated maximum injection stroke S and the screw diameter D is called S / D.

In order to have the same injection capacity as that of the injection molding machine of S / D = 3 to 4 when the screw diameter is reduced with respect to the screw having the general design of S / D of 3 to 4 as described above. Need to set S / D to about 6, for example. An injection molding machine equipped with such a screw having a small screw diameter is disclosed by the applicant of the present application in Japanese Patent Application No. 6-302.
As previously proposed in No. 111, the drive source and mechanism of the injection system can be made smaller and lighter.

[0005]

[Problems to be Solved by the Invention] S / D is usually 3-4.
If the screw diameter is made larger, the injection capacity (injection / filling amount for one shot) is S / D = 3 to
It is comparable to the injection molding machine with screws of general design No. 4, and as the screw diameter is reduced, the drive source and mechanism of the injection system can be made smaller and lighter as described above. However, in the injection molding machine in which the screw diameter is reduced and the S / D is increased in this way,
As described below, there is a problem that the weighing capacity deteriorates (the weighing speed decreases) during the weighing process. This will be described below with reference to FIGS. 5 and 6.

FIGS. 6A and 6B are views showing a main structure of an injection molding machine with S / D = 6, for example, FIG. 6A shows an injection completed state, and FIG. 6B shows a rated maximum injection stroke. The measurement completion state in each is shown.

In FIG. 6, 1 is a holding plate, 2 is a heating cylinder whose rear end is held by the holding plate 1, and 3 is arranged in the heating cylinder 2 so that it can rotate and move back and forth. Screws 4 are raw material input ports (raw material input holes) provided in the holding plate 1 and the heating cylinder 2, 5 are band heaters wound around the outer periphery of the heating cylinder 2, 6
Is a pipe for circulating the cooling water embedded in the holding plate 1.

Here, in the prior art, the band heater 5 is wound up to the end of the externally exposed region of the heating cylinder 2, that is, around the base of the heating cylinder 2 close to the holding plate 1. It was The band heater 5a at the rearmost portion is also appropriately energized during the molding operation so that the resin material is positively heated even in the rear portion of the heating cylinder around which the band heater 5a at the rearmost portion is wound. It was The reason for doing so is that the heating cylinder 2 is originally intended to apply heat to the resin material to promote its softening, so that during the molding operation, the external exposed area of the heating cylinder 2 is entirely covered by the band heater 5. This is because the conventional practice of heating control should be followed.

In FIG. 6, the region of the screw 3 marked with a circled number is the feed zone (feed zone).
In the latter half, since the screw 3 shown in FIG. 6 has S / D = 6 as described above, the number of screw threads in the feed zone is S / D = 3-4. Two more threads are provided than that of the screw. Here, for convenience of explanation, they are referred to as a pitch portion, a pitch portion, ... Pitch portion in order from the rearmost portion of the rear half of the feed zone toward the front side.

At the injection completion position (measurement start position) shown in FIG. 6 (a), the entire pitch portion of the feed zone and the rear half of the pitch portion are located immediately below the raw material inlet 4. The resin material falling from the raw material input port 4 can be supplied to the screw portion immediately below the raw material input port 4. Further, in the pitch portion to the front half of the pitch portion, the screw 3 is rapidly advanced to perform injection / filling, and as a result, how the resin material is clogged is sparse. The pitch part to the pitch part are located in the heating cylinder portion around which the band heater 5a is wound, and are in a state where heat is transferred from the heating cylinder 2.

From the state of FIG. 6A, when the screw 3 is rotationally driven in a predetermined direction with the start of measurement, the resin material dropped and supplied from the raw material inlet 4 is fed by screw rotation. It begins to be transported forward by the action. Immediately after the start of this measuring process, the screw 3
Since there is a part where the resin density is low (the part where the resin is clogged is sparse) in a part of the feed zone, the metering speed (amount of molten resin accumulated per unit time to the screw tip side) is low and As the density of the lower part increases, the metering speed also gradually increases.

FIG. 7 shows the relationship between the weighing speed and time during this weighing process. From the start of the weighing process to the time T3 in FIG. 7, the weighing speed increases due to the above reason. This T3 time point substantially corresponds to the time point when the pitch portion in FIG. 6 has retracted to just below the raw material charging port 4. However, after the time point T3, the portion after the pitch portion heated by the heating cylinder 2 begins to recede immediately below the raw material charging port 4, so that the resin material is fed to the screw at the start portion of the resin supply to the screw. The applied heat becomes excessive, and the softening of the resin material proceeds excessively in the feed zone of the screw 3. Therefore, the resin feeding performance of the feed zone is remarkably lowered, and the measuring speed is lowered. Therefore, the cycle time of the metering process is not stable, and the density of the molten resin that is metered and stored becomes unstable.

It should be noted that the phenomenon that the above-mentioned metering speed once increases and then decreases is also observed in an injection molding machine having a general screw of S / D = 3 to 4 when the metering stroke is set to the rated maximum injection stroke. Although it is a phenomenon that is observed to some extent, it is not as remarkable as when S / D is set to S / D = 6.

The present invention has been made in view of the above points,
The purpose thereof is to prevent deterioration of the weighing performance in the weighing process in an inline screw type injection molding machine in which the S / D is set to 5 or more.

[0015]

In order to achieve the above-mentioned object, the present invention is an in-line screw type injection molding machine in which the S / D is set to 5 or more. The external exposed area of the heating cylinder is controlled to a temperature that ensures that the feed zone of the screw does not slow down the metering speed that transfers the resin material forward even during the metering stroke in which the screw moves backward by the amount corresponding to the rated maximum injection stroke. It is configured to be a temperature management region that is lower in temperature than other regions.

[0016]

The last part of the externally exposed region of the heating cylinder is set as a temperature control region having a temperature lower than that of other parts of the externally exposed region of the heating cylinder. For example, a band heater is not attached to this low temperature control region. To Therefore, during the molding operation, the above-mentioned low temperature control region receives heat conduction from a portion adjacent to the heating cylinder around which the band heater is wound, but is cooled by atmospheric cooling. Therefore, if the set temperature of the band heater in the area adjacent to the low temperature temperature control area and the length of the low temperature temperature control area are appropriately set, if the atmospheric temperature is constant, the low temperature temperature control is performed. The temperature of the region can be generally within the desired temperature range.

Further, by providing the above-mentioned low temperature control region, the raw material when the screw retreats to the metering completion position (injection start position) during the metering stroke in which the screw retracts by an amount commensurate with the rated maximum injection stroke. Even when the screw portion located immediately below the charging port is at the injection completion position (measurement start position), the temperature is prevented from being excessively increased. Therefore, unnecessary heat is not given to the resin material at the starting portion of the resin supply to the screw, and it is possible to prevent the measuring speed from rapidly decreasing during the measuring process.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a diagram showing a main part configuration of an in-line screw type injection molding machine according to the first embodiment of the present invention. FIG. 1 (a) shows an injection completed state, and FIG. 1 (b) shows a rated maximum. The measurement completion state at the injection stroke is shown.
In the present embodiment and the embodiments described later, S / D is set to S / D = 6 for convenience of comparison with the prior art, but the S / D in the present invention is not limited to this, and S / D is not limited to this. It is sufficient that D is 5 or more.

In FIG. 1, 1 is a holding plate, 2 is a heating cylinder whose rear end is held by the holding plate 1, and 3 is arranged in the heating cylinder 2 so that it can rotate and move back and forth. Screws 4 are raw material input ports (raw material input holes) provided in the holding plate 1 and the heating cylinder 2, 5 are band heaters wound around the outer periphery of the heating cylinder 2, 6
Is a pipe for circulating the cooling water embedded in the holding plate 1.
As described above, the screw 3 is the same as that shown in FIG. 6, and the circled numbers attached to the rear half of the feed zone of the screw 3 represent the same as those described above (this). Is the same in the examples described later).

Further, 7 is the heating cylinder 2 referred to in the present invention.
Is a low temperature control region provided in the outermost exposed region of the heating cylinder 2 over a predetermined length. The "low temperature" referred to here is a low temperature for comparison, and means that the temperature is sufficiently lower than other parts of the externally exposed region of the heating cylinder 2, and is lower than the softening point of the resin material. Although the temperature is sufficiently low, it is higher than room temperature. In the present embodiment, the above-mentioned low temperature management area 7 is an area where the band heater is not intentionally attached so as to be exposed to the atmosphere, whereby the low temperature management area 7 is provided during the molding operation. Is subjected to heat conduction from an adjacent portion of the heating cylinder 2 around which the band heater 5 is wound, but is cooled by being left to cool in the atmosphere.

Then, the low temperature control area 7 of this embodiment is used.
Can be set by appropriately setting the set temperature of the band heater 5 in the adjacent region and the length of the low temperature control region 7, so that the screw 3 can be retracted by an amount commensurate with the rated maximum injection stroke. The feed zone of the screw 3 is controlled at a temperature that ensures that the metering speed of the resin material is not lowered.

In addition, in FIG. 1A (at the injection completion position), two pitches of the pitch portion and the pitch portion are
The heating cylinder portion on which the band heater 5 is adhered is hung, but as described above, the pitch portion and the pitch portion are excessively heated by appropriately setting the conditions of the low temperature control region 7. There can be no. According to the experiment, depending on the softening point of the resin, etc.
It is possible to prevent the temperature of these portions from being excessively increased even if the three pitch portions, that is, the pitch portion to the pitch portion, are applied to the heating cylinder portion to which the band heater 5 is adhered, from the pitch portion range. confirmed.

Next, the operation of this embodiment will be described. When the screw 3 is rotationally driven in a predetermined direction with the start of measurement from the state of FIG. 1 (a), the resin material dropped and supplied from the raw material inlet 4 is moved forward by the screw feeding action by the screw rotation. Being transferred. Immediately after the start of this metering process, as described above, there is a low resin density part (a part where the resin is clogged) in a part of the feed zone of the screw 3, so the metering speed is low, and The metering speed gradually increases as the density of the low-density portion increases.

FIG. 2 shows the relationship between the weighing speed and time during this weighing process. From the start of the weighing process to the time T3 in FIG. 2, the weighing speed increases due to the above reason. This T3 time point roughly corresponds to the time point when the pitch portion in FIG. T3
After the time point, the portion after the pitch portion begins to recede immediately below the raw material feeding port 4, but the temperature of the pitch portion to the pitch portion is maintained at a relatively low temperature unlike the case of FIG. 6. Therefore, excessive heat is not applied to the resin material at the starting portion of the resin supply to the screw, and therefore, the measuring speed is kept substantially constant after T3 and the measurement is completed. Therefore, the weighing speed does not drop rapidly from the middle of the weighing process.
The weighing time and the density of the stored resin are stable.

A second embodiment of the present invention will be described next.
FIG. 3 is a view showing the main configuration of an inline screw type injection molding machine according to the second embodiment of the present invention, and FIG.
Shows the injection completed state, and FIG. 3B shows the measurement completed state at the rated maximum injection stroke. In addition,
In FIG. 3, those equivalent to those in FIG.
The explanation is omitted.

This embodiment differs from the first embodiment in that
The band heater 8 for low temperature heating control is wound around the low temperature control area 7 of the heating cylinder 2. The band heater 8 for low temperature heating control of the present embodiment is intended to quickly heat the low temperature management area 7 to a predetermined temperature when the machine (injection molding machine) is completely cooled and the operation of the machine is started up. It is mainly used, and when the low temperature control region 7 is warmed to a predetermined temperature, the energization control is cut off. Then, during the continuous molding operation, as in the case of the first embodiment, the low temperature temperature control region 7 balances the heat conduction from the adjacent region of the heating cylinder 2 and the air cooling by the air cooling to a predetermined temperature. The range is being maintained.

Also in this embodiment having such a configuration, it is possible to prevent a rapid decrease in the weighing speed during the weighing process. In addition, the time from startup to continuous molding operation can be shortened.

Next, a third embodiment of the present invention will be described.
FIG. 4 is a diagram showing a configuration of a main part of an inline screw type injection molding machine according to a third embodiment of the present invention.
Shows the injection completed state, and FIG. 4B shows the measurement completed state at the rated maximum injection stroke. In addition,
4, the same elements as those in FIG. 3 are designated by the same reference numerals,
The explanation is omitted.

This embodiment differs from the second embodiment in that
A pipe 9 for circulating cooling water is embedded in the heating cylinder portion of the low temperature control region 7 around which a band heater 8 for low temperature heating control is wound. The band heater 8 for low temperature heating control of the present embodiment is intended to quickly heat the low temperature management area 7 to a predetermined temperature when the machine (injection molding machine) is completely cooled and the operation of the machine is started up. In addition to being used, it is selectively driven and controlled during continuous molding operation,
The low temperature management area 7 is controlled to a predetermined temperature in cooperation with the cooling action of the water flowing through the cooling water circulation pipe 9.

Also in this embodiment having such a configuration, it is possible to prevent the metering speed from rapidly decreasing during the metering process. In addition, the time from the start-up of operation to the continuous molding operation can be shortened, and the temperature of the low temperature control area 7
You can always control exactly what is appropriate.

Next, a fourth embodiment of the present invention will be described.
FIG. 5 is a diagram showing a main configuration of a screw of an inline screw type injection molding machine according to a fourth embodiment of the present invention. The screw 3 of this embodiment can be applied to any of the injection molding machines having the configurations of the first to third embodiments.

In FIG. 5, the screw head and the mounting portion of the screw root are not shown, and the feed zone (supply zone) 3a of the screw 3, the compression zone (compression) zone 3b, and the metering zone ( Weighing zone) 3c. The feed zone 3a has 14 screw threads, the compression zone zone 3b has 5 screw threads, and the metering zone 3c has 3 screw threads.

The feed zone 3a of the screw 3 of this embodiment is surface-treated so that the dynamic friction coefficient is smaller than that of the other zones of the screw 3. Specifically, first, the entire screw 3 is plated with Cr by electrolytic plating.
After plating, and then selectively masking, only the feed zone 3a is chemically plated (Ni + P +).
After the W) plating is performed and the mask is removed, an annealing process at about 400 ° C. is performed to improve the structure of the (Ni + P + W) plating. As a result, (N of the feed zone 3a is
The i + P + W) plating has a film-like shape and a small dynamic friction coefficient, and the Cr plating of the compression zone zone 3b and the metering zone 3c has a porous composition and a large dynamic friction coefficient as compared with the (Ni + P + W) plating.

As is well known, the feed zone 3a of the screw 3 plays a main role in feeding the resin material forward, and the smaller the coefficient of friction, the higher the transfer efficiency of the solid resin material (resin pellet) (resin). Material is less likely to adhere, which improves transfer efficiency). On the other hand, since the compression zone zone 3b and the metering zone 3c are the parts for kneading and plasticizing the resin material, the higher the coefficient of friction, the higher the kneading / plasticizing efficiency.

Therefore, by applying the screw 3 of this embodiment to the injection molding machine having the constitution of the first to third embodiments described above, the kneading / plasticizing efficiency is not impaired, and
Since it is possible to improve the feeding efficiency of the feed zone, it is possible to perform a better metering operation. Further, in the characteristics of the weighing speed shown in FIG. 2, the rising of the weighing speed can be improved to be steep.

[0036]

As described above, according to the present invention, in the injection molding machine in which the S / D is set to 5 or more, the phenomenon that the measuring speed sharply decreases from the middle of the measuring process, which has been a problem in the past, is caused. It can be solved and the weighing performance can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a main configuration of an inline screw type injection molding machine according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing characteristics of weighing speed according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a main configuration of an inline screw type injection molding machine according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a main configuration of an inline screw type injection molding machine according to a third embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a main configuration of a screw of an inline screw type injection molding machine according to a fourth embodiment of the present invention.

FIG. 6 is an explanatory view showing a main configuration of an inline screw type injection molding machine according to a conventional technique.

FIG. 7 is an explanatory diagram showing characteristics of weighing speed according to a conventional technique.

[Explanation of symbols]

 1 Holding Board 2 Heating Cylinder 3 Screw 3a Feed Zone (Supply Zone) 3b Compression Zone (Compression) Zone 2 3c Metering Zone (Measuring Zone) 4 Raw Material Input Port 5 Band Heater 6 Cooling Water Circulation Pipe 7 Low Temperature Control Area 8 Band heater for low temperature heating control 9 Cooling water circulation pipe

Claims (5)

[Claims] 1. By rotating a screw in a heating cylinder whose heating is controlled by a band heater, the resin material is kneaded and plasticized and transferred to the tip side of the screw, and the molten resin is stored at the tip side of the screw. It is an in-line screw type injection molding machine that injects and fills molten resin into the mold by advancing the screw, and the rated maximum injection stroke of the screw is set to 5 times or more of the screw diameter (screw diameter). In the one, the metering speed at which the feed zone of the screw transfers the resin material forward even during the metering process in which the screw is retracted by the amount corresponding to the rated maximum injection stroke at the rearmost portion in the externally exposed region of the heating cylinder. Exposed area of the heating cylinder, controlled to a temperature that does not reduce Injection molding machine of in-line screw type, characterized in that the low temperature thermal management area than other sites. 2. The inline screw type injection molding machine according to claim 1, wherein a band heater is not attached to the low temperature control region. 3. The in-line screw type injection molding machine according to claim 1, wherein a band heater for low temperature heating control is attached to the low temperature control region. 4. The heating cylinder portion of the low temperature control region according to claim 1, wherein:
An inline screw type injection molding machine characterized in that a pipe for circulating a cooling medium is provided. 5. The feed zone of the screw according to claim 1, wherein the feed zone of the screw has a smaller dynamic friction coefficient than other zones (compression zone and metering zone) of the screw. An in-line screw type injection molding machine characterized by various surface treatments.