JPH1058530A - Blow molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce drawdown and uniform the thickness of a product by arranging a non-contact thermometer for detecting a resin temperature of a parison near a die, receiving the parison at a catch pan fixed to a movable body movable up and down at the lower part of the die, and controlling the descending speed of the movable body based on the resin temperature. SOLUTION: A non-contact thermometer 2 is provided under a die 1 and a resin temperature of a parison P coming out from the die 1 is detected. A catch pan 3 is fixed to a movable body 52b movable up and down, made to descend by holding the parison P, and a servo unit 5 is made to be a moving means of the catch pan 3. By using the resin temperature which is previously set by a speed control device and a basic pattern of the descending speed of the catch pan, the temperature of the parison P detected by the non-contact thermometer 2 is compared and computed so as to decide the descending speeds of the movable body 52b and the catch pan 3. As a result, when a drawdown is reduced and the temperature of the parison resin immediately after start of molding is low, the catch pan 3 descends slowly, so that an excellent product can be obtained at early stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding machine used for extrusion blow molding.

[0002]

2. Description of the Related Art A blow molding machine extrudes a molten resin from a die to form a tube-shaped parison, then forms a bag with a pinch blade, drops the parison at its own weight and at an extrusion speed, and takes it into a blow mold. This is a machine that closes the mold and blows high-pressure gas into the parison to form a hollow product. By the way, when a molded article is manufactured using a blow molding machine, the problem of drawdown of a parison has been raised. Drawdown varies depending on conditions such as the type of resin, resin pressure, die diameter, resin thickness, outside air temperature, and heat generated by shearing resin, causing variations in the length and thickness of burrs to be formed. This results in a loss in increasing the amount of material. Conventionally, the adjustment of the molding conditions of a blow molding machine is mostly performed by a timer control, and the skill of the operator to adjust the adjustment has made it more difficult to solve the above problem. Of course, adjust the current molding conditions to the drawdown amount,
Every time the adjustment work is performed, there is nothing out of control, but it lacks mass productivity. For this reason, for example, the above countermeasure invention has been proposed in Japanese Patent Application Laid-Open No. 4-361018.

[0003]

However, at the time of mass production, the extruded parison often adheres to the die portion and does not descend unless the weight falls down to a predetermined value. The parison speed conversion value used did not always correspond to the actual parison descent speed. In addition, due to variations in the adhesion of the parison to the die portion, it was difficult to reduce the drawdown amount except under specific conditions. Furthermore, at the time of general blow molding, resin temperature, die temperature, etc. are not stable,
Since the amount of drawdown also changed, there were many rising molding defects. The aforementioned resin shearing heat is not stable, and the resin temperature is low, so that the amount of droop of the parison becomes small, causing the pinch blades to be hit and causing loss of time and material until a good quality product is obtained. Had occurred. In addition, in the conventional blow molding, when the shape becomes complicated, it has been difficult to make the wall thickness uniform over the whole.

[0004] The present invention solves the above problems,
Not only in the steady state, but also in the transition process before entering, the lowering speed of the parison is properly controlled to reduce drawdown problems, and furthermore, the product meat is responded to changes in the shape of the molded product An object of the present invention is to provide a blow molding machine capable of achieving a uniform thickness.

[0005]

In order to achieve the above object,
The gist of the invention according to claim 1 is a blow molding machine that guides a parison into a blow mold, blows a gas into the parison, and expands the parison to form the parison into a predetermined shape.
A dice for hanging the parison, a non-contact thermometer arranged near the dice and detecting a resin temperature of the parison coming out of the dice, and a parison fixed below and below the dice to a movable body which can move vertically. A blow molding machine, comprising: a tray capable of supporting the parison; and a speed control device that detects a resin temperature of the parison with the non-contact thermometer and controls a lowering speed of the movable body based on the resin temperature. It is in.
According to a second aspect of the present invention, the speed control mechanism of the first aspect divides not only the resin temperature but also a parison descent section and adds a correction value in the section to reduce the descent speed of the movable body. It is characterized by controlling.

Since the lowering speed of the parison greatly depends on the resin temperature, if a non-contact thermometer, a pan and a speed control mechanism are provided as in the first aspect of the present invention, not only the steady state but also the steady state is obtained. Even in the transitional period of the above, the saucer can be applied to the lower part of the parison, and the parison can be brought to an appropriate descending speed. Since the non-contact thermometer is used, there is no damage to the parison. As in the invention of claim 2,
By dividing the descending section of the parison and adding the correction value of that section to control the descending speed of the movable body, the descending speed of the parison can be partially changed, so even if the shape of the blow molded product becomes somewhat complicated, It becomes possible to approach a constant wall thickness over the whole.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the blow molding machine according to the present invention will be described in detail. 1 to 6 show one embodiment of the blow molding machine of the present invention. FIG. 1 is a longitudinal sectional view of a main part of the blow molding machine, FIG. 2 is a view taken in the direction of arrow A in FIG. 1, and FIG. Explanatory diagrams showing the control system of the blow molding machine No. 1 and FIGS.
FIG. 6 shows a setting pattern diagram of the receiving speed, and FIG. 6 shows a control flowchart of the blow molding machine. This is applied to a blow molding machine for producing a spoiler (blow molded product).

The blow molding machine includes a die 1, a non-contact thermometer 2, a tray 3, a speed controller 4, a servo unit 5, and detectors 6, 7. The die 1 is a die for plasticizing a thermoplastic resin with an extruder (not shown) and hanging a tubular parison P. The non-contact thermometer 2 detects the resin temperature of the parison P coming out of the dice 1.
It is located near and slightly below the dice 1 in vertical level (FIGS. 1 and 2). The detection information of the resin temperature is:
The data can be sent to the arithmetic control unit 41 in the speed control device 4 described later. Examples of the non-contact thermometer 2 include a radiation thermometer, a color thermometer, and the like. Here, an IK3 type manufactured by Optex Corporation is used.

The receiving tray 3 is a dish container that is warped up toward the periphery as shown in FIG. 1, and is disposed almost directly below the parison P and has a shape capable of receiving the parison P. The receiving tray 3 is fixed to a movable body 52b that can move up and down, and can move down the parison P from the upper point position L ₀ (original position) to the lowermost position L ₄ where the mold can be closed while holding the parison P. ing. In the present embodiment, the movable body 52b corresponds to a nut of the ball screw 52 (strictly, a nut provided with a mounting piece for the tray 3), and is a component of the servo unit 5.

The servo unit 5 as a means for moving the tray 3 is a known single-axis servo unit,
And a ball screw 52 for accurately transmitting the rotation of the servo motor 51 to the ball screw 52. The axial direction of the bolt 52a of the ball screw 52 matches the direction in which the parison P hangs. The rotation of the ball screw 52 allows the movable body 52b, which is a nut, to freely move up and down.
But it will be lowered while maintaining the top point position L ₀ to the lowest end position L ₄ a parison P as described above.

The speed control device 4 has a sequencer CP
The resin temperature of the parison P detected by the non-contact thermometer 2 is compared and increased or decreased using the basic pattern of the resin temperature VS. It is about to determine the descent speed. Here, in the arithmetic and control unit 41 of the speed control device 4, for example, a speed command value linearly increasing with respect to the resin temperature as shown in FIG. 4 is stored. Thus, the higher the resin temperature, and increase the lowering speed V ₁ of the saucer 3 correspondingly. Further, in the present embodiment, as shown in FIG. 5, not only the resin temperature but also the descending section of the parison P is divided, and the correction value of the section is added (multiplied) to control the descending speed of the movable body 52b. I have to. The blow molded product as a spoiler has a flat portion at the center and both side portions are bent, but even with such a shape, the pan speed V is adjusted so that a constant thickness is obtained over the entire region. correction value η is multiplied to _1, saucer 3 is to be lowered by the correction pan speed V _2. Specifically, in FIG. 3 and FIG. 4, the speed of the section between the positions L0 to L1 and L3 to L4 of the movable body 52b forming both side portions is relatively decreased, and the positions L1 to L3 of the movable body 52b are relatively reduced.
Then, the speed is increased so as not to cause uneven thickness in the blow molded product. The speed control 42 includes an arithmetic control unit 41
Based on a signal correction pan speed V ₂ from the controls the rotation of the servo motor 51. The lowering speed of the movable body 52b is controlled by the rotation control of the servo motor 51. For example, attach an encoder to the back of the servomotor,
Speed control 4 by detecting the feed speed and position that change every moment
Give feedback to 2. Then, the electrical signal comparison processing in the speed control 42 to the lowering speed of the movable body 52b controls the servo motor 51 to the command information serving the correction pan speed V _2.

The detector 6 uses a photoelectric sensor (for example, a combination of a light emitting element and a light receiving element) here, and is arranged at a level slightly lower than the pinch blade 8 as shown in FIG. Pinch blade 8
Are arranged in the vicinity of the parison P coming out of the dice 1. By detecting the parison P coming out of the dice 1 by applying the photoelectric sensor 6, the pinch blade 8 is closed by this information, and the lower part of the parison P is pre-pinched.

The detector 7 also uses a photoelectric sensor (for example, a combination of a light-emitting element and a light-receiving element) and is arranged on the raised edge of the tray 3. Parison P coming out of dice 1 descends,
When the light signal of the photoelectric sensor 7 is interrupted (the chain line in FIG. 3), it is detected that the parison P has approached the tray. Information detected by the photoelectric sensor 7 is transmitted to the calculation control unit 41, a falling start command of the pan 3 at the top point position L _0. The lowermost position L the pan 3 in the pan speed V ₂
It is a setup to lower to ₄ .

Reference numeral 9 denotes a blow mold, which forms a cavity C of a spoiler when the mold is closed. When the pan 3 at the lowermost end position L ₄ is reached, it closes the blow mold 9, then, has become gimmick making blow molded article by blowing a gas into the parison P from a blow pin (not shown). The other components are basically the same as those of a known blow molding machine, and a description thereof will be omitted.

Next, the operation of the blow molding machine having the above configuration will be described with reference to a control flowchart. First, the mold is opened, and it is confirmed that the tray 3 is at the origin L ₀ (upper point position), and the start switch is turned on. Then, the extruder operates and the parison P is extruded from the die 1. In the initial stage, not only the die 1 but also the parison P coming out of the die 1 has a low temperature. In step 101 of FIG. 6, the non-contact thermometer 2 detects the resin temperature of the parison P and sends it to the arithmetic and control unit 41. The calculation control unit 41, based on the resin temperature VS. pan lowering speed information input in advance from the input unit, pan speed V ₁ is set from the resin temperature (step 102). Further, in the present embodiment, the receiving speed V ₁
Is multiplied by a correction value η to set a corrected receiving speed V ₂ corresponding to the shape change (step 103).

Thereafter, the parison P passes the pinch blade 8,
When the arrival of the parison P is detected by the photoelectric tube 6 (step 105), the pinch blade 8 is activated (step 106).
Pre-pinch and close the lower parison.

The pre-pinch parison P continues to descend, and the phototube 7 detects the arrival of the parison P (step 107). This detection information is sent to the speed control device 4, and the tray 3 starts descending while applying the lower part of the parison. Lowering speed becomes the correction pan speed V _2. Here, the resin temperature detection of the parison P is carried out for each shot, further correction pan speed V ₂ which was in the shape is set. Therefore, even in a transitional period (transition state) in which the temperature of the parison P increases with time, the pan 3 descends while well supporting the parison P. There are no drawdown problems. by the way,
On behalf of the process for obtaining the correction pan speed V _2, set the parison P velocity V _n to match the blow molding shape drooping direction of each section (for example, 7 segment) of _{(V 1, V 2, ...} V 7) advance, may be increased or decreased in speed by this speed V _n is proportional to the resin temperature (actually employing this scheme). In this way, the receiving pan 3 is moved to the lowermost end L ₄ at the corrected receiving speed V _2.
(Step 109), the blow mold 9 closes,
Blow molding is performed. Then, after the molding, after mold opening, pan 3 is returned to the original position L ₀ (step 110),
It returns to its original state and one blow molding (one cycle) is completed. Such a series of operations is repeated as many times as necessary to produce a predetermined amount of molded article. In step 109, if the saucer 3 does not arrive at the lowermost end L _4, back to the resin temperature detection point of the parison P (step 101), prompting the lowering of the pan 3.
At this time, it is determined whether or not the pinch blade 8 has been operated in Step 104. If the pinch blade 8 has been operated, Step 1
In step 07, the double punching of the pinch blade 8 is avoided.

The blow molding machine thus configured pays attention to the fact that the hanging speed of the parison P greatly depends on the resin temperature, and appropriately controls the descending speed of the pan 3 by detecting the non-contact thermometer 2. Conventional drawdown problems can be reduced. Further, when the parison resin temperature immediately after the start of molding is low, the tray 3 is slowly lowered based on the resin temperature information, so that a good product can be manufactured from an early stage. In addition, since the non-contact thermometer 2 detects the parison temperature every one shot and transmits it to the speed control device 4, even in the transition state before entering the steady state, the descending speed of the pan 3 is finely controlled, and Molding defects can be greatly reduced. Further, in the case of a shape such as a spoiler having a straight portion and a bent portion, the receiving portion 3
By increasing the relative speed (FIG. 5), it is possible to produce a product having a constant wall thickness throughout the entire product, which greatly contributes to quality improvement. In this way, it is possible to produce a stable product every shot from an early point in time of the start of molding, and a great effect is obtained especially for a large product. Then, the parison P is formed by the photoelectric tube 6 located slightly below the pinch blade 8.
Is detected, and the pinch blade 8 is closed, so that the pinch blade 8 does not hit empty and the lower part of the parison P can be closed in a bag-like manner.

In the present invention, the present invention is not limited to the above-described embodiment, but can be variously changed within the scope of the present invention depending on the purpose and application. The shape, size, number, and the like of the die 1, the non-contact thermometer 2, the tray 3, the detectors 6, 7, and the like are appropriately selected according to the application. The photoelectric sensor 6 and the pinch blade 8 of the embodiment are not essential components, and when the lower part of the parison P coming out of the die 1 is not closed, the photoelectric sensor 6 and the pinch blade 8
Need not be provided. In the above-described embodiment, the resin temperature of the parison P is detected for each one shot, and this is multiplied by the correction value η regarding the parison descending section.
Alternatively, over time performs sequential resin temperature detection of the parison P (for example, every 0.5 seconds), correction pan speed V ₂ may be adapted can cope with temperature changes of the parison P to be constantly changing .

[0020]

As described above, the blow molding machine according to the present invention improves the yield by applying the lower part of the parison with the saucer and appropriately controlling the lowering speed of the parison from the early stage of the production start. Can make the product thickness uniform, which is extremely useful.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of a blow molding machine according to one embodiment of the present invention.

FIG. 2 is a view taken in the direction of arrow A in FIG. 1;

FIG. 3 is an explanatory diagram showing a control system of the blow molding machine in FIG.

[4] In one embodiment of the present invention, a set pattern diagram of the pan speed V _1.

FIG. 5 is a setting pattern diagram of a receiving speed V _{2 according to} an embodiment of the present invention.

FIG. 6 is a control flowchart of the blow molding machine.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 die 2 non-contact thermometer 3 saucer 4 speed controller 52 b movable body η correction value P parison

Claims (2)

[Claims] 1. A blow molding machine for guiding a parison into a blow mold, blowing gas into the parison and expanding the parison to form the parison into a predetermined shape, wherein the die (1) for hanging the parison, and the die A non-contact thermometer (2) for detecting the resin temperature of the parison coming out of the die, and a tray fixed to a vertically movable body below the die and capable of supporting the parison ( 3) and a speed control device (4) for detecting the resin temperature of the parison with the non-contact thermometer and controlling the lowering speed of the movable body based on the resin temperature. . 2. The lowering speed of the movable body according to claim 1, wherein the speed control mechanism controls not only the resin temperature but also a lowering section of the parison and adds a correction value in the lowering section. Blow molding machine.