JP2000062012A - Method for blow molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for blow molding which can stabilize mechanical action of a blow molding machine and make the length of a parison const. and prepare a molded body with a uniform quality. SOLUTION: A method for blow molding wherein a mold closable time T is measured and T is compared with the max. mold closable time, T0 measured during molding of the preceeding cycle and when T is larger than T0, the value of T0 is replaced with the value of T and after T0 has passed from a mold opening instruction, a mold closing instruction is issued to perform mold closing action and after a definite time has passed from the mold closing instruction, a cutter driving instruction is issued to cut the parison, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding method in which a mechanical operation of a molding machine in a blow molding method is stabilized, a parison length can be made constant, and a molded product of uniform quality can be manufactured.

[0002]

2. Description of the Related Art Conventionally, as a method of controlling a blow molding machine for keeping a parison length constant, a time from a mold closing completion in the previous cycle to a mold closing command in this cycle is preset by a cycle timer. There is a method in which the mold closing timing is controlled to be constant, and the parison cutter is operated after a fixed time has elapsed from the completion of mold closing to cut the parison at a constant length. In addition, JP-A-7-227
The method described in Japanese Patent No. 899 cancels the fluctuation of the machine operation time from the mold opening command of the blow molding machine to the start of driving down of the blow pin to the parison by offsetting the exhaust time in the blowing process to reduce the molding cycle time. By making it constant, the length of the parison is made constant.

[0003]

However, the conventional method of controlling the parison length of the blow molding machine has the following problems. (1) When the mold closing operation time changes, the mold closing timing also changes, and the molding cycle itself also changes. Also, the time from the completion of mold closing in the previous cycle to the mold closing command in this cycle needs to be set in advance in the cycle timer, but this value must be determined by trial and error and is easy. is not. (2) In the blow molding machine, the machine operation time from the mold opening command to the operation of the parison cutter fluctuates, so the operation interval of the parison cutter in each cycle fluctuates, and the parison cannot be cut at regular intervals, and the parison length increases. Will fluctuate.

Accordingly, it is an object of the present invention to provide a blow molding method in which the mechanical operation of a blow molding machine is stabilized, the parison length can be made constant, and a molded product of uniform quality can be manufactured.

[0005]

The present inventors have found that the above object can be achieved by making the mold closing timing of the blow molding machine and the operation timing of the parison cutter constant in each molding cycle.

The present invention has been made based on the above findings, and in a blow molding method in which a mold opening command is issued, a mold clamping device is opened, and a molded product is taken out repeatedly, a measured mold closing time is measured. Is compared with the maximum mold closure possible time which is the maximum value of the mold closure possible times measured during molding in the previous cycle, and the larger value is updated to the value of the mold closure possible time. A blow molding method in which the mold closing command is issued to perform the mold closing operation after the maximum mold closing time has elapsed from the mold opening command, and the parison cutter drive command is issued after a certain time has elapsed from the mold closing command to cut the parison. The above object is achieved by providing

In the blow molding method of the present invention, the mold closing possible time is always measured while measuring the time from the mold opening command to the mold closing possible in each cycle (mold closing possible time). The mold closing command is always issued at the maximum value of the mold closing possible time in order to perform the mold closing operation, and the parison is cut off after a certain time has passed from the mold closing command. It is possible to automatically set constant mold closing timing and cutter timing without being affected by fluctuations in machine operating time and differences in machine operating time among multiple mold clamping devices. As a result, parison length Is constant, and a molded product of uniform quality can be manufactured.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The blow molding method of the present invention will be described below based on its preferred embodiments with reference to the drawings.

The blow molding machine 1 shown in FIG.
And two mold clamping devices 3, each consisting of a pair of split molds.
It is a double lung type molding machine equipped with 3 ', and a mold clamping device 3, 3'
Are alternately switched to hang the parison P pushed out from the head 4 of the extruder 2 in the mold closing device which is open, and after a predetermined time has elapsed, a mold closing command is issued to close the mold closing device. Then, the parison is sandwiched, the parison is cut by the parison cutter 5, and blown pins (not shown) are blown into the cut parison to blow a gas to perform molding. The controller 6 is composed of a program controller or the like that measures the time from the mold opening command until the mold can be closed and issues a mold closing command and a parison cutter drive command, etc., and realizes the operation shown in the flowchart of FIG. In addition, an in-mold labeler (not shown) is attached to the blow molding machine 1, and a predetermined label is attached to the inner surface of the mold in the mold clamping device before the mold is closed. The extruder 2 is capable of continuously extruding the same parison pattern in a constant cycle by controlling the parison thickness (that is, parison control) or the parison length control (parison length control). Such a double-lung type molding machine is described in JP-A-9-123262. The parison control is also disclosed in JP-A-10-11917.
Further, the parison length control is disclosed in Japanese Patent Application Laid-Open No. 7-2.
It is described in Japanese Patent Publication No. 27899 and is a known technique.

The operation of the blow molding machine will be described with reference to FIGS. Although the following description relates to the operation of one of the two mold clamping devices, the operation of the other mold clamping device is the same. First, the molding cycle time S is set for the controller 6. Further, when the expected mold closing time T ₀ is known in advance based on the results of the previous molding operation, the time is set to T ₀ . Further, when it is desired to monitor the upper and lower limits of the mold closing time T, the upper and lower mold closing times T _max and T _{min are} possible.
Is also set in advance. However, the respective times are set so that T _min ≤T ₀ ≤T _max . T _0, T _{ma x} and T
_{For min} , as system initial values, T ₀ = 0,
Since T _max = S and T _min = 0 are preset,
These settings can be omitted.

In the present specification, the molding cycle time S means the time from the mold opening command to the exhaust completion, as shown in FIG. 3, and the mold closing possible time T is the mold closing command to mold closing. The scheduled mold closing time T ₀ is the time from the mold opening command to the mold closing command, and in the present invention, the mold closing possible time measured during molding in the previous cycle. It corresponds to the maximum mold closing possible time which is the maximum value of T (hence the term maximum mold closing possible time is used instead of the planned mold closing time in the following description). Further, as described later, in the present invention, the timing at which the mold closing command is issued is guaranteed by the maximum mold closing possible time T ₀ , and T ₀
The mold closing command will not be issued beyond. Incidentally, in FIG. 3, the mold row is a process of moving each mold clamping device to a predetermined position by switching between the two mold clamping devices 3 and 3 ′, and IML is an in-mold label attaching process. is there.

Next, the molding operation is actually started and the mold closing time T is measured. When starting up the blow molding machine,
If operation is not started from the mold opening command but the mold clamping device is already in the mold opening state, replace the first command at start-up with the mold opening command to continue the command from the next cycle onward. You can The mold closing possible time T is measured by measuring the machine operation time from the mold opening command to the completion of in-mold label sticking using a counting function such as a program controller. If there is no step of attaching the in-mold label, it is performed by measuring the machine operation time until the completion of the mold movement.

The measured mold closing time T is displayed on a display device or the like.
Is displayed (can be omitted), and the mold closing time T and maximum mold closing
Available time T₀And are compared. And T is T₀than
If larger (T> T₀), T₀Is updated to the value of T
(That is, T is T₀Is assigned to). Conversely, T is T₀Less than
If (T ≦ T₀), T₀The value of
It Continue to T₀At the timing of (ie
Et T₀After a lapse of time) a mold closing command was issued and Paris drooped.
Son is clamped by the mold clamping device. Therefore, T ≦ T₀
In case of, attach in-mold label as shown in Fig. 3.
After completion, (T₀-T) waiting time (wait for timing adjustment)
Mold closing command is issued after a certain period of time, and conversely T> T₀Place
If there is no such waiting time, after the elapse of T from the mold opening command
Immediately (ie updated T₀Immediately after passing) Mold closing command
Is emitted. Thus, T> T ₀And T ≦ T₀Someday
In the case of, the mold closing command is₀Progress
It will be emitted later. In other words, each operation is
The mold closing command is issued from the mold opening command in the shape cycle
Up to each operation time (die opening operation time, die moving operation time, IML
Fluctuations in operating time etc.) are settled.

After a certain time has elapsed since the mold closing command was issued, a parison cutter drive command is issued and the parison is cut. As described above, since the mold closing command in each cycle is always issued after T _{0 has} elapsed from the mold opening command,
The interval at which the parison cutter drive command is issued is constant. As a result, the length of the cut parison becomes constant and the quality of the obtained molded product becomes uniform.

Next, T₀And upper limit type closing time T_maxAnd
Compared, if for some reason T₀> T_maxBecomes
If so, a mold closing time upper limit warning is issued (only
However, such a thing is rare). This warning was issued
In the molding cycle, the mold closing was completed later than usual,
Since the length of the cord is longer than usual, this molding support
Is the molded product obtained from Uclus a production line as a nonstandard product?
Be removed from. When this warning is issued, T₀Value of T
_maxIs updated to the value of. That is, T₀Against the increase in
It takes a lot of time, T₀Value of T_maxNever exceeds the value of
Yes. Conversely, T₀≤T _maxIn case of, T₀The value of
It is retained and no special operation is performed.

Further, T and the lower limit mold closing time T _min are compared, and T <T _min for reasons such as shortening of machine operation time.
If, the lower limit of mold closing time warning is issued.
On the contrary, when T ≧ T _min, no special operation is performed.
However, when the mold closing possible time upper limit alarm or the mold closing possible time lower limit alarm is frequently issued, the value is changed to an optimum value, for example, by reducing the value of T ₀ . Or, adjust the machine operating condition.

As shown in FIG. 3, after the mold is closed and the parison is completely cut, a blow pin is driven, and a predetermined gas is blown into the cut parison to perform pre-blowing and main-blowing. The shape corresponds to the shape of the cavity formed in the mold. Then, the blow pin is pulled out, and the gas blown into the parison is exhausted. Then, the blowing and / or exhausting time of this gas is adjusted so that the mold opening command of the next cycle is possible (synchronized) with the above molding cycle time S. By this adjustment, the fluctuation of the mold closing operation time in each molding cycle is settled. After that, a mold opening command is issued, the split mold is opened, and the molded body is taken out. After that, the above molding cycle is alternately and repeatedly performed in the two mold clamping devices to manufacture a molded body.

As described above, in the above molding method,
The timing at which the mold closing command is issued in each cycle is T ₀ . Since the parison cutter drive command is issued after a certain time has elapsed from the mold closing command, even if the machine operating time such as the mold opening operation, the mold moving operation, and the mold closing operation varies in each molding cycle, The length of the cut parison is constant, and the quality of the obtained molded product is uniform. Especially when performing blow molding on a parison whose parison control and parison length control are performed as described above,
The point deviation of the parison cutting position does not occur, and the parison can be gripped and cut in a fixed cycle, and the quality of the molded product becomes more uniform.

Although one embodiment of the blow molding method of the present invention has been described above, the present invention can be modified to the following embodiments. For example, in the above embodiment, the blow molding is performed on the parison controlled and the parison length-controlled parison, but it is also possible to perform the blow molding on the parison where these are not performed instead. Further, although the in-mold labeler is used in the blow molding machine in the above-described embodiment, it may not be used depending on the type and intended use of the target molded product. Further, the blow pins in the blow molding machine may be top-driving or bottom-driving. Further, the blow molding machine has two mold clamping devices, but instead of this, a blow molding machine having one or three or more mold clamping devices may be used.

[0020]

As described above in detail, according to the blow molding method of the present invention, the mechanical operation of the blow molding machine is stabilized, the parison length can be made constant, and a molded product of uniform quality is manufactured. be able to. The blow molding method of the present invention is extremely effective particularly when blow molding is performed on a parison controlled and a parison whose parison length is controlled.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a blow molding machine used in an embodiment of a blow molding method of the present invention.

FIG. 2 is a flowchart showing the operation of the blow molding machine in the above embodiment.

FIG. 3 is a time chart showing the operation of the blow molding machine in the above embodiment.

[Explanation of symbols]

1 Blow molding machine 2 extruder 3,3 'mold clamping device 5 parison cutter 6 controller P parison

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F202 AM22 AP10 AR11 AR12 CA15                       CB01 CL01                 4F208 AM22 AP10 AR11 AR12 LA01                       LA05 LA08 LB01 LH19 LJ10

Claims (3)

[Claims] 1. A blow molding method in which a mold opening command is issued, a mold closing device is opened, and a molding cycle for taking out a molded body is repeated, and a measured mold closing time is measured during molding in a previous cycle. Compared with the maximum mold closing possible time which is the maximum value of the mold closing possible time, the larger value is updated to the value of the mold closing possible time, and the maximum mold closing possible time from the mold opening command. A blow molding method in which after the lapse of time, the mold closing command is issued to perform the mold closing operation, and after a lapse of a certain time from the mold closing command, a parison cutter drive command is issued to cut the parison. 2. The blow molding method according to claim 1, wherein the parison has a thickness controlled in the molding cycle. 3. The upper limit type closing time is set in advance,
The blow according to claim 1 or 2, wherein if the updated or held maximum mold closing possible time is larger than the upper limit mold closing possible time, the value of the maximum mold closing possible time is updated to the value of the upper limit mold closing possible time. Molding method.