JPH0414865B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for increasing the temperature of an injection molding machine that can be used to increase the temperature of a portion of the injection molding machine adjacent to a molding material.

[Conventional technology]

Generally, parts of an injection molding machine adjacent to the molding material, such as the heating cylinder and injection nozzle of the injection device,
Alternatively, a hot runner block or the like of a molding die has a temperature control function to maintain the molding material inside in a molten state. The temperature control function controls heating means using heaters etc. to maintain a predetermined set temperature (including the proportional band, which is the temperature range), and the control method is as follows:
ON/OFF control, proportional control, PI (proportional/integral) control, PD (proportional/derivative) control, PID (proportional/integral/
There are various methods such as differential) control.

Incidentally, such temperature conditions during molding are essential requirements for stable molding, and therefore, it is desirable from the viewpoint of productivity improvement etc. that the temperature be raised quickly prior to the start of molding.

For this reason, conventionally, in order to reach the set temperature in the shortest possible time after the injection molding machine is powered on, a heater with a large amount of heating per unit area is used, and the temperature rise rate of the temperature rise characteristic RI shown in Fig. 4 is used. was set so that it was large.

[Problem that the invention seeks to solve]

However, in the conventional temperature raising method described above, the amount of heat generated from the heater is transmitted to the molding material inside the injection molding machine through the components of the injection molding machine such as the heating cylinder, injection nozzle, or hot runner block. A time lag occurs between the temperature rise of the part and the molding material. As a result, when the temperature rises, a gap is temporarily generated between the two due to the difference in the amount of expansion, causing a problem in which air is caught in the gap. For this reason, molding defects such as voids and burns may occur in the molded product in the initial stage of molding, or when molding materials that easily deteriorate due to heat such as hard vinyl chloride, polyacetal, acetyl cellulose, and methacrylic resin are used, the heater may There was a problem in which the molding material (molten resin) in nearby areas deteriorated or decomposed due to local heating.

Therefore, prior to the start of molding, a large amount of molding material was used to empty the mold and the interior was cleaned, but this method not only resulted in a large amount of molding material and energy loss due to emptying. However, there was a problem in that this caused a delay in setup time and ultimately reduced productivity.

[Means for solving problems]

The object of the present invention is to provide a method for raising temperature in an injection molding machine that solves the problems existing in the above-mentioned prior art, and is achieved by the temperature raising method shown below.

That is, the temperature raising method according to the present invention involves raising the temperature of parts of the injection molding machine M adjacent to the molding material 2, such as the heating tube of the injection device, the injection nozzle, and the hot runner block 3 of the molding die. Characteristic R2
It is characterized by controlling, for example, by setting an intermittent heating time, so that the temperature increase rate a2 of the whole area or a part of the area is smaller than the original temperature increase rate a1 depending on at least the molding material 2. do.

[Effect]

Next, the operation of the present invention will be explained.

The temperature increasing method according to the present invention changes the temperature increasing rate in the temperature increasing characteristic in accordance with the temperature characteristics of the molding material, etc. The molding material 2 and the hot runner block 3, which is a part adjacent to this molding material, can be set small depending on the type of molding material, for example, temperature characteristics, etc.
The temperature difference between them becomes smaller, and eventually the difference in local heating and expansion amount between the two is reduced or eliminated.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

First, a temperature raising device 1 that can carry out the method of the present invention will be described.

The embodiment illustrates a hot runner block of a mold that is heated by a heater. In FIG. 2 (block system diagram of the temperature raising device), reference numeral 10 is a molding die attached to a mold clamping device (not shown);
It consists of a movable mold 11 and a fixed mold 12. Both types 11
and cavity 13 on the partying line of 12
The cavity 13 is connected to the mold 1 through a resin path formed in the hot runner block 3.
The injection nozzle 16 of the injection device 15 is connected to the injection nozzle 16 of the injection device 15 .

On the other hand, the hot runner block 3 includes a heater 18 whose energization is controlled by a temperature controller 17. Further, a thermocouple 19 is provided in the wiring part of this heater 18 and a part of the hot runner block 3,
Connect to temperature controller 17. The temperature controller 17 is further connected to a temperature setting device 20 for setting a set temperature Ts during molding and a temperature rising characteristic setting device 21 for setting arbitrary temperature rising characteristics by setting time and temperature. A feedback control system is configured to maintain the molding material 2 present in the path in a predetermined molten state. Also,
Based on the characteristics of the heater 18 and the control characteristics of the temperature controller 17, the original temperature increase characteristic R1 in the feedback control system is as shown in FIG. 4 (temperature increase characteristic diagram). When the method of the present invention is not applied, the respective times t1 to t3 for reaching the predetermined set temperatures T1 to T3 are fixed.

Next, a method for increasing the temperature of the injection molding machine according to the present invention will be explained.

In FIG. 1 (temperature increase characteristic diagram according to the method of the present invention), R1 is the original temperature increase characteristic based on the temperature increase device 1. Under this temperature increase characteristic R1, a general molding material such as a styrene synthetic resin or a molded product whose molding quality is not critical is used as the molding material. On the other hand, the temperature increase characteristic indicated by R2 is the case where the temperature increase rate a2 is controlled to be relatively smaller than the temperature increase rate a1 of the above temperature increase characteristic R1 according to the method of the present invention, and it has a large coefficient of thermal expansion as a molding material. Applicable to molded products that require high molding quality.

A specific method for obtaining the temperature increase characteristic R2 will be described below. First, the temperature setter 20 is set to the set temperature Ts during molding, and the temperature rise characteristic setter 21 is set to the step temperature K and the temperature rise rate a2 (°C/
sec).

If you turn on the power with the above settings, the thermocouple 19
detects the initial temperature To and controls the temperature controller 17.
Grant to. On the other hand, the temperature controller 17 sets the temperature T1 obtained by adding the step temperature K to the initial temperature To as the target temperature, and at the same time sets the temperature T1 as the target temperature.
Turn on. As a result, heating is performed by the heater 18, and the temperature of the hot runner block 3 is increased by the temperature increase a1 of the original temperature increase characteristic R1. When the temperature rises by the step temperature K and reaches the temperature T1, the thermocouple 19 detects this and the temperature controller 17 turns off the heater 18. On the other hand, the temperature increase rate a is set smaller than the temperature increase rate a1.
2, the time t1 until the temperature reaches T1 is calculated by calculation processing, and the time t1 is calculated by the timer function in the temperature controller 17.
1, the heater 18 remains in the OFF state. When time t1 is reached, the heater 18 is turned on again, and this
The ON period continues until the temperature T2 (=T1+K) is the sum of the temperature T1 and the step temperature K.
Thereafter, the target temperatures T3, T4, . . . are set by sequentially adding the step temperatures K, and if the same procedure is repeated, the temperature will be raised with the temperature increase characteristic R2 that approximates the target temperature increase rate a2. And the predetermined set temperature
After reaching Ts, the molding temperature is maintained at a constant temperature using control methods such as ON/OFF control, PI control, PD control, and PID control.

Therefore, in FIG. 1, the temperature increase characteristic R2 is delayed by the time td with respect to the original temperature increase characteristic R1, but the temperature increase rate a2 is set to be relatively small. Although the temperature is repeatedly raised and lowered by intermittent heating, a more linear temperature increase characteristic can be obtained by setting the step temperature K to a small value. In addition, it is possible to change the temperature rise characteristics by reducing the amount of power continuously supplied to the heater, but according to the method of the embodiment, special equipment and methods are required. It has the advantage that it can be implemented easily and at low cost without having to adopt it.

On the other hand, FIG. 3 (temperature rise characteristic diagram) shows another embodiment.

The temperature increase characteristic R2 shown in FIG. 1 shows the case where the temperature increase rate a2 in all regions is controlled to be small, but the embodiment shown in FIG. 3 shows the case where the temperature increase rate in some regions is controlled to be small.

First, the temperature increase characteristic R3 is when molding is performed using a molding material that completely melts and no air entrainment occurs when the temperature exceeds a predetermined temperature Tc. In this case, the temperature is raised at a relatively small temperature increase rate a3 until the temperature Tc is reached, and when the temperature exceeds the temperature Tc, it is quickly raised at the original temperature increase rate a1. on the other hand,
On the other hand, the temperature increase characteristic R4 is a case where molding is performed using a molding material that does not adversely affect molding in a low temperature region. In this case, the temperature is quickly raised to a predetermined temperature Th at the original temperature increase rate a1, and after exceeding this temperature Th, the temperature is gradually increased at a relatively small temperature increase rate a4. Further, if necessary, the temperature increase characteristic can be set using an arbitrary function such as a quadratic function.

Although the embodiments have been described in detail above, the present invention is not limited to these embodiments.
For example, although the hot runner block of a molding die is illustrated, the present invention can be similarly applied to any part adjacent to the molding material, such as a heating cylinder of an injection device, an injection nozzle, etc. Other changes may be made in the detailed structure, method, etc., without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, the temperature increase method of the injection molding machine according to the present invention is such that the temperature increase rate in all or part of the temperature increase characteristic is controlled to be smaller than the original temperature increase rate depending on at least the molding material. , obtain the following effects:

Optimal temperature rise characteristics can be set for the molding material to be molded. Therefore, it is possible to prevent decomposition and deterioration of the material due to air entrainment and local heating when the temperature rises, so it is possible to eliminate wasteful use of molding material and loss of energy due to emptying before the start of molding.

Since unnecessary blanking work is eliminated, the molding work can be started up quickly, contributing to shortening setup time and improving productivity.

Since it can be easily implemented using existing equipment, it can contribute to cost reduction, size reduction, and weight reduction.

[Brief explanation of drawings]

Figure 1: Temperature increase characteristics diagram according to the temperature increase method according to the present invention, Figure 2: Block system diagram of a temperature increase device that can implement the same method, Figure 3: Temperature increase characteristics according to the same method according to other embodiments. FIG. 4: Temperature increase characteristic diagram according to a conventional temperature increase method. In the drawings, 1: temperature raising device, 2: molding material, 3:
Hot runner block, M: Injection molding machine, R2:
Temperature increase characteristics, a1, a2: temperature increase rate.

Claims (1)

[Scope of Claims] 1. When increasing the temperature of a portion adjacent to the molding material in an injection molding machine, the temperature increase rate in the entire region or a partial region of the temperature increase characteristic is at least equal to the original temperature increase rate depending on the molding material. A method for increasing the temperature of an injection molding machine, which is characterized by controlling the temperature to be lower than that of the injection molding machine. 2. The method for increasing the temperature of an injection molding machine according to claim 1, wherein the control is performed by setting an intermittent heating time.