JPS60139424A - Resin temperature control for plastics molding machine - Google Patents

Abstract

PURPOSE:To achieve a larger discharge capacity of resin, a less scorching and a saved energy by predetermining the temperature distribution in the cylinder itself to be optimal for molding as desired with the type of resin and the revolution of the screw as parameters to control the temperature of the cylinder properly. CONSTITUTION:A microcomputer 11 separately determines what temperature distribution of resin in the cylinder can eliminate troubles such as scorching to ensure a better extrusion work. To secure such a pattern, the temperature of individual temperature measuring zones of the cylinder is controlled for respective revolutions of the screw and the optimum cylinder temperature distributions thus set are recorded individually. Then, this setting is done separately in terms of the brand of resin. The actual temperatures of the individual temperature measuring zones obtained from temperature measuring elements TC2-TC5 are compared with optimum cylinder temperature distributions previously inputted referring to the revolutions of the screw to determine a deviation, based on which a heater 6 or cooler 7 is operated.

Description

Detailed Description of the Invention Technical Field The present invention relates to a plastic molding machine for controlling the resin temperature in the molding machine to the optimum temperature for molding when molding plastic using a plastic molding machine such as an extruder. Leech temperature i8! Regarding the control method.

Conventional technology and its disadvantages In plastic extrusion molding, controlling the resin temperature in each zone in the extruder cylinder to a temperature suitable for the resin used increases extrusion rate, reduces scorch, reduces energy costs, Furthermore, 11 cable M! It has a very important meaning from the point of view of improving the thermal characteristics as a third-edge material.

Conventional extruder resin temperature control involves drilling a plurality of temperature measuring holes 3...in the cylinder 2 of the extruder 1, which do not penetrate the cylinder 2, as shown in Figure gg1.・Insert the temperature measuring element 4... into each temperature measuring zone of the cylinder 2,
(' l s C, e C, I Measure the temperature of C4,
These warm temperatures are input to the temperature controller 5..., and the heating device t6, such as a band heater or embedded heater, provided on the outside of the cylinder 2, and the cooling device 7, such as a cooling blower.
... is controlled by these temperature controls 1f-i5....

However, it has become clear that this method has the following problems. That is, in the above control method, the difference between the temperature measured by the side temperature element 4 and the temperature of the molten resin in the cylinder 2 is as follows. Temperature differences (Δ'l') as shown in Figure 2 occur in each of the 6111 temperature zones (CI, C1, C4), and when the resin is poured into the extruder 1, Due to the change in the rotational speed of the screw 8 of the extruder 1, the temperature difference between the actual resin temperature and the temperature of the cylinder 2 as shown in FIG. 3 further increases by 618 minutes.

Therefore, it was found that due to these influences, the temperature of the molten resin in the cylinder 2 was heated to a temperature higher than the desired temperature, and energy was wasted.

(C, C, C4 in Figures 2 and 3 represent the temperature measurement positions of the cylinder 2, and the CI e shown in each temperature controller 5 in Figure 1. (It corresponds to each temperature measurement zone of C1 + C4.) Furthermore, according to recent research, the temperature of the molten resin in cylinder 2 is determined not only by room temperature and screw rotation speed as described above, but also by the extrusion rG 1 setting. It has become clear that this is influenced by temperature, the shape and structure of the screw, the type of molten resin (even differences in grades of the same resin), etc. For example, when extruding polyethylene resin, set the temperature of the temperature controller 5 to 12
Even if the temperature is 0°C and the temperature measured by the thermometer 4 is 120°C, the actual temperature of the molten resin is 130 to 150°C.

Therefore, it has been impossible to accurately determine the actual temperature of the molten resin by simply measuring the temperature using the temperature measuring holes 3.

Therefore, the present inventors have previously proposed a resin temperature control method capable of controlling the resin temperature with high accuracy in Japanese Patent Application No. 58-41038 and Tokutsumugisho S8241039.

In these methods, two or more side heating elements are arranged at different distances from the inner surface of the cylinder in the thickness direction of the cylinder wall of a plastic molding machine, and the temperature of the cylinder measured by these side heating elements is -[7J >1# on the inner surface of the cylinder! 1 K, and at least 3 degrees including the screw rotation speed, room temperature, temperature of the bath melt resin, etc. Increase the correction temperature using the above parameters,
Predict the temperature of the molten resin in the cylinder, calculate the deviation between this predicted temperature and the desired resin temperature, and measure the mFIL of the cylinder of the plastic molding machine and the one that controls the temperature of the molten resin in the cylinder based on this deviation. Then, the correction temperature is increased from at least three parameters including room temperature, screw rotation speed, among the parameters that vary the molten resin temperature such as room temperature, screw rotation speed, screw shape, set temperature, resin type, etc. The temperature of the molten resin in the cylinder is predicted, the deviation between this predicted temperature and the desired resin temperature is determined, and the temperature of the 't# molten resin in the cylinder is controlled based on this deviation.

These methods can be used regardless of the distribution of the desired resin temperature of the m#Am resin in the cylinder (the temperature in each side temperature zone in the cylinder) by setting the operating temperature and the desired resin temperature. , No matter how much the above parameters change, automatic fishing spot control is possible, and the accuracy is ±0.
．． It has the advantage of extremely high accuracy of about 5"C to ±1°C.

However, in implementing these methods,
It is necessary to create basic data in advance of the influence # (temperature fluctuation) that these parameters have on the molten resin temperature by changing each of the above parameters variously. There was a moment when I needed time.

Purpose of the Invention This invention was made in view of the above circumstances, and it can greatly reduce the effort and cost of creating basic data, and moreover, it can control the resin temperature with high precision, increase the amount of resin discharged, and reduce scorch. The object of the present invention is to provide a resin temperature key control method for a plastic molding machine that saves energy.

Structure of the Invention The resin temperature control method for a plastic molding machine of the present invention is as follows:
In order to make the temperature distribution on the melting side 11 in the cylinder of the plastic molding machine a desired temperature distribution that is optimal for molding, the temperature distribution of the cylinder itself is preliminarily determined using the resin temperature and the screw rotation speed as parameters. process and this first
Compare the temperature distribution of the cylinder itself to achieve the above-mentioned optimal desired temperature distribution determined in the process with the actual temperature distribution of the cylinder, and set the set temperature of each temperature measurement zone of the cylinder based on the deviation. and a second step of controlling.

Principle of the Invention In general, if plastic molding is limited to a specific task, such as extrusion coating of insulators made of polyethylene resin for electric wires, cables, etc., then the cylinder of the extruder that is most suitable for that extrusion task is determined. The resin temperature distribution (this temperature distribution is sometimes called a pattern) is limited to only a few.

Therefore, in order to reproduce such a limited pattern, it is not necessary to select many parameters and examine their effects as in the previous patent application No. 58-41038. There is no need to predict the resin temperature distribution; all you need to do is prepare the cylinder temperature distribution necessary to reproduce this pattern in accordance with this pattern, which greatly reduces the effort required to create basic data. becomes possible.

Specific Structure and Function of the Invention Hereinafter, an example in which the present invention is applied to an extruder will be specifically explained.

First, the operation of determining the temperature distribution of the cylinder itself (abbreviated as M-optimal cylinder temperature) in order to obtain the desired temperature distribution optimal for molding in the first step will be explained.

An extruder equipped with a temperature-measuring screw that has a temperature-measuring element exposed on the surface and can directly measure the temperature of the bath melted resin is prepared, and the resin used during the main extrusion operation, such as cross-linking agent-added polyethylene resin, is prepared. We actually carry out extrusion work for each brand.

For extrusion of cross-linking agent-added polyethylene resin, the temperature of the molten cross-linking agent-added polyethylene resin in the cylinder is 0 (
Separately determine what kind of pattern (pattern) is needed to ensure good extrusion without causing problems such as scorch, and then determine the screw rotation speed and speed to obtain this pattern.
For example, the temperature in the valley temperature measuring zone of the cylinder is controlled at 5 rpm.

Then, at the screw rotation speed srpm, the temperature distribution of the cylinder when the above pattern was obtained (outside the optimum cylinder temperature at 5rprn; fli) is recorded.

Next, the screw rotation speed is changed to, for example, 10 rPm, and the temperature IW of each temperature measurement zone of the cylinder is changed and controlled so that the same desired temperature A6 as before is obtained. As mentioned above, if the screw rotation speed changes, the resin temperature will change accordingly, so the optimum temperature distribution of the cylinder will naturally differ from that in the case of 5r4. In this way, the optimal cylinder distribution for 10 rl)m is determined once. Then, the screw rotation speed was 15 rpm one after another.

The optimum cylinder temperature distribution at each screw rotation speed is calculated as 2Qrprrt...

It will be expressed as If the screw rotation speed is divided into narrow ranges such as 5~xorpm, ii~15rpm, etc., the above function becomes Y=a
It can be expressed by a linear equation of x+b.

Therefore, by dividing the commonly used screw rotation speed into, for example, four ranges for each temperature measurement zone of the cylinder, the following relational expression can be obtained.

Side temperature zone Screw rotation speed Formula 0 Formula % Y: Optimal cylinder temperature , and are classified according to this one pressure.

Then, these relational expressions are recorded for each brand of crosslinking agent-added polyethylene resin, for example, by storing them in a computer memory.

FIGS. 4 and 5 are graphs of the above relationship. The graph in Figure 4 shows the melt index (MI) of 3.
．． 2, the graph in Figure 5 shows the optimum cylinder temperature when changing the screw rotation speed from 5 to aorpm for crosslinking agent-added polyethylene resins with melt indexes of 1 and 2. It is plotted for each part (C1).Then, from this graph, we can see that "1%1%...5" in the above Hd relational expression.
It is understood that bts, m, . . . can be determined from the direct fM portion of each curve.

From these graphs, the melt index is 3.2.
Optimal cylinder for extrusion work using cross-linking agent-added polyethylene resin with a screw rotation speed of, for example, zorpm.
The temperature is C9, 123.3°C.

119.6℃ on C island, 116.2℃ on C4, 11 on C3
It was found that the temperature was 5.6℃, and the screw rotation speed was 2Qr.
When changing from pm to 3grptn, the temperature of each zone can be changed along the straight line of the graph according to the relational expression expressed by the above-following equation.

With the above steps, basic data creation in the first step is completed.

Next, the second step of controlling the resin temperature during actual extrusion work will be explained.

FIGS. 6(a) and 6(b) show an example of the configuration of an extruder that performs the above-mentioned side. The extruder 1 of this example has an aluminum cast heater 6a as a heating device 6 for the cylinder 2. In addition, a cooling oil jacket 7a serving as a cooling device 7 through which cooling oil circulates is provided on the outer peripheral surface of the cylinder 2. The cooling oil jacket 7a is formed with a spiral groove 7b provided for each temperature measurement zone, and serves to perform the following steps. In this example, control is performed in the temperature measuring zone CI'pCsFc,tc of the cylinder 2 corresponding to FIGS. Child IlI C,
,Ill U,.

'l'c'4, TC, is approximately lo from the inner surface of cylinder 2
J at my level! It is inserted into the temperature measuring hole 3, which is drilled with a J gap. The depth of this temperature measurement hole 3 is determined by considering the extruder l, extrusion conditions, etc., but it is the same as the depth of the temperature measurement hole when creating the basic data in the first step. It is necessary to. Further, a rotary generator 9 is attached to the base of the screw 8 for detecting the rotation speed of the screw 8 and outputting one pressure proportional to the rotation speed.

And the above measurements! Element+il C,, Ill C,
, Ill C,.

The output signals from the +1+ CB and rotation source machine 9 are sent to a processing system as shown in FIG. 7, for example, and
It is processed.

The output from the rotary generator 9 is input to the A/L converter 10ζ, digitized, and input to the microcomputer 11. The above relational expression (optimum cylinder temperature corresponding to changes in screw rotation speed and resin brand) determined in the first step is input into the microcomputer 11 in advance.

In other words, the optimum cylinder temperature distribution (pattern) using the screw rotation speed and the type of resin as parameters is input.

In addition, each of the above-mentioned side temperature elements T, C,, Ill C,, Il
l (, +4° The output signal sent from the TCs is sent to the temperature controllers 12... provided corresponding to these temperature measuring elements. These temperature controllers 12... are A/1) conversion function.

Equipped with D/A conversion function and linearization function,
The above output signal is linearized and A/D converted here, and then input to the microcomputer ft'i. Then, the microcomputer 11 calculates the optimal cylinder temperature distribution inputted in advance and the side temperature element TO, ~r1.
Compare the temperature of each temperature measurement zone from y C1 with reference to the screw rotation speed input separately as described above,
Based on this deviation, the temperature controller 12...
・Calculate the set temperature.

This set temperature is sent from the microcomputer 11 to each temperature controller 12 corresponding to the temperature measuring zone. The temperature controller 12... is set to this set temperature and the temperature measuring cord 1゛C.
! Compare the temperature 11 of the cylinder 2 in the valley temperature measurement zone from ~fil e, and compare it with the temperature 11 of the cylinder 2 in the valley temperature measurement zone, and compare it with the temperature 11 of the cylinder 2 in the valley temperature measurement zone from
Operate the cylinder to match the set temperature and cylinder temperature. Thus, by repeating the above calculation and comparison process 2 to 3 times, the temperature distribution in each temperature measurement zone of cylinder 2 will be -1 to the optimum cylinder temperature distribution, and the temperature of the molten resin in cylinder 2 will be the same as the extrusion temperature distribution. matches the optimum temperature distribution (desired resin temperature distribution).

Furthermore, when the screw rotation speed is changed during extrusion work, the screw rotation speed signal input to the microcomputer 11 changes, and the optimum cylinder temperature 1 (distribution) at the new screw rotation speed is calculated and determined using the above relational expression.

Then, the same process as before is performed on this new optimum cylinder temperature distribution, and the temperature distribution of the bath melting resin in the cylinder 2 is made to match the desired resin temperature distribution.

In addition, when resin rods and brands change, new ridges,
- The above-mentioned relational expression, which is set in advance at °C for the brand of resin, is read into the microcomputer 11, and the above-mentioned calculation and control processing is performed.

The above is the second step in this invention.

According to such a temperature control method, the optimum cylinder temperature corresponding to several desired resin temperature distributions determined in advance is determined, and control is performed using this optimum cylinder temperature as an index. The cost to raise the temperature (amount of resin used, test time) is minimal. However, although only a limited temperature distribution can be controlled, in the case of general extrusion work, the extrusion work conditions are naturally limited as described above, so this does not cause any practical problems. In addition, since the optimum cylinder temperature is determined in response to the screw rotation speed, which is a parameter that greatly changes the resin temperature, and temperature fluctuations due to resin 44, highly accurate control is always possible. Furthermore, in the present invention, the desired resin temperature distribution is within a limited range and there is no process of predicting the resin temperature during one force control, so there is no need to particularly consider the room temperature.
Even the temperature distribution of the cylinder itself is maintained at a determined temperature.
If you set C, you can always obtain the desired fat temperature distribution.

In the above example, the temperature measuring elements 'l'c, TC, TC4, and TC corresponding to the temperature measuring zones of the extruder 1.

Although this temperature control method is applied only to the temperature measurement zone on the popper side, this temperature/f control method may be similarly applied to the temperature measurement element IllC2 corresponding to the temperature measurement zone on the popper side. However, for ordinary extrusion strips, temperature control in the four zones described above is sufficient. Further, the heating and cooling means for the cylinder 2 are not limited to the above examples, and heating and cooling means using a fluid heat medium such as silicone oil, cooling means using a blower, etc. may also be used.

Moving bed of the invention As explained above, according to the resin temperature control method of the present invention, although the bath melt resin temperature can only be controlled within a certain limited resin temperature distribution, the cost of creating base sulfur data is negligible. If the commonly used resin temperature distribution is uniform, there will be no practical inconvenience. In addition, since the resin temperature can be controlled with high precision at all times, it is possible to increase discharge capacity, reduce scorch, and save thermal energy.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram showing an extruder using a conventional resin temperature control method, Figure 2 is a graph showing the relationship between room temperature and ΔT, and Figure 3 is a graph showing the relationship between screw rotation speed and ΔT! Figures 4 and 5 are graphs showing the optimum cylinder temperature distribution for cross-linking agent-added polyethylene resin as the screw rotation speed is changed, and Figure 6 (a) is a graph showing the relationship between fi.
Schematic configuration diagram showing an example of an extruder to which method 11 is applied, No. 6
Figure (b) is a schematic sectional view of the cylinder of this extruder, and Figure 7 is a block diagram showing an example of a control processing system used in this temperature control method. 1... Extruder, 2... Cylinder, 6...
...Heating device, 7...Cooling device, 8...
・：・・・Screw, 9・・・Rotating power generation M, 11・
...Microcomputer, 12...Temperature-saving meter, TC,, TC number IlI C,, Ill C
1... Temperature measuring element. Applicant Fujikura Kansen Co., Ltd. Figure 2 Room □ ;L ('CJ

Claims (1)

[Claims] To make the temperature distribution of the bath #Is resin in the cylinder of a plastic molding machine a desired temperature distribution optimal for molding, the cylinder itself! [A first step in which the distribution is pre-prepared using resin mmM and screw rotation speed as parameters, the optimum temperature distribution of the cylinder itself determined in this first step, and the actual temperature distribution of the cylinder. A method for controlling a resin temperature in a plastic molding machine, comprising a second step of softening the temperature and controlling the set temperature of each temperature measurement zone of the cylinder based on the deviation.