JPH03187721A - Control of mold temperature - Google Patents

Abstract

PURPOSE:To rise a mold temperature smoothly and shorten a time until the mold temperature arrives at the final mold temperature by a method wherein the temperature for heating medium is risen to a high temperature until the time immediately before the mold temperature arrives at a predetermined temperature to heat a mold quickly while the set value of the temperature of the heating medium is lowered toward the vicinity of the point of inter-section between the tangential line of the temperature rising speed curve and the set temperature of the mold immediately before the mold temperature arrives at the predetermined temperature. CONSTITUTION:The final desired mold temperature Ti is set by the setter of a controller 44 for an injection molding machine 40 to start automatic molding and the set temperature Ts of heating medium for a temperature controlling machine is set at a temperature near the maximum temperature available in the temperature controlling machine to rise the mold temperature quickly. A mold temperature T is measured actually by the temperature sensor 34 of a mold 30. DELTAT=Ti-T is operated by the CPU of the controller 44 and a vertical line is described from a time point (t1) when the DELTAT has become 3-5 deg.C to obtain the point of intersection A between the vertical line and the line of the initial set value Ts of the medium while the increasing line of the mold temperature T at the time point (t1) is extended linearly to obtain the point of intersection B between the line of the set temperature Ti of the mold, then, the set value Ts of the medium temperature is lowered from the point A toward the point B.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the adjustment of mold temperature in an injection molding machine, and in particular, the temperature setting of the mold temperature controller is controlled at a constant value by a signal from the molding machine. By changing the mold temperature step by step, the mold temperature can be raised smoothly and the time required to reach the final mold temperature can be shortened.

[Conventional technology]

When performing continuous automatic molding with a certain mold and certain resin material, a mold temperature controller (hereinafter referred to as a temperature controller) is used to ensure that high-quality molded products are stably produced and to minimize cooling time. The mold temperature is controlled by

At that time, the heat flow Q + C carried from the resin material to the mold
al/H and the heat flow Q removed from the mold toward the temperature controller
, Cal/H are balanced, the final stable mold surface temperature (hereinafter referred to as mold temperature) Ti is maintained.

During actual injection molding, this stable mold temperature Ti is
Desired values are assumed based on experience in software technology, taking into account the conditions that allow continuous ejection without damaging the molded product, but the temperature Ts of the circulating medium of the temperature controller, the temperature of the resin injected into the cavity, and the shot cycle. All that was required was to make efforts to bring the mold temperature closer to the desired value Ti by variously changing the cooling time.

[Problem that the invention seeks to solve]

In the above efforts, the medium setting temperature Ts of the temperature controller is handled in the usual manner.

If Td is the temperature drop in the medium circuit from the tank of the temperature controller, through the pressure pump, the medium passage of the mold, and back to the tank of the temperature controller via the return port, then Ts =T
It should be i+Td. However, since the temperature difference in Td is not so large, it can be considered as Ts#Ti.

However, if the medium temperature is set to Ts#Ti from the beginning and the medium is circulated, the heat capacity of the mold is quite large.
It takes quite a while for the final temperature of the mold surface to reach Ti, and during that time the molded product becomes unstable and cannot be called a good product, and the start-up of injection molding using a temperature controller is quite smooth. I couldn't go.

Therefore, as a wisdom at the molding site, initially set the medium temperature Ts to a temperature close to the maximum that can be set by the temperature controller, and then change the setting to Ts#Ti after the mold temperature T rises to a certain degree. This seems to be happening to some extent. For example, in the case shown in Fig. 4 (al), there is a delay in resetting Ts#Ti, and the mold temperature overshoots and is difficult to stabilize.Also, as in the case shown in Fig. 4 (b), , If the setting was changed to Ts#Ti too early, it would take an extremely long time for the mold temperature to approach the desired Ti, and this would not be easy.

[Means for solving problems]

In order to solve the above-mentioned problem, claim (1) provides (1)
) In a mold temperature control method in which a medium is circulated between the temperature controller 01 and the mold (30) to adjust the mold (30) to a predetermined temperature, immediately before the mold temperature reaches the predetermined temperature. The mold (30) is rapidly heated by raising the temperature of the medium as high as possible until then, and then, just before the mold temperature reaches a predetermined temperature (Ti), the temperature increase rate curve of the mold (30) is A method of finding the intersection of the tangent line and the set temperature of the mold (30) and lowering the medium temperature set value near this intersection to raise and stabilize the mold temperature to the predetermined temperature (Ti) in the shortest possible time. More specifically, in claim (2), (
2) The point at which the medium starts to fall is set when the mold temperature reaches a predetermined temperature (T
It is assumed that the temperature reaches 3 to 5 degrees Celsius lower than i), and the type of resin is also considered. According to claim (3), (3) When the mold set temperature (Ti) is 40 to 50 degrees Celsius or lower, the medium temperature is lowered so that the descending line of the medium almost coincides with the intersection point, and the medium temperature reaches the mold setting. When the temperature is reached, the medium temperature is controlled to almost match the mold set temperature, and conversely, (4) If the mold set temperature is 40 to 50 °C or higher, the medium temperature is set The temperature is controlled to be about 10°C higher than Ti).

A technical method called: is adopted.

[For production]

■ After completing a manual molding trial with a certain mold and a certain resin material, and before starting continuous automatic molding, set the molding conditions for continuous automatic molding from the setting device of the control device, and also set the mold temperature Ti. .

■ When starting automatic molding, set the set temperature Ts of the temperature controller medium to a temperature close to the highest that can be achieved with the temperature controller, such as Ts"1.5 XTi, and quickly Raise the mold temperature to .

(2) Realize the rising mold temperature T using a temperature sensor, input it to the control device, calculate ΔT=Ti−T, and treat the decrease in ΔT as an increase in mold temperature.

(2) The point in time when ΔT becomes small, for example, about 3 to 5 degrees Celsius, is defined as point 15, and from point L1 onwards, the set temperature Ts of the temperature regulator medium is lowered.

■ The method will be described in detail in the examples, but depending on the type of molding resin, the desired mold temperature Ti is, for example, 40 to 50°C.
The amount of heat dissipated from the mold is quite different depending on whether it is below or above, so taking this into consideration, set temperature Ts of the temperature controller medium.
After the temperature Ts reaches the calculated target temperature drop of Ts, the target temperature Ts is maintained at the target temperature drop.

A feature of the present invention is that the microcomputer type control panel of the injection molding machine is used to vary the set temperature of the temperature controller according to the above processes (1) to (2).

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, am is a mold temperature controller, (30) is a mold, and (40) is an injection molding machine.

(In the IIO mold temperature controller, αD can be a heat medium tank, a so-called oven tank system of a hot water circulator, but in response to recent demands for engineering resins, the mold temperature Ti can be raised to about 130℃, for example. , it is better to use a closed container type heating water circulation type.

(A) is a heater device that heats the medium in the tank, (A) is a cooling pipe that cools the medium in the tank, (B), (A) is a coolant on/off valve, and (Ae) controls the heating and cooling mentioned above. The control device, aη is a temperature sensor that measures the temperature of the medium in the tank, α field is the pump that sends the medium to the mold, Ol is the valve for opening and closing the medium delivery port, (to) is the valve for opening and closing the return medium port, ( 2) is a regulating valve for adjusting the pressure for sending the medium from the medium feeding port to the cavity. The mold (30) is a fixed side female mold (
31), consists of a moving side male mold (32) and a cavity (33) into which molten resin is injected, and is equipped with a temperature sensor (34) that measures the temperature of the cavity, and its signal output is transmitted to the molding machine. It is connected to a microcomputer type control device (44). In the injection molding machine (40), (41) is a heating cylinder, (42) is a nozzle, and (43) is a hopper for supplying plastic resin.

The optimally heated and kneaded molten resin is injected into the mold cavity (33) from the nozzle (42). (44) is a microcomputer type control device that controls the entire system of the injection molding machine and mold temperature controller, and as is well known, the CPU (44a)
), input device (44b), output device (44c), RO
M memory (44d), RAM memory (44e), numeric keypad device for digitally inputting molding conditions for the entire system (
44f) and the input molding conditions, the tank medium temperature sensor αη mentioned above, and the mold cavity temperature sensor (34f).
) consists of a display device (44g) that displays measured values in an easy-to-read manner.

Input device 11F (44) of microcomputer type control panel (44)
b) Mold temperature controller QlO tank medium temperature sensor Q
An electrical signal from η is input via the control device Q19,
An electric signal from a temperature sensor (34) in the cavity of the mold (32) is also input. The output device (44c) outputs electrical signals for operating each part of the injection molding machine, and also changes the set temperature Ts of the heat medium tank OD via the control device (+19) of the mold temperature regulator Ql. , a heater device ano that heats the medium in the tank, a cooling medium on/off valve Q4), and an α valve for sending and stopping the medium to the cooling corrugated pipe α that cools the medium in the tank. emit electrical signals for operation.

The functions of the mold temperature controller, mold, and injection molding operation system configured as described above will be explained.

■ For a certain mold and a certain resin material, after completing a manual molding trial and before entering the continuous automatic molding machine, the injection pressure, injection speed, charge amount, holding pressure switching position, mold opening position, and eject stroke for continuous automatic molding are determined. In addition to molding conditions such as , cooling time, and intermediate time, the final desired mold temperature Ti is also set from the setting device of the control device I (44) of the injection molding machine (40). All of these molding conditions are controlled by the control system R (44
) display device (44g), and check the RAM memory (
44d).

■ At the same time as starting automatic molding, set the set temperature Ts of the temperature controller medium to the highest medium temperature that can be achieved with the temperature controller, such as Ts#1.5 Raise mold temperature.

■ At a certain time in each shot (for example, at the start of injection), the rising mold temperature T is actually measured by the temperature sensor (34) of the mold (30), and the control device of the injection molding machine (40) (44), and the CPU of the control device (44) (
In step 44a), ΔT=Ti −T is calculated, and the decrease in T is taken as an increase in mold temperature T.

(2) The point in time when 8T becomes, for example, 3 to 5° C. (leprosy) is defined as point 11, and from point 1 onwards, the medium temperature set value Ts of the temperature controller medium is lowered.

■ The method is to raise the vertical line from time point 11 in Figure 3 and set the intersection with the initial setting value Ts line of the medium as A, and extend the line of increase in mold temperature T at time point 11 linearly. (i.e., the tangent to the temperature increase rate curve of the mold), the point where it intersects with the mold set temperature Ti line is designated as B, and that time point is t2
shall be.

■ Medium temperature set value T from point A to point B.
s is lowered, but the method differs slightly depending on the type of resin used for molding. The mold setting temperature Ti may be 40 to 50°C for general-purpose resins such as polystyrene, polyethylene, and polypropylene, but it should be approximately 80°C for acrylic resins, and more than 100°C for engineering resins such as polycarbonate and POM. Therefore, if the Ti temperature exceeds 40 to 50℃,
Since the amount of heat dissipated from the mold surface increases, the final set temperature Ts of the medium must also differ by, for example, 10°C.

Therefore, when the mold temperature Ti is -40 to 50°C with a general-purpose resin, the medium temperature setting value Ts is lowered from point A to point B so that it becomes TsζTi, and when point B is reached, Ts #Ti is constant.

However, like engineering resins, Ti>40~5
When the temperature is 0℃, at time t2, the temperature is lowered from point A to point B'' toward point B°, which is approximately 10℃ higher than point B, and when it reaches point B', Ts = Ti + 10℃. Make it constant.

Of course, in the above description, the temperature value is not limited to the above example. Furthermore, when setting the temperature controller from the molding machine side, the heater on time of the temperature controller can be set variably depending on the day of the week using a calendar timer or the like. Conversely, by controlling the temperature controller, it is also possible to take countermeasures such as sending an alarm signal to the molding machine to stop the molding machine when the set temperature Ts exceeds the control range and becomes abnormal.

〔Effect of the invention〕

As described above, the present invention provides a mold temperature control method in which a medium is circulated between a temperature controller and a mold to adjust the mold to a predetermined temperature, in which the mold temperature reaches a predetermined temperature. The mold is rapidly heated by raising the temperature of the medium as high as possible, and then, just before the mold temperature reaches a predetermined temperature, the tangent of the mold heating rate curve and the mold set temperature are Since the intersection point is found and the medium temperature set value is lowered toward the vicinity of this intersection point, the mold temperature can be raised and stabilized to the specified temperature in the shortest possible time.As a result, as in the conventional method, There is no need for operators to perform various operations, and they can concentrate on fine adjustments for automation without worrying about mold temperature control, which has the advantage of improving work efficiency. This method has the advantage that molding defects, which were considered to be inevitable at the start of molding, can be significantly reduced. In addition, ■ By setting the heater on time of the temperature controller using a calendar timer, etc., it is possible to mold good products at the same time as the start of work in the morning. It is also possible to control the temperature regulator, including calculations, to smoothly reach the optimum mold temperature in the shortest possible time at the start of automatic molding.

[Brief explanation of drawings]

Figures 1 to 3 show one embodiment of the present invention.
The figure is an explanatory diagram showing the overall configuration of the mold temperature controller, mold, and injection molding machine, Figure 2 is a flowchart explaining the operation, and Figure 3 is a line diagram explaining the transition of mold temperature. is time,
The vertical axis is temperature. Figures 4-a and 4-b are diagrams illustrating changes in mold temperature when the present invention is not used. Ql...mold temperature controller, Ql)...tank,
@... Heater device, α To... Cooling pipe, α
a...On, off valve, 09...On, off valve, Ql...Control device, (171...Temperature sensor, 0 odor...Pump, al...Valve for opening/closing medium port , (to)... Return medium opening/closing valve, (2
1)...Adjusting valve, (30)...Mold,
(31)...Female mold, (32)...Male mold,
(33)...Cavity, (34)...Temperature sensor, (40)...Injection molding machine, (41)...
... Heating cylinder, (42) ... Nozzle, (43
)...hopper, (44)...mycin system control device, (44a) ・= CPU, (
44b) - input device, (44c) - output device,
(44d) ・ROM memory, (44e) -R
AM memory, (44f)...Numeric keypad device, (
Ti)...Mold set temperature, (Ts)...Medium temperature set value. ! 4.3 Time t (sec)

Claims (4)

[Claims] (1) In a mold temperature control method in which a medium is circulated between a temperature controller and a mold to adjust the mold to a predetermined temperature, the temperature of the medium is maintained until just before the mold temperature reaches the predetermined temperature. The mold is heated as quickly as possible, and then, just before the mold temperature reaches a predetermined temperature, find the intersection of the tangent of the mold's heating rate curve and the mold's set temperature. A mold temperature control method characterized by lowering the medium temperature setting value of the temperature controller toward the vicinity of the intersection, raising and stabilizing the mold temperature to a predetermined temperature in the shortest possible time. (2) The mold temperature control method according to claim (1), characterized in that the time when the medium starts to fall is when the mold temperature reaches a temperature 3 to 5 degrees Celsius lower than a predetermined temperature. (3) If the mold set temperature is 40 to 50 degrees Celsius or lower, lower the medium so that the descending line almost coincides with the intersection, and when the medium temperature reaches the mold set temperature, change the medium temperature to the mold set temperature. 2. The mold temperature control method according to claim 1, wherein the temperature is controlled so as to substantially match the temperature. (4) The mold temperature according to claim (1), characterized in that when the mold set temperature is 40 to 50 °C or higher, the temperature is controlled so that the medium temperature is about 10 °C higher than the mold set temperature. Adjustment method.