DE102009014311A1 - Method for monitoring and / or controlling and / or regulating functions of and in injection molding machines - Google Patents

Abstract

In a method for monitoring and / or controlling and / or regulating functions of and in injection molding machines by means of sensors (7), in particular temperature and / or pressure sensors, which od a melt in at least one hot runner, a nozzle, a cavity. monitor, the sensor (7) at the beginning of a temperature and / or pressure increase trigger a signal for a monitoring and / or control process in the injection molding machine.

Description

The The invention relates to a method for monitoring and / or Control and / or regulation of functions of and in injection molding machines, by means of Sensors, in particular temperature and / or pressure sensors, which a flow of the melt through at least one hot runner, a nozzle, od in a cavity or the like.

State of the art

It is known to have significant injection molding parameters in injection molding detect with the help of sensors and monitor them, To use taxes and rules of the respective injection molding process. In this case, a distinction is made between sensors that are used for one to be built into the structure of the tool plates to anschießend to determine the metal temperature, and to the other both the Metal temperature on the surface as well as the immediate Determine the contact temperature of a plastic melt.

For example, shows the DE 34 25 459 A1 a temperature sensor placed within an injection mold near its cavity surface to detect not only changes in steel / tool temperature but also indirectly changes in the absolute melt temperature in the cavity.

With However, such a temperature sensor will be measured curves or Get temperature-time characteristics that are very sluggish Show course, d. H. the measurement data that can be measured with it, are by no means usable for a so-called real-time control.

Except Temperature sensors are also used in many applications Pressure sensors used. Both temperature and pressure sensors can anywhere on the injection molding machine or injection molding tool be provided. This is especially true for the area hot-channels, nozzles and cavities. However, the invention should not be restricted to this. There are many places in an injection molding machine conceivable where certain Parameters to be included.

Object of the invention

Here employs the invention, which is the object of a method of the above type, with which it is easy and simple cost-effective way becomes possible while an injection molding process relatively fast, d. H. timely changes to capture as a parameter for manipulation of the injection molding process.

Solution of the task

According to the invention this task is solved by not only especially when the melt reaches the sensor, the sensor should at the beginning of a temperature and / or pressure increase, a signal for trigger a monitoring and / or control process in the injection molding machine. The sensor can also z. B. monitor the degree of compression of the melt and if necessary regulate.

controlled not only are the actual functions of an injection molding machine but all the possible functions of the capture are dependent on the melt front. This also belongs the regulation or control of closing nozzles or moving Cores and pins or the melt front-dependent initialization an embossing process, after the melt a certain Reached position.

today Due to their design, sensors are much more sensitive on temperature and / or pressure changes than conventional Sensors, d. H. the sensor used according to the invention has despite its indirect temperature and / or pressure measurement at a temperature and / or pressure change a steep Signal rise, which then in fractions of seconds a required Switching signal can trigger. Through him is no longer the History of the temperature or pressure monitors (what but still possible), but it is quasi used as a switch. This use is especially under protection and applies especially to the supervised Temperature, but is also possible with pressure monitoring.

To According to the invention, it is particularly expedient if the at least one sensor is just below a wall surface, for example, a hot runner inner surface, a nozzle surface or a Kavitätsinnenfläche is provided. This has the particular advantage that the sensor no direct Load is exposed, which also causes damage is excluded by a possible overload. As a result, the sensor used according to the invention can turn designed simpler in its construction and thus more cost-effective be manufactured as comparable direct measuring sensors. The over The sensor has a permanent bridge of preferably 0.2-3 mm Thickness acts as a membrane for transmission in the case of the pressure sensor of the pressure.

Due to the encapsulated design, ie by the indirect measurement method, the sensor is not touched by the plastic melt, which is why its contamination or leakage is excluded, although it has a relatively steep characteristic, such as almost a sensor with direct melt contact. Also, such a sensor leaves no impressions on a molded part, which is why this type of measurement is particularly applicable for injection molding processes in which no impression is permitted, which is the case for example with optical components such as lenses, contact lenses.

Out for the same reason is a damage of the invention used by abrasion - for example, in glass or carbon filled melts - excluded. Furthermore, the lifetime of the sensor is many times higher than that of a direct-contact sensor. Furthermore, they are in contrast to a melt directly touching sensor for whose encapsulated installation requires no tight tolerances; it is sufficient or is preferred when the tip of the sensor touched the bottom of a hole in the injection mold enough. Otherwise, a bore wall surrounding the sensor tip can be essential greater than that of a direct measuring sensor.

Already In the past, an indirect method was used to measure the Pressure in a mold cavity or in a nozzle used. This was a strain sensor in a tool plate or installed in a nozzle and with the help of a direct calibrated (strain = proportional to pressure). According to the present invention, however, the Force measured across the thin bridge between Sensor and cavity is transmitted. This jetty acts as a sort of "membrane". In this case is Pressure = force per area. The inventive Method is therefore to be preferred since calibration during manufacture, So a calibration of the sensor at the manufacturer is conceivable, which is why to a second, direct measuring sensor for calibration during Users can be dispensed with, which is necessary in the method with the strain sensor is. In addition, a strain sensor in the tool plate measures quasi integral, d. h., based on an area, which is why he does not for switching depending on the melt front can be used. According to the present Invention, there is a pressure increase when the melt at the Sensor position flows past.

There the inventive sensor under the wall surface is provided, this advantageously does not have on its sensor front specially processed, d. H. he does not have the contour of a wall be adapted, which in some cases in direct-measuring Sensors is the case.

Especially it is advantageous if the sensor operating according to the invention at least approximately the same sensitivity with respect to temperature and / or pressure changes has like a feeler with direct contact with a melt, with its reaction due to different sensor materials.

Finally, it has proved to be particularly positive that the respective melt position can be determined in an almost real time by the sensors used according to the method according to the invention. Due to these detectable real-time temperature and / or pressure changes may advantageously z. B. an automatic switching to the process step emphasis, which is exposed to a melt in at least one cavity towards the end or at the end of their flow path, are excellently controlled or regulated. In contrast, in the prior art ( DE 101 55 162 A1 ) For the process step emphasis against the end of the flow path of the melt determines the mold wall temperature and based on an increase of this temperature of the switching point for holding pressure phase.

Furthermore, the use of a sensor operating according to the invention allows an automatic, melt-front-dependent opening and closing of shut-off nozzles due to the determinable real times for temperature and / or pressure changes. This is done independently of an automatic balancing of the volumetric filling, as in the DE 101 12 126 is described in more detail, to which reference is expressly made. However, the melt flow is controlled by an automatic adjustment of the hot runner nozzles in such a way that the opening and closing always takes place when the melt has reached the sensor position.

Also may be advantageous when using the inventive method an automatic venting by a melt front-dependent closure a Kernzuges done or an embossing process during injection molding be initialized.

A particularly expedient use of the method according to the invention can also be that, due to the determinable real times for temperature and / or pressure changes, an automatic sequential filling of cascade tools takes place in which a melt is introduced under pressure from a plurality of nozzles into a cavity, wherein at least one nozzle is associated with the sensor operating according to the invention, by which the melt flow in the cavity is then indirectly determined and the filling process by the nozzles is thereby automatically coordinated with one another, wherein here on the DE 10 2004 031 546 A1 express reference is made.

Furthermore, it may be useful in Spritzgiessprozessen, mentioned real life times for a controlled displacement of soge called to use weld lines or to provide melt frontage control in family injection molds.

Also offer the ascertainable real times for temperature and / or Pressure changes advantageous the possibility that thus an automatic balancing of hot runner injection molding tools is set up.

After all can with the aforementioned real-lives also the Viscosity of the melt better within at least one Cavity through an interaction of direct or indirect pressure or direct or indirect temperature.

As a general rule Everything can be done with the indirect sensors direct sensor can also be made. This is first and foremost the monitoring of the process on the basis of maximum pressure, Pressure integral, rate of pressure rise, etc., temperatures, Temperaturvorlauf etc .. In addition, the indirect signal as well as the direct signal can be used for process optimization by the waveform is optimized accordingly.

figure description

Further Details and advantages of the present invention will become apparent from the following description of an embodiment in connection with the drawing; show it:

1 a real-time diagram with two temperature-time characteristics compared between a direct and an indirect measuring temperature sensor and

2 a simplified longitudinal section through a mold plate of an injection molding tool in the region of an indirectly measuring temperature sensor provided in this.

At the in 1 The real time diagram shown on the abscissa shows the time in seconds and the ordinate the temperature. With 1 referred lower temperature-time characteristic derived from a directly come into contact with a melt temperature sensor with 2 designated temperature-time characteristic of an in 2 shown indirectly measuring temperature sensor is for comparison.

As from the real-time diagram according to 1 can be seen, takes place within a few milliseconds, a virtually vertical steep rise of the characteristics 1 and 2 , which then drop relatively slowly in about 20 seconds, ie the two characteristics 1 and 2 run according to the characteristic of a sawtooth.

The small time difference between the two characteristics 1 and 2 in 1 is practically negligible in relation to the enormous advantages described at the beginning, which result from indirect acquisition of the measurement data.

The in 2 simplified cutout from an injection mold 3 shows a mold plate 4 which is a cavity surface 5 has, to which a receiving bore 6 directed, which ends as a blind hole, in which a temperature sensor 7 has been used. This only needs to be interpreted so that it determines a melt front, where he is very well a whole temperature-time characteristic 2 determined.

The temperature sensor 7 is by means of a spacer sleeve 8th (or a mounting nipple not shown) against the 9 designated base of the blind hole pressed against contact, which only a small distance 10 (0.2 to 3.0 mm) to the cavity surface 5 Has. This base area 9 Can be rounded on the side, thus breaking a bridge 16 is avoided.

In the in 2 the embodiment shown, the sensor has approximately the same outer diameter as the inner diameter of the receiving bore 6 on. In a preferred embodiment, however, the diameter of the receiving bore 6 as the outside diameter of the sensor. In individual cases, even a spherical sensor surface to the base 9 be sought in order to achieve a selective power transmission instead of an unfavorable surface transmission.

The temperature sensor 7 is at its free end with a cable 11 connected by a cable channel 12 to an evaluation unit 13 runs. The latter is replaced by a mounting plate 14 held, in turn, by means of a screw 15 on the mold plate 4 is fixed.

The operation of the present invention is as follows:
The injection mold 3 , this in 2 is shown simplified in sections, is provided with at least one temperature sensor. For this purpose, in the receiving bore 6 the temperature sensor 6 by means of the spacer sleeve 8th fed, ie pressed in contact closing, so that this over the web-shaped distance 10 rapidly, ie in real time, can accurately absorb temperature changes caused by a cavity surface 5 incoming melt front are caused.

About the cable 11 then the respective temperature change signal (steep rise of the characteristic 2 ) almost as a switching value to the evaluation unit 13 passed, which then passes a corresponding switching signal in the process flow of injection molding. This rapid sequence of detection of the respective temperature change within a cavity and its immediate implementation in switching signals, the monitoring and control or regulation of injection molding processes is optimized in a technical and cost-effective manner, so that virtually all process steps in injection molding can be improved. 1 Characteristic direct measurement 2 Characteristic curve indirect measurement 3 injection mold 4 mold plate 5 cavity surface 6 location hole 7 temperature sensor 8th Stand Off 9 Floor space 10 distance 11 electric wire 12 Cabel Canal 13 evaluation 14 mounting plate 15 screw 16 web

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3425459 A1 [0003]
• - DE 10155162 A1 [0016]
• - DE 10112126 [0017]
• DE 102004031546 A1 [0019]

Claims (24)

Method for monitoring and / or controlling and / or regulating functions of and in injection molding machines, by means of sensors ( 7 ), in particular temperature and / or pressure sensors which monitor a melt in at least one hot runner, a nozzle, a cavity or the like, characterized in that the sensor ( 7 ) triggers a signal for a monitoring and / or control process in the injection molding machine at the beginning of a temperature and / or pressure increase. Method according to claim 1, characterized in that the sensor ( 7 ) triggers a signal for a monitoring and / or control process in the injection molding machine at the beginning of a temperature and / or pressure increase. Method according to claim 1 or 2, characterized that optimizes a signal course with regard to a process optimization becomes. Method according to at least one of claims 1 to 3, characterized in that the at least one sensor ( 7 ) detects an incoming melt front by the beginning of a temperature and / or pressure increase. Method according to at least one of claims 1 to 4, characterized in that the at least one sensor ( 7 ) has approximately the same sensitivity with respect to changes in temperature and / or pressure, such as a sensor with direct contact with a melt located in at least one hot runner, nozzle, cavity or the like. Method according to claim 5, characterized in that the reaction of the at least one sensor ( 7 ) due to different sensor materials. Method according to one of the preceding claims, characterized in that with the at least one sensor ( 7 ) in at least one hot runner, a nozzle, a cavity od. Like. Due to temperature and / or pressure changes, the respective position of the melt is determined in approximately real time. Device for monitoring and / or controlling and / or regulating functions of and in injection molding machines, by means of sensors ( 7 ), in particular temperature and / or pressure sensors which monitor a flow of the melt through at least one hot runner, a nozzle, in a cavity or the like, characterized in that between sensor ( 7 ) and melt a bridge ( 16 ) of a hot runner, nozzle or cavity wall of 0.2 to 3 mm thickness ( 10 ) is trained. Device according to claim 8, characterized in that the web ( 16 ) a base area ( 9 ) of a blind hole ( 6 ) into which the sensor ( 7 ), optionally in contact with this base. Device according to claim 9, characterized in that that the base has a rounded corner area. Apparatus according to claim 9 or 10, characterized in that an outer diameter of the sensor 87 ) smaller than an inner diameter of the blind hole ( 6 ). Device according to at least one of claims 9 to 11, characterized in that a surface of the sensor ( 7 ) to the base area ( 9 ) is rounded off. Use of the method according to at least one of claims 1 to 7, characterized in that due the determinable real times of the temperature and / or pressure change a switching operation to a predetermined function takes place. Use of the method according to claim 13, characterized characterized in that an automatic switching to reprinting takes place, the melt in at least one cavity against End or end of their flow path is suspended. Use according to claim 14, characterized in that for an artificial delay of the switching signal for the reprinting the at least one sensor ( 7 ) is provided in front of the flow path end of the melt. Use of the method according to claim 7, characterized characterized in that due to the determinable real times for Temperature and / or pressure changes an automatic melting front dependent opening and closing of Shutter nozzles preferably always at the same time he follows. Use of the method according to claim 7, characterized characterized in that due to the determinable real times for Temperature and / or pressure changes an automatic Bleeding by a melt front-dependent closure a core train takes place. Use of the method according to claim 7, characterized characterized in that due to the determinable real times for Temperature and / or pressure changes at least one embossing process when Injection molding is initialized. Use of the method according to claim 7, characterized in that due to the determinable real time for temperature and / or pressure changes, an automatic sequential filling of cascade injection molds takes place, in which a melt is introduced under pressure from a plurality of nozzles in a cavity, wherein at least one Nozzle of the sensor operating according to the invention ( 7 ) is assigned, indirectly determined by the melt flow into the cavity and thus the filling process is automatically matched by the nozzles. Use of the method according to claim 7, characterized characterized in that due to the determinable real times for Temperature and / or pressure changes a controlled Moving of binding seams takes place. Use of the method according to claim 7, characterized characterized in that due to the determinable real times for Temperature and / or pressure changes a rules at least a melt front takes place in family injection molds. Use of the method according to claim 7, characterized characterized in that due to the determinable real times for Temperature and / or pressure changes an automatic Balancing of hot runner injection molds takes place. Use of the method according to claim 7, characterized characterized in that due to the determinable real times for Temperature and / or pressure changes a determination of Viscosity of a melt within at least one cavity an interaction of direct pressure and / or indirect pressure and / or direct temperature and / or indirect temperature. Injection molding machine ( 3 ) with according to at least one of claims 1 to 12 specific sensor ( 7 ) for use according to at least one of claims 10 to 20, characterized in that the at least one sensor ( 7 ) in a receiving bore ( 6 ) a wall ( 3 ) and with its sensor tip to just below (distance 10 ) of the wall surface ( 5 ) with the help of a spacer sleeve ( 8th ) or a mounting nipple is used and optionally at the base ( 9 ) of the receiving bore ( 6 ) abuts contact closing.