DE102012023041A1 - Method for monitoring moderate temperature device of plastic processing tool of injection molding machine, involves comparing flow meters data which shows pressure fluctuations in flow line or in return line - Google Patents

Abstract

The method involves connecting two branch lines (4,5) in parallel between a flow line (3) and a return line (6). The flow meters (8,8') are connected at the branch lines respectively. The presence of leakage is determined by comparison of the flow meters data which shows the pressure fluctuations in the flow line or in the return line.

Description

The present invention relates to a method for monitoring a temperature control of a tool of an injection molding machine, wherein the temperature control device has a flow and a return, between which at least two branch lines are arranged fluidically parallel, wherein in each of the at least two branch lines, a flow sensor is arranged.

Tools for plastics processing are usually performed with a channel system having at least one flow, a return and interposed branch lines (channel circles). This channel system allows fluids to enter areas within a tool where energy is to be supplied or removed. In many plastic processing methods - including in injection molding - it is important to be able to influence the temperature in specific areas of a tool in a targeted manner, which is why the entire channel system in the tool often consists of several channel circuits. The supply of fluids to tools takes place in the processing of plastics usually centrally, which is why in tools with multiple channel circuits a distribution of the volume flows before entering the tool is required. The distribution of a central fluid flow to individual channel circuits is done by distributor units.

Depending on the fluid used, number of branches, flow rate and other requirements, different distributor units are available on the market. For some time, a trend towards high-quality distribution units, which are equipped with sensors, is increasingly being observed. With these sensors, flows, temperatures and, in rare cases, pressures are usually measured to monitor processes and conditions surrounding the temperature control of tools. More and more frequently, the integration of additional sensors for the detection of fluid losses from the circulation system takes place.

Fluid losses from the circulation system - also known as leaks or leaks - generally represent recurrent problems for production companies and can result in considerable economic damage. Especially when unnoticed - for example, outside the operating time - large amounts of fluids through hose breaks, ripping out of connections, etc. flow out. Systems for detecting fluid losses are therefore suitable for integration in distributor units.

• – Im Vorlauf und im Rücklauf erfolgt die Messung der Durchflussmenge. Dazu werden an den entsprechenden Positionen zusätzliche Sensoren zur Messung integriert. Fluidverluste, welche zwischen den Sensoren auftreten, ergeben sich aus der Berechnung der Durchflussdifferenz.

A number of methods for detecting fluid losses from temperature control circuits are known:

• - In flow and return, the flow rate is measured. For this purpose, additional sensors for measuring are integrated at the corresponding positions. Fluid losses that occur between the sensors result from the calculation of the flow difference.

• – In den parallelen Zweigleitungen sind mindestens zwei Sensoren zur Durchflussmessung integriert. Die Berechnung der Durchflussdifferenz stellt die Überwachungsbasis von Fluidverlusten für jene Zweigleitungen dar, welche zwischen den Sensoren angeordnet sind.

This method has the disadvantage that additional sensors for measuring the flow rates are required. In addition to the additional costs for the sensors, an increased space requirement is recorded. In the event of a sensor failure or signal fluctuations, reliable detection of fluid losses is no longer guaranteed.

• - At least two sensors for flow measurement are integrated in the parallel branches. The calculation of the flow difference represents the monitoring basis of fluid losses for those branch lines which are arranged between the sensors.

• – Im gesamten System wird mindestens ein Druckwert erfasst. Dessen rascher Abfall kann auf einen plötzlich entstandenen Fluidverlust aus dem System hinwiesen.

This method has the disadvantage that each parallel branch line at least two sensors for measuring the flow rates are used, resulting in significant additional costs. In addition to the additional costs, each additional sensor in the system means an increased risk of sensor failure.

• - At least one pressure value is recorded throughout the system. Its rapid drop may indicate a sudden loss of fluid from the system.

This method has the disadvantage that only very large fluid losses are detected. Conscious pressure changes in the circulatory system can not be distinguished from fluid losses. Furthermore, the detection of fluid losses is highly dependent on the position of the pressure measurement to the location of fluid loss.

The object of the invention is to provide a comparison with the prior art simplified method for monitoring a temperature control of a tool of an injection molding machine.

This object is achieved by a method according to claim 1. Advantageous embodiments are defined in the dependent claims.

The fluids used are preferably liquids, in particular water.

Each state and each event in the circulatory system of the temperature control device can be described by evaluating the measurement signals from pressure and flow sensors. The detection of states and events takes place from the interaction of measurement data from the pressure and / or flow sensors introduced the temperature control circuits, wherein preferably at least one pressure or flow sensor is in the flow and at least one flow sensor in each branch line.

The stationary state and the events "fluid loss from the circulatory system", "pressure and flow fluctuation in Fluidzu- and fluid drain" and "changing the resistance after division of the fluid to the parallel branches by an actuator" are distinguished. The interaction of measurement data from at least two sensors makes it possible to characterize a state or an event. In the case of measurement data, a distinction is made between increasing progressions, falling gradients and gradients that do not change substantially. The characteristics of the measured data depend not only on the sensors used, but also on the position of a fluid loss in the circuit to the sensor and on the position of possible actuators present to the sensor.

With the method according to the invention leaks between the sensors can be detected. Leakage after a flow sensor in one of the parallel branch lines can not initially be distinguished from a change in the actuator. In a fluid distributor with automatic flow control, however, the controller is aware of when a control process takes place. Here is a distinction to the leakage after the sensor given and this can be detected (see table "Leak in branch line 4 after flow sensor 8th in this line ").

With regulated distributors or with distributors without the possibility of setting the quantity, one can go one step further and save the sensor in the central flow by knowing the control process or that no control process can take place. In this case, leakages only have to be differentiated from pressure fluctuations. In the case of pressure fluctuations, the flow rates in the individual branch lines change proportionally; in the case of leaks, the affected branch line reacts more and more strongly than the others.

Advantages of the invention over the prior art:

• - For most distribution units available on the market, sensors for measuring flows in the parallel branches are already integrated. In order to integrate the fluid loss detection in the distribution unit only an additional pressure sensor is necessary. In rare cases, the pressure sensor is already installed in the distributor unit. This eliminates additional costs for additional sensors.
• - Integrating the sensors into the distribution unit eliminates the need for additional sensors, which reduces the space required by the distribution units.
• - By the addition of additional flow sensors to the distribution unit, although a detection of fluid losses is possible, however, the fluid loss can not be assigned to a circle. By evaluating the interaction of measurement signals from pressure and flow sensors, the fluid loss can be assigned to the respective parallel branch line.
• - By evaluating the interaction of measurement signals from multiple sensors states and events can be detected in the circulatory system. These include, for example, pressure and flow fluctuations in the central fluid supply or the change of flows in individual parallel branch lines, which are caused by setting operations.

Details of the invention will be discussed with reference to the figures of various embodiments. By way of example, only two branch lines are shown. Of course, more branches could be provided.

Fig. 1:

• • Pressure sensor 9 in the central forerun 3
• • Flow sensor 8th . 8th' in each parallel branch line 4 . 5

event waveform pressure sensor 9 Flow Sensor 8th Flow Sensor 8th' a Leak in branch line 4 between pressure sensor 9 and flow sensor 8th ↓↓ ↓↓ ↑ / ↔ / ↓ b Actuator in branch line 4 to open ↓↓ ↑↑ ↓↓ c Actuator in branch line 4 shut down ↑↑ ↓↓ ↑↑ d Pressure in the central flow 3 increases ↑↑ ↑↑ ↑↑ e Pressure in the central flow 3 sinks ↓↓ ↓↓ ↓↓ f Pressure in the central return 6 increases ↑↑ ↓↓ ↓↓ G Pressure in the central return 6 sinks ↓↓ ↑↑ ↑↑

Discussions about the individual events

• a) By a leak in the branch line 1 the total flow resistance in the duct system decreases and consequently the measured pressure at the pressure sensor also drops 9 , At the same time, the measured volume flow at the flow sensor decreases 8th because a part of the actual volume flow is lost via the leak from the branch line. The from the flow sensor 8th' measured volume flow behaves in case of a leak in branch line 1 rising, falling or steady. The behavior of the volume flow in branch line 2 depends on the position of the leak in branch line 1 , The signal change of the flow sensor 8th' at a leak in branch line 1 is always significantly lower than that of the flow sensor 8th ,
• b) By opening an actuator (flow control valve 7 ), the flow in branch line increases 1 and the measured pressure at the pressure sensor 9 falls. Because of the pressure in the central flow 3 decreases, and the geometric relationships in branch line 2 do not change, the pressure difference between central flow decreases 3 and return 6 , Consequently, the flow falls in branch line 2 from. By opening an actuator, the total flow always increases. As a rule: signal increase flow sensor 8th ≠ signal drop flow sensor 8th'
• c) By closing an actuator (flow control valve 7 ) the flow sinks in branch line 1 and the measured pressure at the pressure sensor 9 increases. Because of the pressure in the central flow 3 rises, and the geometric relationships in branch line 2 do not change, the pressure difference between central flow increases 3 and return 6 , Consequently, the flow in branch line increases 2 at. By closing an actuator, the overall throughput always drops. As a rule: signal drop flow sensor 8th ≠ signal rise flow sensor 8th'
• d) An increase in pressure in the central supply 3 means an increase in the pressure difference between the central flow 3 and return 6 , Consequently, the flow rates in all branch lines increase 4 . 5 , The increase of the flow in the branches 4 . 5 behaves about the same percentage.
• e) A pressure drop in the central flow 3 behaves contrary to point d)
• f) If the pressure in the central return increases 6 so there is also an increase in pressure in the central flow 3 , The pressure difference between the central supply 3 and return 6 is reduced overall and the flows in the branch lines 4 . 5 decline. The drop in the flows in the parallel branches 4 . 5 behaves about the same percentage.
• g) A pressure drop in the central reflux 6 behaves in the opposite direction to point f)

Fig. 2:

• • Flow sensor 10 in the central forerun 3
• • Flow sensors 8th . 8th' in each parallel branch line 4 . 5

event waveform Flow Sensor 10 Flow Sensor 8th Flow Sensor 8th' a Leak in branch line 4 between flow sensor 10 and flow sensor 8th ↑↑ ↓↓ ↑ / ↔ / ↓ b Actuator in branch line 4 to open ↑↑ ↑↑ ↓↓ c Actuator in branch line 4 shut down ↓↓ ↓↓ ↑↑ d Pressure in the central flow 3 increases ↑↑ ↑↑ ↑↑ e Pressure in the central flow 3 sinks ↓↓ ↓↓ ↓↓ f Pressure in the central return 6 increases ↓↓ ↓↓ ↓↓ G Pressure in the central return 6 sinks ↑↑ ↑↑ ↑↑

Discussions about the individual events:

• a) By a leak in the parallel branch line 4 decreases the total flow resistance in the duct system and the total flow in the flow 3 increases. At the same time, the measured volume flow at the flow sensor decreases 8th because part of the actual flow through the leak from the branch line 4 get lost. The through the flow sensor 8th' measured volume flow behaves in the event of a leak in the branch line 4 rising, falling or steady. The behavior of the volume flow in branch line 5 depends on the position of the leak in the branch line 4 , The signal change of the flow sensor 8th' at a leak in branch line 4 is always significantly lower than that of the flow sensor 8th ,
• b) By opening an actuator (flow control valve 7 ), the flow in branch line increases 4 and the total flow in the flow 3 , Because of the pressure in the central flow 3 decreases, and the geometric relationships in branch line 5 do not change, the pressure difference between central flow decreases 3 and return 6 , Consequently, the flow falls in branch line 5 from. By opening an actuator, the total flow always increases. As a rule: signal increase flow sensor 8th ≠ signal drop flow sensor 8th'
• c) By closing an actuator (flow control valve 7 ) the flow sinks in branch line 4 and the total flow in the flow 3 , Because of the pressure in the central flow 3 rises, and the geometric relationships in branch line 5 do not change, the pressure difference between central flow increases 3 and return 6 , Consequently, the flow in branch line increases 5 at. By closing an actuator, the overall throughput always drops. As a rule: signal drop flow sensor 8th ≠ signal rise flow sensor 8th'
• d) An increase in pressure in the central supply 3 means an increase in the pressure difference between the central flow 3 and return 6 , Consequently, the flow rates in all branch lines increase 4 . 5 , The increase of the flow in the branches 4 . 5 behaves the same percentage.
• e) A pressure drop in the central flow 3 behaves contrary to point d)
• f) If the pressure in the central return increases 6 , so there is also an increase in pressure in the central flow 3 , The pressure difference between the central supply 4 and return 6 is reduced overall and the flows in the branch lines 4 . 5 decline. The drop in the flows in the branches 4 . 5 behaves the same percentage.
• g) A pressure drop in the central return is opposite to point f)

Claims (3)

Method for monitoring a temperature control device ( 1 ) of a tool ( 2 ) of an injection molding machine, wherein the tempering device ( 1 ) a flow ( 3 ) and a return ( 6 ), between which at least two branch lines ( 4 . 5 ) are arranged in parallel in flow, wherein in each of the at least two branch lines ( 4 . 5 ) a flow sensor ( 8th . 8th' ), characterized in that by comparing the from the flow sensors ( 8th . 8th' ) supplied measurement data between pressure fluctuations in the temperature control device ( 1 ) and the presence of a leak. Method according to claim 1, characterized in that in the flow ( 3 ) a pressure or flow sensor ( 9 . 10 ) whose measured data are compared with those of the at least two branch lines ( 4 . 5 ) arranged flow sensors ( 8th . 8th' ) are taken into account. Method according to claim 1 or 2, characterized in that, with a proportional change of the flows in the at least two branches ( 4 . 5 ) to a pressure fluctuation in the temperature control device ( 1 ) and with disproportionate changes of one of the at least two branch lines ( 4 . 5 ) on a leak in these branches ( 4 . 5 ) is inferred.

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