AT13006U1 - Plasticizing screw with tempering device - Google Patents

Abstract

Arrangement with a plasticizing screw (1) of a plasticizing unit (2) of an injection molding machine and a tempering device for tempering the plasticizing screw (1), the temperature control device comprising a feed line (5), a temperature control channel (6) in the plasticizing screw (1) and a discharge line (7 ), through which a temperature control medium flows, wherein a heating and / or cooling unit (4) for heating and / or cooling of the temperature control between drain line (7) and inlet line (5) is arranged and the supply line (5), the temperature control channel ( 6) and the drain line (7) to a closed temperature control circuit (3) connects.

Description

Austrian Patent Office AT 13 0006 U1 2013-03-15

Description: The invention relates to an arrangement with a plasticizing screw of a plasticizing unit of an injection molding machine and a tempering device for tempering the plasticizing screw, wherein the tempering device has a supply line, a temperature control channel in the plasticizing screw and a drain line through which a temperature control flows Tempering channel reaches to the top of the plasticizing screw. In addition, the invention relates to an injection molding machine with such an arrangement and to a method for controlling the temperature of a plasticizing screw of a plasticizing unit of an injection molding machine by a tempering device.

When plasticizing in a plasticizing a plastic from a starting temperature, usually room temperature, heated to the necessary melting or processing temperature. The temperature entry takes place both via the heat conduction from the heating of the mass cylinder surrounding the screw in the plastic and via the drive of the plasticizing screw. The torque transmitted to the worm via the worm drive is converted into frictional energy (dissipation) and thus into heat, thus heating the plastic in the mass cylinder. How high this dissipative energy component is depends essentially on the plastic. The higher the viscosity of the plastic, the higher the energy input via dissipation. If this energy input is too high, this leads to high melt temperatures. In the case of thermally sensitive plastics, this can lead to material damage and thus streaking or poor mechanical properties.

For these thermally sensitive plastics such as e.g. PVC or PVC-C or very difficult to flow plastics such as e.g. PE-HD with MVR (190 ^ / 2,16kg) of less than 1g / 10min, cooled screws are used to reduce the melt temperature and thus the temperature load of the plastic.

A procedurally optimal setting with continuous temperature control of the screw is difficult. If the cooling effect is too low, the thermal load can only be reduced slightly. Dosing time fluctuations can also occur due to excessive intake zone temperature. If the cooling effect is too high, the torque requirement increases, poor melt quality, dosing time fluctuations and also the danger of breakage for the screw are the result.

A significant improvement for the process management is not permanently turn on the cooling or temperature control. It makes sense to turn on the temperature control or cooling depending on the dosing and in the standstill phase, when no Dissipationsenergie is supplied to turn off the temperature control or cooling.

A simple solution is to connect a temperature control unit via a valve with the screw cooling. When dosing, the screw cooling or temperature control is activated, in the standstill phase, the valve switches to a bypass position and the screw is not tempered.

As mentioned, energy is supplied via heat conduction from the heaters of the mass cylinder as well as via friction energy (dissipation) via the metering drive. If the dissipative portion of the energy supplied is very high, e.g. not only heated in temperature-sensitive plastics such as PVC but also cooled to keep the melt temperature as low as possible. The cooling can be done both on the mass cylinder and in the screw.

It is known to arrange temperature sensors along the mass cylinder, which measure a temperature per heating zone. In the controller, a setpoint temperature is specified. If the measured temperature per zone is below the setpoint temperature, the heating is activated via a suitable control system. If the temperature is above the setpoint temperature, this zone will be cooled.

The disadvantage is that the screw temperature for the operator is largely unknown 1/11 Austrian Patent Office AT 13 0006 U1 2013-03-15. The screw is a thermally short-circuited system, i. Energy is supplied via dissipation and heat conduction and thus the worm is heated in the front area of the melting and metering zone. At the same time, the screw also transfers energy from the hot, melt-carrying area into the cool catchment area and the worm shaft. The cold plastic trickling into the intake zone absorbs energy, cools the screw and is itself preheated.

In DE 76 01 482 an extruder screw is described in which a screw cooling is provided, wherein a coolant is introduced into a central bore in order to specifically temper the screw over its entire length.

DE 2 057 989 relates to extruder screws in which achieved by cavities in the screw via heating or cooling means a homogeneous heating and thereby a uniform plasticization of the plastic is made possible. It is essential in this invention that the cooling holes or cooling chambers extend into the screw flights, as a result of which the distance to the surface is essentially constant over substantially the entire surface. This is called differential cooling.

DE 10 2007 009 027 A1 shows a screw with a heat transport device, which can cool certain areas internally via a profile with ribbing. The exact control of the cooling is not mentioned.

DE 1 246 222 shows a screw injection molding machine for processing plastics, heating and / or cooling zones of any length or any volume in the screw being provided by a longitudinal bore. The working process or the influencing of the function fulfillment is adapted to the rhythm of the Schnecken axialbewegungen and thus to the cycle. Any number of heating and / or cooling zones can be present in the screw. The temperature of the individual zones is advantageously monitored and controlled by thermostatic measuring points, on the basis of which control pulses are forwarded to a control box.

A disadvantage of the entire prior art is that although the exact temperatures in the screw can be partially adjusted, but never the entire temperature change in the screw can be observed. This results in the disadvantage that the known from the prior art arrangements are inaccurate. In addition, only at certain points around or in the screw is measured, so that the evaluation always lags the true temperature losses or temperature gains in the entire screw.

The object of the present invention is therefore to provide a comparison with the prior art improved arrangement of plasticizing screw and temperature control or an improved method for controlling the temperature of a plasticizing screw. In particular, an easily controllable and manageable tempering is to be created, which can perform as possible, the entire tempering without external influence. In addition, the temperature should be able to be performed as constant as possible. Furthermore, the temperature control medium should be handled as sparingly as possible.

This is achieved for an arrangement with the features of the preamble of claim 1, characterized in that a heating and / or cooling unit is arranged for heating and / or cooling of the temperature control between drain line and supply line and the supply line, the temperature control channel and the drain line connects to a closed temperature control circuit. By means of this closed temperature control circuit, the temperature control medium (service water) can be reused compared with the prior art. In addition, a better monitorable temperature control is given and the temperature control is no longer directly dependent on the temperature of the supplied temperature (usually normal tap water), but can control or regulate the temperature exactly by the heating and / or cooling unit.

According to a preferred embodiment of the present invention can be provided that the temperature control a temperature sensor for measuring the temperature of the temperature in the supply line or in the heating and / or cooling unit 2/11 Austrian Patent Office AT 13 0006 Ul 2013-03- 15 has. Only if a water supply is provided which provides a constant temperature, can be dispensed with a preferred inlet temperature sensor for the present invention.

To be able to conclude even better on the energy loss or gain in the temperature control during the passage of the tempering, may preferably be provided that the temperature control device has a temperature sensor for measuring the temperature of the temperature in the drain line.

If you want to know the flow rate of temperature control through the temperature control, it can be provided according to a variant of the invention that the temperature control device, preferably in the supply line, has a flow stabilizer. This has a certain cross-section, which can be deduced at a certain flow pressure on the flow rate.

According to another variant of the invention, however, it can also be provided that the temperature control device has a quantity sensor, preferably arranged in the supply line, for measuring the flow rate of tempering medium through the temperature control circuit.

To avoid enthalpy changes of the plastic material produced with the plasticizing over a longest possible production time or to keep constant, may preferably be provided that the temperature control a flow regulator for controlling the introduction of temperature control in the temperature control, a data memory in which at least the measured temperatures of the temperature control medium in the supply line or in the heating and / or cooling unit and in the drain line and the measured flow rate can be stored as current actual values and a control unit, by the measured actual values and stored setpoint values or read out documented actual values of previous injection molding cycles by outputting control signals to the heating and / or cooling unit and / or to the flow controller the temperature of the temperature control in the temperature control of the plasticizing screw is controlled or regulated has. Through this design, the temperature in the entire screw can be closely monitored and for the temperature control can be learned from previous injection molding cycles.

A preferred embodiment of the arrangement may provide that in the plasticizing screw, preferably in the region of the screw tip, at least a third temperature sensor is arranged. For this purpose, it may be provided to carry out the screw preferably in the critical range (that is, in the region of the maximum temperature at the screw tip) with a temperature measuring point. The temperature information is forwarded to the controller and can be used as a quality parameter for process monitoring or as a control parameter for the screw temperature control.

The information of the screw temperature or generally the stored thermal energy can also be obtained with this embodiment. If, per cycle, the cooling bore of the screws preferably conveys the amount of cooling medium which corresponds to the volume of the bore in the screw and at the same time measures the flow and return temperature per unit of time, an average screw temperature can be estimated. This temperature information can be used as a process parameter for process monitoring or as a control parameter. A complex measuring sensors in the screw can be avoided. With these temperature curves of flow and return temperature per unit time and the volume flow of the cooling medium in the screw can also be concluded on the energy that is discharged per cycle of the screw with the cooling medium. One goal could be to always dissipate the same amount of energy per cycle. In this case, a constant dissipated amount of energy would be achieved by varying the flow rate. Thus, the temperature can be done in principle, for example, on the temperature of the temperature, on the amount of water supplied, starting from the temperature of the temperature in the drain line, due to a temperature difference or on the amount of heat dissipated. A preferred embodiment of the invention may provide that the temperature control channel in the plasticizing screw is formed by a tube in the plasticizing screw, this tube being arranged in a bore in the plasticizing screw is.

Although it should in principle not be ruled out that an inventive arrangement is used for an extruder, however, it is preferably provided that the plasti-fiziereinheit is also designed as an injection unit, wherein the plasticizing screw is axially displaceably mounted in a plasticizing. The overall advantages of the cycle-dependent temperature control are particularly useful in a common plasticizing and injection unit for an injection molding machine.

With the closed temperature control circuit according to the invention a constant water supply is achieved, wherein it can be particularly preferably provided that the temperature of the temperature control by the heating and / or cooling unit to about 60'C, preferably to above 75 ° C, is adjustable. Particularly preferably, the water temperature can be above 80 ° C. Preferably, the cooling or heating unit is as a kind of "air conditioner". executed, which heats or cools the tempering medium flowing back from the drain line to a desired temperature - as needed. However, it should not be ruled out that this temperature control is designed as a pure heating unit or as a pure cooling unit. This depends essentially on the positive or negative difference of the desired temperature from the supplied.

In principle, the tempering device can always have a certain total amount of tempering medium. If there is insufficient medium (water) in the entire circuit, a corresponding warning can be issued. But it is also possible to have the level checked by an operator regularly. If the level is too low (eg due to a small leak), the temperature control medium can be refilled into the self-contained circuit. However, it is preferably provided that the entire tempering device (or the heating and / or cooling unit) is connected to a normal water supply line in spite of its design as a closed circuit and itself supplied with fresh water if required (eg if the degree of filling is too low) ,

The object of the invention is also achieved by a method having the features of claim 12.

The plasticizing process is a very complex process that can also be represented as an energy balance. On the one hand energy is supplied, such as • Drive energy (dissipation) and • Heat conduction via the heating bands on the outer diameter of the cylinder.

On the other hand, energy is dissipated via • loss energy through convection, heat conduction and heat radiation and • deliberately dissipated energy via cooling jackets on the outside diameter of the cylinder or the screw cooling.

The residual energy, i. supplied energy minus dissipated energy is the proportion used for heating the plastic. These energy components per cycle or generally per unit of time provide important information about the overall process in terms of energy consumption and process stability. These energy shares or energy share per unit of time (power) are therefore documented to analyze, optimize and monitor the process.

By means of a suitable measuring sensor system, it is also possible to calculate and document the proportion of energy or power component which is introduced by means of a screw temperature control. Required for this according to the invention is the flow rate of a known medium and the temperature difference between the flow and the return flow. [0033] FIG.

The higher the flow rate and the greater the temperature difference between forward and reverse, the higher the amount of energy dissipated per unit time. If the amount of energy is related to the cycle time, this parameter can be used for process analysis, process optimization and process monitoring. If this value changes, it can be assumed that the melt quality and thus also the quality of the parts will change.

With the likewise measurable energy components of the drive energy and the heating energy, an energy analysis can be calculated and, if the loss rate of the plasticizing unit is known to be closed on the enthalpy of the plastic.

By the parameter flow rate and flow temperature of the screw temperature, the plasticizing process can be selectively changed by e.g. to reduce the required torque during dosing to prevent excessive loading of the screw. Furthermore, there is the possibility of process changes occurring over a long period, e.g. by batch fluctuations or temperature or humidity differences of the environment to counteract. Through targeted changes in the flow temperature and / or the flow rate, the process can be optimized with the aim of keeping the enthalpy of the plastic over a long production time as constant as possible.

In order to achieve a respectively adapted to the current process temperature in the plasticizing, especially with long injection molding cycles, may preferably be provided that the temperature of the temperature control in the temperature of the plasticizing screw injection molding cycle dependent, preferably based on the current screw position or the current Spritzgießzykluszeitpunkts regulated becomes. That is, the control unit is also provided information that is specific to the current cycle time or the current screw position, whereby a change in the temperature control circuit is performed.

To improve the overall learning effect, so to speak, it can preferably be provided that the measured actual values temperature of the temperature in the supply line, temperature of the temperature in the drain line, flow rate and optionally flow time injection molding depending on the data in the memory as actual values of previous injection molding documented become. This means that the individual, respectively measured data are stored linked with injection cycle times, whereby the documentation is cycle-time-specific.

Particularly preferably, it can result from the fact that process parameters for the temperature control process are calculated by the control or regulation unit as a function of read-out documented actual values which, as time- or cycle-dependent control signals, the flow rate of the quantity regulator, the temperature control of the heating and / or or regulating the cooling unit and / or the pure switch-on time of the heating and / or cooling unit.

Further details and advantages of the present invention will be explained in more detail below with reference to the description of the figures with reference to the exemplary embodiments illustrated in the drawings. 1 shows schematically the components of a plasticizing unit, and [0043] FIG. 2 shows schematically an entire tempering circuit.

Fig. 1 shows - greatly simplified - a plasticizing unit 2 with a rotatably mounted and axially displaceable screw 1, which is mounted in a worm shaft 24 and is surrounded by a plasticizing cylinder 23. This plasticizing cylinder 23 has in the front region a - pointing in the direction of the dies not shown - Injector 22 and in the rear of a funnel-shaped filling opening 21. The plasticizing cylinder 23 surrounding heating bands 25th

Fig. 2 shows the essential components of a temperature control with a tempering 3 comprising the tempering 6 in the plasticizing screw 1, the drain line 5/11 Austrian Patent Office AT 13 0006 Ul 2013-03-15 7, the heating and / or cooling unit 4 and the supply line 3, wherein it is irrelevant in which concrete components of the plasticizing unit 2 or the entire injection molding machine, the heating and / or cooling unit 4 and thus parts of the lines 7 and 5 are formed. In principle, the heating and / or cooling unit 4 serves to cool or heat the temperature control medium circulating in the temperature control circuit 3 of the temperature control device and also to circulate it by means of a suitable pump (not shown).

After the tempering has left the heating and / or cooling unit 4, it passes to a flow regulator 11, which controls the flow rate. Subsequently, the temperature control medium flows through the quantity sensor 10, which measures the flow rate D, and then passes to the temperature sensor 8 in the supply line 5. Instead of the flow regulator 11 and the quantity sensor 10 may also be provided a flow stabilizer. From the supply line 5, the temperature control finally passes into the temperature control channel 6 in the plasticizing screw 1. During the flow through the supply line 5 of the sensors 10 and 8 respectively the current actual values Wakt measured and as concrete values in degrees Celsius or in liters in one entered table-shaped data memory 12, wherein the amount of flow rate D and flow time Dt from the quantity sensor 10 and from the temperature sensor 8, the temperature Tz in the supply line 5 come. The temperature sensor 8 can also be arranged in the cooling and / or heating unit 4.

The tempering 6 is formed in a tube 15, which in turn is arranged in a hollow bore 16 in the plasticizing screw 1. In the region of the screw tip 1a of the plasticizing screw 1, a third temperature sensor 14 is provided, which is connected via a signal line 17 to the transmission unit 18. From this transmission unit 18, the measured temperature Tz of the third temperature sensor 14 is also forwarded to the data memory 12. This temperature sensor 14 need not necessarily be provided for the present invention, but can provide helpful process parameters for the entire control.

After the temperature control in the plasticizing screw 1 has given and / or absorbed energy, it passes through the drain line 7 to the temperature sensor 9, which measures the temperature TA in the drain line 7 and supplies a corresponding value to the data memory 12. Subsequently, the temperature control medium passes to the valve 19, which - depending on the level of the temperature control circuit 3 or depending on the temperature TA temperature - directs the temperature in the heating and / or cooling unit 4 or via a bypass line 20 back into the feed line. 5 redirects. The bypass line 20 can be used above all when the temperature TA in the drain line 7 is already equal to a desired temperature in the inlet line 5.

In the data memory 12, the current actual values Wakt are stored in each case at the current time t0. In order to effect corresponding changes in the temperature control circuit 3 from this information, the control or regulation unit 13 either uses documented actual values Wdok of preceding injection molding cycles or other stored desired values Wson. Of course, a combination of these values Wdok and Wson can be used for the regulation. The control or regulation unit 13 determines from the collected or stored data control signals L, which regulate either the heating power of the heating and / or cooling unit 4 or the mass flow rate of the flow regulator 11 or the pure on time of the heating and / or cooling unit 4 Taxes. Through the appropriate monitoring and consideration of all values, the energy balance of the entire plasticizing process can be reproduced as accurately as possible and a constant amount of energy dissipated in the field of plasticizing screw 1 by varying the parameters flow rate in the flow regulator 11 or heating power or on time of the heating and / or cooling unit. 4 be achieved.

With regard to the schematic representation of the data memory 12 and the control or regulating unit 13 it should be noted that they can be arranged in a single board or on different computers. It is essential that a logical combination of the individual values Wakt and Wdok or WS0n is made possible. Due to the partial line 6/11

Claims (15)

Austrian Patent Office AT 13 0006 U1 2013-03-15 also shows that the values Wd0k are fed by the current actual values Wakt and represent, as it were, a continuation over time. For this reason, the documented values Wdok are also linked to the injection molding cycle times ti to tn. For an exact calculation of the energy balance, the temperature can not be shown here, the plasticizing cylinder 23 surrounding Temperierbänder be included 25 in the entire control by means of appropriate sensors. It is generally possible that the quantity sensor 10 and the flow regulator 11 are designed as one component. In principle, any fluid can be used as the temperature control medium, water preferably being used. Particularly preferably, the temperature control circuit 3 can function as a type of learning cycle, wherein according to the respective cycle time t, for example, during dosing and cooling heat must be dissipated by the temperature control, while during the injection process or during heating the screw should not be too cold may, whereby a heat supply via the temperature control medium takes place. For the learning cycle can be provided that the enthalpy change in the resulting plastic as an additional parameter by an operator or sensors can be incorporated into the control system. Claims 1. Arrangement with a plasticizing screw (1) of a plasticizing unit (2) of an injection molding machine and a temperature control for tempering the plasticizing screw (1), wherein the temperature control device a feed line (5), a tempering (6) in the plasticizing screw (1) and a Drain line (7) through which flows a temperature control, wherein the temperature control channel (6) extends to the top of the plasticizing screw (1), characterized in that a heating and / or cooling unit (4) for heating and / or cooling of the tempering between drain line (7) and feed line (5) is arranged and the supply line (5), the temperature control channel (6) and the drain line (7) to a closed temperature control circuit (3) connects. 2. Arrangement according to claim 1, characterized in that the temperature control device has a temperature sensor (8) for measuring the temperature (Tz) of the temperature control medium in the feed line (5) or in the heating and / or cooling unit (4). 3. Arrangement according to claim 1 or 2, characterized in that the temperature control device has a temperature sensor (9) for measuring the temperature (TA) of the temperature control medium in the drain line (7). 4. Arrangement according to one of claims 1 to 3, characterized in that the temperature control device, preferably in the feed line (5), has a flow stabilizer. 5. Arrangement according to one of claims 1 to 3, characterized in that the temperature control device, preferably in the supply line (5), arranged quantity sensor (10) for measuring the flow rate (D) of temperature control by the temperature control (3). 6. Arrangement according to claim 5, characterized in that the tempering - a flow regulator (11) for controlling the introduction amount of temperature control in the temperature control circuit (3), - a data memory (12), in which at least the measured temperatures (Tz, TA) the temperature control medium in the feed line (5) or in the heating and / or cooling unit (4) and in the drain line (7) and the measured flow rate (D) as current actual values (Wakt) are stored and 7/11 Austrian Patent Office AT 13 0006 U1 2013-03-15 - a control or regulating unit (13), preceded by the measured actual values (Wakt) and stored nominal values (Wson) or read-out documented actual values (Wdok) Injection molding cycles by outputting control signals (L) to the heating and / or cooling unit (4) and / or to the flow regulator (11) the temperature of the temperature control in the temperature control (6) of the plasticizing screw (1) Steueroder is controllable. 7. Arrangement according to one of claims 1 to 6, characterized in that in the plasticizing screw (1), preferably in the region of the screw tip (1a), at least a third temperature sensor (14) is arranged. 8. Arrangement according to one of claims 1 to 7, characterized in that the temperature control channel (6) in the plasticizing screw (1) by a tube (15) in the plasticizing screw (1) is formed, said tube (15) in a bore (16) in the plasticizing screw (1) is arranged. 9. Arrangement according to one of claims 1 to 8, characterized in that the plasticizing screw (1) is part of a plasticizing unit (2), which is also designed as an injection unit, wherein the plasticizing screw (1) mounted axially displaceable in a plasticizing cylinder (23) is. 10. Arrangement according to one of claims 1 to 9, characterized in that the temperature of the Temperiermediums by the heating and / or cooling unit (4) to above 60 ° C, preferably to above 75 ° C, is adjustable. 11. Injection molding machine with an arrangement according to one of claims 1 to 10. 12. A method for controlling the temperature of a plasticizing screw (1) of a plasticizing unit (2) of an injection molding machine by a tempering device, in particular with an arrangement according to one of claims 1 to 10, wherein the temperature control a supply line (5), a tempering (6) in the plasticizing (1) and a drain line (7) through which a temperature control medium flows, wherein the temperature control channel (6) extends to the top of the plasticizing screw (1), characterized by - a temperature sensor (8) for measuring the temperature (Tz) of the tempering in the feed line (5) or in the heating and / or cooling unit (4), - a temperature sensor (9) for measuring the temperature (TA) of the temperature in the drain line (7), - in the temperature control circuit (3), preferably arranged in the feed line (5), quantity sensor (10) for measuring the flow rate (D) of temperature control through the temperature control circuit (3) or a flow stabilizer, a quantity regulator (11) for regulating the introduction quantity of tempering medium into the temperature control circuit (3), a data memory (12) in which at least the measured temperatures (TA, Tz) of the temperature control medium in the feed line (5) or in the heating and / or cooling unit (4) and in the discharge line (7) and the measured flow rate (D) are stored as current actual values (Wakt) and - a control or regulating unit (13), on the basis of the measured actual Values (Wakt) and stored setpoint values (Wson) or read-out documented actual values (Wakt) previous injection molding cycles by outputting control signals (L) to the tempering device (4) and / or ar the flow regulator (11) the temperature of the tempering in Temperature control channel (6) of the plasticizing screw (1) is controlled or regulated. 13. The method according to claim 12, characterized in that the temperature of the temperature control in the tempering (6) of the plasticizing screw (1) injection molding cycle dependent, preferably on the basis of the current screw position or the current Spritzgießzykluszeitpunkts (t0), is regulated. 8/11 Austrian Patent Office AT 13 0006 U1 2013-03-15 14. The method according to claim 12 or 13, characterized in that the measured actual values (Wakt) temperature (Tz) of the temperature in the supply line (5), temperature (TA) of the temperature in the drain line (7) flow rate (D) and optionally flow time (Dt) injection molding cycle dependent in the data memory (12) as actual values (Wdok) previous injection molding cycles (h, tn) are documented. 15. The method according to claim 13 or 14, characterized in that the control or regulating unit (13) in dependence of read out documented actual values (Wdok) process parameters are calculated for the tempering process, as time or cycle-dependent control signals (L) the flow rate ( D) of the volume controller (11), the temperature control of the temperature control (4) and / or the on time of the temperature control (4) control or regulate. For this 2 sheets drawings 9/11