Method and device for the variothermal temperature control of injection moulds

Abstract

A method for the variothermal temperature control of an injection mould using a temperature control device, the method including at least the following steps: in a learning phase, determining a temperature control characteristic of the temperature-controllable system including at least the injection mould and the temperature control device, in order to obtain individual reference values for the system, with which the temperature control device can be controlled in order to obtain a nominal temperature profile; and in a production phase: temperature control of the injection mould with the reference values determined during the learning phase; determining deviations of an actual temperature profile of the injection mould in relation to the nominal temperature profile during the production cycle and calculating corrected reference values from these deviations; and carrying out a resulting production process using the corrected reference values.

Claims

1. A method for the variothermal temperature control of an injection mould using a temperature control device having at least the steps: A) in a learning phase: determining a temperature control characteristic of a system which is to be temperature-controlled comprising at least the injection mould and the temperature control device, in order to obtain individual control values for the system, with which control elements of the temperature control device can be actuated in order to obtain a nominal temperature profile and B) in a production phase: temperature control of the injection mould with the control values determined during the learning phase; determining deviations of an actual temperature profile of the injection mould in relation to the nominal temperature profile during a production cycle and calculating corrected control values for the control elements from these deviations; carrying out a resulting production process using the corrected control values; and for determining the temperature control characteristic of the system which is to be temperature-controlled, a maximum wall temperature (T.sub.max) of a cavity of the injection mould which is achievable by the system is determined and stored and proceeding from the maximum wall temperature (T.sub.max), cooling is started with heating switched off, wherein a maximum negative increase is determined in Kelvin per second (K/s.sub.cool) at a turning point (W) of a cooling curve (TK) and a tangent (T) is applied at the turning point (W) of the cooling curve (TK), wherein an intersection of the tangent (T) with an abscissa is determined and a delay time (tu.sub.cool) is defined as a chronological interval between a start of cooling and the intersection of the tangent (T) with the abscissa.

2. The method according to claim 1, wherein A) in the learning phase: A1) for determining the temperature control characteristic of the system which is to be temperature-controlled, a calculating takes place of actuation times for heating and/or cooling devices of the temperature control device for achieving the nominal temperature profile of the injection mould for a moulded part which is to be produced; A2) an evaluation of the nominal temperature profile is carried out in at least one evaluation cycle to determine corrected actuation times A3) a storing takes place at least of the corrected actuation times from step A2) as control values for the control elements of the system which is to be temperature-controlled and B) in the production phase: B1) during a first production cycle a starting off of the nominal temperature profile with the control values of step A3) takes place; B2) a determining takes place of actual temperatures and a comparison with corresponding nominal temperatures of the nominal temperature profile of the injection mould; B3) a calculation takes place of corrected control values for the control elements of a subsequent production cycle from deviations determined in step B2) and B4) a carrying out of the subsequent production cycle takes place with the corrected control values from step B3) and B5) the steps B2) to B4) are repeated during further production cycles.

3. The method according to claim 1, wherein heating and/or cooling devices of the temperature control device include at least one of the group: water heating and/or water cooling device; oil heating and/or oil cooling device; electric heating and/or electric cooling device; heating and/or cooling cartridges; heating devices based on induction or by means of laser or ceramic heating arrangements; refrigerant cooling devices and/or CO.sub.2 cooling devices and/or a cooling by means of a gas; a superheated steam.

4. The method according to claim 1, wherein step A is carried out without filling the injection mould with moulding material.

5. The method according to claim 1, for determining the temperature control characteristic of the system which is to be temperature-controlled, a minimum achievable wall temperature (T.sub.min) of the cavity of the injection mould is determined and stored.

6. The method according to claim 5, a maximum rise of a heating curve at a turning point (W) thereof is determined in Kelvin per second (K/s.sub.heat).

7. The method according to claim 6, at the turning point of the heating curve, a tangent (T) is applied to the heating curve, and an intersection of the tangent (T) applied to the heating curve with another abscissa is formed, wherein a chronological interval between a start of heating and the intersection of the tangent (T) applied to the heating curve with the other abscissa is defined as a delay time (tu.sub.heat).

8. The method according to claim 1, wherein a mean temperature (T.sub.Basis) is calculated between a minimum achievable wall temperature (T.sub.min) and the maximum wall temperature (T.sub.max).

9. The method according to claim 8, wherein a maximum rise of a heating curve at a turning point (W) thereof is determined in Kelvin per second (K/s.sub.heat), at the turning point of the heating curve a tangent (T) is applied to the heating curve and an intersection of the tangent (T) applied to the heating curve with another abscissa is formed, wherein a chronological interval between a start of heating and an intersection of the tangent (T) applied to the heating curve with the other abscissa is defined as delay time (tu.sub.heat), wherein from the formula t.sub.basisheat=((T.sub.Basis−T.sub.min)/K/s.sub.heat)+tu.sub.heat an actuation time (t.sub.basisheat) is calculated for a pulse heating from the minimum achievable temperature (T.sub.min) to the mean temperature (T.sub.Basis).

10. The method according to claim 9, wherein after the switching off of heating and after the actuation time (t.sub.basisheat) has elapsed, a time span is measured until no further significant temperature change occurs at a temperature sensor, wherein a temperature (T.sub.basisheat) and a reverberation time (dead time) (t.sub.Basisheatdead) are measured and stored.

11. The method according to claim 10, wherein a deviation is calculated between the mean temperature (T.sub.Basis) and the temperature (T.sub.Basisheat) according to the formula
T.sub.Basisheaterror=T.sub.Basisheat−T.sub.Basis.

12. The method according to claim 11, wherein in a process sequence for at least one pulse heating or at least one pulse cooling step, actuation times of a heating device and/or of a cooling device are measured and stored proceeding from a current temperature of a cavity wall (T.sub.actMld), wherein a nominal temperature (T.sub.Soll) is determined and when the nominal temperature (T.sub.Soll) is greater than the current temperature (T.sub.actMld), a process time (t.sub.Prozess1) is calculated according to the formula
t.sub.Prozess1=((T.sub.Soll1−T.sub.actMld)/K/S.sub.heat)+tu.sub.heat+T.sub.Basisheaterror/K/S.sub.heat.

13. The method according to claim 1, wherein a mean temperature (T.sub.Basis) is calculated between a minimum achievable wall temperature (T.sub.min) and the maximum wall temperature (T.sub.max), wherein the cooling is actuated, while heating is switched off, beginning from the maximum wall temperature (T.sub.max) and from the formula t.sub.basiscool=((T.sub.max−T.sub.Basis)/K/S.sub.cool)+tu.sub.cool, an actuation time (t.sub.basiscool) for a pulse cooling from the maximum wall temperature (T.sub.max) to the mean temperature (T.sub.Basis) is calculated.

14. The method according to claim 13, wherein proceeding from the maximum wall temperature (T.sub.max) cooling is actuated and is switched off after the time (t.sub.basiscool) has elapsed, wherein thereafter a time is measured until no more significant temperature change is measurable at a temperature sensor in the cavity, wherein a temperature (T.sub.basiscool) and a reverberation time (dead time) (t.sub.Basiscooldead) are measured and stored, and a deviation is calculated from (T.sub.Basis) to (T.sub.Basiscool) according to the formula
T.sub.Basiscoolerror=T.sub.Basis−T.sub.Basiscool.

15. The method according to claim 14, wherein when a nominal temperature T.sub.Soll is lower than a current temperature of a cavity wall (T.sub.actMld) a process time (t.sub.Prozess1) is calculated from the formula
t.sub.Prozess1=((T.sub.Soll1−T.sub.actMld)/K/S.sub.cool)+tu.sub.cool+T.sub.Basiscoolerror/KS.sub.cool.

16. The method according to claim 15, wherein the calculation of the time (t.sub.Prozess1) for further heating and/or cooling processes is carried out in the same manner.

17. The method according to claim 16, wherein the calculation of the time (t.sub.Prozess1) for a pulse heating process or for a pulse cooling process is carried out repeatedly.

18. The method according to claim 1, wherein during further heating and/or cooling processes actuation times of a heating device and/or of a cooling device are corrected by a start temperature deviation (T.sub.startOffset) and/or an end temperature deviation (T.sub.endOffset), wherein formulae listed below are used:
T.sub.startOffsetx=T.sub.actMldx−T.sub.(actMldx)n−1
T.sub.endOffsetx=T.sub.Prozessx−T.sub.(Prozessx)n−1 wherein (n−1) is a corresponding temperature from a preceding passage, wherein T.sub.actMldx is a temperature of a cavity wall at a start of a current process, wherein T.sub.(actMldx)n−1 is a temperature of the cavity wall at a start of a previous process, wherein T.sub.Prozessx is a temperature of the cavity wall at an end of the current process, and wherein T.sub.(Prozessx)n−1 is a temperature of the cavity wall at an end of the previous process.

19. The method according to claim 18, wherein a maximum rise of a heating curve at a turning point thereof is determined in Kelvin per second (K/S.sub.heat), wherein a time (t.sub.startOffset) and (t.sub.endOffset) corresponding to the start temperature deviation (T.sub.startOffset) and/or to the end temperature deviation (T.sub.endOffset) is calculated depending on pulse heating (K/S.sub.heat) or pulse cooling (K/s.sub.cool), wherein:
For pulse heating:t.sub.startOffset=T.sub.startOffset/K/s.sub.heat
t.sub.endOffset=T.sub.endOffset/K/s.sub.heat
For pulse cooling:t.sub.startOffset=T.sub.startOffset/K/s.sub.cool
t.sub.endOffset=T.sub.endOffset/K/s.sub.cool.

20. The method according to claim 19, wherein an actuation time (t.sub.Prozess(x)) for a current heating process and/or a cooling process is determined from an actuation time (t.sub.Prozess(x−1)) from a previous heating process and/or cooling process plus the time (t.sub.startOffset) from the current heating process and/or cooling process plus the time (t.sub.endOffset) from the previous heating process and/or cooling process, which can be represented according to a formula as:
t.sub.Prozess(x)=t.sub.Prozess(x−1)+t.sub.startOffsetx+t.sub.endOffset(x−1).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in further detail below by way of example with the aid of the drawings. There are shown:

(2) FIG. 1: schematically a heating curve of an injection mould during a learning phase from a minimum temperature to a maximum temperature;

(3) FIG. 2: schematically a cooling curve of an injection mould during a learning phase from a maximum temperature to a minimum temperature;

(4) FIG. 3: by way of example, a temperature profile of a tool wall or respectively of an injection mould during a production phase;

(5) FIG. 4: schematically a device for carrying out the method for the variothermal temperature control of injection moulds.

DESCRIPTION OF EXAMPLE EMBODIMENTS

(6) A device 1 for carrying out the method according to the invention is illustrated schematically in FIG. 4 and has a temperature control apparatus 2 with a heating device, at least one temperature control apparatus 3 with a cooling device and an injection mould 4, control elements 5 and a regulating unit 6. The regulating unit 6 can act in a regulating manner on the control elements 5, wherein the regulating unit 6 processes signals as a function of a cavity wall temperature, which is determined for example by a temperature sensor 7 which sits in a cavity 8 of the injection mould 4.

(7) The temperature control apparatus 2 with a heating device provides a relatively hot temperature control medium 9 compared to the temperature control apparatus with a cooling device 3, which provides a relatively cold temperature control medium 10.

(8) The temperature control apparatuses 2, 3 are connected with the control elements 5 via suitable pipe lines (illustrated schematically by the arrows 11). The control elements 5 are connected with the injection mould 4 via suitable piping systems or hose systems (arrows 12). The injection mould 4 has at least one temperature control circuit 13, through which hot temperature control medium 9 or cold temperature control medium 10 is able to be directed alternately. Alternatively, it is also possible that the injection mould has two temperature control circuits 13, which are separated from one another hydraulically. One of the two temperature control circuits 13 serves for the directing of the cold temperature control medium 10, the other temperature control circuit serves for the directing of the hot temperature control medium 9 through the injection mould 4 or an injection mould half.

(9) Preferably, the device 1 has a buffer 14 which keeps available a certain store of hot temperature control medium 9 and a store of cold temperature control medium 10. For example, the buffer 14 is equipped with a displaceable piston element 15, which divides a buffer chamber into a compartment for hot temperature control medium 9 and a compartment for cold temperature control medium 10. The compartment containing hot temperature control medium 9 and also the compartment containing cold temperature control medium 10 are respectively connected via suitable pipe lines 16 with corresponding inlets of the control elements 5. By movement of the piston 15 in the double arrow direction 17, an additional amount of cold temperature control medium 10 (movement of the piston 15 in FIG. 4 downwards), or hot temperature control medium 9 (movement of the piston 15 in FIG. 4 upwards), can be briefly fed into the temperature control circuits 13 via the control elements 5.

(10) The control elements 5 are for example an arrangement of various valves 18, which are only indicated schematically. The valves 18 are, for example, electrically actuatable valves, which are connected with the regulating unit 6 and are able to be actuated by the latter. Depending on the actuation of the valves 18, either cold temperature control medium 10 or warm temperature control medium 9 can be fed into the temperature control circuits 13, wherein, as required, additional cold temperature control medium 10 or hot temperature control medium 9 can be fed in through the buffer 14 for example for achieving high cooling- or heating gradients. The provision of a buffer 14 makes it possible to use relatively small heating/cooling- and/or pump units for the temperature control apparatuses 2, 3, and nevertheless to capture injection loads which occur in a learning-and/or production cycle, by means of the buffer 14. This contributes to a saving of energy and reduces the system costs.

(11) The temperature sensor 7 is connected with the regulating unit 6 via a suitable signal line 19. Of course, it is possible that a plurality of temperature sensors 7 are arranged distributed over the cavity wall of the cavity 8 and send separate signals, which represent a local cavity wall temperature, to the regulating unit 6 or respectively make them available to it.

(12) In the present example embodiment according to FIG. 4, for simplification of the illustrated principle only one temperature sensor 7 is shown. It is of course also possible to use several temperature sensors 7 e.g. at different locations of the cavity wall.

(13) Furthermore, in the embodiment according to FIG. 4 a hydraulic temperature control is concerned, in which a liquid cold temperature control medium 10 and a liquid hot temperature control medium 9 is used.

(14) Of course, other types of heating/cooling are also conceivable. For example, electric heating- and/or cooling elements or gases can be used as temperature control medium.

(15) When now for example with the temperature control apparatus 3 switched off or clamped off with cool temperature control medium hot temperature control medium 9 is pumped through the cooling circuits 13, the cavity wall of the cavity 8 will heat up.

(16) Vice versa, it will cool down when instead of the hot temperature control medium 9 cold temperature control medium 10 is sent through the temperature control circuits 13.

(17) With this device, the method according to the invention, described in the following, can be carried out advantageously.

(18) A method according to the invention for the variothermal temperature control of the injection mould 4 is carried out in two phases, a learning phase A and a production phase B. Within the learning phase A, a determining takes place of the temperature control characteristic of the system which is to be temperature-controlled, which has at least the injection mould 4, the temperature control devices 2, 3 and the corresponding (pipe-) line connections and the control elements 5 and the regulating unit 6. Of course, a temperature sensor 7 is to be provided in the cavity 8 of the injection mould 4.

(19) This entire system which is to be temperature-controlled (the injection mould 4) or respectively is to provide for the temperature control (temperature control apparatuses 2, 3, control elements 5 and the corresponding connections with the injection mould 4), has a particular temperature control characteristic which is influenced for example by the cavity shape of the cavity 8 in the injection mould 4. Further influencing variables can be the efficiency of the temperature control apparatuses 2, 3 and the maximum possible through-flow quantity of cold temperature control medium 10 and/or hot temperature control medium 9.

(20) Such a system of the above-mentioned components has a particular temperature control characteristic, i.e. on a particular activity of the temperature control apparatuses 2 or 3 a particular temperature reaction takes place of the cavity wall of the cavity 8 in the injection mould 4. This is to be determined in the learning phase A.

(21) FIG. 1 shows a first partial step hereof.

(22) Within the determining of the temperature control characteristic of the system, proceeding from a current moulding tool temperature (cavity wall temperature T.sub.actMld) with the temperature control apparatus 3 with cooling device switched off, the temperature control apparatus 2 with heating device is switched on. The switching on of the heat temperature control takes place in the illustrated example according to FIG. 1 at the time t.sub.1. The graph VH (valve heating) is illustrated in FIG. 1 and indicates a time span in which the device 1 heats the injection mould. As a reaction to the heating, the graph TW indicates the temperature reaction at the cavity wall of the cavity 8, which is measured by the temperature sensor 7. After the switching on (time t.sub.1), firstly an increasingly more steeply rising temperature rise takes place on the tool wall, which in the further course approaches asymptotically a maximum achievable temperature T.sub.max which is able to be reached with the present system (injection mould 4, temperature control apparatuses 2, 3).

(23) The graph TW has in its course a turning point W. For determining a characteristic value for the temperature control characteristic of the system, it has proved to be successful to apply in the turning point W a tangent T to the graph TW. The maximum rise of the heating curve (graph TW) is present in the turning point W. The tangent forms an intersection S with the abscissa. The period of time between the start of the heating (time t.sub.1) and the intersection S is defined as delay time tu.sub.heat. The maximum rise of the tangent T is defined by a quotient of temperature and heating time, which is indicated in “Kelvin per heating time (K/s.sub.heat)”.

(24) With this procedure, starting from a current temperature T.sub.actMld of the injection mould 4, its heating-up characteristic up to the temperature T.sub.max is able to be determined and herefrom the values K/s.sub.heat and tu.sub.heat are able to be determined.

(25) In an analogous manner, a determining takes place of the cooling-down characteristic of the injection mould 4 starting from a maximum achievable temperature T.sub.max (cf. FIG. 2). In an analogous manner to the heating up, within the determining of the cooling-down characteristic, a cooling curve (graph TK) is determined, which can be reduced from the maximum injection mould temperature T.sub.max to a minimum achievable temperature T.sub.min. For this, with the temperature apparatus 2 (warm temperature control apparatus) switched off, the temperature control apparatus 3 with cool temperature control medium 10 is switched on. The switched on cooling is represented with the graph VK. Also within the determining of the cooling characteristic, a tangent T is applied at the turning point W, the rise of which reflects the maximum cooling-down gradient. This cooling-down gradient can be indicated in the unit Kelvin per cooling time (K/s.sub.cool).

(26) This tangent likewise intersections the abscissa S, so that a cooling delay time tu.sub.cool results, which results from the time t.sub.1 (switching on of the cooling unit) to the intersection S of the tangent T with the abscissa.

(27) This characterizing of the heating up or respectively cooling down behaviour of the system takes place preferably with an empty injection mould, i.e. still entirely without melt. Hereby, it is not necessary to carry out the learning phase with an injection mould which is mounted on a plastic injection moulding machine. A further advantage is that the use of plastic melt does not influence the tool temperature control characteristic or respectively the system temperature control characteristic.

(28) The determined temperature control characteristic of the system is preferably stored in the form of tool-specific, in particular system-specific control values for control elements or is otherwise assigned to the tool/system.

(29) Further steps in the learning phase A are:

(30) From this temperature control characteristic for example through differentiation between the maximum achievable temperature T.sub.max and the minimum achievable temperature T.sub.min a mean temperature T.sub.Basis can be calculated. With the mean temperature T.sub.Basis an activation time can be determined for the corresponding heating valves, which is necessary, which becomes necessary with a heating (pulse heating) from the minimum temperature T.sub.min to the mean temperature T.sub.Basis. This takes place using the determined heating gradient K/S.sub.heat and the correspondingly determined delay time tu.sub.heat according to the formula:
t.sub.basisheat=((T.sub.Basis−T.sub.min)/K/s.sub.heat)+tu.sub.heat.

(31) It has been found that after the switching-off of the heating with a temperature of the injection mould 4 below the maximum achievable temperature T.sub.max, an overshooting of the temperature beyond a desired target value takes place. In order to compensate this overshooting, the time span is measured until after the switching-off of the heating a significant temperature change no longer occurs. The temperature excess occurring here (T.sub.basisheat) and the measured reverberation time (t.sub.basisheatdead) is likewise measured and stored. From this, a deviation is calculated between the mean temperature T.sub.Basis and the temperature T.sub.basisheat according to the formula:
T.sub.Basisheaterror=T.sub.Basisheat−T.sub.Basis

(32) In an analogous manner, the determining of an undershooting takes place in the case of cooling, whereby a reverberation time in the case of cooling (t.sub.basiscool) and a minimum temperature T.sub.basiscool occurring in the case of undershooting is measured and stored. Herefrom, a deviation results between the mean temperature T.sub.Basis and the minimum occurring undershoot temperature T.sub.basiscool according to the formula:
T.sub.Basiscoolerror=T.sub.Basis−T.sub.Basiscool.

(33) With the temperature T.sub.Basiscoolerror or respectively with the temperatures T.sub.Basiscoolheaterror, taking into account the overshoot/undershoot phenomena in the heating/cooling, the process times t.sub.Prozess1 for the case of heating and the case of cooling can be determined more precisely, in order to reach as precisely as possible a nominal temperature T.sub.Soll starting from a current injection mould temperature (cavity wall temperature T.sub.actMld).

(34) A previously described determining of the times t.sub.Prozess1 both for the case of cooling and for the case of heating is carried out several times for a better delimitation and a more precise determining of the error temperatures T.sub.Basisheaterror and T.sub.Basiscoolerror. Here, a repetition several times has proved to be successful.

(35) The actuation times of the heating device and/or of the cooling device are corrected from one process to the next through corresponding start offset temperatures T.sub.startOffset or respectively end temperature deviations T.sub.endOffset in order to also take into account at the start/end of the one process the start/end temperatures of the preceding process. With these offset temperatures T.sub.startOffset and T.sub.endOffset corresponding offset times t.sub.startOffset and t.sub.endOffset can be determined both for the heating and for the cooling. This takes place according to the formulae
For pulse heating:t.sub.startOffset=T.sub.startOffset/K/s.sub.heat
t.sub.endOffset=T.sub.endOffset/K/s.sub.heat
For pulse cooling:t.sub.startOffset=T.sub.startOffset/K/s.sub.cool
t.sub.endOffset=T.sub.endOffset/K/s.sub.cool

(36) Therefore, from the process time t.sub.Prozess(x−1) of the preceding process and the start offset time t.sub.startOffset(x) of the current process and the end offset time t.sub.endOffset(x−1) of the preceding process, the process time t.sub.Prozess(x) can be calculated for the current process, which is used for the current case of heating/case of cooling. Hereby, a learning is successful for the current process from the environmental conditions and the sequence of the preceding process.

(37) As a result, by the method according to the invention and a device 1 suitable for carrying out the method, a targeted start-off of a nominal temperature profile, in particular achieving explicit nominal temperatures T.sub.Soll1, T.sub.Soll2 is possible in a very precise manner and adaptably to varying environmental conditions (cf. FIG. 3).

(38) The graph TW, which indicates the tool temperature over the time t is represented in FIG. 3. Likewise, target temperatures T.sub.Soll1 and T.sub.Soll2 and T.sub.Soll3 are indicated. In the lower half of the illustrated diagram according to FIG. 3, switch-on times are represented for the operation of the temperature control apparatus 2 with a heating device and of the temperature control apparatus 3 with a cooling device. Viewed from left to right, with a time t of approximately 10 seconds a switching-on of the temperature control apparatus 2 with the heating device takes place, so that the graph TW rises starting from this time (taking into account the time tu.sub.heat), up to a nominal temperature T.sub.1, which in the example embodiment lies approximately at 109°. At the temperature level T.sub.Soll1 the temperature of the injection mould 4 is kept approximately constant for a time. At the time t of approximately 20 seconds, the cooling begins by switching on of the temperature control apparatus 3 with the cooling device, so that a cooling of the tool takes place from T.sub.Soll1 to a temperature T.sub.Soll2 lying therebelow. Proceeding from T.sub.Soll2, before the reaching of which the temperature control apparatus 3 with the cooling device is already switched off, a renewed heating up of the tool takes place by switching on of the temperature apparatus 2 with the heating device, so that a further nominal temperature (T.sub.Soll3) is reached, which in the example embodiment lies between the nominal temperatures T.sub.Soll1 and T.sub.Soll2.

(39) Therefore, for achieving the temperature T.sub.Soll1 a so-called pulse heating takes place. Proceeding from the temperature T.sub.Soll a so-called pulse cooling takes place for achieving the temperature T.sub.Soll2, whereas the achieving of the temperature T.sub.Soll3 takes place proceeding from the temperature T.sub.Soll2 by means of a pulse heating.

(40) It has proved to be expedient to bring about the temperature control exclusively through switching on either the temperature control apparatus 2 with heating device or the temperature control apparatus 3 with cooling device. A mixing of the temperature control media preferably does not take place. A system with separate cold temperature control medium 10 and hot temperature control medium 9, viewed as a whole is essentially more dynamic than a system which attempts to achieve a particular temperature by the mixing of cold and warm temperature control medium. Therefore, through the separate temperature control circuits, more dynamic pulse heating—and pulse cooling processes are possible.

LIST OF REFERENCE NUMBERS

(41) 1 device 2, 3 temperature control apparatus 4 injection mould 5 control elements 6 regulating unit 7 temperature sensor 8 cavity 9 hot temperature control medium 10 cold temperature control medium 11, 12 arrows 13 temperature control circuit 14 buffer 15 displaceable piston element 16 pipe lines 17 double arrow direction 18 valves 19 signal line A learning phase B production phase S intersection VH graph TK graph TW graph T.sub.max maximum achievable temperature t1 switch-on time Tmin minimum achievable temperature T tangent W turning point