Method for operating an extrusion system and extrusion system

Abstract

A method for operating an extrusion system with the automatically executed steps of detecting, on a time-dependent basis, at least two operating parameters, which are selected from the following list: a screw rotational speed parameter, from which the number of rotations made by an endless screw of an extruder of the extrusion system as of a predefined point in time can be determined, and/or a torque characteristic value, which describes the torque applied to the endless screw, and/or an operating pressure in a cylinder of the extruder and/or an abrasion parameter, which describes an abrasiveness of material processed in the extruder, calculating, from the operating parameters, a wear parameter, more particularly a time for maintenance, which encodes a wear state of at least one component of the extruder, and outputting a maintenance message, which encodes the wear parameter.

Claims

1. A method for operating an extrusion system (10) with the automatically executed steps: (a) time-dependent detecting of at least two operating parameters (P), which are selected from the following list: (i) a screw rotational speed parameter (U), from which is able to be determined the number of rotations which an endless sceew (26) of an extruder (12) of the extrusion system (10) has carried out since a predefined point in time, and/or (ii) a torque characteristic, which describes the torque (M) which is applied to the endless screw (26), and/or (iii) an operating pressure in a cylinder of the extruder (12) and/or (iv) an abrasion parameter (C), which describes an abrasivenss of material processed in the extruder (12), (b) calculating from the operating parameters (P) a wear parameter (), comprising a time for maintenance (T.sub.w), which encodes a wear state at least of one component of the extruder (12), wherein the time for maintenance (T.sub.w) is calculated from the earliest point in time at which a threshold (B.sub.p, max, B.sub.M, max, U.sub.max, H.sub.max) corresponding to the operating parameters (P) is reached, and (c) outputting of a maintenance message, which encodes the wear parameter.

2. The method according to claim 1, characterized wherein the extrusion system (10) has at least three extruders (12.1, 12.2, 12.3) and that the method comprises the following steps: (a) time-dependent determining of the throughput parameter, whch encodes the specific throughput of an extruder (12) for all extruders (12) and (b) outputting of the maintenance message when the throughput parameter for at least one extruder (12) falls below a predefined throughput parameter threshold.

3. The method according to claim 1, the time-dependent detecting of the operating parameters (P) comprises in addition (a) a detecting of a vibration parameter (a), which describes an intensity of a vibration of at least one component of the extrusion system (10), and/or (b) a detecting of a temperature (T) of a bearing of a motor (24) of the extrusion system (10), and/or (c) a detecting of operating hours (H), during which the extrusion system (10) was in operation.

4. The method according to claim 1. (a) the computing of the wear parameter ({right arrow over (V)}) comprises a calculating of a pressure load (B.sub.p) in the form of the sum of a function (f) of the operating pressure (p(t)) depending on the operating time (t), comprising the sum (B.sub.p=.sub.t=0.sup.t(p(t))) via the operating pressure (p(t)), and a calculating of a torque load (B.sub.M=.sub.t=0.sup.tI(t)) in the form of the sum of products of a function of the torque characteristic (M(t)) and the operating time (t) comprising the sum via the products of torque characteristic (M(t)) and operating time (t), and (b) the time for maintenance (T.sub.W) from the earliest point in time at which the pressure load (B.sub.p) reaches a pressure load threshold (B.sub.p,max) or the torque load (B.sub.M) reaches a torque load threshold (B.sub.M,max).

5. The method according to claim 4, wherein the time for maintenance (T.sub.W) is calculated from the earliest point in time, at which the pressure load (B.sub.p) reaches the pressure load threshold (B.sub.p,max) or the torque load (B.sub.M) reaches the torque load threshold (B.sub.M,max) or the screw rotational speed parameter (U) reaches a screw rotational speed parameter threshold (U.sub.max) or the operating hours number (H) reaches an operating hours threshold (H.sub.max).

6. An extrusion system (10) with (a) a first extruder (12.1) for delivering a first rubber component, (b) at least a second extruder (12.2) for delivering a second rubber component and (c) a machine control (30) for actuating the extruders (12), wherein (d) the machine control (30) is configured for automatically executing a method according to claim 1.

Description

[0022] The invention is explained in further detail below with the aid of the enclosed drawings. There are shown here:

[0023] FIG. 1 a diagrammatic view of an extrusion system according to the invention and

[0024] FIG. 2 a flow diagram of a method according to the invention,

[0025] FIG. 3 shows a flow diagram of an alternative method according to the invention.

[0026] FIG. 1 shows an extrusion system 10 according to the invention, which has a first extruder 12.1, a second extruder 12.2, a third extruder 12.3 and a fourth extruder 12.4. Each extruder delivers a respective strand 14.i(i=1, . . . , N, wherein N is the number of extruders). These are directed through corresponding pipes 16.i to an extrusion head 18. The extrusion head 18 forms from the strands 14.i a multi-component tread 20, which is deposited onto a conveying device 22.

[0027] The extruders 12.i are charged with non-vulcanized rubber material. This material can also be designated as a compound. Each extruder 12.i has an electric motor 24.i, which drives a diagrammatically drawn endless screw 26.i. The motor 26 is actuated by a respective extruder control 28.i. All extruder controls 28.i, . . . , 28.N form jointly a machine control 30. It is possible and preferred that the extruder controls 28 are linked with each other. In addition, it is possible that the machine control 30 has a central control 32, which is connected with the extruder controls 28.i.

[0028] On carrying out a method according to the invention, the extruder controls 28.i detect at regular time intervals t.sub.i, t.sub.2 . . . operating parameters P.sub.j,i(j=1,2, . . . , M, wherein M is the number of the detected operating parameters).

[0029] FIG. 2 shows a flow diagram of a method according to the invention. Within the scope of the method according to the invention, regularly for each extruder 12.i a first operating parameter P.sub.1,i=U.sub.i in the form of a screw rotational speed parameter of the i.sup.th extruder is detected (Step A). This corresponds to the number of the complete rotations of a respective endless screw 26.i after a predefined start point in time t.sub.s. The screw rotational speed parameter U.sub.i is determined by means of the machine control 30, in particular by the associated extruder control 28.i. Therefore, for the first extruder 12.1 the screw rotational speed parameter U.sub.1(t) is detected, and for the second extruder 12.1 the screw rotational speed parameter U.sub.2(t) is detected, for the third extruder 12.3 U.sub.3(t) and for the fourth extruder 12.4 U.sub.4(t) is detected.

[0030] In addition, a second operating parameter P.sub.2,i=p.sub.i(t) is measured in the form of the operating pressure of the i.sup.th extruder. In addition, a third operating parameter P.sub.3,i=I.sub.i(t) is detected in the form of the respective armature current which is applied in the motor 24.i. The armature current I.sub.i is a size measurement for the torque M.sub.i which is applied to the endless screw 26.i. In addition, the extruder controls 28.i detect the number of operating hours H.sub.i and the abrasion parameters C.sub.i, which indicate how great the abrasive and/or corrosive effect is described of the compound which is processed at the point in time t in the i.sup.th extruder.

[0031] In order to make it clear that the respective operating parameters P.sub.j are received from the extruder control 28.1, they bear respectively the index 1. The further extruder controls 28.2, . . . , 28.N detects preferably the same operating parameters, wherein it is possible that not all extruder controls detect the same operating parameters.

[0032] The operating parameter C.sub.i(t) is detected for example in that a corresponding input request is presented on a screen, so that an operator can input this value. The torque characteristic M.sub.i can alternatively be determined in that the torque applied to the endless screw 26.i is detected for example by means of a strain gauge. Again alternatively, instead of the armature current I.sub.i , also the output P.sub.24.i of the respective motor 24.i can be detected.

[0033] The machine control 30 or the respective extruder control 28.i calculates in a following Step B from the detected operating parameters P.sub.j,i a wear parameter {right arrow over (V)} which owing to its vector nature could also be designated as wear parameter vector. The pressure loads B.sub.p,i, which are calculated according to the formula B.sub.p,i=.sub.t=0.sup.t(p.sub.i(t)), are components of the wear parameter {right arrow over (V)}. In the present case, the function f is the identical function, which assigns the identical number to each number. In other words, in the present case B.sub.p,i=.sub.t=0.sup.tp.sub.i(t). The pressure load B.sub.p,i describes the contribution which the pressure has on the wear of the i.sup.th extruder 12.i. From the sum it becomes evident that for example 10 seconds at a pressure of 200 bar have the same wear effect as 100 seconds at 20 bar.

[0034] The machine control 30 or the respective extruder control 28.i calculates from the detected operating parameters P.sub.j,i in addition the torque load B.sub.M,i, which is calculated according to the formula B.sub.M,i=.sub.t=0.sup.tg(M.sub.i(t)). In the present case, the function g is the identical function which assigns the identical number to each number. In other words, in the present case B.sub.M,i=.sub.t=0.sup.tM.sub.i(t). The torque load B.sub.M,i describes the contribution which the torque M has on the wear of the i.sup.th extruder 12.i.

[0035] In a subsequent Step C from the pressure load B.sub.p,i and the torque load B.sub.M,i the respective points in time T.sub.p,i and T.sub.M,i are calculated, at which a predefined pressure load threshold B.sub.p,i,grenz or respectively a predefined torque load threshold B.sub.M,i,grenz is reached. This takes place for exmaple by extrapolation of the time profile of the pressure load and torque load. For example, it can be a linear extrapolation. It is to be pointed out that the thresholds can differ from extruder to extruder. This lies for example in that the respective endless screws 26.i can differ from one another with regard to the wear behaviour.

[0036] In addition, respectively the points in time are calculated at which the screw rotational speed parameters U.sub.i reaches a respective screw rotational speed parameter threshold U.sub.i,max. In addition, it is determined when the operating hours number H reaches an operating hours threshold value H.sub.max. It is to be noted that all these calculations are carried out for all operating parameters and therefore for all extruders. Generally, the thus respectively calculated points in time differ from from another.

[0037] In a following Step D, the time for maintenance T.sub.w is calculateed as the smallest of these points in time. In Step E a maintenance message is outputted by the machine control 30, if applicable in response to a corresponding enquiry, which message encodes the time for maintenance. For exmaple, the time for maintenance is displayed on a screen of the machine control 30. At the time for maintenance, the extrusion system undergoes maintenance.

[0038] The extrusion system 10 comprises a metre weight scale 32, by which the length-specfic weight G of the strand 14 is measured. In addition, the extrusion system 10 has a speed meter 34 for measuring a speed v.sub.14 of the strand 14. The machine control 30 is formed for the automatic calculation of the specific throughput from the length-specific weight G, the speed v.sub.14 and the respective surface portion A, which the compound has from the extruder 12.i at the finished strand 14. Thus, the specific throughput D.sub.spez is calculated and stored in a time-dependent manner. In other words, the specific throughput D.sub.spez(t) is determined at regular points in time t and stored in a memory 36 of the machine control 30.

[0039] FIG. 1 shows in addition diagrammatically that the extruder 12.i has here a vibration measurement device 38, by means of which a vibration parameter a is detected. In addiiton, the temperature T.sub.i measured respectively by means of thermometers 40.i. In FIG. 1 the thermometers 40.i are drawn in such a way that they measure the temperature of bearings of the electric motors. However, it is particularly favourable if additionally or alternatively the temperature of the bearings of the endless screw is measured. The measurement data are conveyed to the machine control 30. When one of the temperatures T exceeds a predefined temperature threshold or when one of the vibrations exceeds a defined vibration threshold, an alarm is emitted.

[0040] By means of the metre weight scale, the length-specific weight G is determined constantly. This takes place as described above. The surface portion of the respective extruder 12.i on the finished tread 20 is determined geometrically and is programed-in in the machine control 30.

[0041] FIG. 3 shows a flow diagram of an alternative method according to the invention. At the top left in the flowchart it can be seen that the detecting of the operating parameters P takes place as in the method according to FIG. 2. In addition, it is indicated that after a predefined number of rotations or on reaching a predefined load or a predefined number of drive hours, the indicated maintenance steps are carried out. When in addition the wear threshold is reached, the corresponding component is exchanged.

LIST OF REFERENCE NUMBERS

[0042] 10 extrusion system
12 extruder
14 strand
16 pipe
18 extrusion head
20 tread
22 conveying device
24 24 motor
26 endless screw
28 extruder control
30 machine control
33 metre weight scale
34 speed meter
36 memory
38 vibration measuring device
P operating parameter
wear parameter
H number of operating hours
C abrasion parameter
I armature current
M torque
i running index i=1, . . . , N
N number of extruders
t time
j running index j=1, . . . , M
M number of operating parameters
U screw rotational speed parameter
t.sub.s is start point in time
B.sub.p pressure load
B.sub.M torque load
f function
G vibrate length-specific weight
B.sub.M,max torque load threshold
B.sub.p,max pressure load threshold
U.sub.max screw rotational speed parameter threshold
H.sub.max operating hours threshold
T.sub.w time for maintenance
V.sub.14 speed
A.sub.i surface portion
D.sub.spez specific throughput
a vibration parameter
T temperature