DE3534734C2 - Method for controlling a multiple extruder system - Google Patents

Description

The invention relates to a method according to the preamble of claim 1.

Multiple extruder lines are used to manufacture one certain profile strip type around a target operating point with a certain total throughput and corresponding partial throughputs of the individual Extruder driven. Each extruder runs with one certain target speed at which there is a target pressure sets.

In known extruder systems, the speeds the individual extruders started up by hand when starting up, until the target speeds are reached. Here At the beginning there is a profile in which the mass fractions of the individual components or components do not correspond to the desired or required values. The desired or required quality the profile strip generally only arises in the course of stationary operation. It is therefore a significant part of the extruded profile strip not to use.

Also result when the extrusion process ends through as a result of the intermittent feeding and the resulting in lower pressures on the extrusion head the mass fractions of the individual profile components, so that much of the end the extruded profile strip arises as a committee.  

From the earlier patent application P 34 34 904.9-16 (DE 34 34 904 C1) is a method for monitoring the dimensions one manufactured on a multiple extruder system Profile strip made of soft elastic material known a loop of the redirected during stationary operation Profile strip scanned in the cooling phase and a deviation of the loop from the target shape for correction the dimensions of the profile strip is used by at the same time, the conveying speed of everyone Mixture is changed.

Furthermore, there are in DE-Z. "Rubber + rubber · Kunststoffe "38 (1985) 3, pages 193 to 199 comments on Procedure for automatic control - also arrival and departure Shutdown processes - from multiple extruder systems to production of treads of vehicle tires. According to this information control algorithms before the actual control of the extruder system empirically for the rubber compounds in question determined and saved under code numbers. This data acquisition is for each mix and that associated profile performed once. The constant sizes are automatically monitored, regulated and with the Algorithm linked. This can be done using a keyboard stored data packet retrieved and the production process be started. For multiple extrusion lines each extruder is controlled individually. Integrated is the regulation of meter weight and profile cross section. During the extrusion process, the profile cross section is used and meter weight as target values for the product. They are monitored and the process computer as a reference made available.

The invention has for its object a method to control multiple extruder systems, with which the mass fractions of the individual Components of the extruded Profile strips with each other and to the total mass of the profile largely when starting up the system can be kept constant. Beyond that the mass fractions also to the end and in the stationary Operation when a permissible temperature is exceeded be kept largely constant.

The object underlying the invention is achieved by the measures characterized in claim 1 solved. Because the ratio of the speeds of each Level to each other equal to the ratio of the target speeds corresponds to each other, is already at Start-up of the plant largely at the target operating point corresponding distribution of the mass fractions of the individual profile components.

Advantageous developments of the invention are in described the subclaims. So after the Measure of claim 2 the throughput of each Extruder also through part of the emptying process kept constant so that during this time also the ratio of the mass fractions to each other can hold. When operating the system according to claim 3 can the ratio of the mass fractions also Exceeding an allowable temperature during the keep stationary operation largely constant.

The object of the invention is in the drawing shown and is explained in more detail below. It shows

Fig. 1 shows a triple extruder system in a schematic representation

Fig. 2 shows a three-component profile strip in cross section.

The extrusion system has three extruders 1, 2, 3 . The extruders 1. . . 3 have essentially the same structure, but can be z. T. differ significantly.

The extruders 1. . . 3 are attached with their outlet ends to an extrusion head 4 common to all extruders. At their end pointing away from the extrusion head 4 are the extruders 1. . . 3 equipped with its own speed-adjustable drive 10. i (i = 1, 2, 3) with integrated speed sensor 11. i. In addition, each extruder 1. . . 3 in the vicinity of its drive a hopper 12. I for feeding a soft elastic band-shaped material mixture, a feed strip 13. I, which are processed together to form a multi-part profile strip 5 . The feed strips are supplied 13. i the hoppers 12 i by Fütterbänder 14 i.

At the extrusion head 4 there are 1 for each extruder . . . 3 separately - a temperature sensor 15. i and a pressure sensor 16. i arranged. Further pressure sensors 17 i can look at the individual extruders. 1 . . 3 be evenly distributed over their length. Each extruder 1. . . 3 is also assigned a marker reader 18. i. A meter weight or belt scale 6 is arranged behind the profile exit of the extrusion head 4 (not shown separately). The output of the meter weight scale 6 as well as the outputs of the marking readers 18. i and the speed sensor 11. i are connected to the input of a computing system 20 with an integrated database. The output of the computer system 20 is connected via a control cabinet 21 to the drives 10. I of the individual extruders. In addition, the input of the computing system 20 and the control cabinet 21 are each connected to a control panel or terminal 22 . For the sake of simplicity, the connections described are only shown for the extruder 1 in FIG. 1.

A target operating point with a corresponding target total throughput q _Oges (which is composed of the throughputs q _{Oi ′} (i = 1, 2, 3)), corresponding target speeds n _Oi , target pressures p _Oi and a range of operating temperatures ϑ _{i is} determined for each desired type of profile strip . At this desired operating point, the profile strip 5 has the desired or required quality and the mass content or proportion m _i or the corresponding length-related mass proportions m ' _{i of} the individual components or components of the profile strip corresponding to the mixtures of the feed strips 13. i required values (whereby the individual length-related mass fractions m ′ _i (in%) relate to each other and to the length-related total mass m ′ _{ges of} the entire profile strip 5, like the corresponding mass flow rates q _{i to} one another or to the total flow rate q _ges ). The values that arise for the production of a specific profile or profile strip 5 at the desired operating point, such as in particular the rotational speeds n _Oi , pressures p _Oi and temperatures ϑ _i, are stored in the database of the computing system 20 . Since the pressures p _i occurring in the extrusion head 4 are subject to strong temporal fluctuations, the signals from the pressure sensors 16. I are passed to the computing system 20 via low-pass filters (not shown separately). It is therefore not the momentary fluctuations in pressure that are recorded, but rather the respective pressure level. In the following - as in the claims - the shorter terms "pressure" and "target pressure" are therefore also used for the terms "pressure level" and "target level" for the sake of simplicity.

To produce a profile strip 5 , the operating temperatures ϑ _i (i = 1, 2, 3) at the extruders 1 are first . . 3 and brought to the intended operating temperatures on the extrusion head 4 and all extruders 1. . . 3 including the extrusion head 4 filled with the intended material mixtures of the feed strips 13. i.

For all extruders, the speed n _{i is} ramped up simultaneously on signals from the computing system 20 in increments, the ratio of the speeds n _{i of} each stage to one another corresponding to the ratio of the target speeds n _Oi stored in the computing system to one another. By observing these conditions, a distribution of the mass fractions m _{i of} the individual profile components corresponding to the desired operating point is largely achieved when the system is started up.

To avoid excessive pressure surges, the speed is graded in 10 steps, the speed increase being 0.1 n _Oi each. In order to reduce pressure peaks caused by the speed jumps, the timing of the step jumps is preferably 15 s. When the target speeds n _{Oi have been reached} , ie after the start-up has ended, the mass fractions m _{i of} the individual profile components largely correspond to the required values.

After a brief calming phase, the extrusion system is up driven in stationary operation.  

Exceeds 15 from the temperature sensors measured operating temperature θ i _i a permissible value θ _permissible, so an increase in the rotation speed would _i n an excess of the allowable temperature mean. If the permissible temperature is exceeded, the speed of the other extruders is reduced. If, for example, a pressure p ₁ above the set pressure p _O1 occurs on the extruder 1 , the extruders 2 and 3 become by the amount

.DELTA.n _i = k ₁ · n · _Oi (p ₁ - p _O1) / _O1 p (i = 2, 3)

or

Δn _i = - k ₁ * (p ₁ / p _O1 - 1) * n _Oi

changed (the minus sign indicates the humiliation); k ₁ is a constant inherent to extruder 1 . With this control, the ratio of the mass fractions m _{i to} one another is achieved as at the nominal operating point. It is merely reduces the overall throughput q _ges against the target operating point.

To end the extrusion process, the feed tires 13. i are capped. Because of the different mass flow rates q _{i of} the individual extruders, the feed strips 13. i are capped at different times - or in different lengths from the extruder inlet at the same time - in order to empty the extruders as evenly as possible. Since the extruder 3 has the lowest throughput in the system shown in FIG. 1, the time delays for capping the feed strips 13.1, 13.2 are compared to the capping of the feed strip 13.3

Δt _i = v _i - v ₃ (i = 1, 2),

where v _i (i = 1, 2) and v ₃ mean the line speeds of the individual feed belts 14. i.

The feed strips 13. I can also be capped at the same time with different lengths, the feed strips for the extruders 1, 2 by the partial length

l _i = v _i / Δt _i

be cut longer. If the capping is done by hand, there is definitely a time offset to give the operator the opportunity to cut the feed strips 13. i one after the other. The respective exact point in time can be indicated by an optical or acoustic signal.

After cutting the feed strips 13. i, the operation is continued while maintaining the last operating state. The beginning of the emptying phase is characterized as a result of the lack of feeding by a continuously decreasing pressure p _i at all pressure measuring points and thus a continuously decreasing throughput. To maintain the throughput and thus the ratio of the individual mass fractions of the profile components A, B, C in the profile strip 5 , it is necessary to compensate for the reduction in throughput by increasing the speed of the extruder in question. This is achieved at intervals of 5 to 10 s by increasing the speed n _{i of} the extruder in question, the speed by the amount

Δn _i = - n _Oi · k _i · (p _i - p _Oi ) / p _Oi

is raised above the target speed n _Oi . Pressure changes are thus counteracted with an opposite speed change. The phase of controlled partial emptying starts one after the other on all extruders with the start of feeding interruption and can be maintained for as long as the speed n _i reaches 1.2 times the target speed n _Oi .

Claims (4)

1. A method for controlling a multiple extruder system for producing a profile strip from soft-elastic material mixtures, characterized in that the speeds (n _i ) of the extruders by a process control in 6 to 16, preferably 10, at intervals of 7 to 32 s, preferably 15 s, Steps taking place at the same time are brought to the respective target speeds (n _Oi ) previously stored in a database, the respective speeds (n _i ) in the individual steps behaving in relation to one another like the corresponding target speeds (n _Oi ). 2. The method according to claim 1, characterized in that the speeds (n _i ) of the individual extruders after the cutting of the feed strips ( 13 i) at predetermined intervals of 2 to 32 s, preferably 5 to 10 s, as long as one amount each be raised above the respective target speed (n _Oi ) until the respective speed (n _i ) has reached 1.15 to 1.25 times the relevant target speed (n _Oi ). 3. The method according to claim 1, characterized in that in steady-state operation when a permissible temperature is exceeded in the event of a deviation in the pressure (p _i ) of an extruder (i = 1, 2,...) From its target pressure (p _Oi ) The rotational speed (n _j , j ≠ i) of the other extruders (j ≠ i) is reduced at predetermined time intervals of 2 to 32 s, in particular 5 to 10 s, by an amount (Δn _j ) that follows from the three following factors mentioned

• a constant (k _i ) inherent in the first extruder ( _i ),
• - The difference related to the target pressure (p _Oi ) of the first extruder and formed from the respective pressure (p _i ) and the corresponding target pressure (p _Oi ) and
• - The target speed (n _Oj ) of the other extruder

formed product corresponds.