Patent Application
20090145943
The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2007 059 066.2 filed on Dec. 7, 2007. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d).
The present invention relates to a method for the axle correction of a processing machine, and a related processing machine, a related computer program, and a related computer program product.
Although the text below refers mainly to printing presses, the present invention is not limited thereto, but rather is directed to all types of processing machines with which a continuous material and/or a material web is processed. The present invention may be used, in particular, with printing presses such as newspaper presses, jobbing presses, gravure presses, in-line flexo printing presses, or printing presses for packaging or currency. The continuous material may be paper, cardboard, plastic, metal, rubber, or foil, etc.
With processing machines, in particular printing presses, a continuous material is moved along by driven axles (web conveyance axles), such as tension rollers or feed rollers, and by non-driven axles, such as breaker rollers, guide rollers, drying rollers, or cooling rollers. The continuous material is simultaneously processed—e.g., printed on, punched, cut, folded, etc.—using processing axles, which are usually also driven.
The web tension of the continuous material is influenced via “clamping points” which clamp the continuous material in a frictional, form-fit, or non-positive manner. Driven conveyance or processing units are typically involved. With a gravure press, a clamping point is typically formed by a printing unit, with which a frictional unit exists between the driven impression cylinder, the pressure roller, and the material web. The continuous material is subdividable into web-tension sections, with a web-tension section being limited by two clamping points. Further driven and/or non-driven axles may be located within a web-tension section.
In an acceleration or braking phase (change in rotational speed), a dynamic force must be applied in order to accelerate or brake the non-driven axles. In so doing, the rotational inertia and the friction of the non-driven rollers must be applied.
The machines are usually set up at a slow processing speed (set-up speed), to minimize waste. The subsequent acceleration that occurs in order to reach production speed results in deviations in register and web tension, which must be compensated for.
It is known to counteract—in the run-up phase—the change in extension caused by the acceleration by adjusting the angles of printing units, with consecutive printing units being precontrolled via increasing angular offsets.
It is possible to obtain the angular offsets by carrying out a measurement run. The disadvantage of this, however, is that waste is produced, and evaluations of the register error observed during the measurement run must be carried out. A manual evaluation is susceptible to error, and an automatic evaluation is costly due to the sensor elements required. In addition, a relatively great deal of time is required to perform a measurement run, since it must be carried out for all of the different acceleration phases that occur.
It is also possible to determine the precontrol values via computation, since they are proportional to the inertia of the non-driven axles, to the reciprocal of the elasticity module, and to the acceleration. It is known that the user may manually specify the inertia and the elasticity module.
The disadvantage of this solution according to the prior art is that input errors may occur when the user is specifying data, and that the necessary data, e.g., the elasticity module in particular, are not always exactly known.
The object, therefore, is to provide improved axle correction during an acceleration or braking phase.
This object is attained via a method for performing an axle correction, a processing machine, a computer program, and a computer program product according to the invention.
In a method—according to the present invention—for performing axle correction, with which, in particular, a web-tension adjustment and/or register adjustment or setting are/is carried out, when the rotational speed of a clamping point which limits a web-tension section is changed, a precontrol of this clamping point which limits a web-tension section, and/or a precontrol of a processing axle present in this web-tension section is carried out with consideration for the elasticity module of the material which comprises the continuous material, and with consideration for a rotational inertia of at least one non-driven axle which is present in this web-tension section; the elasticity module of the material which comprises the continuous material is determined automatically. One possibility for determining the elasticity module of the material which comprises a continuous material is disclosed, e.g., in DE 10 2005 056 802 A1.
The disadvantages of the prior art may be prevented via the axle correction—in particular web-tension control and/or register control—according to the present invention, with consideration for the elasticity module of the material which comprises the continuous material and a rotational inertia of at least one non-driven axle which is present in a web-tension section, with automatic determination of the elasticity module of the material which comprises the continuous material.
Advantageously, it is not necessary to enter any production-dependent material data, or to make these data known by calling up earlier production runs, since the data may be ascertained automatically. It is possible to determine the settings of the acceleration compensation while the machine is at a standstill, thereby producing no waste.
The precontrol according to the present invention is a marked improvement over the prior art, since it is now possible to provide a predictive precontrol of the expected errors, instead of having to react to an error that has already occurred. Via the axle correction in the sense of a web-tension setting or control, changes in web tension that occur during an acceleration or braking phase may be reduced, which translates directly into a reduction of waste. The reduced changes in web tension also result in a reduction in register deviations, which are reduced even further—in the sense of a register control—by the axle correction described above. Given the additional precontrol, it is possible to design more effective control strategies, since greater influence may be exerted on the continuous material. If, e.g., the printing press has reached the transient state, deviations in longitudinal register may be compensated for more quickly by using stationary control strategies in which the precontrol is incorporated. If the machine is in a dynamic transition phase, which may occur, e.g., by changing the setpoint value of the web tension or the web speed in the machine, the precontrol makes it possible to perform dynamic register control more quickly.
Via the measure according to the present invention, a greater decoupling of the continuous material is attained during register controls and/or web-tension controls, and the influence of the rotational inertias and friction torques of the non-driven axles is reduced. The stationary and dynamic errors between the individual processing units and printing units decrease. In addition, register errors may be compensated for more quickly. The effect of an acceleration phase or a braking phase on the web tension is reduced, thereby making it possible to carry out faster and/or more dynamic acceleration or braking procedures. Waste is greatly reduced overall, which results, e.g., in lower production costs.
Advantageously, precontrol is applied to all affected axles of the web-processing section. In particular, in order to control and/or set the web tension in a web-tension section, precontrol is carried out for the clamping points that limit the web-tension section, and, to control and/or set the register of a processing axle within a web-tension section, precontrol is carried out for the processing axle and/or the clamping points that limit the web-tension section.
In the case of web-conveyance axles or processing axles, it is typical to perform precontrol of additive speeds, multiplicative speed factors (“fine adjustment”, transmission factors), and/or additive angular offsets.
The effective rotational inertias to take into account advantageously also include the friction torques of the axles. The effective rotational inertias of the non-driven axles may be ascertained in particular via a measurement run. It is therefore possible to back-calculate the effective rotational inertias of the non-driven axles based on an evaluation of the register errors of the products. It is also possible to perform an on-line evaluation of the register errors that were measured. In addition to using a measurement run to ascertain the register errors, it is also possible to ascertain them via an on-line observation of the register errors that occur, and to thereby estimate the rotational inertias, e.g., via model tracking control, observers, Kalman filtering, etc. Finally, the moment of inertia may also be calculated based on the knowledge of the mechanical parameters such as diameter, material, material distribution, etc., of the non-driven axles. Since the mechanical design of a processing machine typically does not change, or rarely changes, the determination of the rotational inertias need only be carried out once or rarely. The determined values are then stored, and they may be used for all subsequent production runs.
Advantageously, the precontrol is carried out with consideration for the particular (effective) rotational inertia of all non-driven axles present in a web-tension section. It is therefore possible to further increase the quality of the precontrol.
The particular rotational inertias of all non-driven axles present in this web-tension section are preferably concentrated into one total rotational inertia to be taken into account for this web-tension section. This is an action that is simple to carry out and still yields good results. A total rotational inertia may be taken into account via a fictitious “calculation of the centroid”. This total rotational inertia may be ascertained, e.g., by using one of the methods (measurement run, etc.) mentioned above.
It is particularly expedient when precontrol values for precontrolling the clamping point and/or the processing axle are cascaded statically and/or dynamically in order to decouple adjacent web-tension sections at clamping points and/or processing axles. The cascading may take place with different factors, e.g., inversely, proportionally, in portions, or dynamically, etc., in order to decouple adjacent web-tension sections from the precontrol in the particular web-tension section.
It is also advantageous for the precontrol to be carried out with consideration for the change in rotational speed of the clamping point. Since the error to be expected is proportional to the change in rotational speed that occurs, i.e., a positive or negative acceleration of the axle, this acceleration is advantageously also taken into account in the precontrol. The acceleration may be determined, e.g., by taking the derivative of certain sensor values, e.g., the second derivative of the position sensor values, or the first derivative of the speed sensor values. To measure position or speed, it is possible, e.g., to sample information printed on the continuous material, such as marks, a perforation, etc. It is also possible to perform the determination using an acceleration sensor. Other possibilities include transferring the values from the machine control to the arithmetic unit for the web-tension control and/or register control, e.g., using field bus communication, it being possible to transfer, e.g., a setpoint position, a setpoint speed, a setpoint acceleration, a setpoint jerk, the actual position, actual speed, actual acceleration, or actual jerk of the machine master position. It is also possible to transfer binary signals that indicate a change in speed from the machine control to the arithmetic unit for the web-tension control and/or register control, and to transfer the knowledge of fixedly specified jerk values or acceleration values in the arithmetic unit for the web-tension control and/or register control. Finally, the acceleration may be estimated based on further process variables, such as the drive torques.
In an advantageous refinement, the arithmetic unit of the processing machine according to the present invention is designed to carry out the steps described above.
Expediently, in a processing machine according to the present invention, the arithmetic unit and the motion control of the driven axles and/or the machine process control are designed such that they are integrated in the same control hardware. Processing machines of this type are available in compact form and result in simpler handling, since it is not necessary to combine them with external components.
The present invention also relates to a computer program with program code means for implementing all steps of a method according to the present invention when the computer program is run on a computer or a related arithmetic unit, in particular in an inventive processing machine according to the present invention.
The computer program product—which is provided according to the present invention—with program code means which are stored on a computer-readable data storage device, is suitable for carrying out all steps of a method when the computer program is run on a computer or a related arithmetic unit, in particular on a processing machine. Suitable data storage devices are, in particular, diskettes, hard drives, Flash drives, EEPROMs, CD-ROMs, DVDs, etc. It is also possible that a program could be downloaded from computer networks (Internet, intranet, etc.).
Further advantages and embodiments of the present invention result from the description and the attached drawing.
It is understood that the features mentioned above and to be described below may be used not only in the combination described, but also in other combinations or alone, without leaving the framework of the present invention.
The present invention is depicted schematically with reference to an exemplary embodiment in the drawing, and it is described in detail below with reference to the drawing.
In
Printing units 111 through 114 each include an impression cylinder 111′ through 114′, against each of which a pressure roller 111″ through 114″ is pressed with strong pressure. Impression cylinders 111′ through 114′ may be driven separately and independently of one another. Associated drives 111′″ through 114′″ are depicted schematically. Pressure rollers 111′″ through 114′″ are designed such that they may rotate freely. Infeed 110 and outfeed 115 each include two cylinders, which rotate in opposite directions and guide paper 101. Infeed 110 and outfeed 115 may also be driven separately by a drive 110′″ and 115′″. Infeed 110 and outfeed 115, and printing units 111 through 114 form—with paper 101 passing through them—one unit that is connected via a friction connection. Infeed 110, outfeed 115, and printing units 111 through 114 therefore each represent a single clamping point.
In the web sections between individual printing units 111 through 114, paper 101 is guided via rollers, which are labeled 102 and are not explained in greater detail. For clarity, not every roller is labeled with reference numeral 102. The rollers may be, in particular, deflection rollers, drying devices, cutting device, etc.
After a printing step, web 101 is guided via cooling rollers in one of the printing units 111 through 114. For this purpose, a cooling roller 121 is located in the web section between first printing unit 111 and second printing unit 112, a cooling roller 122 is located in the section between second printing unit 112 and third printing unit 113, a cooling roller 123 is located in the section between third printing unit 113 and fourth printing unit 114, and a fourth cooling roller 124 is located in the section between fourth printing unit 114 and outfeed 115.
Cooling rollers 121 through 124, and rollers 102 each have an effective rotational inertia which has a negative effect on an acceleration phase of the printing press. According to the preferred embodiment of a printing press shown, all clamping points are precontrolled during an acceleration phase, with consideration for the elasticity module of the material which comprises the continuous material and with consideration for the effective rotational inertias of cooling rollers 121 through 124, and rollers 102. The effective rotational inertias are ascertained in advance, typically once, using a measurement run and a subsequent evaluation. The elasticity module is determined automatically. In an acceleration phase, a precontrol which accounts for the elasticity module, the effective rotational inertias, and the acceleration is carried out. The precontrol may be carried out using dynamic time elements, e.g., with the aid of a DT1-function (a derivative-delaying function), in which case T1 is selected to be proportional to the web length/machine speed. The precontrol may include additive angular values. The result is an approximately constant state of web tension in a desired section of the continuous material, and, therefore, a register deviation that nearly disappears, as shown with reference to
One possibility for determining the elasticity module is described below with reference to
The elasticity module E is calculated as E=(ΔF·l0)/(A·Δl), with ΔF: applied force; ·l0: original length; A: surface area of the material web; Δl: change in length.
Force ΔF may be determined using a load cell (not depicted) located in the web section between infeed 110 and first printing unit 111. Length l0 and surface area A of the continuous material between infeed 110 and first printing unit 111 are known, or they may be easily measured. Finally, change in length Δl may be determined as the product of angular displacement Δφ and the radius of the pressure roller, or by using a position sensor (e.g., the motor sensor). As an alternative, a change in tension may also be brought about by specifying a web tension using the force of a jockey roller in the infeed and/or outfeed. If a jockey roller is present in the infeed or outfeed, a force may be introduced into the continuous material via the specification of the jockey roller pressure. This applied force then results in a web tension. A web tension may also be specified by specifying a force of pressure roller that has not been completely activated. If the pressure roller has been activated, a web tension may also be applied via the wrap-around. Finally, based on the data that are obtained, it is possible to determine a production-dependent constant k=EA.
As an alternative, it is possible, e.g., to use the applied motor torque as the force variable, rather than to perform a measurement with a load cell which is present. It is necessary to account for friction effects, and for tension forces that occur outside of the web-tension path, since they influence the motor torque that is applied. The latter may be disregarded if the material web has become nearly completely slack—during the measurement—outside of the two clamping points that clamp the material web, i.e., infeed 110 and first printing unit 111 in the example shown. Otherwise, a web tension before and/or after the measurement section will corrupt the web tension that is ascertained from the motor torque that is measured.
One possibility for determining the inertial masses is described below, also as an example. If the inertial masses are not known, or if they are stored as constants in the acceleration compensation, they may be ascertained in a measurement run, if the elasticity module of the continuous material is known. Two variants thereof will be described. According to one variant, the resultant change in web tension may be determined during an acceleration phase, e.g., using a load cell. Based on this measurement, and given a known elasticity module, the effective inertial mass is calculated based on the change in web tension and the machine acceleration. According to a second variant, the resultant register error may be determined during an acceleration phase. If the elasticity module is known, the resultant change in web tension may be determined based on the register error. Together with the machine acceleration, it is possible, in turn, to determine the effective inertial mass.
Diagram 10 shows two web tension curves 13 and 14, which are assigned to various web-tension sections. A web-tension section is considered that is subdivided into two adjacent web-tension sections by a non-driven axle, which is a cooling roller in the example shown. A clamping point (driven axle) is located at each of the ends of the web-tension section. In the example shown, the clamping point is a driven pressure roller. With reference to
In the direction of conveyance of the continuous material, the web-tension subsection assigned to web-tension curve 14 is located between a clamping point and a non-driven axle, and the web-tension section assigned to web-tension curve 13 is located directly thereafter—in the direction of conveyance of the continuous material—between the non-driven axle described above and a subsequent clamping point.
As shown in diagram 10, the web tension regularly has a smaller value in the region between a clamping point and a subsequent, non-driven axle than it does in the region between the non-driven axle described above and a subsequent clamping point.
In an acceleration phase 15 according to
After the acceleration, a stationary state sets in, which is indicated in
A resultant register error at a processing unit is shown in
Finally,
It is understood that only one particularly preferred embodiment of the present invention is depicted in the figures shown. Any other type of embodiment is also feasible, without leaving the framework of the present invention.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of methods and constructions differing from the types described above.
While the invention has been illustrated and described as embodied in a method for the axle correction of a processing machine, and a processing machine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 059 066.2 | Dec 2007 | DE | national |
