EP1622732B1 - Spring winding machine and method for controlling a spring winding machine - Google Patents

Description

The invention relates to a spring coiling machine and a method for controlling a spring coiling machine according to the preamble of claims 1 and 5. Such a machine and such a method are known from US 5,865,051 known. In spring winding machines, as used for example for the production of tortuous springs such as mattress and upholstery springs, technical tension and compression springs and torsion springs of any shape, provided that they have at least one tortuous body, spring wire is usually by means of a conveyor of a reel withdrawn and fed to a forming device. The forming device may comprise one or more winding tools, which deflect the spring wire during advancement and thereby transform into a spring. Depending on the mode of operation of the spring coiling machine, the winding tools can be firmly and immovably connected to the machine during the spring production process or can be held movably on the machine. In the latter case, the movement of the tools, for example, by a rotatable cam or by a servo motor and / or a piezotranslator.

Due to inhomogeneities or non-constant chemical and / or physical properties of the wire, the properties of the produced springs may deviate more or less from the desired nominal properties. Thus, for example, material properties such as wire diameter, warping or twisting, composition of the mixed structure, internal stresses or microcracks can affect the tensile strength, the modulus of elasticity or other properties affecting the ductility of the wire. Due to inhomogeneities of the wire and its electrical properties such. the conductivity or impedance or permeability within the wire may be different at different positions. The material inhomogeneities can lead to the properties of the produced springs not being constant. In particular, shape parameters such as e.g. Coil diameter, pitch, etc., and / or mechanical properties, e.g. the spring constants have considerable bandwidths. The production of geometrically accurate springs with properties within close tolerance limits is often difficult.

From the DE-A1-19534189 An adaptive spring winding apparatus is known in which means for improving the constancy of the spring characteristics are provided. Downstream there are after the forming tool Device for monitoring the wire and for generating output signals which are characteristic of the physical characteristics of the bent wire. The output signals are supplied to the controller and used by the latter for fine positioning of the forming tool or of its position, in such a way that the outer diameter or the inner diameter of the springs is maintained.
A disadvantage of this spring winding device is that the influence of different wire properties on physical properties of the spring to be produced are detected only during or after the forming process. Only after the measurement of inner diameters or outside diameters, which deviate from the nominal values, the control can be made to a position correction of the winding tools. It must be expected that springs are produced time and again, whose spring characteristics differ from the desired spring properties. If tight tolerances are to be met, such springs must be sorted out.

It is therefore an object of the invention to provide a spring coiling machine and a method for producing springs, in which desired measurable variables deviate as little as possible from predefinable setpoint variables. This object is achieved by a spring coiling machine with a measuring device and by a method for producing springs according to the features of patent claims 1 and 5.

Figur 1

eine schematische Prinzipskizze von Teilen einer Federwindemaschine,

Figur 2

eine Darstellung von Messwerten eines Wirbelstrommessgeräts,

Figur 3

eine Ansteuerfunktion für einen Umformer

The inventive spring coiling machine comprises a measuring device with at least one measuring sensor arranged in front of the converter in the conveying direction of the wire. The one or more measuring sensors detect measured quantities of the wire to be formed, which are given or co-determined by its physical and / or chemical properties. According to the invention, the machine control system controls the forming device not only as a function of predefined instructions or instructions, but also as a function of measured variables which are detected by the sensors which are located upstream of the wire-forming machine. The processing instructions on how the measured variables are to be processed to control variables for the forming device, the controller can be fixed or predetermined, but they can also be determined by the controller itself. In a preferred embodiment of the invention, the controller can detect other input or measured variables that are related to the properties of manufactured springs. In particular, the controller can record manual inputs to a user interface, for example, correction inputs for the position or attitude control a converter, which cause the springs have the desired desired properties. This corresponds to an open loop in which a model with processing instructions is formed or adapted. Alternatively or additionally, the controller can also detect measured variables of test sensors which represent properties of the springs produced or deviations of these properties from desired nominal properties storable in a storage medium of the controller.
According to the invention, the controller is designed such that it can correlate measured variables of the upstream measuring sensors and input variables or measuring quantities which are associated with the properties of manufactured springs and can produce correlations between the measured variables and / or functions derived from the measured variables. In this way, the controller can determine regularities between the measured variables of the upstream measuring sensors and the properties of the springs produced. In particular, the control, taking into account the measured variables of the measuring sensors, can control or influence the shaping device in such a way that the springs produced have the desired or predetermined nominal properties and thus compensate for fluctuations in the wire properties. On the basis of some figures, a preferred embodiment of the inventive spring coiling machine and the inventive method for the production of springs is described in more detail. Show

FIG. 1

a schematic schematic diagram of parts of a spring coiling machine,

FIG. 2

a representation of measured values of an eddy-current measuring instrument,

FIG. 3

a drive function for a converter

FIG. 1 schematically shows a schematic diagram with parts of a spring coiling machine 1, which are of importance for the invention. The spring coiling machine 1 comprises an electronic machine control, called control 3 for short, a wire conveyor 5 with two wire feed rollers 5a, 5b, a wire former 7 having a feed part 9 comprising two support rollers 9a, 9b or a feedstock (not shown) and at least one converter 11 Controller 3 may include one or more components. In particular, the controller 3 may comprise a conventional machine controller and a PC or industrial computer connected thereto. In the in FIG. 1 As shown embodiment of the invention are as a converter 11, a bender 11a for deflecting a spring wire, short wire 13 called in the radial direction or for forming the turns of a screw or

Mattress spring and a deflector 11b for deflecting the wire 13 in the axial direction or for forming the pitch of the spring 15 is provided. The conveying direction of the wire 13 is indicated by an arrow P. The position and / or position of the bender 11a and the deflector 11b are via actuators, for example via actuators, stepper or servo motors with or without gear or linear motors, which may include, for example, piezoelectric translators or electric motor or pneumatically driven spindles, and controllable. The means 11, 11a, 11b for deforming the wire 13 to a spring 15 are adjustable depending on the configuration of the spring coiling machine 1 before and / or after and / or during the manufacture of a spring 15 by the controller 3, controllable or adjustable. Preferably, the processing cycle or drive intervals for the updating of the position or position of the converters 11 are short and, for example, in the range of a few milliseconds to about 100 ms. The controller 3 comprises means for detecting input or measured variables, for example a user interface 17 with a screen display 19 and a keyboard 21 and / or a device interface 23 for connecting measuring devices 25 and / or programming or data reading devices such as, for example for inputting setpoints or default functions for the control of the converter 11 are required. A first, with the controller 3 Connected measuring device 25a for detecting wire properties comprises a measuring sensor 27 which is arranged upstream of the wire-forming machine 7 so that it can detect wire properties prior to the deformation of the wire 13 into a spring 15. In principle, the measuring sensor 27 can be designed to detect a wide variety of material parameters or properties of the wire 13 with any desired measuring methods. It is also possible to use a plurality of measuring sensors 27 for detecting such measured quantities. For example, an optical CCD sensor dimensions and / or surface structure of the wire 13 and a temperature sensor whose temperature and a coil detect eddy currents or impedances. Preferably, the first measuring device 25a comprises an eddy current measuring device, as offered, for example, by the company IBG Prüfcomputer GmbH in Germany under the brand name eddyliner® and the type designation P or Px. Devices of this type are generally used in the field of material testing and quality assurance. In the application according to the invention, the device comprises an evaluation unit 29 and as a measuring sensor 27 a coil connected thereto. In addition, in certain types of eddy current measuring instruments, a further coil with a piece of reference wire 13a may be connected to the evaluation unit 29 as a reference sensor 31. With this arrangement, a possible offset of the measuring device 25a can be reduced or avoided, whereby the measuring range and the resolution for the wire 13 to be measured are optimized. The evaluation unit 29 controls the measuring sensor 27 sequentially with a sequence of several different frequencies in the range of about 5Hz to about 300kHz. Preferably, the control is carried out with a sinusoidal signal. Alternatively, the drive signal may also be a superposition of different sinusoidal signals. The control can be carried out continuously or in the form of pulse packets. The evaluation unit 29 determines, for example, from the attenuation behavior of the signals and / or from other measured variables that can be influenced by these signals at several or all measurement frequencies f _i, the real part R _i and the imaginary part I _{i of} the impedance Z, where the index i is an integer value between one and can take eight, for example. Instead of or in addition to the impedance Z, other measured quantities could also be detected, which can be influenced by the damping behavior of the excitation signals or by induction or eddy currents which are generated by the excitation signals.

These measured values are transmitted to the controller 3 or can be queried by the controller 3.

FIG. 2 shows by way of example for 4 different wires 13, which are designated WA, WB, WC and WD, the measured values acquired or determined by the measuring device 25a at the measuring frequencies f ₁ = 25 Hz, f ₂ = 80 Hz, f ₃ = 250 Hz, f ₄ = 630Hz, f ₅ = 1.6kHz, f ₆ = 4kHz, f ₇ = 10kHz, f ₈ = 25kHz, with the real parts R _i and then the imaginary parts I _{i given} in a constant order for each of the frequencies f _i are. The scale on the ordinate indicates normalized values with respect to a reference value of the impedance.

It is clearly visible that the real and imaginary parts of the impedance values determined for certain measuring frequencies f _i and for the designated WA, WB, WC and WD wires accept 13 characteristic values. These values correspond to a fingerprint of the respective wire 13, which can be determined by different properties such as chemical composition, structure of the structure, internal mechanical stresses, surface treatment, electrical conductivity, permeability, temperature, external diameter, shape of the cross-sectional area, etc.

When forming the wire 13 into a spring 15, such wire properties, with unchanged setting of the converters 11, can lead to the actual properties deviating from the desired nominal properties of the spring 15. Thus, for example, the inner or outer diameter of a coil spring may be too small or too large and / or the pitch of the spring 15 may differ from the desired spring pitch. It is also possible that the spring 15 while in shape and shape the Default values corresponds, but has a deviating from the setpoint spring constant.

Such deviations can be determined manually by a person, for example by visual inspection and / or by measuring. A person may then instruct the controller 3 via the user interface 17 to adjust the control of the converter 11 in such a way that the subsequently produced springs 15 again have the desired properties. The adjustment or correction may be based on empirically determined data.

FIG. 3 shows a possible drive function for the bender 11a in the manufacture of a mattress spring. The horizontal direction X corresponds to the feed length of the wire 13 during spring production. In the vertical direction Y, the deflection or position or position of the bender 11 a is indicated. The scaling of the two coordinate directions is in each case specified normalized with respect to the maximum possible coordinate values, so that the possible value range of each coordinate extends from zero to one. The control curve marked K ₁ corresponds to the ideal drive function for the bender 11 a for a real reference wire. For each type of spring to be produced, the controller 3 may have deposited such a control cam in a memory (not shown). The control curve can, for example, by parameters of a polynomial function or by Fourier coefficients or Alternatively, stored as a look-up table, wherein for example, a hundred evenly distributed over the entire wire length support points, the corresponding Auslenkwerte are stored.

If the properties of the springs 15 produced with the control function K ₁ deviate from the desired properties, for example, the outer diameter of the springs 15 is too large or too small due to changed wire properties, or the spring pitch outside a tolerance range of, for example, 2% or 5% of a predetermined Setpoint is, the controller 3 by an adapted control function K ₂ (in FIG. 3 represented by a broken line) again produce springs 15 with the desired properties. Such an adaptation of the control function can be effected for example by multiplying the control values stored in the table by a correction factor and / or by adding or subtracting a correction value. Instead of such corrections, which apply to the whole of all interpolation points, different corrections for the values at individual interpolation points or for groups of interpolation points can also be made. Of course, the driving values can also be adjusted in such a way that non-geometric spring properties such as the spring constant or progressive springs a corresponding function with different wire properties are maintained, in which case the Shape of the springs 15, for example, the spring pitch can vary.

Alternatively or additionally, the detection of deviations from spring properties can also be carried out automatically with a second measuring device 25b using suitable test sensors 33. Thus, for example, the outer diameter of an end ring and / or the inner diameter of the narrowest turn and / or the spring pitch can be detected with a camera-based image processing system (no representation). Analogously to the manual adaptation of the drive function K ₁ , the controller 3 can automatically adjust or correct the drive function K ₁ or the drive values at the individual support points on the basis of the measured variables of the second measurement device 25b, as soon as these measured quantities are outside a tolerance range specified by the control 3. The adjustment of the control function K ₁ can be done by means of processing instructions that are specified in the controller 3.

The controller 3 further comprises a monitoring device (not shown) or an algorithm for determining correlations between a) the drive functions and / or corrections of these drive functions and / or spring characteristics detected by the test sensors 33 and / or deviations of these spring characteristics from the desired properties and b) the detected by the measuring sensors 27 wire properties.

The algorithm can take into account the delay between the detection of the wire properties by the measuring sensors 27 spatially upstream of the converter 11 and the effect on the subsequently produced springs 15.

• Nach der erstmaligen Inbetriebnahme der Federwindemaschine 1 startet die Steuerung 3 automatisch oder alternativ auf entsprechende Anweisung einer Bedienperson einen Trainingsmodus. Für jede herzustellende Feder 15 speichert die Steuerung 3 die von der ersten Messvorrichtung 25a ermittelten Werte als Datensätze, vorausgesetzt, dass die Eigenschaften der hergestellten Federn 15 innerhalb der vorgegebenen Toleranzgrenzen liegen.

One way of determining such correlations is exemplified below:

• After the first start-up of the spring coiling machine 1, the controller 3 starts a training mode automatically or alternatively on the appropriate instruction of an operator. For each spring 15 to be manufactured, the controller 3 stores the values determined by the first measuring device 25a as data sets, provided that the properties of the produced springs 15 are within the predetermined tolerance limits.

Each of these, for example, two hundred records is provided with a reference that allows a clear assignment to the drive function K ₁ for the corresponding spring type. This control function K ₁ is also stored in the memory of the controller 3 as a look-up table with, for example, a hundred points uniformly distributed over the wire length required to produce the spring 15. The values stored at the support points correspond to the drive values for the bender 11a at the location of these support points.

The controller 3 may calculate and store a first reference data set with the mean values or the median from the previously stored measured value data sets. Alternatively, the controller 3 can also directly store the measured values, which are preferably filtered and freed from stochastic interference. The first reference data set thus reflects a constellation of values of the first measuring device 25a, in which no correction of the drive function K _{1 is} required.

• Die ursprüngliche Ansteuerfunktion K₁ wurde zu einer neuen bzw. korrigierten Ansteuerfunktion K₂ abgeändert, damit die herzustellenden Federn 15 die erwünschten Solleigenschaften haben
• Eine oder mehrere Messgrössen der ersten Messvorrichtung 25a weichen signifikant von den in den vorgängig gespeicherten Referenzdatensätzen enthaltenen Werten ab
• Die Steuerung 3 stellt aufgrund von Änderungen der Messgrössen der zweiten Messvorrichtung 25b fest, dass die Federeigenschaften signifikant von den Sollwerten abweichen, welche ebenfalls in einem Speichermedium der Steuerung 3 hinterlegt sind

In an analogous manner, the controller 3 can automatically or on manual request form further reference data sets, eg if one of the following criteria is met:

• The original drive function K ₁ has been changed to a new or corrected drive function K ₂ , so that the springs 15 to be produced have the desired nominal properties
• One or more measured quantities of the first measuring device 25a differ significantly from the values contained in the previously stored reference data sets
• The controller 3 determines that the spring characteristics are significantly different from those due to changes in the measured quantities of the second measuring device 25b Deviate setpoints, which are also stored in a storage medium of the controller 3

The second and each further reference data set reflects a constellation of values of the first measuring device 25a, in which a correction of the drive function K ₁ or another drive function K ₂ , K ₃ , etc. is required in order to produce springs 15 with the desired properties.

After the formation of a first or further reference data set, which may include, for example, the real and imaginary parts of the impedance of the wire 13 at one or more frequencies, the controller 3 changes from the training mode to an operating mode in which no further determination of reference data records takes place. The controller 3 now starts a comparison algorithm which correlates the wire characteristics recorded by the measurement sensors 27 and stored as reference data sets and the corrections made at the original drive function K ₁ , eg by means of multiple regression or neural networks, and searches for correlations between these quantities. In this case, in addition to the measured variables of the measuring sensors 27 or to the data of the reference data sets, also linear and non-linear functions of the measured variables or of the data stored in the reference data sets are taken into account. Correlations occur when the control function required for the production of the springs 15 or their difference to the original control function K ₁ from the original control function K ₁ and the measured variables of the measuring sensors 27 or, which derive the data of the reference data records. When determining correlation functions, the controller 3 can limit the number of measured quantities taken into account or the corresponding data in the stored data sets such that only those parameters are taken into account which have a significant contribution to the correlation function.

If such correlations are present, the controller 3 changes the control of the converters 11 in such a way that, in addition to the stored original control function K ₁ , the measured values of the measuring sensors 27 and the associated correction values or the correlation function for controlling the converter 11 are taken into account.

Claims (8)

1. Spring winding machine (1) for the production of springs (15), comprising a wire transport device (5) and a wire transformation system (7) that can be controlled by a machine control (3) with at least one electronically controllable transformer (11), wherein at least one measuring sensor (27) of a measuring device (25a) is arranged in front of the transformer (11) in relation to the direction of transport of the wire (13) which is to be transformed, and wherein the wire transformation system (7) can be influenced by a measuring variable registered by the measuring sensor (27), characterised in that the measuring sensor (27) comprises a measuring coil for non-contact measurement of the measuring variables.
2. Spring winding machine (1) according to claim 4, characterised in that the measuring device (25a) comprises a reference sensor (31).
3. Spring winding machine (1) according to any one of the claims 1 or 2, characterised in that the measuring device (25a) comprises means for registering impedances and/or measuring variables which can be influenced by induction currents or eddy currents.
4. Spring winding machine (1) according to any one of the claims 1 to 3, characterised in that the machine control (3) comprises input devices (21) and/or registration devices (33) for inputting and/or registering spring properties or deviations of the spring properties from predetermined or predeterminable target variables and/or for inputting target variables.
5. A method that can be performed with a spring winding machine (1) according to any one of claims 1 to 4, characterised in that one transformer or a number of transformers (11, 11 a, 11b) is or are controlled depending on one or a number of predetermined or predeterminable control function(s) (K₁) and depending on the at least one measuring variable, registered by the measuring coil, of the measuring device (25a).
6. Method according to claim 5, characterised in that the control (3) saves and further processes values determined by the measuring device (25a).
7. Method according to claim 6, characterised in that the control (3) processes, automatically or on manual request, measuring variables of values determined by the measuring device (25a), to obtain reference data sets which also influence the control of the transformers (11, 11a, 11b) during the production of springs (15).
8. Method according to claim 7, characterised in that the control (3) determines correlations between the reference data sets and the control function of the transformers (11, 11a, 11b).

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