EP0796158B1 - Method and device for the optimized production of helical springs on automatic spring-winding machines - Google Patents

Description

The invention relates to a method and a device for continuous checking and correction Error occurring with spring wires for the optimized production of coil springs Automatic spring coiling, taking a wire from one Unwinder in which a spool or a Coil is stored, unwound and by means of a separate feeding device of a forming device, which contains wind pins or rolls becomes.

Coil springs are used on the industrial side Users increasingly demanding accuracy requirements in terms of adherence to the constructive specified spring characteristics, especially the spring characteristic, posed. The reasons for this are special the increasing demands on machines and devices, in which coil springs are used, as well as the growing level of automation in the Manufacture of machinery and equipment with a tendency to that only tightly tolerated components are processed can be.

The spring wire as the starting material is subject material-related, geometric and processing technology Fluctuations. You express yourself in deviations of the wire diameter, the strength values or material characteristics from their nominal values and in twists due to elastic Torsional stresses. There are also deviations an authoritative role arising from your plastic-elastic deformation behavior of the Spring wire result and mostly in upstream Manufacturing stages have their cause.

The fluctuations mentioned cause considerable deviations of the parameters of the cold-formed coil spring from the design-determined data, the effects of which can be determined in deviations of the spring characteristic from the target characteristic.
In particular, the fluctuating thickness of the wire diameter causes changes in the inclination of the spring characteristic, that is to say fluctuations in the spring rate, and different elastic torsional stresses in the wire coil cause length fluctuations in the spring produced and thereby parallel displacements of the spring characteristic.
As a result, rejects are inevitable in the manufacture of springs, the proportion of which can be considerable in the case of springs with small dimensions and high accuracy requirements. Since this committee can usually only be determined on the finished spring, there are considerable economic losses. In addition, the necessary additional expenses for materials and energy lead to additional environmental pollution.

The state of the art includes machines for spring production, the via feed rollers, mechanical or electrically controlled wind pins or rollers, Incline and form tools are known. Their development was primarily based on it directed to achieve the highest possible number of pieces and with reasonable effort also the conversion to Manufacture of springs with different dimensions and ensure shapes.

Machines with a monitoring and quality assurance system are also known in the prior art, where the spring length is mechanical, optical, capacitive or measured by changing the induction or is checked.

Systems are also known which can be used with the help of these measuring and testing options recognize and sort out as well as independent corrections at the control of the automatic spring coiler. This is usually done on the basis of methods for statistical process control. Other realized variants deliver existing ones Deviations in the manufactured springs via dialog systems corresponding error messages to the operator, which then corrected into the controller must intervene. Systems are also known which after a corresponding number of immediately successively manufactured committee springs the manufacturing process interrupt.

According to JP 55-153 633 (A) an arrangement is known where the twist in a steel cable when unwinding from a spool by controlled rotation of the Unwinder should be prevented. The rotation the unwind spool is used by a sensor detected the rotational movement of a fixed Roller, over which the rope is guided, controls. This arrangement is for identification and Influencing of embossed in a rigid wire Torsional stresses not applicable.

DE 35 38 944 describes a machine for producing coil springs by winding, with which springs with a continuously variable pitch can be produced.
Thereafter, it is provided that the spring manufacturing machine contains an electronic control circuit. A data storage unit stores preselected data indicating spring parameters, such as pitch, length and diameter. When a spring is formed, the corresponding preselected parameter of the spring is monitored and a signal indicating the monitored parameter is generated. The electronically stored data and the monitoring signal are compared with one another. The spring production can be changed in accordance with this comparison for the purpose of producing a spring with the preselected parameter.
This machine makes it possible to freely change the parameters of the coil springs to meet the preselected spring requirements. The dimensions of the spring can be changed during the actual manufacture of the coil springs, so that springs with pitches can be produced which change continuously along the length of the spring.

This is a manufacturing process in which the springs are produced by winding around a mandrel. This type of production does not allow a change in the winding diameter. In addition, wire rods of finite length are fed individually, so that continuous influencing of the wire parameters is not possible.
Although the spring winding parameters can be determined and changed in this way, it is not possible to compensate for tolerances in the spring material parameters during the continuous process of automated manufacture by spring winches.

In the known machines and processes for Spring winches are disadvantageous in that they fluctuate the parameter of the starting material spring wire only record after production.

The invention has for its object a method and a device of the aforementioned Specify type, which also with fluctuating values the wire parameters high accuracy in spring production guarantee and at the same time the Minimize scrap.

According to the invention the problem is solved by a method and an arrangement with the in the claims 1 and 5 specified features. Advantageous embodiments are in the subclaims specified.

The inventive method and the inventive Device are characterized by a number from advantages.

The arrangement according to the invention and the inventive Methods enable the compensation of the elastic torsional stresses of the spring wire, which in particular for the processing of spring-drawn Wire types is important. This torsional stress is not recognizable externally because the drawn wire according to this manufacturing process is wound into a coil under tension. The torsional stresses are released when you get this Force from the spring wire takes. You express yourself in spreading or turning over the wire loops and lead to fluctuations in the length of the spring produced and thus to the parallel shift mentioned above the spring characteristic.

To measure the spring wire diameter in one or two methods are possible on two levels. The detection in two levels enables deviations to know the wire cross section and the process control. Besides are advantageous tactile or non-contact electrical Sensors also optical sensors that change Evaluate lighting parameters.

The correction of the wire diameter fluctuations is particularly important for tempered spring wires. With these wires, the stresses generated during drawing are reduced due to the final hardening process carried out at over 860 ° C, but the wire stretching rejuvenates in the furnace section, even with the smallest obstructions in the wire run-off reel. Fluctuations in wire diameters are therefore much more pronounced here than with patented drawn and stainless steel wires.
By combining the winch tools with force measuring devices, it is possible to measure the forming forces in the spring winch and, by evaluating them, to draw conclusions about changes in the spring parameters and to include these changes in the machine control.
Another special embodiment provides that an E or G module measuring device is used. This consists of rollers, which cause the wire to deform slightly by defined values and measure the required deformation forces.
Since the initial state of the wire is determined before the forming process and is taken into account when controlling the wind tools, the rejects can be significantly reduced.
In addition, the forming result can also be continuously monitored and the target-actual deviation can be traced back to the tool position using a controller. This leads to considerable reductions in wages, materials and energy costs, as well as a reduction in material recycling expenses and a reduction in additional environmental pollution.

The method according to the invention and the device according to the invention can advantageously be used in the production of new automatic spring manufacturing machines, the application not being restricted to automatic coil spring winders, but also being suitable for other machines for producing springs. It can also be retrofitted to existing NC-controlled automatic spring winders, so that the largest possible group of spring manufacturers can use the device according to the invention without major renewal of the machine park and with little financial outlay.
It is also possible to sort the springs into different quality classes based on the measurement results obtained.

Figur 1 eine schematische Darstellung einer Zuführeinrichtung mit loser Schlaufe;

Figur 2 eine Ausführungsform, gemäß Figur 1, bei der Dehnmeßstreifen als Sensoren verwendet werden;

Figur 3 eine Zuführeinrichtung mit drehbarer Drahtabzugsführung;

Figur 4 eine schematische Darstellung der erfindungsgemäßen Vorrichtung;

die Figuren 5 und 6 die Anordnung zur Ermittlung des Federdurchmessers und

Figur 7 die Verknüpfungen der einzelnen Bau-gruppen in Form eines Blockschaltbildes.

The invention is explained in more detail below using an exemplary embodiment. In the accompanying drawing:

Figure 1 is a schematic representation of a feed device with a loose loop;

Figure 2 shows an embodiment, according to Figure 1, in which strain gauges are used as sensors;

FIG. 3 shows a feed device with a rotatable wire take-off guide;

Figure 4 is a schematic representation of the device according to the invention;

Figures 5 and 6, the arrangement for determining the spring diameter and

Figure 7 shows the links of the individual modules in the form of a block diagram.

In the arrangement shown in Figure 1, the Wire from a Coil C that is on a reel is withdrawn via the wire feed rollers R. The reel is from a not shown here controlled drive actuated. To unwind enable, the reel with the coil C in the Bearings L1 and L2 stored. The entire unwinder A is pivotally mounted in the bearing L3. The axis of the bearing L3 coincides with that Direction of the drawn wire D together. From the guide device Z is the wire over the Detection unit E of the wire feeder Machine fed. Between the management facility Z and the unwinder A forms the wire becomes one by the action of gravity Loop S. The length of this loop S is caused by the movements of unwinding device A and guide device Z controlled so that they maintains an approximately constant diameter. The Loop formation is supported by guide rollers FR. If the wire D has no torsional stress the wire loop S hangs vertically below. If the wire has torsional stress, the wire loop S deflected from the vertical position. The deflection is made by the detection unit E1 determines and leads over a separate control unit for a rotation of the Unwinder A in bearing L3 so that the torsional tension is eliminated and affect the following Operations cannot impact. There is another between the machine and the wire loop S. Detection unit E2 attached. This determined the current wire requirements for spring production and controls the drives of the guide rollers R and the bearing L1, L2 depending of the respective wire requirement. In the example shown the sag of the wire is determined.

FIG. 2 shows one possible embodiment for the arrangement of the sensors. In this case, two sensor rollers SR are attached to the wire loop S and are attached to the frame via springs F1 and F2. If the wire D has a torsional tension, this causes a deflection of the wire loop S and thus also a deflection of the springs F1 and F2. Strain gauges DMS are attached to the springs F1 and F2 and are used to determine the deflection. With the help of the strain gauges DMS, a value for the size of the deflection of the wire loop S can be determined and the required pivoting movement of the unwinding device A can be controlled.
In addition to the attachment of strain gauges, various other sensors can also be used for the detection unit. The sensors can both determine the deformation of a plastic element, as shown in FIG. 2, and also detect the displacement of an element by means of a displacement measuring system. In the simplest case, a two-sided stop is sufficient, the contact of which is determined by making contact.

FIG. 3 shows a feed device with a rotatably mounted wire take-off guide DF. The twisted wire is pulled off a reel H under tension. In the detection unit E1, the wire with torsion is guided in a wire loop acting as a torsion indicator around a rotatably mounted wheel. For this purpose, the wheel is arranged in such a way that, in addition to its rotation about the wheel axis caused by the wire run-off movement, it can also perform a pivoting movement about an axis perpendicular thereto. This pivoting movement is dependent on the torsional stress connected in the wire being fed. The recognition unit E1 is connected to a sensor SE, which indicates the deflection of the recognition unit E1. Torsional stresses between the fixed stator L and the wire take-off guide DF therefore lead to a deflection of the detection unit E1 and are displayed by the sensor. When unwinding tension-free wire, the reel pot has to make a 360 ° turn to unwind a full wire loop. The torsional stresses are eliminated by initiating a defined relative movement between the reel and the controllably rotatable wire run guide DF, so that twist-free wire is fed to the winding machine.
It is particularly advantageous that the arrangement enables the controllable additional movement of the wire take-off guide DF to be carried out quickly and precisely. This is achieved in particular in that the movement of the wire take-off guide DF, which has only a very small mass, is separated from the movement of the reel H. The reel H, which has a large mass, must also perform an additional movement to ensure a continuous wire run. The additionally mounted wire take-off guide DF enables these two movements to be separated, so that it is not necessary to accelerate the reel H quickly with high expenditure of force and correspondingly high loads on the moving parts.

D_mk =

mittlerer Federdurchmesser nach der Korrektur

D_mo =

Sollwert des mittleren Federdurchmessers

d_ist =

ermittelter Istwert des Drahtdurchmessers

d_o =

Sollwert(Normwert)

ist.The device according to the invention is shown schematically in FIG. To manufacture a helical spring, the wire is first guided past a wire diameter measuring device 1, at which the current diameter of the spring wire is determined. The wire then enters the measuring device for determining the E or G module. The measuring device consists of rollers 2, of which at least the roller 2.3 is adjustable perpendicular to the roller axis, the pair of rollers 2.2 is driven and the pair of rollers 2.1 runs freely. With this adjustment, the wire is elastically deformed by defined values. Sensors are connected to the rollers, with which the bearing forces N1, N2, and N3 are continuously measured. These bearing forces depend on the material properties of the spring wire and allow the elastic modulus to be determined. This makes it possible to determine the G-module for the current status. In order to carry out the measurement independently of influences of the machine function, the loops 4.1 and 4.2 are arranged. The deformation properties of the wire to be processed can be recognized and appropriate reactions initiated. Such reactions can be, for example, a warning signal or the triggering of corresponding adjustment movements of the molding tools. After the wire has passed through this device, it arrives via the inlet guide EF into the feed device Z and then into the forming device.
The adjustment of the wind pins for wire thickness-dependent control of the spring diameter takes place according to the relationship: D mk = D mo · 3rd d is d O 4th in which

D _mk =

average spring diameter after correction

D _mo =

Setpoint of the mean spring diameter

d _is =

determined actual value of the wire diameter

d _o =

Setpoint (standard value)

is.

With the inlet guide EF, the wire D of the forming device fed into a defined arc. This inlet guide EF is curved Wire is effective and ensures defined wind conditions. The inlet guide EF can consist of an arcuate Pipe exist or from a roller assemblies be formed.

The wind pins are from the forming device in FIG 3.1 and 3.2 are shown electrically are adjustable. By another actuator becomes the adjustment of the gradient wedge enables so that all geometric parameters of the to be manufactured spring can be influenced. On the wind pins 3.1 and 3.2 are force sensors attached with which the wind forces N4 and N5 be continuously determined. With that, too Changes in wire forming properties are recorded and fed to the evaluation of the process control.

Figures 5 and 6 show an arrangement with which the spring outer diameter D _a and the pitch P can be determined after winding. Various solutions are possible as a measuring device. In the example shown, the spring diameter on the spring 5 is determined using a CCD matrix 6. The tongue 5 lies against the V-groove 7 in a defined manner. Fluctuations in the spring diameter can also be detected in a known manner using the silhouette method or the scanning principle with optical measuring devices.

Figure 7 shows a schematic representation of the links between the individual modules. The necessary positioning movements are controlled by a machine computer, which is connected to the individual measuring stations of the machine via signal processing.
The wire is pulled from the wire feeder into the device. It first passes through the wire diameter measuring device DDME. The wire feed is connected in a manner known per se to a path measuring device, from which a signal is obtained over the length of the wire to be processed. This measuring device is not shown here. An E or G module measuring device E / G-ME with a force measuring device KME and a displacement measuring device WME, with which the deformation of the wire and the associated force are determined, is also connected upstream of the wire feed. The current values for the elastic modulus of the wire can be determined from the determined force and deformation values. The G-module can be determined from the E-module. After the wire has passed through the measuring device, it is fed to the drawing-in device and thus to the forming device which contains the wind pins 3 and the gradient wedge. Winding pins 3 and gradient wedge are each connected to linear drives with which the currently required position of these elements is positioned. The wind pins 3 are also connected to a force measuring device KME, which transfers information about the measured forming forces to the signal processing unit for evaluation. After passing through the forming device, the wire is shaped into a spring body. The dimensions of the spring body are determined by the outside diameter measuring device ADME and the pitch measuring device SME. The spring body is cut to the required length using a cutting knife controlled by the signal processing system. The resulting spring is evaluated with a length measuring device LME and a force measuring device KME in such a way that the characteristic curve of the spring is determined. The current data obtained in this way are also fed to the signal processing device. The measuring of the spring length by means of the length measuring device LME as well as the spring forces by means of the force measuring device KME and the determination of the spring characteristic which is possible with it can also be carried out before the spring is cut off.

The arrangement allows spring wire diameter deviations to record as well as corresponding compensations and their effects on the slope the spring characteristics by changing others in a controlled manner Spring parameters, preferably the spring diameter, to realize. Since the actual value of the Sliding module is detected, can be a number further correction information for compliance with the Spring characteristic curve obtained and during the actuating movements be taken into account.

REFERENCE SIGN LIST

1

Wire diameter measuring device

2nd

roll

3rd

Wind pens

4th

Wire loops

5

feather

6

CCD matrix

7

V-groove

N1, N2, N3

Reaction forces

N4, N5

Wind forces

F

feather

P

pitch

D

_a outer spring diameter

MS

Strain gauges

DDME

Wire diameter measuring device

ADME

Outside diameter measuring device

SME

Incline measuring device

LME

Length measuring device

KME

Force measuring device

WME

Angle measuring device

E / G-ME

E or G module measuring device

Z.

Feeding device

L

Diffuser

H

reel

S

Wire loop

DF

Wire take-off guide

EF

Inlet guide

C.

Coil

SP

Kitchen sink

D

wire

A

Unwinding unit

R

roll

L1, L2, L3

camp

FR

Leadership roles

SR

Sensor roles

Claims (13)

1. A procedure for winding coil springs out of wire (D) which is uncoiled by an uncoiling device (A) and fed by means of a separate guiding assembly (Z) to a forming device (3.1; 3.2) for winding the wire in helical shape characterized in that prior to the winding at least one wire parameter, in particular the wire diameter, is determined and the measuring results are directly used for controlling the forming device (3.1; 3.2).
2. A procedure according to claim 1 characterized in that based on the deviation of the wire diameter from its desired value, determined prior to winding, the forming device (3.1; 3.2) is controlled in such a way that the spring diameter is Dmk = Dmo x 3 dist do 4 whereby

   D_mk

   signifies mean spring diameter after the correction

   D_o

   signifies desired value of the mean spring diameter

   d_ist

   signifies mean actual value of the wire diameter and

   d_o

   signifies desired value (standard value) of the wire diameter.

3. Procedure according to claim 1, wherein as a wire parameter the modulus of elasticity (E) and/or transverse elasticity (G) of the wire to be wound (D) is determined.
4. Procedure according to one of claims 1 to 3 in case the uncoiled wire (D) has elastic torsional stresses before winding, wherein the wire (D) between the uncoiling device (A) and the guiding assembly (Z) is guided in a loop (S) whereby any lateral deflection of the wire loop (S) is measured by a recognition unit (E1); and wherein the uncoiling device (A = H + DF) in addition to the rotation movement for uncoiling the wire (D) makes another move-ment the extent and the direction of which are controlled by the recognition unit (E1) in such a way that the torsional stresses are compensated.
5. An apparatus for carrying out the procedure according to claim 4 with an uncoiling device (A) for uncoiling the wire (D) from a spool (Sp) or a coil (C) and with a guiding assembly (Z) for feeding the wire (D) towards a forming device (3.1; 3.2) for the winding of said wire, characterized by the formation of a loop (S) of the wire (D) between the uncoiling device (A) and the guiding assembly (Z), further by a recognition unit (E1) located next to said loop for measuring the lateral deflection of the wire loop (S), and by a wire pull-off guide (DF) of the uncoiling device (A = H + DF) arranged rotatably around the spool or coil axis and controlled by the recognition unit (E1) to carry out the additional movement.
6. Apparatus according to claim 5 wherein the recognition unit (E1) comprises a roller (SR) which takes up the wire loop (S) and which is additionally rotatable around an axis parallel to the wire guiding direction, as well as a sensor (DMS) which produces a signal depending on the lateral deflection of the wire loop (S).
7. Apparatus according to claim 5 wherein the recognition unit (E1) comprises two sensors (SR, DMS) located on both sides of the wire loop (S) the signals of which are controlling a swivel movement of the rotatable uncoiling device (A) around an axis (L3) parallel to the wire pull-off direction.
8. Apparatus according to claim 5 for carrying out the procedure according to claims 1 or 2, wherein a wire diameter measuring device (DDME) is provided between the uncoiling device (A) and the guiding assembly (Z).
9. Apparatus according to claim 5 for carrying out the procedure according to claim 3, wherein a measuring device (G/E-ME) for the determination of the E module or G module is provided between the uncoiling device (A) and the guiding assembly (Z).
10. Apparatus according to claim 9 wherein the E module or G module measuring device (G/E-ME) has rollers (2) which cause an elastic deformation of the wire (D) by defined values whereby it measures the deformation forces and the deformation paths.
11. Apparatus according to claim 5 wherein force sensors (N4, N5) for the determination of the deformation forces are provided at the winding pins (3.1; 3.2) or rollers.
12. Apparatus according to claim 5 wherein the forming device (3.1; 3.2) has one measuring device each (ADME and SME) for measuring the outside diameter of the spring respectively the pitch of the wound spring.
13. Apparatus according to claim 5 wherein an intake guide (EF) is provided between the uncoiling device (A) and the guiding assembly (Z) and the wire (D) is guided by said intake guide in a defined bow towards the forming device (3.1; 3.2).

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