DE102004042370A1 - Spring measurement method, takes image of spring on winding machine and compares it with reference image to measure and classify spring - Google Patents

Abstract

A spring (2) measurement method takes (9) an image (5) of the spring made on a winding machine (1) from an endless metal wire (16), compares it with an image of the machine without spring by removing all unchanged parts and measuring the spring in the purified image and reclassifies (13) the spring if the length or diameter difference exceeds a threshold. Independent claims are included for equipment using the procedure and for inclusion in the procedure of a process for removing background dirt from images by using the spring edge as an exclusion boundary.

Description

The The present invention relates to a method and an apparatus for measuring and / or controlling the dimensions of metal springs during manufacture. In particular, the invention relates to a method and a improved device for measuring at least one measure, for example the length or the diameter of a plurality of metal springs used in a special spring machine, usually from a winding machine, to be mass-produced.

The The present invention relates to both compression, tension, or shaped springs of round, square or other cross section.

Known are different machines for producing metal springs, in particular Wrappers. Patent US-A-4 719 586 describes a conventional Winding machine in which a unwound from a reel metal wire passed between two wire guide blocks and passed between two rollers to a Aufwicklungspunkt, which a concave portion for detecting and for spirally winding the Wire serves. When the last turn is over, the spring becomes measured and the wire cut off. A capacitive probe, which is connected to the winding structure, is located in one certain distance from the spring and sends electrical signals to a Measuring instrument.

The older patent US-A-4 719 586 states that keeping the length constant the production of springs is particularly difficult.

The Deviations are due to many reasons, such as changes in the composition of the wire located on the reel as well on changes in terms of dimensions, strength, drawability and tensile strength of the Wire.

The US-A-4 719 586 provides for the use of an actuator for adjustment the slope before, which after the length measurement of the spring in action occurs to help with any length corrections then made springs.

at the cited conventional Measuring systems should be noted that the electrical capacity of the probe at change the distance between the spring and the probe tip changes. Different expressed decreases with increasing length of the spring, the distance between the spring and the probe tip and consequently the detected signal changes.

Also own conventional Capacitive systems have the disadvantage of being sensitive to dust and lubricants being deposited on the probe over time. The Dirt on the probe generate reading errors, through which the spring longer appears as it is in reality.

Furthermore are methods for length control known feathers, which are based on the use of television cameras. A machine, which uses this control method is determined by the applicant sold under the abbreviation "LED 40".

This Device used a television camera and a lighting element, both in the frame the winding machine are housed.

A corresponding synchronizing connection mounted on the winding machine (Trigger) indicates when the winding of the spring is completed and generates the command to create an image through the TV camera and recording it in the memory of a computer. In the calculator are already the tolerance values of the springs and the production parameters saved.

Of the Calculator is equipped with a program for processing of the image and the calculation of the spring dimensions.

It At this point it should be pointed out briefly that the system for taking pictures with television cameras based on that each pixel of the screen a sensitive element of the television camera corresponds (usually CMOS and CCD), whose output signal depends on the intensity of the light depends that is captured by a particular object. In general chooses the system the shades of gray of a certain intensity and distinguishes them from those of other intensity, which a particular object can be reconstructed.

On Based on the processed results, the computer transmits the correction signals and the command to forward the springs to other lengths corresponding separating element with several channels. Possibly generated the calculator will alert if a specific, pre-set one Number of springs is achieved, which do not meet the required dimensions.

The Method of control by means of television camera is generally satisfactory and represents a significant improvement over the previously known apparatus represents.

In some cases, however, was festge provides that the spring is not sufficiently illuminated, so that they can not be distinguished from the winding machine tools arranged mainly around the winding machine.

If only the spring, the rest On the other hand, it does not light up because normally both the wire as well as the winding have a round cross-section, it can happen that the spring is not evenly lit. Therefore becomes common instead of a spring directly illuminating front lighting one backlight or "backlighting." The backlight is in that a light source - related on the TV camera - behind the spring is arranged so that the television camera with a picture while picking up light background the profile of the spring lies in the shadow of light.

This Backlight system is sometimes difficult because of the mechanical dimensions accommodate. The illuminator must be placed just behind the spring which is not always easy because of the space available is. Furthermore The backlight tends to be more affected by dust and grease to be contaminated from the wire bending zone, as the illuminator off space limitations often attached near the spring. For these reasons, it is therefore difficult to get a high-contrast image to the program in the situation to differentiate the spring from the tools since the tools are always more contrasted than the feathers in the shade are.

The The present invention aims to provide an improved method and a corresponding device for measuring at least one spring dimension below Use of television cameras or the like.

This Purpose is achieved by means of a method according to claim 1. Further advantageous features of the present invention are the subject of Dependent claims. All claims are part of the present description.

In one of its aspects therefore relates to the present invention a method of measuring at least one measure of a spring, by a endless machine supplied spring machine (for example, a winding machine) which method comprises the following phases: a) acquisition a picture of the spring on the machine; b) Acquisition of a reference image the machine without spring; c) Comparison of the image of the spring in the Machine with the reference image; d) removal of the parts from the spring picture, in which there are no deviations from the reference image, to get a cleaned picture; and e) measuring at least a feather measure the cleaned up picture.

Preferably With the help of the cleaned picture the length of the spring is related to a End determined in a constant, predetermined position, the possible deviations of the spring length in relation to the previously defined, constant position calculated and springs with one opposite the specified dimensions different length be classified accordingly.

Usually The method includes the phase for length measurement of the spring between the free end and the end that still with the machine supplied metal wire connected is.

Usually is the reference image when the machine is stationary or even while running Machine recorded.

advantageously, The method includes the phase of image acquisition by means of. a television camera and a corresponding element for frontal or backlighting.

advantageously, includes the method as well the phases for removing images with traces of pollution and burrs after taking a picture of the spring.

advantageously, the method includes the phase for defining the spring outline and to eliminate everything that does not correspond to that outline.

advantageously, The method includes the phase to control the dimensions of the spring with vibrations.

in the The following describes the invention in detail, wherein the Description is for illustrative purposes only and has no limiting effect has; Reference is made to the accompanying drawings. Show it:

1 a very schematic front view of a winding machine of known type;

2 the block diagram of the circuit for controlling the dimensions of the winding machine according to 1 manufactured spring;

3 the image of a spring made by a winding machine;

4 the picture of a winding machine without Feather;

5 the picture of the spring after comparing the pictures of 3 and 4 ;

6 the picture off 5 after removing the burrs and dirt marks;

7 the picture taken by a television camera of a spring and some details of particular points of the spring in vibration;

8th an example of lateral vibrations of the spring 7 ;

9 an example of axial vibrations of the spring 7 ,

The inventive method refers to the measurement and / or the control of at least a measure a variety of springs, the continuous process of a winding machine or another spring production machine (e.g., a spring type machine) were manufactured.

The description of the following example refers to a winding machine 1 (in 1 shown schematically) for the endless production of coil springs 2 made of metal wire.

In particular, the method of control refers to the measurement of the length of each one of the winding machine 1 manufactured spring.

The method uses a device 3 for control / measurement ( 2 ), which is a calculator 4 includes a screen 5 has a keyboard for displaying the pictures taken during the operating and resting phases of the winding machine 6 (or similar means such as "touch screens") for entering the data in the memory of the computer, a correction device 8th , which is connected to the mechanical parts (typically means for changing the pitch or actuators) or to the electronic control means (not shown) of a numerically controlled winding machine.

The Correction device makes the appropriate corrections when other than the length values stored in the computer are determined.

The control / measuring device also includes a television camera 9 and a lighting element mounted in front of or behind the television camera 10 which are both on a rack 11 the winding machine are attached.

The from the television camera 9 taken pictures are sent to the memory of the computer 4 sent and moment by moment on the screen 5 displayed.

According to a preferred embodiment, the illumination element 10 is activated by the computer, while in an alternative embodiment it is activated by the television camera 9 is activated. In a further embodiment, the lighting element remains constantly on during operation of the machine.

A special scanning sensor 12 Or, in some cases, a signal generated by an electronic machine part - controls the computer and / or the television camera to take the pictures.

On the basis of the recorded images and the computer program of the computer sends these signals to a separation element 13 whose task is to collect springs of other lengths in special subdivided spaces.

at The software program loaded in the computer is a mathematical program based on the comparison of received data based on the previously stored data and that for different Applications in production cycles developed and distributed programs corresponds, for example, by the company DS GmbH under the name "NeuroCheck" are sold.

The winding machine 1 for the production of springs with a connected separating element 13 corresponds to any machine known type, which is why only the most important parts are described below, which are required for understanding the control and / or measurement method according to the invention.

The winding machine 1 includes various mechanisms and tools for making and cutting the springs. To simplify the drawing, the winding machine was in 1 without the connecting parts with the various mechanisms and the corresponding mounting plates of the tools on the frame 11 shown.

As in 1 can be clearly seen, includes the winding machine 1 two rollers 14 . 15 between which the metal wire 16 for making a variety of springs 2 is trapped.

The rollers 14 . 15 are arranged coaxially with the two (not shown) meshing gears. One of the gears serves as a drive wheel and is connected to one of the two rollers so that after the rotation of the wire 16 a wire guide 17 passes through and is then led head-on to the concave surface of a groove that emerges from the contrasting foot 18 is worked out, where it is bent to the spiral.

At the end of the winding, the spring is first with a knife 20 cut by a cam mechanism or the like, and then separated from the remainder of the wire so that it falls by gravity into a container in which the finished springs are collected.

During the fall, the spring may pass through a separator 13 provided with different outputs, one intended to receive springs corresponding to the intended length, while the other outputs serve to accommodate shorter or longer springs.

The following describes the length control of the springs. Before winding the springs, the sensor sends 12 or the on the winding machine 1 mounted sync connection a first signal to the TV camera 9 and possibly the lighting element 10 to start a new phase for taking an image of the winding machine at rest, or in any case without a spring, which will be referred to hereinafter as the "reference image".

As an alternative to the previous automatic phase, an operator can use a button to select the TV camera 9 and the lighting element 10 Manually control to record the reference image.

It will now be assumed that the winding machine has completed the winding of a spring and is in the phase in which the sensor 12 was activated by parts of the winding machine to a first signal for the purpose of notification of the completed winding of the spring 2 to the device 3 to send.

The computer or the sensor itself now sends a second signal to the TV camera 9 for capturing an image (or image section) of the spring. This recording of the spring image is in itself a similar phase to that taken during the conventional control method by means of television cameras.

Now sees the new control method according to the invention Another phase before, in which the image of the finished spring, the was taken before the cut with the reference image of the winding machine without Spring is compared.

Finally, according to the method according to the invention, the phase begins in which the image, that of the still with the wire 16 the winding machine connected to the spring has been removed, all parts are removed in which no deviation from the reference image are observed.

For a better understanding of the individual phases of the method according to the invention is in 3 a picture of the spring at the end of the winding shown in 4 a reference image, in 5 a picture of the spring after comparing the two pictures taken and in 6 a picture of the spring shown after the removal of all those parts in which there is no deviation from the reference image. The 3 . 4 and 5 refer in particular to an application example with background illuminator.

As in 3 can be clearly seen, the image of the spring at the end of the winding process shows a wide zone 21 produced by the tools and mechanical parts of the winding machine which, due to the fact that they are also picked up by the television camera, could cause confusion in the previous method and influence the length measurement of the spring.

When examining the 5 however, it clearly shows that the captured image shows only the feather, as all details not belonging to the feather have been removed.

Finally, in 5 Also, those parts of the winding machine, in particular tools and mechanisms, no longer visible, which are arranged around the spring and have been removed because they have no deviation from the reference image.

Summarized This method is a kind of filter with which a sharp Picture exclusively is generated by the spring.

Now can be done by the computer editing the image of the spring make a clear calculation of the position of the outermost turn, from the length the spring can be determined after the cut.

At this point it should be noted that the spring 2 still on the wire during the measurement 16 which is fixed at a certain point, so that a deviation of the position of the - related to the winding machine - outermost turn compared to the stored position in the computer on the winding machine corresponds to a deviation of the total length of the spring even after the cut.

Preferably, the invention provides Method according to the cited phases for optimizing the spring image for comparison with the reference image before another phase in which from the recorded spring image any burrs and dirt 22 . 23 removed during the measurement of the spring. This phase is based on a shape control of the spring.

Practically becomes an outline shape before the working phases of the winding machine The spring is recorded and stored, which in the following as a pattern outline referred to as.

The Pattern outline shape is created by means of a spring image, which under optimal Conditions on the part of the operator or by calculation of the average all previous spring shapes entered into the memory of the computer.

To return to the work phases, the method sees the elimination of all impurities 22 . 23 ( 5 ) present on the image of the spring, which has a different appearance and shapes than the already stored pattern outline.

The result of the image taken by the spring after the second cleanup, which is also a kind of filter, is in 6 to see.

The computer is after taking the picture according to 6 Being able to calculate the dimensions of the spring and / or display it on the screen After determining this measurement information, the device according to the invention controls the means (eg motors) for changing the pitch and / or the diameter, if these do not correspond to the tolerance values. Obviously, the changes in pitch and / or diameter affect the springs which are made according to the feather force over the tolerance values.

To At this time, the phases for measuring a spring in the Standstill or in the idle state of the same executed.

at However, some springs can cause vibrations, so that It may be difficult to judge whether the picture taken is that corresponds to the resting state of the spring.

Of course it takes a spring during the vibration when reading a different than the reading desired position and thus does not comply with the standards.

Actually the quantity to be measured by the standards as "free length", that is to say length at rest with no fasteners or external loads Are defined.

advantageously, sees the method according to the invention the measurement of a spring on the basis of the phases before, on based on the analysis of the vibrations.

Around to solve this problem, it was assumed that each spring vibration is a sum of sinusoidal vibrations in axial, lateral, circular Direction, all of which take place around a resting position.

outgoing from this consideration and after defining the spring outline as already explained, sees the method according to the invention it suggests, at the measuring points, small image sections very quickly in succession take.

For a better explanation, see 7 the overall picture of the spring is shown, with the reference numbers 24 . 25 the measuring points are designated. The first measuring point is preferably subject to axial vibrations, the second, however, lateral vibrations.

In 8th show the solid lines 26 the various turns of the spring while the offset to the solid lines 26 arranged dashed lines 27 show the spring in another moment of vibration. That's why shows 8th a schematic representation of lateral vibrations of the spring coils.

In 9 is on the other hand with dotted, offset to the solid lines 26 drawn lines 28 an example of axial vibrations is shown.

The method according to the invention uses a television camera with the possibility of "subwindows" to record the vibrations of the measuring points, which is capable of producing very small recording cut-outs 29 . 30 the points 24 . 25 ( 8th ).

This Feature of the TV camera allows it, the recording and editing speed proportional to Decrease in cut-size.

advantageously, receives one using only one for the control of the axial or lateral vibration needed Window the desired Recording times.

According to the method of the invention, the multiple measurements of the vibrations of the points 24 . 25 on each individual axis for a sufficiently long time of 1-100 milliseconds, from the television camera transferred to the computer.

Therefore the computer is able to determine the average of the measurements and to calculate the average duration of the vibration of the spring.

To Determining the average duration of the vibration will be during the Production of the springs in the subsequent production cycles instead just one measurement several measurements on each spring over the entire duration of the oscillation made; by means of processing these recordings or by determining the simple average value results to a more accurate measurement of the spring length than a simple Single shot.

alternative For this purpose, the vibration duration value can also be determined by the operator via the Keyboard or similar be entered.

Claims (19)

Method for measuring at least one dimension of a spring ( 2 ), by a winding machine ( 1 ) produced with an endless metal wire ( 16 ), the method being the phase a) of taking an image of the spring ( 2 ) on the winding machine ( 1 ) and characterized by the following phases: b) recording a reference image of the winding machine ( 1 ) without feather ( 2 ); c) comparing the image of the spring on the winding machine with the reference image; d) removal of all parts without deviations from the reference image from the pen image to obtain a cleaned image; and e) measuring at least one measure of the spring from the cleaned image. Method according to claim 1, characterized in that the phase e) has a phase for measuring the length of the spring as the distance between its free end and the opposite, still on the endless wire ( 16 ) hanging end comprises. Method according to claim 2, characterized in that any deviations of the spring length from the nominal spring length calculated and classified the measured spring accordingly if the calculated length deviations exceed the previously defined limits. Method according to one any claim from 1 to 3, characterized in that the Phase e) comprises a phase for measuring the diameter of the spring. Method according to claim 4, characterized in that it has a further phase for calculation possible deviations of the spring diameter from the nominal spring diameter and classification the spring comprises, if the calculated diameter deviations exceed the previously defined limits. Method according to one any claim from 1 to 5, characterized in that the Reference image essentially taken at standing winding machine becomes. Method according to one any claim from 1 to 5, characterized in that the Reference image essentially taken while the winding machine is running becomes. Method according to any one of claims 1 to 7, characterized in that in the vicinity of the winding machine at least one television camera ( 9 ) and the illumination of the image pick-up area by means of a lighting element ( 10 ) is provided. Method according to claim 8, characterized in that the illumination phase is a lighting the spring from behind covers. Method according to claim 8, characterized in that the illumination phase is a lighting includes the spring from the front. Method according to any one of claims 1 to 10, characterized in that after phase d) a further phase for removing any traces of dirt and / or burrs ( 22 . 23 ) is provided from recorded image that occur during the recording phase of the spring. Method according to claim 11, characterized in that the phase to remove eventual Dirt and / or burrs a phase to define a pattern outline the spring and the distance of all that does not provide that Pattern outline corresponds. Method according to claim 12, characterized in that previously an average shape the pattern outlines of feathers is determined in previous Production cycles were produced and that this average Form is used as a spring pattern outline. Method according to claim 13, characterized in that the dimensions of the spring on the basis of the average Pattern outline shape is measured. Method according to any one of claims 12 to 14, characterized in that the Measurement of spring dimensions during vibration is performed. Method according to claim 15, characterized in that it comprises the phase of taking an image of certain areas of the spring in which predetermined measuring points ( 24 . 25 ) and a multiplicity of measurements of the oscillations are made at these measuring points. Method according to claim 16, characterized in that the average value of the vibration frequencies and the duration of the oscillation. Method according to claim 17, characterized in that the phases for the execution of a Variety of measurements on each spring over the whole, this average the period corresponding to the period of oscillation and the determination the average of the results and the calculation of the spring length around them Average results includes. Device, which means for taking pictures and a computer cooperating with the image acquisition means and has a program which is capable of the phases of Method according to one or more of the preceding claims.