Note: Descriptions are shown in the official language in which they were submitted.
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OPTICAL TESTING DEVI~E FOR THE ON-LINE ASSESSMENT OF ~ELDMENTS OR
SOLDERED JO~N~S
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In order to optimize their weight and strength, structural
members are dimensioned in accordance with local loading.
Particularly in the motor car industry there has been a
transition towards dimensioning individual structural members
with different thicknesses, for example, dimensioning collapsi~le
zones ~ore thinly than the passenger compartment. To ~eet these
demands, structural members are used which consist of parts of
different dimensions which are connected to one another via a
joint, more particularly a weldment. To ena~l2 such structural
members to perform their function during operation, the quality
of the weldment is a decisive factor.
The usual method of checking a weldment is optical inspection by
a skilled operative. It is self-evident that that method cannot
ensure objective inspection using identical yardsticks. Optical
fault detection ~y an operative is absolutely impossible when a
structural member passes through a testing station at the very
usual processing speed of, for example, 12 ~/min. Moreover, it
is often difficult to distinguish a real ~ault from an apparent
one by visual inspection. This may also be due to the different
reflection properties of the surfaces of structural members,
which may or may not have metallic coatings. Surface dirt and
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annealing colours in the zone of the weldment make it difficult
to distinguish between actual and merely apparent faults.
In a process which has just become known for joint measuring in
the course of a joint follow-up system (DE 43 12 241 A1), the
surface of a workpiece is illuminated in the zone of the joint
and registered by an area-image recorder for grey-key image
evaluation. The joint is also intermittently examined by the
light-section procedure. Grey-key image evaluation is performed
by the light-section procedure between the projection phases.
The object of that procedure is to locate the position of the
weldment on the surface and not to assess its ~uality.
It is an object of the invention to provide a testing device for
the weldments or soldered joints of parts connected to one
another, which identifies and analyzes faults even with high
rates of throughput.
This problem is solved by a testing device which has the
following ~eatures:
a) The parts connected to one another are retained at a given
distance from a sensor unit by means of a ~uide unit.
b) Information concerning the position of the joint is supplied
by a joint-seeking unit having an optical sensor in whose
measuring field the joint lies, and an evaluating unit
connected to the sensor.
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c) In dependence on the information concerning the position of
the joint, an optical bidimensional sensor whose measuring
field is adapted to the width of the joint is so positioned
by an adjusting member that the centre of the joint and the
centre of the measuring field register, and
d) in dependence on the bidimensional faults detected by the
bidimensional sensorS a fault-detecting unit is activated
which analyzes the location of the fault.
The testing device according to the invention brings those
elements which are decisive for the geometrical and qualitative
assessment of the joint into an optimum measuring position, so
that surface faults and the width of the joint can be
satisfactorily identified even at high rates of throughput. The
result of the analysis can be displayed and recorded, for
example, in the form of a report on the article tested, or else
used for controlling the welding or soldering process.
More particularly the known light-section procedure has become
established for analyzing the location of faults (German Journal:
"Kontrollel', September 1991, pages 5-14). However, if the sole
objective is to determine the area over which the fault detected
extends, it may be enough not to study the joint by the liaht-
section procedure, but to make the joint recognizable to a
suitable sensor by the use of suitable additional lighting.
Since the ~uality of a joint also depends, for example, on
whether it has fallen or is too high, according to one feature
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of the invention the joint geometry is determined by means of a
threedimensional joint profile sensor which operates by the
light-section procedure and is based on the principle of light
beam triangulation.
To obtain the optimum position for precise optical determination
of the joint, according to a first feature of the invention in
dependence on information concerning the position of the joint
supplied by the joint-seeking unit with the optical sensor and
the connected evaluating unit, an optical threedimensional joint
profile sensor is so positioned by the adjusting member that the
centre of the joint and the centre of the measuring field
register.
Preferably an optical threedimensional joint profile sensor is
disposed on each of the sides of the parts connected to one
another.
For the precise optical determination of the joint width, a
distinction must be made between the joint, smoke deposit and
annealing colours of the metallic surfaces. To eliminate these
interferences, according to one feature of the invention a
structured area lightina, more particularly using infrared light,
is used to illuminate the joint.
For the optical examination of a weldment or soldered joint it is
as a rule not enough to examine the joint solely from one side of
the parts connected to one another. Accordingly, according to
another feature of the invention an optical bidimensional sensor
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and a fault-detecting unit are provided on each of the two sides
of the parts connected to one another.
The invention will now be explained in greater detail with
reference to an embodiment thereof illustrated in the drawings,
which show:
Fig. 1 a testing device without evaluating unit for a weldment,
viewed in the direction in which the joint runs,
Fig. 2 the testing device shown in Fig. 1 shown diagrammatically
without evaluating and guide units and viewed
transversely of the direction in which the joint runs.
Fig. 3 a diagram illustrating the measuring principle of light
beam triangulation,
Fig. ~ a diagrammatic presentation of the light-section
procedure used in conjunction with light beam
triangulation,
Fig. 5a a picture of a weldment supplied by a bidimensional
sensor, and
Fig. 5b the picture of a fault location, which a fault-detecting
unit supplies an~ analyzes.
~eferring to Fig. 1, a structural member comprising two metal
sheets 1, 2 of different thicknesses which are connected to one
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another via a weldment 3 is positioned between rollers 4, 5, 6, 7
of a guide unit. The structural member 1, 2 can therefore be
moved in the direction of the weldment 3. Disposed in rigid
spatial relationship to the rollers 4 to 7 is a testing device
which comprises an uppér sensor unit 8a and a lower sensor unit
8~. The weldment 3 and the adjoining zones are illuminated by a
structured area lighting 9a, 9b more particularly using infrared
light. The angle of incidence, wave length and the like of the
lighting 9a, 9b are so selected that interferences, such as dirt,
reflections and the like are substantially suppressed to the
maximum extent for the picture to be taken.
As Fig. 2 shows, the upper testing device has a number of units
11, 12, 13, 14 disposed one after the other in the direction in
which the weldment 3 runs. The weldment 3 is first scanned by a
joint-seeking unit 11 having an optical sensor lla. Since the
position o~ the weldment 3 may also be situated laterally offset
in relation to the centre shown in Fig. 1, the joint-seeking unit
11 with its sensor lla must cover the whole range of possible
positions of the joint 3. A connected evaluating unit (not
shown) then analyzes where the ioint 3 is situated. The
evaluating unit delivers an adjusting signal to an adjusting
member 15. In accordance with the adjusting sianal, the
adjusting member 15 so adjusts the sensor unit 8a-8b transversely
of the direction in which the weldment 3 runs that the optical
bidimensional sensor 12a can be serially followin~ sensors 13a,
14a of the following units 13, 14 are disposed centrally in
relation to the weldment 3. The bidimensional sensor 12a then
supplies pictures, as shown in Fig. 5a. The evaluating unit of
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the hidimensional sensor 12a analyzes the pictures for actual and
apparent faults and also for joint width. However, this
information concerning faults does not yet allow a distinction to
be made between actual and apparent faults.
To enable apparent and actual faults to be distinguished fro~ one
another, a fault-detecting unit 13 is connected to the
bidimensional sensor 12. The fault-detecting unit 13 operates by
the light-section procedure and has for this purpose an optical
sensor 13a, more particularly a CCD matrix camera, a light beam
projector 13b and an evaluating unit (not shown). Fig. 5b shows
the picture ta~en by the optical sensor 13a.
Using the sensor unit 8a disclosed hereinbefore, therefore, it is
possible to determine ~oint width and actual faults. ~ince in
many cases this information is insufficient to enable the ~uality
of a weldment to 'oe assessed, the aforementioned threedimensional
~oint pro~ile sensor 14 having a laser diode 14a and a CCD matrix
camera 14b is connected to the fault-detecting unit 13. The
threedimensional joint profile sensor 14a operates by the light-
section procedure in conjunction with light beam trianaulation.
The principle of operation is illustrated in Figs. 3 and 4.
Since the optical assessment of the quality of a weldment 3 from
only one side is inadequate, in the embodiment of the invention
both sides of the weldment 3 are tested. For this purpose,
however, not all the units described for one side must be
provided. It is enough to have a further bidimensional sensor, a
further fault-detecting unit and a further threedimensional weld
' CA 02208480 1997-06-20
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profile sensor, since the information from the joint-seeking uni~
can be used for the adjustment o~ the sensor units on both sides.
The special advantages of the testing device according to the
invention are that it enables the quality of a weldment or
soldered joint to be determined non-destructively and on-line as
regards joint faults, joint width and joint profile. The results
obtained can be recorded and~or used to control the welding or
soldering process and also the production installation. The
invention can be used for dif~erent kinds of weldments and/or
soldered ~oints in different metallic materials with and without
metallic coatings, including in mixed constructions, and for
weldments and soldered joints produced by different processes.
It can ~e used for both stationary and also moving structural
components. The testing device according to the invention can be
more particularly advantageously used in conjunction with a
welding or soldering unit. If th~ sensor unit is coupled to the
processing head, said unit is auto~atically guided along the
weldment. In that case only the precise position of the joint
need be determined via the joint-seeking unit for the adjust~ent
of the actual sensor unit.
