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The HQ-Tubes workplan is divided into 7 work packages.
Work packages 14 deal with the development of the individual
key components and process know-how on which the proposed HQ-TUBES
system is based on. Work package 5 deals with the integration of the
key components into a demonstrator and evaluates the performance.
Work package 6 covers the dissemination activities and exploitation
actions and work package 7 covers consortium management and assessment
of progress and results related tasks.
Work package 1: Specification and requirements
The main objective was the establishment of the general
project development frame through the synthesis of specifications
and requirements for the different tasks. These tasks contain definitions
for workpiece, hybrid laser-arc welding application, quality and the
implemented hard- and software for the HQ-TUBES prototype, determination
of the SMEs requirements and of the international state of the art for
hybrid laser-arc welding as well as definition of a pilot case for validating
the hybrid laser-arc welding process in tube and pipe manufacturing.
Work package 2: Hybrid laser-MIG/MAG process development
The main objective was the development of hybrid laser-MIG/MAG welding
procedures for agreed applications, focusing on filler material and gas
mixture specification, weld profile optimisation and heat input minimisation,
to achieve the required quality for welded tube and pipe.
Welding conditions were developed for the material grades of steel and austenitic
stainless steel in thickness ranging from 4 to 10 mm. Process development has been
carried out with two laser sources: CO2- and Disk lasers as well as with Yb-fibre
lasers of beam powers up to 10 kW.
A complete literature survey has been carried out before the start of experiments
concerning the hybrid laser-arc welding process of steel with reviewing of applicable
literature to focus on parameters, material, laser source etc.
Work package 3: Process monitoring
The main objectives were the development, evaluation and provision of systems for
process monitoring. The monitoring system includes an Open Diagnostics System (ODS)
that supervises and documents parameters of the hybrid laser-arc welding process.
A seam tracker has been applied to assure the correct position of the processing head.
A root monitor inspects the seam from below. A coaxial process monitor records images
of the hybrid welding process using a high-speed camera. These systems have been set up,
tested and fitted out with suitable interfaces to assure an easy integration into
the HQ-Tubes prototype system.
The concept of the Open Diagnostics System (ODS) has been designed (see Figure 2).
The ODS is set up to collate data simultaneously from different interfaces and make
them available for a real time evaluation of the welding process quality. The ODS is
designed as an operator-supporting system for process set-up, processing, documentation and analysis.
Figure 2 Concept of the ODS-system
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The ODS enables the operator to operate a range of different sensor devices,
to visualise, record and control the process conditions relevant for the resulting
welding process quality. The ODS is set up as a modular open framework which links
monitoring and inspection systems from different vendors into a multisensory network
for process supervision and recording. The main objective of the ODS is to link the
distributed stand alone systems to enable synchronised recording of all data identified
to be relevant for the traceability of quality characteristics.
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The development of joint geometry and position measuring system has also been
finalized: The communication between Seam Tracking Control PC (STC-PC) and
Reis Robot System (RRS) via Ethernet has been established. A XML-interface was
introduced as a proprietary software protocol for receiving and sending axis
position values in a robot related tool coordinate system. User variables were
implemented into the RRS control for bidirectional communication. The robot
position is submitted in six values for X-, Y- and Z-coordinates as well as for
A-, B- and C-angle positions and additional the actual speed of linear axis is
transmitted. The STC-PC calculates the desired position of the processing head
and transfers the set point values to the RRS control. For the demonstrator II at
ILT the seam tracking was adapted to the seam conditions of the spiral tube specimen.
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Figure 3 Seam root monitor
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Root camera image of a hybrid laser-arc butt joint welding of 8 mm
mild steel S355J2G3 (parameters: PL = 6.8 kW, feed rate of 1.5 m/min,
image size of 1024 x 1024 pixel, exposure time of 50 µs and frame rate of 100 fps)
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The Root Monitor and Inspection System (RMIS) which serves as an element of the open
diagnostics system (ODS) is designed, assembled, installed and set into operation (see Figure 3).
The RIMS consist of both a root monitor and a seam geometry inspection sensor.
The functionality and reliability of RMIS is tested within a robot system and with a
disc laser on flat steel probe sheets of different thicknesses and with varied beam
power and welding velocities. Both, the robot system and the disc laser are elements
of the pre-production demonstrator which is setup for HQ-TUBES at Fraunhofer ILT.
Welding tests were performed with beat on plate welds as well as with welds of square
butt joints both in down hand position. The root monitor enables the observation of the
melt pool during welding. With the help of the root monitor welding imperfections due to
misalignment of the laser beam with respect to the joint gap as well as spatter, sagging
and drop through of molten material can be detected.
The post process seam geometry inspection sensor (SGM from PRECITEC) is attached in
line with the root monitor. The SGM uses the triangulation principle to measure the
geometry of surface of the root seam perpendicular to the welding direction. The SGM
enables the detection of imperfections like sagging, undercut, high low mismatch and notches.
The coaxial monitoring system for the hybrid CO2-laser-arc welding process is designed and brought
into operation. For hybrid laser-arc welding with a CO2-laser a first test series was carried out
to start-up the hybrid laser-arc welding equipment and to determine the requirements of the CPC-system
and the imaging optic. After the requirements were determined the monitoring system was optimised
regarding to the capability of the optical system. Test series have been carried out to investigate
the performance of the monitoring system.
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Figure 4 Coaxial process monitor
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Coaxial camera image of a hybrid laser-arc butt joint welding of 8 mm mild steel
S355J2G3 (parameters: PL = 6.8 kW, feed rate of 1.5 m/min, image size of 1024 x 1024
pixel, exposure time of 50 µs and frame rate of 100 fps)
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After the design of the 1 µm processing head and the integration of the coaxial
monitoring system the entire monitoring system is integrated into the HQ-TUBES
demonstrator I (see Figure 4).
The coaxial process monitor, the root monitor as well as a seam tracking system are integrated into
the demonstrator in a pre production environment and linked to the open diagnostic system (ODS)
which collates data from all these different sources into an object relational data base.
Finally the image analysis algorithm are tested and refined. The model based background
subtraction algorithm Min Max Deviation is found to be most suitable to identify joint gap,
key hole and melt pool under pre-production conditions.
Download example video.
Work package 4: Adaptive control
The main objective was the development of algorithms for adapting welding conditions,
e.g., welding or wire feed speed, to fit a given measured joint geometry, to ensure the
output meets weld quality requirements.
Within the HQ-Tubes project, methods for adaptive control were developed successfully
in WP4. Hybrid laser-arc welding trials were carried out, using a high brightness
(6mm.mrad) 5 kW Yb fibre laser. Different sets of fixed conditions were used,
along joints between 8 mm thickness S355 steel plates, with different amounts
of joint gap and/or hi/lo mismatch. These trials identified suitable changes in
parameters which might increase tolerance to joint fit-up.
Following appropriately accurate calibration, a laser-camera was used for
both seam tracking and real-time adaptive control of robotic manipulation
and welding equipment. Adaptive changes, in those welding parameters identified
in the fixed condition trials, were used successfully to extend the tolerance of
the hybrid process beyond that which would be achieved using fixed conditions (Figure 5).
Close fitting joints (with a 6 mm broad root face joint preparation) were welded to
ISO 13919-1:1997 Class B at 1.6 m/min. The same welding conditions were also suitable
for making Class B welds along joints with up to ~0.6 mm hi/lo mismatch, or along joints
with ~0.3 mm joint gap.
Figure 5 Adaptive controlled welding
With an adaptive reduction in welding speed to 1.2 m/min, the tolerance to mismatch could
be increased from ~0.6 to ~1 mm. Similarly, with an adaptive increase in wire feed rate of
~60% (by volume), Class B welds could made along joints with gaps up to 0.6 mm in width.
Joints with a combination of both mismatch and gap could also be welded with adaptive control,
although the tolerance to joint gap in these cases appeared to reduce slightly.
Without adaptive control, re-entrant weld toes, or excessively deep weld top
bead underfill, resulted along joints with values of mismatch >0.6 mm in height,
or gaps >0.3 mm in width, respectively.
From this work, an outline system specification has been compiled,
with set-up guidelines given, and the tolerances that can be achieved have been documented.
Download example video.
Work package 5: Implementation and evaluation of the HQ-Tubes system in pre-production environment
In this work package, the systems developed in work packages WP3 and WP4 for the hybrid
laser-MIG/MAG welding of tube and pipe material are assembled to form the HQ-TUBES system.
This includes the ODS, the joint geometry and position system, the root monitoring and the
coaxial process monitoring systems, as well as the adaptive control algorithms.
As pilot case the seam guided hybrid welding of spiral pipe probes has been
demonstrated with the 10 kW disc laser on the robot plant at ILT. The required
pipe probes were prepared and pre-tagged by the SME partner CSEPEL. The setup of
the robot handling system, which could be used right in the same way in the production
facility of the tube manufacturers CSEPEL or others, is shown in Figure 6.
Figure 6 HQ-TUBES demonstrator with spiral tube specimen
Work package 6: Dissemination and exploitation
The main objective is to carry out dissemination activities and exploitation actions
in order to promote the results of the project to the European industrial & scientific
community and exploit these results so as to be beneficial for the participating SMEs,
as well as other EU SMEs not part of the current Consortium.
The dissemination activities represent a very important part of the HQ Tubes
project work programme. For this, the R & D performers play an important role.
Among the most important such activities envisaged in the project, the following
key dissemination actions have been taken: Project Web site; Appearance on trade fairs;
Newsletters and scientific papers; Conference presentation.
It was agreed among the consortium, that two complementary directions will be gone
to exploit the HQ TUBES project results. First, the project partners will pursue the
exploitation of the system as a whole, integrated system to be installed tube and pipe
manufacturing companies in the partners countries and abroad. The HQ TUBES system will
be exploited as a whole product to be sold (the hybrid welding process, the sensor systems
for guiding and monitoring, the software including the open diagnostic system).
Exploitation will also come from the usage of specialized personnel to install and
maintain the system (which means physical system installation on machines on side).
Secondly, the consortium will exploit individual HQ TUBES components, to be included
in other systems finding applications in similar or different domain problems. As an example,
the ODS Software (open diagnostics systems software) module could be used independently of the
other laser welding applications. The developed version of ODS software system could be distributed
to potential customers in order to collect all important welding data and so be able to let minor
qualified personnel run the welding system just by selecting the complete parameter setup
for a specific application.
The project partners themselves will perform further market analysis for
each potential market where the various components of HQ TUBES might find
demand, and in those markets that will be deemed fruitful, the partners will
actively promote the components. For this end, the dissemination activities of
the consortium will prove invaluable, since they will make known to the potential
customers the availability and quality of the systems.
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