Combine welding and machining with the automatic tool changer
Every second counts on a production line. And in this time management, the workpiece is rarely the most important factor. No, it’s the tool change that takes away from the efficiency of the machining process. The Stirweld teams have tackled this problem and developed a fully automatic solution. The changeover between the machining tool and the FSW welding tool is done in less than a minute, without human intervention.
How can this be done? To go fast during the changeover, Stirweld’s engineers from Rennes came up with the idea of a machining system to be clipped onto the FSW welding head.
“We call it quite simply a ‘milling add-on’,” explains Laurent Dubourg, a Doctor of Engineering and co-founder of the company. “The mechanism is stored on the side of the production bench and, when machining is required, the welding head takes this tool to change function.
Welding & machining: key points
Friction stir welding is suitable for workpieces ranging from a few centimetres to several metres. The workpiece must be flat (2 dimensions), or circular (2.5 dimensions).
Fast welding at a speed of 1.5 metres per minute.
The FSW welding head can be mounted on any CNC machine.
The transition from welding to machining is done in less than a minute.
The process is fully automatic.
Lubrication is provided by a closed oil/water mixture.
The consumables in the welding head can be used continuously for 2000 metres.
This automation allows friction stir welding to be competitive in many sectors. In the aerospace and automotive industries, for example, the arrival of this standardised welding process has halved or even tripled the production cost of cold plates. These aluminium parts containing a heat exchanger need to be machined after welding.
Usually, the workpiece must be transported from the welding area to the machining area. By combining the two jobs on the same machine, manufacturers gain in several ways. They save on the movement of the workpiece and the need for a second machine.
Friction Stir Welding: the answer of automotive industry needs
Saving time on machining after welding improves cycle time. This is particularly important for the assembly of heat sinks, which are essential for cooling electric and hybrid vehicles. They are found in all current electric vehicle ranges.
These aluminium heat exchangers are filled with glycol water. This heat sink is currently the only technique capable of absorbing the excess heat generated by the electric cells efficiently and at low cost.
Its function is essential: it must protect the battery from a thermal runaway that would damage the electric cells. It also prevents the risk of the battery catching fire.
By standardising the welding of a crucial part of electric mobility, Stirweld’s engineers are demonstrating that this efficiency gain can be applied to other parts requiring precise welding. In the automotive industry, of course, but not only.
Efficiency gains already quantified in the aerospace and automotive industries
“One of our customers in the aerospace sector produces 600 cold plates each year,” reveals Laurent Dubourg. “By using the automatic tool changer system on the Stirweld welding head, he is able to produce these cold plates in just two days. Then he puts the welding head and the milling add-on back on a shelf and can use his machining centre for other operations. Our automatic tool changer, or milling add-on, for FSW welding heads makes the factory more versatile, more adaptive, and at a very reasonable cost because the machine itself remains the same. This friction stir welding in series has already cut the cost of manufacturing by a factor of three. By adding machining on the same machine, we estimate that it will halve the cost. In just a few years, the manufacturing cost has been reduced by 85%. All this without changing the machine.
What is friction stir welding?
Friction Stir Welding (FSW) is a welding method that does not require the materials to reach their melting point. It was invented in 1991 by Wayne Thomas of the Welding Institute in the UK. “It is the contact of the milling cutter on the metal that will soften the material and mix the parts together,” explains Valentin Pecqueur, IWE engineer and Head of Prototyping/Processing at Stirweld. “It’s totally counter-intuitive and that’s what makes this technology so great. In fact, the friction raises the temperature to 80% of the melting point. At this temperature, the material becomes like play dough, which allows it to be mixed. And there’s no need to get carried away: the operation can’ t reach the melting point. “As the melting temperature is approached, the material becomes increasingly malleable and the FSW tool can advance and thus create the weld bead.” Without friction, the material immediately drops in temperature.
The benefits of repeatable, adaptable, and low temperature FSW weld
This gain in efficiency (and therefore ROI – Return on Investement) is based on three advantages at the heart of Stirweld’s strategy.
The first advantage is the repeatability offered by the friction stir welding process. This technique, invented in 1991 by Wayne Thomas of the Welding Institute in the UK, can be implemented using a machine tool equipped with a Stirweld FSW head. The repeatability of the process improves standardised mass production. To put it in perspective, only a few parts are discarded in a production run of one million. That changes everything! Mass production takes on a new dimension.
The second advantage of friction stir welding comes from the technique itself: there is no need to reach the melting point of the metals being worked. In the case of aluminium, for example, at 80% of the melting point, the material becomes as malleable as modelling clay, which makes welding possible. The advantage? A stronger joint because it is free of defects.
Third advantage: adaptability. The FSW head allows welding from existing CNC machine tools, whether it is a 3, 4 or 5 axis machines. The Stirweld Friction Stir Welding Head provides the machining centre with the necessary functions for FSW welding: force control and recording, cooling, spindle protection against vibrations.
Although there is no standard for machining centres, Stirweld’s FSW head can be adapted to all CNC machines. The offer of this equipment allows to drastically reduce the investment cost of an FSW machine while offering the same performance as a special friction stir welding machine.
ROI gain compared to arc welding followed by a machining operation:
Standardisation and automation of the process,
Smooth welding and limited machining,
Adaptable and removable FSW welding head.
Want to know more about FSW temperature control ?
How to integrate the friction stir welding head and its machining equipment?
Changing a manufacturing process is no small task. “It can be scary,” says Gilles Sevestre, Stirweld CTO and co-founder. “We are aware of this, and we have set up a change management system. We carry out the development of the finished product in-house on a pilot line, to check that everything will work smoothly for our customers. The aim is to integrate the welding and machining tools without stopping production.
Whether for the automotive or aerospace industry, the industrial study includes:
In addition to this focus on production line optimisation, Stirweld also offers training in friction stir welding. A machinist can be trained quickly in FSW welding and the use of the milling add-on. This training can take place in person or remotely as several webinars are offered by Stirweld to train in FSW:
By 2021, Stirweld has trained 453 people in friction stir welding technology worldwide.
The Stirweld team, experts in the field of friction stir welding, will assist you in defining your welding parameters, in choosing your tool and in designing your clamping system.
What is the risk to the machine operator?
A risk analysis has been carried out on the Stirweld FSW head and it is CE certified: considering the European requirements for health, safety, efficiency, and environmental protection.
What risk for a machine?
Integrating an FSW head on an existing machine has no more impact than adding an angle gear. In other words: there is no fundamental change to the machine. The manufacturer’s warranty is therefore not affected. Today, the FSW head has been installed on more than 25 machine models
In summary, mounting an FSW head with its tool changer on a CNC machine tool is simple, safe, and reliable. Indeed, with its various systems (claw coupling, tool and head cooling, bearings, force sensor), the Stirweld FSW head and its tool changer are safe for the operator and secure the equipment.
In addition to this, integrating an FSW head and its tool changer into a machine park allows:
Increase the flexibility of the machine park,
Record the welding force to ensure quality control of the weld,
Record welding parameters for effective part quality control,
Switch from welding to machining without removing the head and automatically.