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Faster from wire: 3D metal printing in the arc welding process

3D-Druck Metall OTC (2)

Arc welding processes such as the SynchroFeed system from OTC DAIHEN EUROPE are increasingly involved in the production of three-dimensional metallic components. Whether and to what extent it will prevail in the future against powder bed-based systems is likely to be of interest to designers and small series producers.

 

Large parts of the industry have long been relying on digitally controlled manufacturing solutions that are indispensable for mass production. Regardless of the desired production size, all geometric designs are now being handled by intelligent CAD systems that have taken the lead in industrial production and can be found in all manufacturing plants.

With the help of CAD systems, the metal industry had traditionally relied on subtractive manufacturing processes such as milling and turning, which can generate up to 90% of material waste, before the desired shape is finally achieved.

What about the possibilities of additive manufacturing, which only bring in as much material as is needed? We already know the advantage of 3D printers in plastics production, which have impressed us for a long time with diversified shapes. If one changes the perspective, one realizes, on the other hand, that the choice of technical options in the metal sector is rather clear.

 

Filigree from the laser-melt

 

For some time now, the additive manufacturing processes in the metal sector has been based on laser sintering, as well as, laser or electron beam melting. The starting materials for these processes are metal powders, which are first brought into a liquid state via the laser beam, and then subsequently cooled. The production of the desired components takes place in layers and can certainly keep up with the quality of conventionally cast components.

These processes are mainly suitable for the production of filigree as well as format-limited work components. It should be noted that powder-bed-based processes, which admittedly provide impressive results, cannot be called "rapid" technologies. The average material utilization is at a maximum of 70%.

In addition, the energy input during laser cladding / laser sintering is higher in comparison to 3D metal printing in the arc welding process, which usually also leads to limitations in the use of different materials. Some of these processes sometimes fail due to the necessary cooling.

It is not for nothing that software simulations for powder-bed-based laser beam melting are now available to virtually anticipate the build-up process. In this way, one stands to timely gain knowledge about potential disorders such as cracking or instability.

Behind such simulation solutions is the desire to save time and costs: The layered structure of a component takes a long time via the laser beam melting. Not every producer can afford faulty prototypes.

Three-dimensional components made of powdered starting materials also require construction platforms or support structures to prevent unwanted deformations. A reproducible derivative of the heat introduced via the laser is usually possible only via such supporting components. After completion, these must first be mechanically separated or removed from the new workpiece. This is followed by the machining of the surface to clean it of powder particles.

 

New process in shift operation

 

The range of additive molding processes of the metal sector has now been expanded to include 3D arc welding: OTC DAIHEN EUROPE GmbH from Mönchengladbach has taken advantage of the self-developed SynchroFeed process *) to first apply a carrier surface by melting down a material, as it’s always the case in welding, and then building it up layer by layer. As with all other processes, the result is a 3D software that ultimately turns into a physical body.

The SynchroFeed process is responsible for the precisely controlling the arc and for melting the material. If the temperatures are too high, the material would simply drain off, and if the temperature were too low, there would be no metallurgical connection between the applied layer and the underlying layer. The arc welding construction therefore depends on the optimum heat input, in accordance with the material used for this purpose.

Already at the last exhibition, "Welding & Cutting", it was successfully demonstrated with aluminum that this process leads to the desired result without interruption. For the production of larger 3D objects, only the cooling needs to be adjusted to the respectively applied position.

 

 

3D-Druck Metall OTC (1)

 

With particularly strong materials such as steel, it is important to bring more energy into the process, but also, this energy must be dispersed in a timely manner. Under no circumstances should the material "overflow", as it would otherwise result in harmful metallurgical influences or compounds. The particular challenge is therefore to cool down the material in a timely manner, according to a corresponding temperature curve. Particularly, 3D welded structures made of stainless steel must meet this requirement.

 

Large workpieces are a mere formality

 

2-Türme

 

3D print products using arc welding offers similar design freedom as in laser deposition welding and laser sintering - including all the benefits of material savings that additive manufacturing processes generally have to offer.

 

However, the speed with which workpieces are produced is crucial. The robot-assisted SynchroFeed welding process from OTC allows the modeling of new aluminum components at a speed of up to 80 cm / min. In any case, such high build-up rates of the layers cannot be achieved by powder-bed-based methods.

 

As far as the end formats of the workpieces are concerned; the work area for a robot at OTC is about two square meters, for it to be able to produce larger components. If the range of the robot used is even higher, there will be virtually no limit to the format of the new 3D designs. Besides, the speed in the manufacturing process is another positive point with the SynchroFeed welding process.

 

In some industrial sectors, such as the aviation industry, where large quantities are not needed, OTC sees interesting challenges for the arc welding process. A larger circle of users of 3D metal printing, however, is likely to be the profession of metal workers, who set up small series of railings, mounts, frames and profiles, who like to have certain free spaces open in their range of services.

 

 

Burgform

 

 

"Metalworking companies that want to produce fancy banisters or molds should be economically well positioned with SynchroFeed and the possibility of 3D printing. Especially after a failed prototype goes into series after a quality check in small print-runs”, said the technical director at OTC.

In large-scale production, injection molding technology continues to be the front-runner. Anyone who enters mass production also calculates a significantly higher break-even point from the outset.
Approaches to a meaningful division of labor, however, also exist in such manufacturing processes, for example in the manufacture of truck radiators in the automotive industry: a pre-fabricated mass circulation of cooling network terminations via the casting technology could be complemented by individual complementary connection pieces, which would be made through the 3D printing via the electric arc. These attachments could also be connected directly to the radiators, which would be an additional relief.

 

 

3-Türme

 

Another possibility would be to armor a base body from mass production with a hardening material. In this case, contours or shapes could be specifically applied to this object, which would then not have to be sanded out.

 

Synchronization of welding current and wire feed


Through a highly dynamic control process, SynchroFeed applies the welding wire with reduced heat input and is therefore able to work without deformation and spatter. Post-processing processes such as milling are dispensable after the coating.

 

Compared to welds with different arcs, SynchroFeed proves to be the lowest-spattering process and is therefore particularly suitable for 3D printing.

 

Kurzlichtbogen Geregelter Kurzlichtbogen SynchroFeed 

Left picture: Short electric arc, Picture in the middle: Regulated modified short electric arc, Right picture: SynchroFeed von OTC

 

 

The basic equipment required is a SynchroFeed welding robot system with the OTC robot (FD-B6), welding power source (OTC Welbee P500L), push feeder unit, wire buffer, high-performance replacement neck torch, robot control, work table and the necessary safety technology.

 

Economic efficiency and forecasts

 

The acquisition costs for the necessary equipment of the laser-supported build-up welding or the laser sintering are correspondingly high. In comparison, only a fraction of these costs can be expected if pne chooses the SynchroFeed 3D arc welding system from OTC.

In the future, it can be assumed that a large part of industrial forms is going to be accounted for by arc welding systems via additive manufacturing processes. Although it cannot be denied that highly filigreed forms can be produced by laser sintering / laser deposition welding, one must also ask oneself the question of whether such a complex manufacturing process is justified in all cases.

"Robust or lightweight components with larger dimensions are already an issue for robotic technology in combination with an intelligent arc welding process, as they can also be produced at acceptable speed. In my opinion, shorter process times, a material utilization of up to 90% and the far lower acquisition costs speak for the SynchroFeed system”, said the technical director at OTC.

Currently, research facilities are particularly interested in the new technology and work is been done to produce welding technology that doesn’t only weld from a vertical position, but also to use inclinations of approx. 30° of the welding torch, in future.

 

3D-Druck Metall OTC (3)

 

*) SynchroFeed is a spatter-free welding process from OTC DAIHEN Europe, characterized by increased deposition rate and reduced heat input.

 

 

For more information, please contact:
Katharina Klötergens,
Marketing Assistant OTC DAIHEN EUROPE GmbH,
Tel .: +49 2161 69 49 7 14,
EMail: Katharina.Kloetergens@otc-daihen.de

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