Let’s help you find out if WAAM technology is right for you.

WAAM stands for Wire Arc Additive Manufacturing. It is based on the use of electric arcs as heat-source and metallic wires as feedstock. The former melts the latter, and material is deposited in a layer-by-layer fashion.

The process described by the WAAM acronym is known in several other ways: AW-DED, Additive Layer Manufacture, Buttering, Digital manufacture, Metal Rapid Prototyping, Net shape manufacture, Net shape engineering, Shaped deposition manufacturing, Shaped melting, Shaped Metal Deposition, Shape Melting Technology, Shape welding, Solid freeform fabrication, plus several more. It was in the Welding Engineering and Laser Processing Centre, Cranfield University that WAAM was coined as an acronym around 2010. It then became featured regularly in the group’s academic publications, finally becoming a registered trademark in 2016.

In principle, anything based on electric arcs can be used as the heat-source in the WAAM process. Tungsten Inert Gas (TIG), Metal Inert Gas (MIG), Metal Active Gas (MAG), Plasma Transferred Arc (PTA), Plasma Non Transferred Arc (PNTA) have all been adopted, with one or more wires fed (e.g. tandem MIG). There are also further variants, including also hybridisation with more heat sources. Each of these processes has specific advantages and drawbacks, related to their energy density, the level of control they provide, the deposition rate they can achieve, and the types of defects they might produce. At WAAM3D, we base our selection on material type, part complexity, and target deposition rate.

If a material or alloy can be drawn into wire, fed into the arc, and melted, then in principle it can be printed. For instance, we have managed to print even Tungsten, which has the highest melting point! However, for arc processes based on synergic lines, then one of such lines must be available to the user.

If we compare the two feedstock, we can conclude that powder has high cost, variable quality, complicated feeding unless done from the side, material efficiency between 40% and 60%, high safety issues especially with titanium or aluminium, difficult out-of-position deposition, and no rotation problems if a coaxial feed is used. Wire, instead, has medium cost, high quality in titanium, iron, nickel alloys (and variable quality in aluminium), a well-established feeding process, 100% material efficiency, no particular safety issues, easy out-of-position deposition, and rotation challenges only with off-axis feed processes.

If we compare the two heat sources, we can conclude that lasers have a very high capital cost (£40k/kW), medium running cost, low power source efficiency of 25%, low coupling efficiency of 40%, a very low total efficiency of 10%, very high safety issues, medium – high build rates, and feature size of 0.2mm upwards. Electric arcs have a low capital cost (£4k/kW), low running costs, very high power source efficiency of 90%, very high coupling efficiency of 85%, very high total efficiency of 80%, medium safety issues, high – very high build rates, and feature size of 1mm upwards.

WAAM is suitable to replace or complement forging, machining, casting and fabrication for metal parts of low and medium complexity. Our RoboWAAM systems can accommodate parts up to 2 m in size (in all three dimensions), however we have also printed parts up to 6 m on prototype systems.

AM is of course very different from casting and forging in terms of thermal cycles and requires new chemistries that match the process. To accommodate this, we have a series of signature aluminium based alloys with the addition of scandium and other niche elements that work extremely well with the WAAM process. Crucially we have also been improving the wire making process to achieve better wires in terms of their geometrical stability and surface characteristics, together with larger and larger spools and more controlled packaging.

It depends on whether the alloys have good miscibility (i.e., they do not form intermetallic compounds), and on their respective properties. For example, if they have radically different coefficient of thermal expansion, the likelihood of cracking at the interface between the two is very high.

Being able to print parts by WAAM with the required level of integrity requires mastering the interaction of the many variables often involved in different steps of the engineer’s workflow. This is no different from any other process within AM, which truly is the epitome of multidisciplinarity with complex interactions of material science, physics, mechanical engineering, software and hardware frameworks and, indeed, human factors. The scale at which these complex phenomena occurs in WAAM makes them even more evident. Therefore, we have had to mature the technology in the direction of 1) integration of the tools needed to go from a part’s concept to a successful print, 2) automation and control of the underlaying processes, 3) improvement in print speeds to being able to tackle even more components in a timely manner. This should help WAAM becoming more and more widespread.

Just like other AM technologies, WAAM can be very advantageous for one offs, spare parts, and small batches. However, we believe it can deliver its full potential also for larger runs. Ultimately it depends on what matters to your business: cost reduction, waste minimisation, lead time compression, etc. We look at these variables critically and mathematically, and we understand together with you whether WAAM makes sense for your application(s).

Like in all fusion-based processes, parts made by WAAM will show some degree of distortion, which is a manifestation of the residual stress locked into them.

We have several options. We can clamp the part very rigidly to restrain as much movement as possible; however, this increases the likelihood of cracking. We can let the part move using compliant tooling, but then we need to predict how the part will move to design the preform appropriately. We can remove unnecessary bits of the starting plate and clamp the part snugly using conformal tooling, but this increase the complexity of pre-processing operations. Finally, we can deploy cold-work methods, in-process, to strain the crystal opposite to residual stress, which sometimes increases processing times or makes the machine more expensive. Ultimately, what we end up doing depends on the geometry and material of the part.

No! We sometime print in a double-sided fashion (i.e., with the starting plate feedstock in the middle) to balance the build and control distortion. However we can build single-sided structures, or rotational parts (with and without coordinated motion). Remember – RoboWAAM’s build environment is reconfigurable and you can clamp starting feedstock of all sorts of types in all sorts of ways.

From a microstructural and mechanical property point of view, these are very much dependent on the alloy chosen. From the distortion point of view, normally we would do at least a stress-relieve heat treatment, but we have been able to machine parts to final tolerance even without it. It depends!

Being a near-net-shape process, in most instances machining will be required. Depending on part geometry, the starting feedstock will have to be machined to some extent, or removed entirely. Various types of heat treatments can also be helpful.

Very little. We normally build our WAAM preforms with 2mm to 3mm of machining stock.

WAAM parts in the as-deposited conditions look a little wavy, due to WAAM’s layer height, which is usually well over 1 mm. We call this appearance the “waviness”. It looks much worse than it actually is, with the depth of the valleys being normally just around 0.5 mm.

Yes, although the surface generated by the WAAM process, with its peaks and valleys (the ”waviness”), means that the cutter won’t see a regular surface to begin with. This requires a little extra care when carrying out the first machining pass.

We have carried out x-ray, ultrasound and computer tomography on several components. CT is very powerful, but most of our parts are too big to fit within scanning systems at present. X-ray investigation is normally used to look for lack-of-fusion and porosity, whilst ultrasounds are helpful for other discontinuities such as cracks.

There’s a minor risk of porosity due to external contamination, but certainly a lot less than powder-based processes (unless it’s aluminium, which is naturally prone to this type of defect). Lack of fusion is normally associated with wrong process parameters, so its risk is negligible, provided these are calibrated correctly.

These are very much industry-dependent. We suggest you consult your local certification authority or standardisation body. In general, they require testing campaigns of different types, e.g. microstructural, mechanical, chemical, corrosion, etc.

We encourage everyone to try and do Wire Arc Additive Manufacturing with whatever they have available. It is a low-cost, low-risk way to explore what Wire Arc Additive Manufacturing can do in its simplest form. Succeeding in depositing basic shapes such as linear walls, round geometries, etc will be quite straightforward, especially with alloys such as aluminium and steel. But to move the whole technology forward, at WAAM3D we have developed entirely new WAAM variants that cannot be found elsewhere, capable of reaching new levels of productivity and integrity. We have developed new sensors. We have incorporated helpful hardware such as that to do fume treatment. We have written new software. So when it comes to build larger parts, or make them even cheaper, or to work with more tricky materials like titanium, or geometries or relevant complexity, or whenever sophisticated monitoring and control are needed for certification purposes, our specialised software and hardware come to the rescue and make your life a little bit easier.

It really depends on the feature size, part complexity, part size, and material you are interested in. The quickest we have done is 15 kg/h in steel using our new WAAM variant. Keep in mind that there is always a trade-off between how small (or accurate) you want to get and how quick you can deposit. Heat loves to build up!

Thermal effects are the consequences of thermal mass variation (independent variable) on resulting characteristics (dependent variables) such as geometry, microstructure, mechanical properties, oxidation, etc. However thermal mass itself is influenced by the geometry variation, accumulated heat, etc. We want to ensure our process’ dependent variables are as under control as possible: predictable and within spec. This is key to deliver a robust process which can run smoothly and with minimal human intervention.

Local thermal effects due to variations in geometry are managed by having local sets of process parameters (this is exactly what our Level 2 WAAMKeys take care of). We also use the front pyrometer to monitor global changes in the part’s temperature before we start a new section, to ensure consistent deposition.

The main issue with TIG is that the electrode is exposed and also very close to the melt pool. This leaves little room for the wire to be fed, and the risk that the wire touches the electrode, forcing the process to be stopped requiring electrode replacement, is very high. Moreover, there is higher danger of electrode contamination. In PTA, the electrode is tucked away, and the clearance between the plasma orifice and the workpiece is plenty.

In PTA we have almost complete freedom to control key parameters such as wire feed speed, current, and travel speed truly independently from each other. This gives us greater capability to manage thermal effects in key areas of the component. In MIG/MAG, it is the power source that in the background plays with current and voltage, depending on the set wire feed speed. This control is based on so-called “synergic lines”. When it comes to managing thermal effects, the process leaves very little room to maneuver. However for some materials and applications, where there is limited concern for thermal effects, MIG/MAG is a perfectly viable option.

We see why you might want to pick WAAMCtrl, or our End Effectors, or in fact any other of our hardware or software sub-elements in isolation, to combine them with your existing hardware. However, our software and hardware solutions work to the fullest extent of their capability when they are used together. Having said this, we have made exceptions in the past, and we can consider supplying some of the software or hardware independently on a case-by-case basis.

With quality end-user experience in mind, we have been developing WAAM-specific software that cover the whole digital chain: life cycle assessment and business case analysis, tool-path planning, process parameters calculation, trajectory simulation and collision detection, residual stress prediction, machine control, data analysis, and health and safety management. This is complemented by our hardware backbone that comprises the motion system, power source, a suite of really innovative sensors, the fume management system, the automatic wire reload, and the whole machine enclosure – everything managed centrally from the operator’s station. This really is a massive step forward, in terms of robustness and usability, compared to the less functional approach of relying on a standard welding cell as used for WAAM purposes. The intimate level of integration means that, at any point in time, anyone in the organisation is able to know what the machine’s performances are, with any undesired deviation from the ideal behaviour being also flagged immediately. Finally, our premium wires, and decades of academic experience available on tap within our team.

In AM properties and geometries are created at the same time. Therefore, we have moved away from more traditional part-based qualification and are focusing on advanced process monitoring and control, especially around fundamental variables such as thermal field and real-time defect analysis and characterisation. By looking at the process as a whole, the validation process is quicker, unlocking the potential for continuous design improvements (as there are potentially no retooling costs) as well as mass customisation.

We are happy to discuss any type of order. If for whatever reason, we cannot support your enquiry from our MK site, we can reach out to partners within our extended network, including our own JV companies.

We have experience and own software that works with all major robot brands. However, for the time being, RoboWAAM ships with Kuka.

Yes, and we can do that in a few different ways. We can reorient the End Effector relative to the part and, provided the correct parameters are used, the surface tension of the molten metal holds the melt pool together, enabling out-of-position deposition. Alternatively, we can reorient the part relative to the End Effector (using the two-axis servo) and keep our deposition in 1G. We have also been successful in using local removable tooling.

It is not always possible – we have to consider distortion, surface roughness, etc., but we have indeed printed on previously-deposited material. We call this approach ”multi-hierarchical deposition”.

This is something we would assess using our modelling tools. There is a lower limit to the thickness of what we print on. Remember, fusion processes have the challenge of managing the resulting distortion.

Yes, especially if our variable layer height resolution is used. However, you must keep in mind your requirements for surface finish. If your part is meant to be fully machined, then tool access might be a problem when trying to machine lattice structures.

We have done plenty of mechanical testing, from tensile to fatigue to toughness to crack propagation rate, etc, and for a wide range of materials, and for a wide range of conditions. Reach out to us and we will happily share all of our knowledge with you.

It really depends on the material we are depositing. We have essentially three approaches: torch shielding only; local End Effector shielding; and global shielding. Torch shielding only is normally good enough for materials like aluminium or steel when deposited using some MIG variants. When depositing with PTA and working with materials such as titanium, we have the choice of creating an inert atmosphere locally (using our local shielding solutions) which protects the material only where it is above a certain critical temperature; or depositing inside an enclosed environment which is entirely filled with argon gas.

We could, but it would be much more expensive and difficult to transport than our flexible enclosure. With this, we have managed to achieve the same level of performance, at a fraction of the cost.