As mentioned in the introduction, PBF-LB, then referred to as SLS, was one of the first AM technologies tested for hardmetals. The tests conducted at UT Austin used agglomerated hardmetal powder (presumably thermal spray powders) with a composition of WC-12 wt.% Co and showed that the principle of fabrication of hardmetal parts is possible [2]. However, these parts were nowhere near dense, reaching approximately 60% TD. Further work by Kruth at the KU Leuven, Belgium, between 1996 to 2003, showed that, even with an increase of metallic Co to 30 wt.%, no dense parts could be made by PBF directly [8, 9]. Work in 1999 by Fraunhofer IKTS and IWS in Dresden, in cooperation with the University of Mittweida, all in Germany [10], showed that, with optimised granulated and pre-sintered granules, samples with densities above 60% of theoretical density can be achieved, which can be increased to nearly full density by a subsequent step combining sintering and Hot Isostatic Pressing (SinterHIP).

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This is what has happened with Sandvik Coromant’s CoroTurn Prime tools and inserts, which have been developed to allow cutting in both directions on the spindle axis.

[24] Scheithauer U, Schwarzer E, Poitzsch C, Richter H-J, Moritz T, Stelter M. Method for producing ceramic and/or metal components (WO-Patent 2015/177128 A1).

Of course, this means that your internal inspection processes might need to adapt to having your CNC machine effectively ‘marking its own homework’, but given confidence in your machine tools, there are some serious time savings to be had here.

Today’s system looks as fresh and modern as ever and its emphasis remains on making life easy for the machinist. What’s changed, perhaps, is how the system goes about meeting that not-inconsiderable challenge, as well as the range of production techniques that it now supports.

It’s also good to see that the system is expanding its reach to cover both new machining technologies (such as those fancy cutters from Sandvik) as well as exploring the future promise of DED additive processes.

[15] Schwanekamp T, Marginean G, Reuber M. Thermal Post-Treatment of Additively Manufactured WC-Co Processed by Laser Powder Bed Fusion. In: Euro PM2019 Congress & Exhibition Euro PM2019 proceedings 13-16 October 2019, Maastricht Exhibition & Congress Centre (MECC), Maastricht, Netherlands. Shrewsbury, United Kingdom: European Powder Metallurgy Association (EPMA); 2019, 1–6.

Most tools used in the oil, gas, and mining sectors, as well as in the metal machining or forming industries, are made from hardmetals. This material class, also known as cemented carbides or sometimes just carbides, can be categorised as composite materials. Hardmetals possess the necessary properties for their intended use, namely high hardness, strength and toughness. As implied by the name cemented carbide, hardmetals primarily consist of very hard carbide grains which are ‘cemented’ together by a comparatively low amount of a ductile metallic binder. The most used hard phase material is tungsten carbide (WC) and the binder metal is mainly cobalt (Co), with typical binder compositions in the range of 10 to 30 vol.% (equivalent to 6 to 18 wt.% Co).

These are specially shaped inserts, so the Edgecam team has had to do a fair bit of development to enable its programming to not only support their use, but also to ensure that their advantages are properly supported (for example, gouge-protecting the inserts and various lead in/lead out strategies specific to this tooling). In addition, a new finishing concept, Up-Turning, is now available to enable highproductivity finishing with the use of these specific tooling inserts.

For existing users, there’s plenty to get stuck into in the 2019 release. For those working at the more complex end of the spectrum (such as mill/turn and 5-axis), it’s clear that there has been a good amount of work done to make tools more efficient, both during programming time as well as on the machine.

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This has meant that you can now insert inspection processes into your workflow more directly and remove some of the bottlenecks typically found in industrial workflows; for example, moving parts to the inspection department and back again, with all of the repetition this entails, as well as the potential for set-up errors.

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Introduced back in 2014, Waveform is Edgecam’s take on trochoidal roughing, whereby the CAM system attempts to maintain a constant load between cutter and stock. What varies between each vendor is how they deliver this capability.

[13] Gläser T, Arntz K, Schlüter M, John T, Bechmann F, Döhler R et al. Generative Fertigung von Extrusionswerkzeugen aus Hartmetall – GENIAL. Aachen; 2009.

To address these issues, researchers at the University of Applied Sciences, Cologne, Germany, came up with the idea of preheating the powder bed to avoid thermal cracks and lowering the required energy input [14]. As shown in Fig. 5, preheating of the WC-12Co powder bed resulted in crack- and pore-free parts with five times higher bending strength values (~1000 MPa instead of ~200 MPa) as compared with parts produced with the standard PBF process.

In the context of Edgecam’s technology, rather than changing speeds and feeds, Waveform adjusts the toolpath to maintain the tool engagement angle (the portion of the cutter in contact with the stock) to within a workable, optimal range (between 20% and 30%) and thus ensures consistent material removal.

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Edgecam has been through something of a renaissance and some of the updates made in the last few releases show that it’s one of the more advanced and current tools in the Hexagon armoury.

What has also become clear is that there’s been some serious reorganisation of how this range of tools is developed and I’m told that the company’s internal development teams are now organised according to competency rather than product, so we should start to see more meaningful updates across all the key Hexagon machining products as we move forward.

In the future, adjusted materials for BJT and optimised process parameters for MEX and MJT will most likely overcome the current limitations of the Additive Manufacturing of hardmetals and will open the field to even more challenging possibilities, such as the multi-material printing of tools with different hardmetal compositions, resulting in specific tailored properties in different parts of a tool.

There are also a couple of new operations brought across from elsewhere in the Hexagon portfolio. A good example here is the lace cycle. Again, this is a pretty common or garden operation in the machining world (typically for more complex surface machining), but when flipped into deposition operation, it makes huge sense, because it allows the user to programme stock build-up using a form and parallel runs of material, combined with an exterior boundary (or vice versa).

[3] Kurlov AS, Gusev AI. Tungsten Carbides: Structure, Properties and Application in Hardmetals. 184th ed.: Springer; 2013.

Edgecam has been through something of a renaissance and some of the updates made in the last few releases show that it is one of the more advanced and current tools in the Hexagon armoury

[8] Laoui T, Bonse J, Kruth J-P, Froyen L. Influence of Powder Parameters on Selective Laser Sintering of Tungsten-Carbide Cobalt. In: Campbell (Hg.) 1998 – Proceedings of the 8th European; 1998, 271–280.

Thus, and in contrast with PBF and BJT, MEX can achieve dense parts with low cobalt contents and high hardness values. However, due to the high amount of organic thermoplastic backbone binder, debinding has to be calibrated to the thickest dimension of the as-built part, thus limiting the manufacture of larger parts without inner channels because of the very long debinding time needed to remove the binder components. Furthermore, MEX using filaments is, in standard machines, a single process, meaning one part is created at a time, making it significantly slower than PBF – even more so when compared with BJT.

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Then you start to add in the parts you want to machine. The process uses a common datum to position parts; the idea here is that you do all of the programming for each individual part, then have the system work out how to link multiple instances or different parts, in terms of consolidating common operations (by plane/datum or to minimise tool changes).

On the subject of Hexagon, the move to rebrand all of its CAM systems under the parent company name will surprise a few, particularly considering it’s only relatively recently that some of them took on the Vero name – but this change was inevitable.

It is also noteworthy that, in contrast to many ceramics, hardmetals are not transparent to light. Light-based lithography AM technologies could therefore only be used with indirect crosslinking approaches, limiting resolution and speed.

The author thanks Markus Mayer, Uwe Scheithauer, Steven Weingarten, Hans-Jürgen Richter, Christian Berger and Tassilo Moritz (all Fraunhofer IKTS) as well as Tobias Schwanenkamp (University of Applied Sciences Cologne) for their input and additional material for this article.

Using the concept of masks, it’s possible to hard-code in options and variables within a command, and then ensure that only the options that the user needs to change are exposed. If you’re looking at this as a means to clearly establish corporate standards and best practices for users, you begin with a single seat, make all of the customisations (a task that has to be performed ‘in product’), then export a theme to be used across the whole user group. This is also a great way of GUI simplification for occasional users.

[14] Schwanekamp T, Reuber M. Parameter study on laser beam melting of WC-Co at 800°C pre-heating temperature. In: Proceedings of 7th International Conference on Additive Technologies: Interesansa – zavod, Ljubljana; 2018, 78–84.

There is a full set of inspection tools in the Edgecam environment, with a probe tool store supporting Hexagon, m&h and Renishaw probes. The tools automate some functions, such as automatically finding matching features such as holes on a single PCD, for example, and automating inspection set-ups.

Considering the above, Electron Beam Powder Bed Fusion (PBF-EB) has to be excluded because of its intensive energy input, resulting in the decomposition of WC and the evaporation of Co. Also, VAT Photopolymerisation (VPP), also known as Stereolithography (SLA), is excluded because of the non-transparency of WC. Even though there are a few publications concerning both the PBF-EB [6] and VPP [7] of hardmetals, these processes are excluded from this report for the previously mentioned reasons and the results that can be anticipated.

As a result, Hexagon has adapted the most suitable operations from Edgecam to enable programming of DED set-ups, adding in those key parameters that need to be fed to the machine alongside movement coordinates, including laser power, gas and powder/rod control, speeds and so on.

Work done on FFF of hardmetals at Fraunhofer IKTS shows that cavity- and pore-free parts can be produced (Fig. 7) and that, due to the low shrinkage, hardmetal compositions with Co contents as low as 8 wt.% and with nickel as a binder element can also be produced (Table 2), resulting in hardness values of up to 1700 HV [23].

These properties are similar to conventionally manufactured parts with the same grain size and metallic binder content. PBF-produced hardmetal parts currently show significantly inferior properties due to the formation of cracks, unwanted phases and inhomogeneous microstructures.

This is focused, for the time being at least, on button-style turning tooling, which allows you to cut both directions on the spindle axis. When combined with Waveform’s efficiencies, the end result is a set of operations that maximises material removal with less wear on your inserts and a more efficient operation. Set-up is, as you would expect, pretty simple, as it’s focused on maintaining engagement angle, speeds and feeds.

So far, however, dense hardmetal parts with mechanical properties comparable to conventionally produced parts have only been achieved by Binder Jetting for hardmetal compositions with ≥ 12 wt.% Co. Results for the widely used hardmetals compositions with 6 to 10 wt.% Co have, to date, not been published.

There are a number of benefits to this approach, ranging from more efficient toolpaths to a decrease in cutter wear (and reduced cost as it focuses on cheaper carbide-style tooling), as well as less heat build-up and machine wear.

[26] Scheithauer U, Pötschke J, Weingarten S, Schwarzer E, Vornberger A, Moritz T et al. Droplet-Based Additive Manufacturing of Hard Metal Components by Thermoplastic 3D Printing (T3DP). Journal of Ceramic Science and Technology 2017;8(1):155–60.

[5] Kurlov AS, Gusev A-I. Tungsten Carbides and W-C Phase Diagram. Inorganic Materials 2006;42(2):121–7.

For those that are unfamiliar with this, it involves using a CNC-controlled head that deposits molten metal in layers, just as any 3D printer would, either by using a rod-fed process similar to welding or using a powder feed and plasma torch.

Another key focus for the latest set of releases is greater support for tombstone machining. While Edgecam has supported tombstone in the past, where multiple parts are loaded onto specialised fixtures to enable rapid production, the workflow involved was complex, particularly if you were working across multiple different parts and at the same time trying to maintain a rationalised tooling library.

For 2019, the workflow has been overhauled to make the process both easier and more intelligent. It’s an additional licence requirement, but if you’re carrying out this type of work, that’s probably to be expected.

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[22] Lengauer W, Duretek I, Fürst M, Schwarz V, Gonzalez-Gutierrez J, Schuschnigg S et al. Fabrication and properties of extrusion-based 3D-printed hardmetal and cermet components. Int. J. Refract. Met. H. 2019;82:141–9.

[7] Rieger T, Schubert T, Schurr J, Kolb D, Riegel H, Bernthaler T et al. Cemented Carbide Development for Additive Manufacturing (AM). In: Euro PM2019 Congress & Exhibition Euro PM2019 proceedings 13-16 October 2019, Maastricht Exhibition & Congress Centre (MECC), Maastricht, Netherlands. Shrewsbury, United Kingdom: European Powder Metallurgy Association (EPMA); 2019, 1–6.

[12] Gläser T. Untersuchungen zum Lasersintern von Wolframkarbid-Kobalt. 1st ed. Aachen: Apprimus Verlag; 2010.

Essentially, you pick the form you want to build and define the parameters.The system will build up that form using layers of parallel laces and boundaries. You have control over the order of those operations and can add in variations, such as rotating the lace orientation by 90 degrees per layer.

From its origins as a 3-axis focused production CAM system, Hexagon’s Edgecam has come a long way in recent years.

[23] Berger C, Abel J, Pötschke J, Moritz T. Properties of Additive Manufactured Hardmetal Components Produced by Fused Filament Fabrication (FFF). In: Euro PM2018 Congress & Exhibition Euro PM2018 proceedings 14-18 October 2018, Bilbao Exhibition Centre (BEC), Bilbao, Spain. Shrewsbury, United Kingdom: European Powder Metallurgy Association (EPMA); 2018.

Another powder bed-based AM technology is Binder Jetting (BJT). When it was first developed in 1990 by Prof. Sachs at MIT it was simply called ‘three-dimensional printing,’ or 3DP [16]. In contrast to PBF processes, BJT is a two-step sinter-based AM technology in which the built green part must undergo a subsequent densification process achieved through sintering.

PBF-LB processes, also known as Selective Laser Melting, Direct Metal Laser Sintering, Selective Laser Sintering, Laser Beam Melting etc., belong to the powder bed-based group of AM technologies and were among the first AM technologies evaluated for the production of hardmetal parts. In contrast to Binder Jetting or filament-based Material Extrusion processes, the PBF-LB process ideally creates a fully dense part in a single-step.

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While this can be beneficial, the reality is that there is a certain class of edits where it’s not necessary for the whole programme to be checked; for example, a change in coolant. This might sound like a small change, but when you consider the iterative nature of part programming (and particularly optimisation), time eliminated from the process quickly mounts up over the course of an average working week.

For Additive Manufacturing to mature as an industrial production process, believe Tommaso Tamarozzi (Oqton) and Juan Carlos Flores (Baker Hughes), ...»

With an even further increase of sintering temperature (ca. > 2,800°C), the hard phase tungsten carbide can disintegrate due to decomposition of WC into W2C and C [3]. For handling and safety reasons it has to be further noted that cobalt is classified as a Cancerogenic Mutagen Reprotoxic (CMR) material, for which special care has be taken during processing [4].

[9] Kruth J-P, van der Schueren B, Bonse JE, Morren B. Basic Powder Metallurgical Aspects in Selective Metal Powder Sintering. CIRP Annals 1996;45(1):183–6.

Further work was done in a national project at Fraunhofer IPT with partners from the tooling industry from 2007 to 2009 [18]. They used a granulated and pre-sintered WC-25 wt.% Co powder and a R2 BJT machine from Prometal RTC, Augsburg, Germany, now part of ExOne. After sintering (presumably gas pressure assisted SinterHIP sintering), crack free microstructures with densities above 99% TD and hardness values of around 1020 HV0.5 could be achieved.

In principle, the whole range of AM technologies is available for hardmetals and quite a few have been tried already. However, due to the peculiarities of hardmetals, the following aspects limit the choice:

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In recent years, a slightly modified process called ‘Solvent on Granule 3D-Printing’ was also successfully used to produce similar complex parts with Co-contents of 17.7 wt.% Co [21].

[21] Carreño-Morelli E, Alveen P, Moseley S, Rodriguez-Arbaizar M, Cardoso K. Three-dimensional printing of hard materials. Hardmetals – raw materials, technologies and applications 2020;87:105110.

For the last two or three versions, Edgecam has offered inspection capabilities, as you would expect, based on Hexagon’s PC-DMIS.

Using the gateway, it’s also possible to build up links between Edgecam, inspection and a feedback loop. To do this, you would set up inspection entities and operations, then create the inspection cycle which incorporates an element of calibration.

However, as also shown by other studies, the required energy input (laser power) to achieve sufficiently dense samples resulted in defects such as abnormal grain growth and local decomposition of WC into W2C and carbon, as well as the unwanted formation of eta phases. Furthermore, the evaporation of Co, reducing the residual Co content of the hardmetal, led to the fact that often the composition of the produced part did not match that of the starting powders used [11].

If you’re not familiar with how the CAM industry works, it’s often the case that a tooling vendor will develop a new method of removing material (or a variation thereof) and then must wait for CAM vendors to provide a way to programme parts to take advantage of that tooling. Conversely, the CAM vendor needs to ensure that its leading edge customers can take advantage of the latest innovations in tooling design.

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The actual CNC mechanism that moves these DED heads can vary from pretty standard CNC machines (either specially built or retrofitted), gantry-based systems or industrial robot arms.

In the first work in the area of hardmetals Sachs and colleagues between 1995 and 1998 used spray granulated WC-10 wt.% Co powders and produced simple bars with a green density of around 25% TD. However, due to this low green density (conventional pressed parts have ca. 55% TD), sintering at conventional temperatures (1,440°C) led only to sintered part densities of 60.9% TD [1, 17].

[1] Caradonna MA. The fabrication of high packing density ceramic powder beds for the three dimensional printing process. Thesis (Master of Science). Boston, MA; 1997.

There is huge potential here, assuming the correct machine tools are in place, to combine these additive tools with more traditional machining. We’re certainly seeing a move towards finding new ways to integrate additive deposition and traditional removal of material more closely; for example, alternating between deposition layers and machining passes to improve accuracy, reduce post-processing and better handle thermal issues that arise in such processes.

To begin, you start with an ‘Insert Tombstone’ command and set up the usual machine options, clearances and so on.

Alongside the big headline updates, there are always a number of smaller updates that are just as key, particularly for existing users, but which are hard to categorise.

The last update to Edgecam that we’re going to look at is a new set of functionality built into Edgecam to add support for DED (Directed Energy Deposition) additive manufacturing.

Since, in MEX, layers and volumes are produced by a layer-wise deposition of filaments, the production of 100% dense parts (after sintering) is complicated due to the anticipated presence of cavities resulting from the potential gap between deposited filament layers. Examples of such problems, in the case of hardmetals, were shown by Lengauer et al. in 2019 [22].

The system will then generate the G-code to drive your probing process. The machine then performs the operations, captures the data and, via Hexagon’s NC Gateway, returns it to the machine as a report that can be used for standard inspection or perhaps as the basis for on-machine verification and adaptive set-ups.

Further work done at Fraunhofer IKTS in Dresden, Germany, with pre-sintered WC-Co granules in 2015 to 2016 [19, 20] showed, for the first time, that hardmetal compositions with typical Co contents in the range of 12 to 20 wt.% could also be successfully processed by BJT (Fig. 6). As seen in Table 1, different compositions can be processed and different properties achieved.

Another technology investigated for the Additive Manufacturing of hardmetals is the thermoplastic 3D printing (T3DP) process developed by Fraunhofer IKTS [24]. Because of its jetting-like process, it belongs to the MJT category of AM processes. Like MEX, thermoplastic 3D-Printing is based on the selective deposition of molten, particle-filled thermoplastics. However, in T3DP, droplets rather than filaments are deposited. The thermoplastic binder system used consists of different waxes and additives. This results in low viscosities at relatively low temperatures and solidification by cooling. Work done at IKTS, starting in 2016, showed that T3DP can be used for hardmetals with low Co contents and small tungsten carbide grain sizes [25, 26]. Work done for the manufacture of cutting inserts and test structures showed that, with nanoscaled WC powders and Co contents of just 10 wt.%, fully dense parts with a perfect microstructure (Fig. 8) and hardness values of above 1900 HV can be achieved (Table 3).

There are a number of benefits to this approach. First, those originating part programmes are live-linked, rather than inserted as a copy, so any edits to underlying operations can very quickly be propagated to your tombstone set-ups. Second, it means that common operations can be collated and split out as individual sub-routines, such as drilling cycles.

As ever, the Edgecam interface is up-todate with modern standards, but continues to offer the customisability that many users have come to expect and regularly use. What’s interesting here is that rather than just being a case of configuration – the moving around of toolbars and icons, for example – users now have more granular control over how the system presents commands, options and operations.

The most promising results, however, have so far been achieved with Laser Beam Powder Bed Fusion (PBF-LB), Binder Jetting (BJT), Material Extrusion (MEX) and Material Jetting (MJT). In the following subsections, results for each of these AM technologies will be summarised and discussed accordingly.

Waveform has expanded beyond Edgecam, in fact, and is now available in the majority of Hexagon’s milling systems, including Alphacam, Edgecam, Surfcam, VISI and WorkNC. What’s new for the 2019 release is that the team has also integrated this capability into the turning environment.

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[2] Zong G, Wu Y, Tran N, Lee I, Bourell DL, Beaman JJ et al. Direct Selective Laser Sintering of High Temperature Materials. Center for Materials Science & Engineering 1992:72–85.

Whilst hardmetals are interesting as new materials for Additive Manufacturing, it should be noted that they were one of the first materials studied, as shown by early tests done in the US by Sachs at MIT in 1995 [1] using Binder Jetting (BJT) or by Zong at UT Austin in 1992 by means of Powder Bed Fusion (PBF) [2]. These early studies showed that the successful processing of hardmetals by AM is by no means an easy task.

[16] Sachs EM, Cima M, Cornie J. Three-Dimensional Printing: Rapid Tooling and Prototypes Directly from a CAD Model. CIRP Annals 1990;39(1):201–4.

Sintering of hardmetals takes place slightly above the eutectic temperature within the W-C-Co system of 1,310°C, as so-called liquid phase sintering. With a further increase of sintering temperature, more and more W and C can be dissolved within Co, increasing the amount of the liquid phase. However, if the temperature is too high, the metallic binder can evaporate.

EdgeCAM Inspect allows you to programme in inspection routines as well as building more intelligent feedback loops where needed

Currently, the vertical resolution of T3DP is around 80 to 100 µm and the horizontal resolution is 250 to 350 µm, bringing it in the range of standard BJT produced parts. In T3DP, a quite high solid loading in the range of 50 to 60% ensures low shrinkage and subsequent distortions. However, as with MEX, debinding has to be addressed, limiting the parts sizes in the case of larger bulk parts.

[25] Pötschke J, Weingarten S, Scheithauer U, Mayer M, Moritz T. Thermoplastic 3D Printing of Hardmetals. In: Euro PM2019 Congress & Exhibition Euro PM2019 proceedings 13-16 October 2019, Maastricht Exhibition & Congress Centre (MECC), Maastricht, Netherlands. Shrewsbury, United Kingdom: European Powder Metallurgy Association (EPMA); 2019, 1–6.

A good example is the work done to reduce the number of checks that the system makes when you make certain edits to your operations. Previously, edits would force Edgecam to run its full set of checks to ensure the part is as should be.

In addition, the evaporated Co can deposit within the PBF-LB machine and is a risk regarding CMR issues. Nevertheless, nearly dense samples (98.5% TD) were achieved by researchers from Fraunhofer IPT, Aachen, between 2007 and 2009 [12, 13] with Co contents as low as 25 wt.%. However, in addition to unwanted phases, thermal stress induced cracks and pores within the more or less dense microstructure now appeared due to the high laser power used. Similar results in 2015 at Fraunhofer IPK, Berlin, showed (Figs. 3–4) that interesting geometries are possible, but that the microstructure and the mechanical properties were significantly inferior to conventionally produced parts [11].

Material Extrusion (MEX), widely known as Fused Filament Fabrication (FFF) when using a filament-based feedstock, is, like Binder Jetting, a two-step sinter-based AM technology. However, in contrast to BJT or PBF, it is not powder bed based but is a ‘free form’ AM process. Here, particle-filled thermoplastic filaments are produced by mixing, kneading and extrusion. These can then be used in standard MEX machines. Within these filaments, the volume percentage of particles (solid content) can easily be in the range of 50 to 60%, resulting, for hardmetals, in shrinkage ratios comparable to conventional powder injection moulded or even pressed parts.

Also, as should be obvious, this approach relies on many of the core competencies of any CAM system, with the key difference being that the machines are typically depositing material, rather than removing it from a billet or a casting.

Additional heat treatment by SinterHIPing of the PBF + preheating resulted in parts with further improved properties. However, abnormal grain growth as well as Co evaporation and the local decomposition of the WC phase still resulted in significantly inferior properties in comparison with conventionally shaped and sintered hardmetal parts [15].

Dr.-Ing. Johannes PötschkeGroup Leader, Hardmetals and CermetsFraunhofer Institute for Ceramic Technologies and Systems IKTSWinterbergstrasse 2801277 DresdenGermanyTel: +49 351 2553-7641[email protected]www.ikts.fraunhofer.de

Finally, it also allows post processors to be rationalised. It may be the case, for example, that each part on your tombstone is set up for a different machine tool. Now, Edgecam will consolidate these and ensure that every operation is ready for your machine at hand. It also makes light work of moving jobs to match your machine tool capacity.

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As stated above, hardmetals are composites, consisting of the hard phase tungsten carbide and the metallic binder cobalt. Properties such as high hardness (up to 20 GPa), high bending strength (up to 5000 MPa) and high fracture toughness values (up to 20 MPa*m1/2) are only achieved if the three elements (tungsten, carbon and cobalt) are present in the two phase state of tungsten carbide and cobalt alloy (WC+Co). To achieve this, the carbon content must be within a small compositional window, to avoid free carbon (C) or the formation of complex eta phases (M6C or M12C) when too low amounts of carbon are present, as shown in the phase diagram of W, C and Co (Fig. 1).

Hexagon is applying its knowledge of machine control to the additive world, and in particular, DED machines

Furthermore, it should be kept in mind that, due to the comparatively low green density of BJT green parts, shrinkage is greater than with conventional pressed parts, resulting in more problems with distortion after sintering. The reason why the use of lower Co levels is difficult is because of an insufficient amount of liquid phase during sintering, which in turn is needed for the greater shrinkage of BJT parts.

Even though hardmetals have not yet been successfully commercialised by the AM industry, they are a promising material for a number of AM processes. Sinter-based AM technologies, such as Binder Jetting, Material Extrusion and Material Jetting, seem to be the AM technologies with the highest potential for industrial use, as they appear to be the only ones capable of delivering the specific requirements for hardmetal tooling, namely full density, microstructures with a homogeneous distribution of WC and Co and the maximum possible ratio of hardness and fracture toughness combined with high bending strength values above 3000 MPa.

[11] Uhlmann E, Bergmann A, Gridin W. Investigation on Additive Manufacturing of Tungsten Carbide-cobalt by Selective Laser Melting. Procedia CIRP 2015;35:8–15.

The growing use of titanium Additive Manufacturing for the production of medical implants is a major success story for the industry. With this grow...»

[18] Gläser T, Arntz K, Schlüter M, John T, Bechmann F, Döhler R et al. Gemeinsamer Ergebnisbericht zum BMBF – Verbundprojekt: Generative Fertigung von Extrusions-werkzeugen aus Hartmetall – GENIAL. Bericht Lasersintern HM; Förderkennzeichen 02PU2220. Aachen; 2009.

In both these cases, mechanical properties will drop off drastically and a product’s use in tooling would be impractical. Furthermore, to achieve the required properties, the material has to be 100% dense, with only a very small amount of pores (< 0.2 vol.%) in the range of up to 25 µm being allowed. As for microstructural requirements, the tungsten carbide grains, as well as the metallic binder phase, must be distributed within the tool materials as homogenously as possible to guarantee the aforementioned properties, as can be seen in Fig. 2.

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The future of Additive Manufacturing lies in part production at scale. Innovation must, therefore, focus on how to reduce part cost and improve per...»

[20] Pötschke J, Berger C, Richter H-J, Scheithauer U, Weingarten S. ADDITIVE MANUFACTURING OF HARDMETALS. In: EPMA – European Powder Metallurgy Association, editor. Euro PM2017 Proceedings; 2017.

[4] ECHA. Substance information on: Information on, https://echa.europa.eu/substance-information/-/substanceinfo/100.028.325.

Edgecam 2019 – Since Hexagon took over the Vero portfolio, things have moved on apace. We take a look at the latest updates to its production machining-focused system

For hardmetals parts with sizes of up to several centimetres and hardness values of up to 1400 HV, BJT is a fast and suitable process. However, for smaller parts with higher hardness values up to 1800 HV, MEX and, for delicate parts with hardness values of up to 1900 HV, MJT, appear most suitable.

Traditionally, hardmetal parts are produced by a standard Powder Metallurgy shaping process to create green parts that have densities in the range of 55% theoretical density (TD). These green parts are then sintered in vacuum and protective gas atmospheres to 100% TD. While traditionally parts such as cutting inserts or dies are produced by uniaxial pressing, cylindrical parts are often produced by extrusion and more complex parts by Powder Injection Moulding (PIM). Even though this already allows the production of cooling channels for drills or milling cutters, more complex internal shapes and outer tool geometry are currently only possible with a high level of green machining and finishing – if possible at all.

[10] Mattiza D. Untersuchungen zum Selektiven Laser-Sintern von Hartmetallen und hochschmelzenden Nichteisen-Metallen: Diplomarbeit. 1st ed; 1999.

So far, each of the potential technologies that have been highlighted appear to have strengths and weaknesses, depending on the material composition, production speed, accuracy and part size achievable.

As for processing, it is important to keep in mind that tungsten is a quite heavy element and that tungsten carbide based hardmetals, therefore, have densities in the range of 13 to 15 g/cm³. Even small green parts therefore have a high weight, which can influence the green part stability or shrinkage during sintering.

[6] Konyashin I, Hinners H, Ries B, Kirchner A, Klöden B, Kieback B et al. Additive manufacturing of WC-13%Co by selective electron beam melting: Achievements and challenges. Hardmetals – raw materials, technologies and applications 2019;84:105028.