In terms of economic as well as ecological sustainability, this call is absolutely true and future-oriented. When it comes to repairing moulds and components instead of producing new ones, laser metal deposition (LMD) is a proven key technology - with a growing potential for new areas of application.
The focus of the "reFORM" workshop at the CHIRON Group's OPEN HOUSE 2022 was on the automation of LMD repair processes. And one thing became clear: it's not that simple. But those who know how to implement it gain time, save costs and - act in an extremely sustainable manner.
Actually, it's like machining, only LMD works the other way round. Instead of taking away material, it is applied. By means of powder or wire, or both in combination. What is the feed rate and cutting depth for one is the application rate and layer thickness for the other. Where one cools his workpiece, the other heats it. Either way, at the end of the day the component must be produced in the required quality and cost-effectively - with the increasingly important additional criteria of energy sustainability and resource conservation.
LMD process technology - automated repair
With the goal of discussing the prerequisites and possibilities of automated LMD processes in mind, concentrated expertise was represented at the CHIRON Group's "reFORM" workshop in Tuttlingen. Cedric Bardenhagen, Key Account Manager at Siemens AG, gave a very vivid picture of the motivation to take on this challenge in his presentation on programming additive manufacturing processes: A newly produced gear wheel with Ø 500 mm and 230 kg weight requires almost 2,000 kW/h in its entire production chain. This is 90 per cent of the energy for steel production and forging the mould, and the remaining ten per cent for machining and post-treatment. In comparison, a gear wheel made from recycled steel consumes "only" 39 per cent of the energy used to manufacture it. If you now repair such a wheel with an automated LMD process, you only need 17 per cent of the energy of a new wheel, or 42 per cent of that of a recycled one, in order to get a wind turbine, for example, running with this component that has been brought back into shape. In short: repairing with additive manufacturing is highly positive for the climate balance!
Materials and welding - that's science
But first, let's go back to the very beginning of the process, to the source. And there is always the material. Heat-resistant chromium steels are usually used for moulds and tools. The stresses to which a forming tool is subjected can be very different. Whether it is a forging tool for the production of a generator shaft with a dead weight of 250 tonnes or a taper roller for the production of seamless rings - the loads that occur are sometimes fundamentally different. This was impressively demonstrated by Dr. Michael Nolde, in the management of Capilla Schweißmaterialien GmbH, using the example of a fully automated forging plant from the forging blank to the finished part. In order to make the mould and tool more wear-resistant, protective layers of iron, cobalt or nickel alloys are applied by means of various welding processes. What has to be taken into account in terms of materials and processes when manufacturing new tools, but also when repairing them in a worn condition, e.g. chipping and worn-out punching surfaces, is indeed a science in itself. However, this is the only way to achieve good mould and tool quality - long tool life is the result. At best, these even exceed those of unwelded new dies. This knowledge is indispensably valuable for the successful implementation of automated LMD processes. The workshop participants, who numbered around 30, could really sense the 40 years of experience.
Multifunctional system for automated LMD processes - AM Cube 3D metal printer proves itself in practice
This highly specialised knowledge of material properties in welding processes was used by the CHIRON Group's Additive Manufacturing team, the hosts of the workshop, to develop the AM Cube. With today's very large variety of materials, the flexibility of the system is an important criterion for an automated LMD process: so many shapes and contours, so many materials are used in daily practice, it makes sense for the system to have application heads that can be changed easily and quickly - up to three are possible. Once powder is the preferred welding material, once wire - the user has all options.
Dominik Hipp, head of toolmaking at Hammerwerk Fridingen GmbH, is one such user, responsible for the production of dies and tools to ensure a daily tonnage of around 200 tonnes. Together with the CHIRON Group, he is working on several projects, including the repair of cutting rings. "Automated welding on the AM Cube meets our quality requirements and increases tool life by a factor of 2.5 to 3," Hipp reported in his presentation. "Another decisive factor in automating LMD repair was the fact that it is almost impossible to find qualified specialists for manual welding. Now that the automated process is in place, it is important to introduce employees to the automated LMD process and get them excited about it so that we can repair even more moulds in the future and thus improve our products as well as our carbon footprint," says Dominik Hipp.
Data is the key - basic knowledge, control and digital systems combined
"Process control and data effectiveness are a must for automated LMD solutions," Till Oeschger, Project Manager AM Cube at CHIRON Group, is convinced. Why he thinks this way, must think this way, is particularly evident in the very impressive presentation by Prof. Dr. Hadi Mozaffari-Jovein, materials scientist at Furtwangen University. What the participants of the workshop realised in the lecture was the complexity of the topic: from the physical, chemical and mechanical requirements on tool and material to build-up welding for graduated alloys. A lot of factors come together. And ultimately parameters and data that have to be used in the design of the component to make automated LMD processes reliable and reproducible.
This data is valuable on several levels. With Siemens NX CAM, the machining processes can be conveniently programmed with the system and workpiece data and simulated in advance with the help of the digital twin. An error-free and already optimised program can be transferred 1:1 to the system. "The time required for CAD/CAM programming is a good 90 minutes for a cutting ring, and that's fast," emphasises Quentin Leibinger, Application Engineer AM at the CHIRON Group. Data also plays an important role during machining on the real machine. All relevant process data is recorded via two new digital systems from the CHIRON Group: Via DataLine AM, all relevant process data can be continuously displayed live, recorded and documented in a compact quality report. Product and process quality can thus be reliably assessed. VisioLine AM visualises and saves video files that are captured via several camera systems. Parameters and tolerances that have been entered once serve as a reference and in the event of deviations, targeted intervention is possible immediately. A big plus for the worker:in. The continuous collection and analysis of data helps enormously in defining the ideal process, Leibinger and Oeschger agree.
At the end of the day, it's a turnkey solution - push the button and go
If one were to draw a conclusion to the workshop, it would be this: The call to "Repair, don't re-produce!" with automated laser build-up welding is certainly not an easy process to implement. But not unlike the metal-cutting process, new innovative solutions emerge from technology partnerships, expert knowledge with its finger on the pulse of practice and finally the experience gained from joint projects. The results and findings from the workshop give justified reason to do so. In terms of sustainability, very good prospects.
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