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Robotic Arc-Weld Additive Manufacturing

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Holistic simulations free from trial and error processes

Did you know that it is possible to generate programs for all manufacturing steps from nothing but CAD data? A joint project of CENIT and FANUC is based on the approach of hybrid manufacturing. The feasibility of the project is demonstrated by the exemplary process of build-up welding functioning as additive manufacturing method.

"It’s more than it might appear to be." In build-up welding, a robot welds layer by layer. The assembled metal part is then placed in a Robodrill machine for the final milling procedure. This entire process can be programmed and simulated offline.

The project initiated by Fanuc and CENIT, deals with a process of this kind. A generative free-space process with standardized welding technology is to be combined with a well-proven metal-cutting manufacturing method. Robots and metal-cutting machines are programmed directly from the CAD data of the component using digital factory software. The software provides offline programming tools for additive processes as well as links between modern CAM strategies.

Additive processes have become attractive for numerous industries. In the repair of turbines and generators, for example, build-up welding was an established technique already before the term "additive manufacturing" emerged. Fanuc’s machines are proficient in handling the steps incorporated in these processes. Arc-welding robots, machine loading robots and CNC processing machines have long been part of factory automation.

Specially developed software is available for each individual process step. However, this software has always been developed and optimized for each of the respective types of machining or also for robot handling. The separate programming may cause a gap between each individual process step. To overcome this gap, an additional tool may be required.

At CENIT, we believe that there is be a better solution. Leo Bartevyan, Senior Account Manager, Digital Factory Solutions, explains, “FASTSUITE supports industrial processes by the means of OLP/PLM software that pursues a new approach. This approach sets the conditions for early-stage programming with exact parameters for each technology, conducted by the designers or the workpiece itself. The program would be created autonomously from the data as opposed to traditional programming of machines and robots.” In simple terms, the goal is to generate a robot path or a machining program directly from the provided CAD data. The software that Cenit is currently developing allows for programming and simulation of additive machining processes, independently of whether material is applied, transported or removed. Our product does not only question the existing programming protocols but intends to break them. What might look like a conventionally programmed process, is in reality much more than meets the eye.

Leo Bartevyan is not concerned with optimizing the existing process here and there. “We are developing the next generation of software.” This software would have to be both integrative and flexible to the extent that it can adapt to existing hardware and control structures on all levels. Oliver Moschner-Schweder, Product Manager Arc Welding at Fanuc Germany, says, “In the case of Fanuc, it is simple because the controls of robots and the CNC of processing machines are structured in a similar way.”

First, the designed workpiece is virtually disassembled into its individual layers and a robot path is generated for each layer. This creates a 2D process that is known from layer welding. Oliver Moschner-Schweder sees the motion data generated from the CAD program as a success. “This works really well.” he says. For testing, convenient workpiece dimensions are used. An inquiry for a 1,500 mm long workpiece has been placed. The range of the robot and the machining area of the machine are defined by a set of limits. In build-up welding, a number of so-called cold processes are available and according to Mr. Moschner-Schweder, “CMT currently works best.” In ‘arc printing’, attention has to be paid to the homogeneous application of layers, especially in the boundary areas of the blank - a criterion that also applies to the much more delicate method of 3D printing with metal powder. The production speed, however, is considerably much faster in additively produced blanks than in milling and turning of parts from their solids. In fact, the big plus for additive manufacturing is that certain parts can only be produced from such processes. "The process," says Leo Bartevyan, "is economically ideal for prototypes, individual items and small to medium-sized batches."

The central topic of future experiments will be what measurements have to be considered and where they have to be applied. Neither process times nor time savings could be quantified to date. Only one thing is for certain: Within a reasonable time, deposition welding can produce components of precise dimensions in a way that powder printing cannot compete with, at least not economically.

Arc based Additive Manufacturing

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