Fraunhofer ILT and Aachen University develop streamlined Open Vector Format software for PBF-LB

April 27, 2022

A test run of the OVF software using the standard test model Stanford Bunny (Courtesy RWTH DAP)
A test run of the OVF software using the standard test model Stanford Bunny (Courtesy RWTH DAP)

Research work undertaken by scientists at the Chairs of Laser Technology and Digital Additive Production (DAP) at RWTH Aachen University, in cooperation with the Fraunhofer Institute for Laser Technology (Fraunhofer ILT), both located in Aachen, Germany, have developed a method of streamlining data volumes while simultaneously increasing data depth of 2D manufacturing data for Laser Beam Powder Bed Fusion (PBF-LB) Additive Manufacturing. The resulting Open Vector Format (OVF), in addition to a significant reduction in data volume, is also said to enable the efficient transport of component metadata to the production plant.

In the PBF-LB process, the manufactured component is planned as a 3D model via computer-aided design (CAD) software and placed in the virtual build space of the manufacturing plant. Next, this model is converted into a collection of 2D layer data of the component (known as slicing), which serves as input on the layers that are melted one by one in the powder bed. This data output, however, doesn’t have a standard format, and some can miss relevant information. This was the impetus to develop the Open Vector Format.

The technical basis for OVF is the widely used serialisation technology Protocol Buffers (’Protobuf’). Protobuf handles the transfer of information from complex structured data objects into a byte stream (e.g., storing information in a file or sending data via networks). Using the Protobuf code generator infrastructure enables broad compatibility and support for several dozen programming languages and platforms. The researchers were also said to have been able to exploit some of Protobuf’s other advantages, such as high performance, compact binary storage of all data, as well as flexible forward and backward compatibility. In addition, it is possible to efficiently transport PBF-LB Additive Manufacturing process-relevant metadata – such as the manufacturing parameters, laser power, and scanning speed – along the process chain.

The definition of the technology-specific data structures is done in a low-threshold way by open-source publication via the OVF Github repository, facilitating access for both industry and research. The structures are optimised for broad compatibility and are flexibly extendable to be able to map the latest digital developments in Additive Manufacturing. A broad portfolio of tools such as converters for legacy formats (e.g., converting CLI to OVF files) or integrity check routines (e.g., checking whether contours are closed, parameters are assigned and layers are without gaps) are also available on Github.

OVF can be used to address the versatile requirements for an ideal format for processing 2D layer output data in the PBF-LB process. In addition, the format can also be used for other scanner-based laser processing applications, such as laser micro structuring and polishing.

The researchers believe that the applications of OVF are versatile, as streamlining the link between the digital and physical process chain via OVF enables an efficient manufacturing process. The manual effort of data transfer to the plant can be significantly reduced and, thus, automated with the help of this standardised format.

For this reason, OVF is utilised in the multi-organisation project ‘Industrialization and Digitization of Additive Manufacturing for Automotive Series Processes’ (IDAM). IDAM uses OVF to combine the output of different programs or automated sub-steps along the process chain across manufacturers and to merge the corresponding data. It is thus part of the scalable, modular, and automatically linked PBF-LB Additive Manufacturing production concept, which was developed within the project to flexibly control and utilise the individual process steps.

OVF is also used in the project ‘Slicing for industrial 3D printing in a protected cloud environment’ (ProCloud3D).’ Here, OVF is said to enable layer-by-layer streaming of PBF-LB build jobs out of the cloud directly to the plant. By sequentially sending the layer data – including the parameters, which are also contained in OVF – the exchange of sensitive component CAD files can be avoided. The newly developed format is said to thus makes a significant contribution to the project goal of secure data transfer in Additive Manufacturing.

The ‘Internet of Production’ (IoP) excellence cluster also utilises OVF. Due to its openness and language independence, it enables the generation of individual scan jobs for the post-processing of flawed surfaces. Using this technology, controllable scanners, which can be supported by data analysis in the cloud, are developed. After a layer has been fabricated, for example, a photo of the surface can be sent to a data centre. There, image analysis generates a post-processing OVF file that contains information about insufficiently exposed areas. In the next step, this file is sent to the scanner and the necessary post-processing is done. Following this post-processing, the currently active job is continued, or the next layer is additively manufactured.

More information about the Open Vector Format software is available here.

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