Towards Robotic Fabrication in Joining of Steel

2014

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Welding in the World

This paper presents a concept and practical topics involved in digitized production. The term “production” denotes the design, fabrication, and service life of a product, which in this case elaborates on welded steel structures. This includes the required information for guiding all the process stages of the chosen material back to its re-melting, following the material flow in a fully digitized form. This concept enables an increase in production quality at a higher level while minimizing the risk of human errors. Automation of the short-run production of steel structures for demanding applications is also a key goal, together with securing a cost-efficient process. Typically, such structures are fabricated from high- or ultra-high-strength steels. Though challenging, reaching these aims seems to be realistic by applying advanced fatigue design methods, using high-quality robotic welding and receiving information about the real loading of the structure.

Mechanics & Industry, 2023

In conjunction with mechanical joining processes. Mechanical joining processes play a key role for the realization of multi-material lightweight structures, which are essential with regard to environmental protection. However, joining of dissimilar high-strength materials is challenging due to the varying properties of the joining partners and due to their high flow stresses and often limited ductility. Thus, the evolution of established processes as well as the development of innovative and highly productive joining technologies are necessary. Requirements for a highly volatile production environment are versatility, flexibility, resilience and robustness. Within this contribution, current trends and innovations related to selected mechanical joining processes for enabling the material mix are outlined in order to point out opportunities to address these requirements in the future. In this context, joining using cold formed pin structures is presented as a promising approach for connecting dissimilar materials like metals to fibre-reinforced plastics. Furthermore, it is shown how the shear-clinching technology can be combined with a process-adapted application of locally limited heat treatment in order to promote the joinability and control the material flow during joining. A novel approach for reducing process forces and expanding process windows is the use of ultrasonic assistance for mechanical joining operations, which is demonstrated by the example of a nut staking process with superimposed high frequency oscillation. As concerns the widely used self-piercing riveting technique, current research activities relate not only to the further development of the joining process itself, for example by combining self-piercing riveting and tumbling, but also to the use of new rivet materials like high strain hardening stainless steels. In addition, the evolution towards mechanical joining 4.0 against the background of data-based process control in conjunction with of mechanical joining processes is also subject of the considerations.

Direct metal laser sintering (DMLS) is an additive manufacturing (AM) technology for the fabrication of near netshaped parts directly from computer-aided design (CAD) data by melting together different layers with the help of a laser source. Its application for manufacturing three-dimensional objects represents one of the promising directions to solve challenging industrial problems. This approach permits to extend significantly the freedom of design and manufacture by allowing, for example, to create an object with desired shape and internal structure in a single fabrication step. The design of the part can be tailored to meet specific functions and properties (e.g. physical, mechanical, chemical, biological, etc.)

1998

With increasing part complexity and requirements for long production runs, tooling has become an expensive process that requires long lead times to manufacture. This lengthens the amount of time from "art to part". Rapid tooling via stereolithography (SLA), filled epoxies, etc. have been stopgap measures to produce limited prototyping runs from (10 to 500 parts). This gives poor dimensional analysis and does not allow for limited production runs of 1000+ parts. The method of producing prototype tooling with a powdered metal process has been developed that produces tooling with a hardness greater than 35 HRC and total shrinkage less than 0.5%. This tooling process manufactures production ready tooling that will perform extended cycle runs (100,000+). Manufacturing of this tooling takes 1 to 2 weeks and will compare favorably with production grade steel tooling. Originals drawn in 3D CAD can be used to prototype the master that will allow for the production of the rapid metal tool set. process starts with a rapid prototyped model made by whatever process is desired or a machined master. For this paper a Sander's Model Maker II® rapid prototyping machine was used to fabricate the model. After the model of the tool set is made, a silicone rubber negative is cast around that model. After the silicone rubber model is made, a heated slurry of metal powders and polymers is poured into the mold to create the green tool set. The tool set is left to cool, and then removed from the silicone rubber mold. The tool set is then debound and sintered to produce a final tool set with properties approaching hardened tool steel.

IOP Conference Series: Materials Science and Engineering, 2019

Curved buildings and structures are getting popular and digital fabrication of the structural steels has been successfully tried in several ways. This study presents a development of a robotic system cutting structural steels and marking texts on the steels using digital information of shapes. A configuration of the overall system is explained based on functional decomposition of conventional cutting systems. The cutting system consists of a robotic system and a handling system, and the main functions of the cutting system are classified as translation, orientation, alignment, and cutting. A digital model of the system was created and tested in a robot simulation system. A robot tool-path generation system was also developed. The tool-path generation system uses the DSTV file, an industry standard for the shape of a structural steel, to generate robot job files. This study also provides robot workspaces in which the cutting tool can safely access and cut the workpieces. The proposed...

International Journal of 3D Printing Technologies and Digital Industry, 2021

Additive manufacturing technologies are applied in different industrial fields. It is possible to produce 3D parts in complex form at a lower cost with faster production capability using additive manufacturing compared to traditional subtractive manufacturing. Robotic welding-based wire arc additive manufacturing (WAAM) is a novel additive manufacturing technology which offers various solutions. Many products can be produced through the additive manufacturing in the fields of defense, aerospace, and automotive industries. In this study, multi-material metallic parts were produced by depositing ferritic ER 70 S-6 and stainless steel ER316L welding wires using robotic WAAM technology. Detailed microstructural analysis and hardness tests were conducted on the manufactured samples including interfaces between two different materials. Characterization of Fe-austenite weld interfaces has shown the presence of hard phases due to migration of hardening elements. The microhardness examination revealed that the highest hardness values are recorded at the bimetallic interface due to Fe and C migration through the interface layer.

2018

Challenging energy efficiency and pollution emissions goals have been set forth in civil aviation as in other transport sectors. Developing and implementing new manufacturing processes is key to face these challenges. However in load carrying structures, the fulfillment of safety regulations and well established design criteria while simultaneously incorporating new materials, processes and designs presents significant challenges. A multi-disciplinary approach is required to address the complex issues associated with the implementation of new materials and technologies in all product development stages, design, development, manufacturing, operation and maintenance, and finally disposal and recycling. This thesis aims at advancing the knowledge related to manufacturing technologies of lightweight integral metallic structures. Current fuselage design use differential structures assembled through riveting. The advent of newer joining methods prompt the possibility for new integral structures with reduced weight and easier manufacturing automation. Through the development of manufacturing technologies for integral metallic components, as presented in this study, competitiveness of metallic structures regarding composite structures is kept and with it, the available options of structural designers are increased. Although the emphasis of this PhD project is on aeronautical applications, the proposed technologies may be extrapolated to diverse industries with disruptive potential. The radical disruptive nature of the adoption of butt joining friction stir welding (FSW) in metallic fuselages, especially at major component assembly level, has hinder its fast adoption, even though the technology potential has been demonstrated in previous works. Geometric tolerance management requirements along with requirements for complete new tooling and quality assurance processes, have pushed fully integral butt-joined FSW fuselages into the future. One variation of FSW that could address the gap between the state of the art riveting process and the disruptive FSW butt-joining is overlap FSW, albeit this methodology results in lower mechanical performance, and lower weight and lead time savings. To overcome these drawbacks a new hybrid joining method, combining overlap FSW and adhesive bonding was developed. The aim of this thesis is to develop an innovative joining method for fuselage components at major component assembly level. Considering the complexity of technology infusion processes in aerostructures, an initial study was made on technology adoption and product development with special focus on the aeronautical industry. Following this study, a state of the art of relevant joining technologies was made, encompassing issued patents in this field to assess possible future trends. Upon having a well established literary study, v vi the development of the technology in itself was done. Mechanical performance of the joints was assessed and benchmarking against FSW and adhesive bonding was made throughout the joining process development. The high ductility and fracture toughness of the adhesive associated with the better stress distribution in the hybrid joints overlap led to significant mechanical performance improvements, both in quasi-static loading and cyclic loading. Some scenarios of technology infusion were made and studied for weight and assembly labor time changes. Fatigue testing of a proposed joint design was made and the results were benchmarked against riveted and butt-joined FSW joints. Similar or higher fatigue strength than riveted joints was found, while structural weight of the joints was reduced. The potential for a new joining methodology for integral metallic structures was demonstrated in this thesis. It aims to serve as a catalyst for future development within this field, expanding the design applications and technology maturity levels.

This paper discusses the way of enriching design methods that embrace a broader spectrum of multiple disciplines in the milieu of digital fabrication. In the first part of this paper, the potential of robotic fabrication and different strategies of design and fabrication are generally discussed; And in the second part a typical case study of robotic fabrication is represented in detail. The Robotic 6-Axis 3D Printing project (Also known as Robotic Extrusion), from Shanghai Digital future 2014 summer workshop, indicates the integration of design concept, parametric tooling, bio-science, materiality and robotic technology.

Springer Tracts in Advanced Robotics, 2014