Additive Manufacturing of Metal Parts by Welding

Proceedigs of the 15th IFAC Symposium on Available online at www.sciencedirect.com Information Control Problems in Manufacturing Proceedigs of theOttawa, 15th IFAC Symposium on May 11-13, 2015. Canada Information Control Problems in Manufacturing May 11-13, 2015. Ottawa, Canada

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Additive Manufacturing of Metal Parts by Welding Additive Manufacturing of Metal Parts by Welding Silva, R. J.1 · Barbosa, G. F.2 · Carvalho, J.3 G. F.2 · Carvalho, J.3 Silva, R. J.1 · Barbosa,  1

  Brazil 

University of Sao Paulo, Sao Carlos, – Production Engineering department Zip code 13566-590 (Tel: 55 16 99606-5650); e-mail: [email protected]. University of Sao Paulo, Sao Carlos, Brazil – Production Engineering department Zip code 13566-590 (Tel: 55 16 99606-5650); e-mail: [email protected]. 2,3 University of Sao Paulo, Sao Carlos, Brazil – Mechanical Engineering department Zip code 13566-590 (Tel: 55 16 99761-3151); e-mail: [email protected] ; [email protected]. 2,3 University of Sao Paulo, Sao Carlos, Brazil – Mechanical Engineering department Zip code 13566-590 (Tel: 55 16 99761-3151); e-mail: [email protected] ; [email protected]. 1

Abstract: New technologies can be justified with the advent of the additive manufacturing, excels by its flexibility in manufacturing parts of various geometries, good accuracy and material waste reduction Abstract: New technologies can be the justified with the advent of the additive manufacturing, excels by its savings. This circumstance requires application of techniques to determine the reliability of the results flexibility in manufacturing parts of various geometries, good accuracy and material waste reduction in the deposition of layers in order to have a good accuracy. This work aims to present a new technology savings.to This circumstance requiresfocusing the application of techniques to determine the reliability of the results applied additive manufacturing, on accuracy in the deposition of layers, lower cost and user in the deposition of layers in order to have a good accuracy. This work aims to present a new technology friendliness man-machine. New method was proposed in order to obtain advantages regarding the use of applied additive manufacturing, focusing accuracyplasma in the deposition of obtain layers, the lower cost and user Plasma to welding process. An apparatus for on generating was used to arc. Devices to friendliness man-machine. New method was proposed in order to obtain advantages regarding the use of control speed and position were used to determine essential variables in the deposition of layers’ process. Plasma welding process. An apparatus for generating used to obtain theinarc. Devicesthe to Correlated magnitudes helped in determining Efficient plasma Model was of Deposition for use offsetting control speed and position were used to determine essential variables in the deposition of layers’ process. geometric and thermal errors. Computer simulations were applied to the new concept of deposition and Correlated magnitudes helpedsystem in determining Efficient of Deposition in offsetting the efficiency of the presented was performed, but Model no experimental resultsfor areuse provided herein. the geometric and thermal errors. Computer simulations were applied to the new concept of deposition and the efficiency of the presented systemMetal, was performed, but no Hosting experimental results areAll provided herein. Keywords: Additive Manufacturing, Deposition, Layers, Welding. © 2015, IFAC (International Federation of Automatic Control) by Elsevier Ltd. rights reserved. Keywords: Additive Manufacturing, Metal, Deposition, Layers, Welding.  1. INTRODUCTION

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1. INTRODUCTION Due to the high competition in the additive manufacturing industry, the focus on developing new technologies become Due to the competition in the additive manufacturing evident, thushigh requiring more detailed qualification processes. industry, the focus on developing new technologies become The competitiveness in this sector requires the introduction of evident, thus requiring more detailed qualification processes. new machines and new concepts seeking greater flexibility in The competitiveness this sectorand requires theofintroduction of designs, lower costs, in production quality manufactured new machines and new concepts seeking greater flexibility in products. To illustrate this concern, there may be mentioned designs, lower costs, production and quality of manufactured industries that produce thousands of parts of the most diverse products. To illustrate this concern, there may be mentioned geometries, whose manufacturing processes must be industries that produce thousands of parts of the most diverse continuously improved in order to obtain flexibility, quality geometries, whose manufacturing must be and production efficiency. On this way,processes the implementation continuously improved to obtain flexibility,is quality of an automated system infororder additive manufacturing highly and production efficiency. On this way, the implementation desirable. Some parts manufactured in machine tools require of an system additive manufacturing is highly the useautomated of more than onefor type of manufacturing process. The desirable. Some parts manufactured in machine tools require manufacturing processes with this type of machinery require the use labor, of more one type of manufacturing process. The skilled arethan generally time-consuming productions and manufacturing processes with this type of machinery require have a high level of uncertainty when related with complex skilled labor,The areevolution generallyoftime-consuming geometries. technology and productions developmentand of have a high level of uncertainty when related with complex new integrated systems related to the manufacturing process geometries. The evolution of technology development of allow the execution of tasks previously and performed only by new integrated systems related to the manufacturing process men and today is performed by machines [1]. allow the execution of tasks previously performed only by men and today is performed by machines [1].

2. TECHNOLOGICAL TRENDS 2. TECHNOLOGICAL From the mid of 70s, theTRENDS technological evolution has brought the machine tools on the productive environment, introducing Fromdesign the midmethodologies of 70s, the technological evolution has brought new related to the systematization of the machine tools on the productive environment, knowledge, guidelines for development of projectsintroducing focused to new manufacturing, design methodologies related to the systematization of the assembly, adjustments, among others, knowledge, guidelines for development of projects focused to allowing rationalization and optimization of machine tools the manufacturing, assembly, adjustments, among others, development. allowing rationalization and optimization of machine tools development. Among the several innovations, in 1987 appears the Additive Manufacturing process initially called Rapid Prototyping in Amongtotheenhance several innovations, appears the Additive order essentially inall1987 aspects involving the Manufacturing process initially called Rapid Prototyping in manufacturing of products. However, the application of this order to enhance essentially all aspects involving the technology has a significant impact concentrated in the area manufacturing of molds, products. the application of this of tools (patterns, jigsHowever, and accessories used during the technology has a significant impact concentrated in the manufacturing process). Natural imperfections during area the of tools (patterns, jigs and during melting of metal molds, alloys and the accessories geometricalused aspects of the the manufacturing imperfections during with the deposited layersprocess). leads to Natural the impossibility of knowing melting of metal the alloys and the geometrical the absolute certainty manufacturing process byaspects layers. of Every deposited layers leads to the impossibility of knowing with process that generates electrical arc demands high control of absolute certainty the manufacturing process by layers. Every its variables. process that generates electrical arc demands high control of its variables.

2405-8963 © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Peer review under responsibility of International Federation of Automatic Control. Copyright © 2015 IFAC 2392 10.1016/j.ifacol.2015.06.433

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2.1 Rapid Prototyping The rapid prototyping technologies increasingly as interesting technology in the additive manufacturing, since they use the technique of adding layers. These have major advantages over other processing methods due to the versatility in the production of free and complex shapes, by computer aided CAD / CAM [2]. With the progress of rapid prototyping, other names emerged to better express the technology that developers and users have thought better express it, translating succinctly all the capability required. They are: 3D printing, layer fabrication, manufacturing by layers, manufacturing of free forms and solid free training [3]. These terms were entered in the industry in order to designate processes of creation of systems or parts of them, in order to represent a possible part or object before its final version. In other words, the meaning of it is to create a fast object to be a model-based or prototype, generating other models improved from these ones. Rapid Prototyping process helps you validate your part design and gets your product to market faster by making sure your production tool is right the first time. Figure 1 shows the way to get your zinc or plastic parts into production.

Nowadays, the rapid prototyping nomenclature has been considered inappropriate, even by not describe some of the more recent cases of this technology and improvements in the quality of these machines production have created a much stronger correlation with the final product [5]. 2.2 Additive Manufacturing Considering the rapid prototyping nomenclature a limited term, a technical committee formed by the body of the ASTM (American Society for Testing and Materials) agreed on a new technical term to be adopted, called Additive Manufacturing (AM). The purpose of this new nomenclature is clear that some machines with this technology can build final objects from part models generated in CAD without the need for further planning. Moreover, the problem of mentioning basic construction technique of this technology (overlapping layers) was resolved with the use of the new term [6]. In the manufacturing of a part held by additive manufacturing each technology shares the same technical guidelines: the computer analyzes a solid modeled on virtual environment (CAD) and it defines the manufacturing of the object through layer. These layers are systematically recreated and combined to form a 3D object [7]. According to [8], some stages of the process by addition of materials have been determined: 

Modeling for obtaining the 3D model on CAD system;

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CAD models conversion to "STL" format (surface tessellation language or standard tessellation language);

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Check if no error occurred in the conversion;

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Creation of fixtures;

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Orientation to manufacturing (vertical / horizontal);

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Slicing and preparaion for manufacturing (construction parameters and numerical control program);

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Manufacturing (model execution in machine);

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Post-processing (removal of fixtures and resin excess, post-curing and finishing of surface).

Fig. 1. Rapid Prototyping example (source: [4])

As [12], the reasons of rapid prototyping are: 

To increase effective communication;

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To decrease development time;

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To decrease costly mistakes;

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To minimize sustaining engineering changes;

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To extend product lifetime by adding necessary features and eliminating redundant features early in the design.

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Additive Manufacturing enables the fast, flexible and costefficient production of parts directly from 3D CAD data – a technology that helps you to perform your tasks in an innovative way [9].

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Figure 2 illustrates the steps of adding layers process from the design to the final part (end item):

2.4 Welding on Additive Manufacturig All additive manufacturing equipment sold today is based on the concept "layer by layer" and the material to be processed is what makes these devices different. However, the additive manufacturing using metal alloys is still restricted to a few components. The metal deposition in additive manufacturing technology may occur at different arc welding process (MIG, TIG and Plasma) Electro Beam Melting, Sective Laser Melting, Laser Cladding, Powders Sintering, among others [11]. The geometry of the part or object to be manufactured is a determining factor for the additive manufacturing process to be adopted. Small parts with complex geometries require low deposition rates, and thus the laser processes, micro-plasma and electron beam are the most suitable. Since with the bigger pieces of processing processes using higher deposition rates, for example, arc welding. The insertion of the welding in the context of additive manufacturing makes the knowledge in this manufacturing process to be a great importance for the early development of the manufacturing technology, thus enabling fast evolution of this process and tests performed. Currently, the increase of competitiveness in the additive manufacturing is evident with the use of alternative processes that use the electrical arc.

Fig. 2. Additive Manufacturing process

2.3 Welding 3. WORK MOTIVATION Due to its relative operational simplicity, welding has become the most important industrial process used for manufacturing of metal parts. Considered as a joining method, this process or its variations are used for the deposition of material on a surface in order to recover worn parts or to form a coating with special characteristics. It was from the 19th century that the welding technology has emerged on the world scenario contributing to the apperance of fusion welding processes with the discovery of acetylene by Edmund Davy, Sir Humphrey Davy experiences (18011806) with the electrical arc and with the development of production sources of electricity [10]. The electrical arc used as a source of energy is the fusion welding process more used industrially Figure 3 represent a pioneer conception of this process.

The motivation of this work is to develop and propose an innovated method for using in additive manufacturing. A proposed apparatus for generating plasma is applied to obtain the electrical arc. Most of processes widely employed in the industries are done using laser process to generate the electrical arc. In this paper the novelty is to propose a specific method to perform additive manufacturing by plasma as a welding process for metal parts fabrication.

4. METHOD PROPOSED This research aims to improve control, understanding and the influence of the arc welding process’ variable in the additive manufacturing. The proposed method has the following objectives: 1.

Develop a controlled mechanical device named torch holder, to generate speed and constant or variable position on displacement axis for deposition welding layers.

2.

Check parameters such as: level of current, current pulse frequency, operating voltage, arc length, torch travel speed in translation of axes, feed speed of filler metal, composition of filler material, distance from the outlet point to the part, torch angle related to the piece, type of

Fig. 3. Fusion welding process

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shielding gas or flow, proportionality in the mixture of shielding gases and following the deposition of layers. 3.

Relation study between arc welding parameters and weld bead geometry in individual and multi-layered deposition

4.

Development of process control algorithms based on this study.

5.

Evaluation of the behavior and stability of the process;

6.

To investigate the suitability of the welding process used for depositing other alloys.

5. EXPECTED RESULTS The work proposal aims to integrate the control systems of individual parameter in a closed loop system composed by software of parameters’ control and data processing, data acquisition interface and an integrated control interface governed by computer system. The machine has been able to control the main 03 parameters as explained below: a)

4.1 Experimental procedure The controlled mechanical device named torch holder (Figure 4) proposed herein has been developed in order to control the speed and position on translation of XY axis displacement for deposition of welding layers.

Current level: this parameter set as the maximum value for the process according to the characteristics of the metal to be deposited with the travel speed and temperature of surface, pulse rate, or a combination of all parameters in order to obtain the optimal point of melting. It is controlled by software through the setting of current parameter of the generator control interface.

b) Current pulse’s frequency: the system’s ability to operate in a pulsed mode with parameter of variable frequency that confers flexibility to deposition rate adjustment, controlling of string surface characteristics for each alloy, and temperature in spray mode. The interface control operates in the changing of parameter in the current generator.

Some features of the proposed system are presented as high control of the basic parameters for process’ stability when it’s compared to existing technologies for welding alloys. The Figure 4 illustrates the torch holder proposed: z

c) y

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x TOCH HOLDER

Voltage of operation: this parameter depends on the characteristics of metal deposition as well as its temperature during the melting, the frequency of the current pulse, the arc length and level of current. This parameter is set directly on current generator by the interface of control.

All modelling, simulation and analysis of dynamical systems have been developed in Simulink software. Fig. 4. Torch holder The construction of a Manufacturing Additive component has several issues to determine the success of the procedure [14]. Deposition of the first string is among the factors that require careful consideration. For this first string, it’s looked for a good metallurgical bond with the substrate and a suitable thickness and morphology. On tests for a "wall" formation by deposition of multiple layers, the morphology and microstructure of deposition are analysed. Morphology control aims to assure the continuity, height variation or defects of strings. The continuity of the strings is associated to the selection of the process parameters. An improper selection may result in strings with wide variation in width or lack of fusion on the welding metal [15].

6. CONCLUSION Based on this research and development work, an innovated method for using in additive manufacturing is presented. The differential of this paper is to propose a specific method to perform additive manufacturing by plasma as a welding process for metal parts fabrication and that differs the most of processes used in the industries as described above. It is expecting a break of paradigms in the environment of Additive Manufacturing for metallic parts fabrication. Also, it will be used for new trials and as a source of data for studies related to this technology. During the development of this research, new proposals come up for future works and they are listed below: 

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Development of an additive manufacturing machine with the developed technology;

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Use of hardware and software co-design technology for embedded systems, aiming to exchange of highperformance controllers for FPGA (Field Programmable Gate Array).

[14] ALBERTI, E. A. SILVA, L. J.; OLIVEIRA, A. S. C. M. (2014). Manufatura Aditiva: o papel da soldagem nesta janela de oportunidade. Soldag. insp. [online]. vol.19, n. 2, ISSN 0104-9224.

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Adjust the welding process used for the deposition of other alloys.

[15] MARTINA, F. et al. (2012). Investigation of the benefits of plasma deposition for the additive layer manufacture of Ti6Al-4V. Journal of Materials Processing Technology, p.13771386.

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