Extrusion Finishes & Fabrication

Pinakin Patel and Tej Patel, Techevon LLC, USA

This presentation discusses the various applications of aluminum with special emphasis on the use of aluminum for architectural anodizing and how the selection of the type of finish is critical to the application.  There will be a discussion on how anodizing is uniquely desirable for applications such as marine components, sunroof, and seal tracks for automobile components. Some of the test methods used in the paint industry will be considered along with some side-by-side comparisons of the durability of anodized components as compared to painted components. The phenomenon of filiform corrosion will also be considered as it relates to a painted finish or an anodized finish. Some wear testing will be performed on both finishes to compare durability. Environmental impacts of each finish will also be considered.

M. Rossi, T. Sondermann and G. Neervoot, Alufinish GmbH & Co. KG, Germany

The aluminum market demands new processes and improved technologies suitable to produce attractive finishings on industrial production. In addition to reproducing "stainless steel" colors on aluminum, achieving significantly darker, decorative gray tones is desirable. This is now achievable with the "Decor Gray" process. The latest available technologies in terms of process control, allow one to apply theories and knowledge; by choosing appropriate coloring parameters, both light and dark gray colored oxide layers can be produced in one bath. Depending on the mechanical pretreatment, decorative surfaces with their own characteristics are possible. Coloring is done analogously to the well-known electrolytic two-step coloring process by a special mixture of different metal salts. The incorporation of metals guarantees good light resistance of the incorporated color and offers new design possibilities, especially in the architectural field.

All available technologies suitable for coloring anodized aluminum are described, including the electro-coloring and dipping processes.

Anne Deacon Juhl, AluConsult, Denmark; and Amelie Haupt, Freelance Green Marketing Specialist, Lithuania

Anodizing as a sustainable choice for protection of aluminum is one of the most important topics when talking about sustainable products made of aluminum.  On the one hand, a more sustainable choice can be made by using primary aluminum with a low CO2 footprint (e.g., primary production fueled by wind or solar energy). On the other hand, recycled aluminum is a sustainable choice, too. As aluminum does not change its properties when melted, recycling does not compromise the quality.

Why this is true and how to get around the pitfalls will be elaborated in this paper, mainly as state-of-the-art for the topic, but spiced with case studies. There are a lot of questions to ask, so the five mistakes to avoid when using recycled anodized aluminum (whether you anodize yourself or get your parts from an anodizing supplier), are also presented and how to avoid them.

Andrea Trevisan, Alessandro Guerrini and Stéphane Sénéchal, SAT (Surface Aluminium Technologies) Srl, Italy; and SAT North America – a Division of GEMA USA Inc., USA

In the last few years, cost, and difficulty of finding qualified manpower has increased the research of more automated systems for all the aluminum-related production processes (extrusion, anodizing, vertical powder coating, fabrication). The introduction of new auxiliary machines represents a fundamental step in vertical powder coating lines since it permits the reduction of manpower and an increase in production consistency and quality. The process becomes more repeatable, traceable, risk and damage free, ergonomic, and involves safer and healthier working conditions.

The paper analyzes the evolution and the latest development of automation in vertical powder coating lines, underlying the integration of all the ancillary operations involved in the system: from profile recognition to processes assignment, from powder storage to profile unloading.

David Mann, Syed Ali and Borja Lopez, Innerspec Technologies, Inc., USA

This paper covers the development and implementation of an automated ultrasonic measurement system for tubes using Electromagnetic Acoustic Transducers (EMAT). Extruded tubes are often produced as blanks that will undergo one or more stages of cold drawing. To guarantee the quality of the final product, it is paramount that the blanks are within the required specifications. Traditionally these measurements are taken with manual calipers at discrete points near the tube ends. This is a labor-intensive process that doesn't leave an electronic record, has low accuracy, and is prone to human error.

The EMAT solution implemented provides a dry ultrasonic system, paired with a laser micrometer, which can automatically test the tube samples. The final system provides a full map of the tube shape (thickness, eccentricity, ovality) and can alarm when any value is out of specification. The steps taken during the development of the technique are explained.

George Oh and Ryan Bermingham, Quaker Houghton, USA

The causes in appearance of over-tempered anodized AA6063 due to precipitate coarsening have been reported in detail, with reports focusing on streaking and discoloration on clear anodized metal.  In this study, we look at the differences between commonly used tempers of AA6063, including T4, T5, T6, and T52, after sulfuric acid anodizing under standard industry processes. We examine their performance on AAMA-611 quality tests including ADT, coating weight density, and anodic oxide thickness. We also evaluate the appearance and color of both clear and electrolytically colored anodized parts. These results are analyzed in the context of the alloy metallurgy and show the importance of knowing the temper of each piece of aluminum anodized.

Malgorzata Chojak Halseid, Jon Aaby Møretrø, and Jan Tore Gundersen, Hydro Aluminium Metal, R&D, Norway; and Jan-Olov Nilsson, Retired, Hydro Extruded Solutions, Sweden

An increased demand for products made of post-consumer scrap may lead to somewhat higher levels of trace elements like Fe, Cu and Zn in 6xxx-series aluminum alloys. Therefore, it is important to understand if these trace elements can affect properties of anodized or powder-coated products.

During normal alkaline etching prior to anodizing, one can experience that some grains are etched deeper than others, called “preferential grain etching” (PGE). The effect of Zn, Cu and Mn concentration in 6060 alloy as well as temper on PGE are studied in detail. The etching is also an important pretreatment step before powder coating. The goal of this study is to understand to what degree the etching pretreatment changes the chemistry on the profile surface and its influence on the corrosion properties of the coated profiles.

Jon Møretrø, Eystein Vada, Knut Tveito, and Ulf Tundal, Hydro Aluminium Metal, Norway

Floating crystals are a well-known defect in DC-cast aluminum alloys, associated with low melt temperatures during casting. They take the form of abnormally large, lean grains in the ingot. In this work, AA6063 is cast as extrusion ingot at a reduced temperature, provoking severe floating crystal formation. This material is extruded and anodized.  No anodizing defects are found in the anodized as-extruded surface, even where flow of floating crystals to the surface during extrusion was expected based on the die design. After milling away the profiles' surface layer and anodizing the exposed subsurface structure, reflective marks are found. These are attributed to floating crystals drawn out during extrusion, forming a band of recrystallized grains with leaner alloy composition and thus different anodizing response. The high deformation in the surface layer of extruded profiles likely dilutes this chemical difference, thus avoiding defects in the as-extruded surface.

Alberto Abad Fuentes, Alvarez-Schaer, S.L.U., Spain

Since the early 80's when the first electrolytic coloring technologies were introduced in the anodized aluminum market, advancement has not stopped. Advancing to cover one of the clearly differentiating points between anodizing and powder coating of aluminum: the possibility of choosing from a wide range of colors.

In this presentation we will go through the different existing coloring technologies, and present two new coloring processes capable of reproducibly and accurately obtaining a wide range of light resistance (ISO 2135:2017-10) gray and orange-copper colors for anodized aluminum. It will be shown how these new coloring techniques can be electrically controlled to get the desired tone of gray and orange-copper colors, respectively. The mechanism behind each new coloring process will also be discussed.

Ole T. Midling, Marine Aluminium AS, Norway; and Johnny Pangborn, Metalstar Consulting LLC, USA

Modern product development continues to drive new processes and new applications in old processes, no less in extrusion than in other areas. One little-utilized added-value process applicable to extrusion is Friction Stir Welding (FSW), whereby a high-integrity solid-state weld is formed to join extrusions into structures enabling a higher degree of effective modularization.

The design flexibility imparted by combining extrusions through FSW is a big technical advantage. Close cooperation at the design stage and highly proficient personnel ensure that results comply with all specifications and requirements, with considerable competitive advantage compared with standard process flow.

Based on practical experience within engineering, design, and fabrication of aluminum structures for the marine and offshore industry, coupled with current applications to the production and use of extrusions for automotive components, it is anticipated that FSW will see major opportunities for impact in the near future.

Melih Caylak, Ilyas A. Sari, Zeynep T. Ozen, Tolgahan Cali and Gorkem Ozcelik, ASAS Aluminum A.S., Turkey

This study investigates the three-point bending behavior of an aluminum thin-walled structure through both experimental and finite element analysis (FEA) tests. The aim of the investigation is to compare the results of the FE model with experimental tests to evaluate the accuracy and reliability of the FE method in predicting the mechanical behavior of thin-walled structures. The experimental tests were conducted on a custom-designed test rig, while the FEA was performed using commercial software. The results of both the experimental and FEA tests were analyzed and compared to investigate the load-deflection response and stresses induced in the structure during the bending process. The findings suggest that the FE method provided an accurate prediction of the mechanical behavior of the thin-walled structure, and that the FEA model can be a reliable tool for predicting the behavior of similar structures in engineering applications.

Anne Tofte, Esma Senel, Anders Nordeide, and Randi Mørkrid, Hydro Aluminium Metal, Norway

Various surface defects are observed on surface treated profiles.  In many cases, such defects may not be visible until surface treatment is applied or even during the end use.  This makes failure analysis very complex, as various post-extrusion steps may hide the root cause.  Additionally, the evidence of an issue may be gone during one of the processes, mostly during surface treatments. Inspection of such cases requires competences of both relevant analysis methodologies as well as understanding of the processes along the value chain of a product. In this paper we discuss selected examples of real surface defect cases that were visible only after powder coating and anodizing. Although the defects seemed similar, investigations showed unexpected root causes that could be tracked to either casting, extrusion, surface pretreatment or the powder coating step.

Fatih Zafer Zorlu and Baris Yazici, ASAS Alüminyum, Turkey

Statistical analysis of narrow extrusion production tolerances and international extrusion tolerance standards (EN 755-9, EN 12020, ANSI H35-2 etc.) is presented as an experimental comparison.  While the automotive sector requires a Cpk value of 1.67 for capability analysis, which is generally requested at the sample stage, it demands a Cpk value of 1.33 in mass production.  It is difficult to reach these levels due to demands over the limits on extrusion method capabilities.  Within the study’s scope, the cover plate product used in the battery transport system in 6063-T6 and 6082-T6 conditions and combined with friction stir welding (FSW) is taken as a basis.  Optimal parameters are determined by the experiment design, capability, feasibility, capacity, etc., in two different alloys.  The study is completed by making analyses and sent to the OEM in the prototype phase, and the design was returned and reference made for the engineering change.

Tony Da Silva and Derek Byrne, Apex Aluminum Extrusions Ltd., Canada

Customers continue to push for tighter color tolerances in the anodizing process. These tighter tolerances can lead to higher rates of rework and scrap. Although the study of process capability is well understood for most unidimensional measurements, the capability of color becomes challenging due to its three-dimensional measurement (L a b). The presented paper provides a clear understanding of the minimum color difference (delta E) that one's anodizing process generates and discusses the effects of several variables on the resultant color. This process capability methodology can be applied for the color measurement in anodizing, painting, and any other processes that generate color.

Andrea Trevisan and Alessandro Guerrini, SAT (Surface Aluminium Technologies) Srl, Italy; and SAT North America – a Division of GEMA USA Inc., USA

Many of the current anodizing lines are still partially or totally subjected to human management when dealing with process scheduling, productive flow, and production priorities. This is mainly due to the nature of the process where different batches may need to follow paths with possible interferences, and human action is still regarded as the only possibility to straighten out possible conflicts.

The ability to implement production management automatic routines and combine them with all the process control data that are available in a modern plant, can really boost the efficiency and productivity of an anodizing line.  This paper is mainly an introduction of a new programming approach with a completely renewed control technology that has led to several advantages in terms of process uptime improvement and achievement of quality targets like, for example, coating accuracy and color tone achievement independently from continuous human control.

Jude M. Runge, CompCote International, Inc.; Peter Totaro and Fred Schaedel, Aerotech Processing Solutions, USA

With increased recycled content, alloys become more complex, exhibiting intermetallic particles of varying solubility in the matrix aluminum, as well as in the anodizing electrolyte. These variations pose challenges to metal finishing, especially anodizing, because the anodic oxide grows and develops from the substrate material. In this paper, the metallurgy of some recycled alloys used in the aerospace/aircraft industry will be presented. The impact of slight variations in alloy content, and the size, shape and distribution of resultant intermetallic particles will be discussed as to how they impact anodic oxide growth and development. The reactions that occur in the first 0-5 minutes of anodizing, together with predictions for the reactions that occur with different intermetallic particles and phases are explained, as well as strategies to mitigate their effects on the anodic oxide.

Raffaele D’Andrea, Emmebi srl, Italy

This paper will provide an overview of the latest robotic technologies for handling aluminum profiles. Up-to-date vision systems for robotic packing of aluminum profiles with an innovative robotic configuration (e-Vision II), a robotic system for hanging aluminum profiles on vertical powder coating lines (Patent Pending), and other robotic applications to profile handling and packing are presented.

Jun Ma and Torgeir Welo, Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology (NTNU), Norway

Today’s increased demand for automotive lightweighting creates many opportunities for aluminum extrusions. Although extrusion is effective for producing 2D lengths, its full potential can only be realized through integration with other value-adding manufacturing operations. Forming is perhaps the most important downstream operation since it provides opportunities for accommodating functionalities, integration, packaging constraints, part consolidation, etc. However, successful forming requires knowledge-based strategies due to complex (inter)relationships between materials, technologies, parameters, and mechanisms. In this systematic analysis—composing two papers Part I and Part II—we aim to combine hindsight, outsight and foresight to create new insights into successful forming of aluminum extrusions. Part I presents the historical use of aluminum extrusions in structural automotive applications, along with an overview of theoretical foundations and their implications when considering practical aspects such as manufacturing chains and quality control strategies in industrial practice. Part II focuses on recent advances in forming technologies and perspectives.

Jun Ma and Torgeir Welo, Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology (NTNU), Norway

Today’s increased demand for automotive lightweighting creates many opportunities for aluminum extrusions. Although extrusion is effective for producing 2D lengths, its full potential can only be realized through integration with other value-adding manufacturing operations. Forming is perhaps the most important downstream operation since it provides opportunities for accommodating functionalities, integration, packaging constraints, part consolidation, etc. However, successful forming requires knowledge-based strategies due to complex (inter)relationships between materials, technologies, parameters, and mechanisms. In this systematic analysis—composing two papers Part I and Part II—we aim to combine hindsight, outsight and foresight to create new insights into successful forming of aluminum extrusions. Part I presents the history, foundations, and practical implications of automotive aluminium extrusions. Part II herein presents the recent advances in key forming operations—calibration, stretch forming, bending, and hydroforming. Furthermore, we share the perspective on aluminum extrusion forming technologies within the context of Industry 4.0 and carbon-neutrality.