8,154 research outputs found
Thin-Wall Machining of Light Alloys: A Review of Models and Industrial Approaches
Thin-wall parts are common in the aeronautical sector. However, their machining presents
serious challenges such as vibrations and part deflections. To deal with these challenges, di erent
approaches have been followed in recent years. This work presents the state of the art of thin-wall
light-alloy machining, analyzing the problems related to each type of thin-wall parts, exposing the
causes of both instability and deformation through analytical models, summarizing the computational
techniques used, and presenting the solutions proposed by di erent authors from an industrial point
of view. Finally, some further research lines are proposed
Intelligent systems in manufacturing: current developments and future prospects
Global competition and rapidly changing customer requirements are demanding increasing changes in manufacturing environments. Enterprises are required to constantly redesign their products and continuously reconfigure their manufacturing systems. Traditional approaches to manufacturing systems do not fully satisfy this new situation. Many authors have proposed that artificial intelligence will bring the flexibility and efficiency needed by manufacturing systems. This paper is a review of artificial intelligence techniques used in manufacturing systems. The paper first defines the components of a simplified intelligent manufacturing systems (IMS), the different Artificial Intelligence (AI) techniques to be considered and then shows how these AI techniques are used for the components of IMS
Latest Developments in Industrial Hybrid Machine Tools that Combine Additive and Subtractive Operations
Hybrid machine tools combining additive and subtractive processes have arisen as a solution to increasing manufacture requirements, boosting the potentials of both technologies, while compensating and minimizing their limitations. Nevertheless, the idea of hybrid machines is relatively new and there is a notable lack of knowledge about the implications arisen from their in-practice use. Therefore, the main goal of the present paper is to fill the existing gap, giving an insight into the current advancements and pending tasks of hybrid machines both from an academic and industrial perspective. To that end, the technical-economical potentials and challenges emerging from their use are identified and critically discussed. In addition, the current situation and future perspectives of hybrid machines from the point of view of process planning, monitoring, and inspection are analyzed. On the one hand, it is found that hybrid machines enable a more efficient use of the resources available, as well as the production of previously unattainable complex parts. On the other hand, it is concluded that there are still some technological challenges derived from the interaction of additive and subtractive processes to be overcome (e.g., process planning, decision planning, use of cutting fluids, and need for a post-processing) before a full implantation of hybrid machines is fulfilledSpecial thanks are addressed to the Industry and Competitiveness Spanish Ministry for the support on the DPI2016-79889-R INTEGRADDI project and to the PARADDISE project H2020-IND-CE-2016-17/H2020-FOF-2016 of the European Union's Horizon 2020 research and innovation program
Improvements in energy consumption and environmental impact by novel single shot melting process for casting
The CRIMSON (Constrained Rapid Induction Melting Single Shot Up-Casting) method uses a rapid induction furnace to melt just enough metal for a single mould rather than bulk melting used in traditional casting process. The molten metal is then transferred to a computer – controlled platform to complete the counter-gravity up filling. The highly controlled metal flow is pushed into the mould to finish the pouring and solidification. In the present paper the energy saving capability of CRIMSON approach is compared with conventional sand casting process. The paper focuses on the energy and resource efficiency optimization of casting stages through simulation and life cycle assessment analysis simulation for proposing alternative means for the better performance of such processes. It is proven that the CRIMSON process can produce high quality castings with higher energy efficiency and lower environmental impact
Eco-efficient process based on conventional machining as an alternative technology to chemical milling of aeronautical metal skin panels
El fresado quÃmico es un proceso diseñado para la reducción de peso de pieles metálicas que, a
pesar de los problemas medioambientales asociados, se utiliza en la industria aeronáutica desde los
años 50. Entre sus ventajas figuran el cumplimiento de las estrictas tolerancias de diseño de piezas
aeroespaciales y que pese a ser un proceso de mecanizado, no induce tensiones residuales. Sin
embargo, el fresado quÃmico es una tecnologÃa contaminante y costosa que tiende a ser sustituida.
Gracias a los avances realizados en el mecanizado, la tecnologÃa de fresado convencional permite
alcanzar las tolerancias requeridas siempre y cuando se consigan evitar las vibraciones y la flexión
de la pieza, ambas relacionadas con los parámetros del proceso y con los sistemas de utillaje
empleados.
Esta tesis analiza las causas de la inestabilidad del corte y la deformación de las piezas a través
de una revisión bibliográfica que cubre los modelos analÃticos, las técnicas computacionales y las
soluciones industriales en estudio actualmente. En ella, se aprecia cómo los modelos analÃticos y las
soluciones computacionales y de simulación se centran principalmente en la predicción off-line de
vibraciones y de posibles flexiones de la pieza. Sin embargo, un enfoque más industrial ha llevado al
diseño de sistemas de fijación, utillajes, amortiguadores basados en actuadores, sistemas de rigidez
y controles adaptativos apoyados en simulaciones o en la selección estadÃstica de parámetros.
Además se han desarrollado distintas soluciones CAM basadas en la aplicación de gemelos virtuales.
En la revisión bibliográfica se han encontrado pocos documentos relativos a pieles y suelos
delgados por lo que se ha estudiado experimentalmente el efecto de los parámetros de corte en su
mecanizado. Este conjunto de experimentos ha demostrado que, pese a usar un sistema que
aseguraba la rigidez de la pieza, las pieles se comportaban de forma diferente a un sólido rÃgido en
términos de fuerzas de mecanizado cuando se utilizaban velocidades de corte cercanas a la alta
velocidad. También se ha verificado que todas las muestras mecanizadas entraban dentro de
tolerancia en cuanto a la rugosidad de la pieza. Paralelamente, se ha comprobado que la correcta
selección de parámetros de mecanizado puede reducir las fuerzas de corte y las tolerancias del
proceso hasta un 20% y un 40%, respectivamente. Estos datos pueden tener aplicación industrial en
la simplificación de los sistemas de amarre o en el incremento de la eficiencia del proceso.
Este proceso también puede mejorarse incrementando la vida de la herramienta al utilizar
fluidos de corte. Una correcta lubricación puede reducir la temperatura del proceso y las tensiones
residuales inducidas a la pieza. Con este objetivo, se han desarrollado diferentes lubricantes, basados
en el uso de lÃquidos iónicos (IL) y se han comparado con el comportamiento tribológico del par de
contacto en seco y con una taladrina comercial. Los resultados obtenidos utilizando 1 wt% de los
lÃquidos iónicos en un tribómetro tipo pin-on-disk demuestran que el IL no halogenado reduce
significativamente el desgaste y la fricción entre el aluminio, material a mecanizar, y el carburo de
tungsteno, material de la herramienta, eliminando casi toda la adhesión del aluminio sobre el pin, lo
que puede incrementar considerablemente la vida de la herramienta.Chemical milling is a process designed to reduce the weight of metals skin panels. This process
has been used since 1950s in the aerospace industry despite its environmental concern. Among its
advantages, chemical milling does not induce residual stress and parts meet the required tolerances.
However, this process is a pollutant and costly technology. Thanks to the last advances in
conventional milling, machining processes can achieve similar quality results meanwhile vibration
and part deflection are avoided. Both problems are usually related to the cutting parameters and the
workholding.
This thesis analyses the causes of the cutting instability and part deformation through a literature
review that covers analytical models, computational techniques and industrial solutions. Analytics
and computational solutions are mainly focused on chatter and deflection prediction and industrial
approaches are focused on the design of workholdings, fixtures, damping actuators, stiffening
devices, adaptive control systems based on simulations and the statistical parameters selection, and
CAM solutions combined with the use of virtual twins applications.
In this literature review, few research works about thin-plates and thin-floors is found so the
effect of the cutting parameters is also studied experimentally. These experiments confirm that even
using rigid workholdings, the behavior of the part is different to a rigid body at high speed machining.
On the one hand, roughness values meet the required tolerances under every set of the tested
parameters. On the other hand, a proper parameter selection reduces the cutting forces and process
tolerances by up to 20% and 40%, respectively. This fact can be industrially used to simplify
workholding and increase the machine efficiency.
Another way to improve the process efficiency is to increase tool life by using cutting fluids.
Their use can also decrease the temperature of the process and the induced stresses. For this purpose,
different water-based lubricants containing three types of Ionic Liquids (IL) are compared to dry and
commercial cutting fluid conditions by studying their tribological behavior. Pin on disk tests prove
that just 1wt% of one of the halogen-free ILs significantly reduces wear and friction between both
materials, aluminum and tungsten carbide. In fact, no wear scar is noticed on the ball when one of
the ILs is used, which, therefore, could considerably increase tool life
AI and OR in management of operations: history and trends
The last decade has seen a considerable growth in the use of Artificial Intelligence (AI) for operations management with the aim of finding solutions to problems that are increasing in complexity and scale. This paper begins by setting the context for the survey through a historical perspective of OR and AI. An extensive survey of applications of AI techniques for operations management, covering a total of over 1200 papers published from 1995 to 2004 is then presented. The survey utilizes Elsevier's ScienceDirect database as a source. Hence, the survey may not cover all the relevant journals but includes a sufficiently wide range of publications to make it representative of the research in the field. The papers are categorized into four areas of operations management: (a) design, (b) scheduling, (c) process planning and control and (d) quality, maintenance and fault diagnosis. Each of the four areas is categorized in terms of the AI techniques used: genetic algorithms, case-based reasoning, knowledge-based systems, fuzzy logic and hybrid techniques. The trends over the last decade are identified, discussed with respect to expected trends and directions for future work suggested
From 3D Models to 3D Prints: an Overview of the Processing Pipeline
Due to the wide diffusion of 3D printing technologies, geometric algorithms
for Additive Manufacturing are being invented at an impressive speed. Each
single step, in particular along the Process Planning pipeline, can now count
on dozens of methods that prepare the 3D model for fabrication, while analysing
and optimizing geometry and machine instructions for various objectives. This
report provides a classification of this huge state of the art, and elicits the
relation between each single algorithm and a list of desirable objectives
during Process Planning. The objectives themselves are listed and discussed,
along with possible needs for tradeoffs. Additive Manufacturing technologies
are broadly categorized to explicitly relate classes of devices and supported
features. Finally, this report offers an analysis of the state of the art while
discussing open and challenging problems from both an academic and an
industrial perspective.Comment: European Union (EU); Horizon 2020; H2020-FoF-2015; RIA - Research and
Innovation action; Grant agreement N. 68044
Design for Wire + Arc Additive Manufacture: design rules and build orientation selection
Wire + Arc Additive Manufacture (WAAM) is an additive manufacturing technology that can produce near net-shape parts layer by layer in an automated manner using welding technology controlled by a robot or CNC machine. WAAM has been shown to produce parts with good structural integrity in a range of materials including titanium, steel and aluminium and has the potential to produce high value structural parts at lower cost with much less waste material and shorter lead times that conventional manufacturing processes.
This paper provides an initial set of design rules for WAAM and presents a methodology for build orientation selection for WAAM parts. The paper begins with a comparison between the design requirements and capabilities of WAAM and other additive manufacturing technologies, design guidelines for WAAM are then presented based on experimental work. A methodology to select the most appropriate build orientation for WAAM parts is then presented using a multi attribute decision matrix approach to compare different design alternatives. Two aerospace case study parts are provided to illustrate the methodology
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