44 research outputs found
Eco-efficient process based on conventional machining as an alternative technology to chemical milling of aeronautical metal skin panels
El fresado químico 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 químico es una tecnología contaminante y costosa que tiende a ser sustituida.
Gracias a los avances realizados en el mecanizado, la tecnología 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 analíticos, las técnicas computacionales y las
soluciones industriales en estudio actualmente. En ella, se aprecia cómo los modelos analíticos 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 estadística 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 rígido 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 líquidos 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
líquidos 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
Effects of Machining Parameters on the Quality in Machining of Aluminium Alloys Thin Plates
Nowadays, the industry looks for sustainable processes to ensure a more environmentally
friendly production. For that reason, more and more aeronautical companies are replacing chemical
milling in the manufacture of skin panels and thin plates components. This is a challenging operation
that requires meeting tight dimensional tolerances and di ers from a rigid body machining due to
the low sti ness of the part. In order to fill the gap of literature research on this field, this work
proposes an experimental study of the e ect of the depth of cut, the feed rate and the cutting speed
on the quality characteristics of the machined parts and on the cutting forces produced during the
process. Whereas surface roughness values meet the specifications for all the machining conditions,
an appropriate cutting parameters selection is likely to lead to a reduction of the final thickness
deviation by up to 40% and the average cutting forces by up to a 20%, which consequently eases the
clamping system and reduces machine consumption. Finally, an experimental model to control the
process quality based on monitoring the machine power consumption is proposed
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
Texturing design of WC-Co through laser parameter selection to improve lubricant retention ability of cutting tools
Laser Surface Texturing (LST) is widely used to modify hard material surfaces improving their physic-chemical and mechanical properties. This technology is particularly relevant for tungsten carbides, a material that requires high complexity methods when other micro-machining processes are used. LST allows innovative cutting tool designs that improve the machining behavior and enlarge the cutting tool lifetime. This research analyses the influence of LST parameters on the track dimensions, roughness, microstructure, hardness, and lubricant retention ability of the modified surfaces. Twelve combinations of energy density of pulse and scanning speed created different geometrical patterns on WC-Co surfaces. LST parameters were related to specific shape and dimensions of the linear grooves. Energy density was proven as the most influential parameter for dimensional characteristics and roughness values. Specific channel morphologies increased the lubricant expansion area up to 50%, leading the lubricant to a linear track direction. Low scanning speed and high energy density also increased the surface hardness up to 20%. The surface composition was also modified. The thermal effect of the laser treatments and the non-protective atmosphere increased the oxygen on the surface and modified the WC-Co microstructure. However, the thermal affected zone is considerably low compared to other texturing processes. © 2022 The AuthorsThis work was supported by the Spanish Government ( MINECO/AEI/FEDER , Grant Project DPI2017–84935-R )
Study of the Tool Wear Process in the Dry Turning of Al–Cu Alloy
Light alloy machining is a widely implemented process that is usually used in the presence
of cutting fluids to reduce wear and increase tool life. The use of coolants during machining presents
negative environmental impacts, which has increased interest in reducing and even eliminating their
use. In order to obtain ecofriendly machining processes, it will be necessary to suppress the use of
cutting fluids, in a trend called “dry machining”. This fact forces machines to work under aggressive
cutting conditions, producing adhesion wear that a ects the integrity of the parts’ surfaces. This
study describes cutting tool wear mechanisms in machining of UNS A92024 samples under dry
cutting conditions. Energy dispersive spectroscopy (EDS) analysis shows the di erent compositions
of the adhered layers. Roughness is also positively a ected by the change of the cutting geometry
produced in the tool
Assessment the SlidingWear Behavior of Laser Microtexturing Ti6Al4V under Wet Conditions
Laser micro-texturing processes, compared to untreated surfaces, can improve the friction,
wear and wettability behavior of sliding parts. This improvement is related to the micro-geometry and
the dimensions of the texture which is also dependent on the processing parameters. This research
studied the effect of laser textured surfaces on the tribological behavior of titanium alloy Ti6Al4V.
The influence of processing parameters was analyzed by changing the scanning speed of the beam
and the energy density of pulse. First, the characterization of dimensional and geometrical features
of the texturized tracks was carried out. Later, their influence on the wetting behavior was also
evaluated through contact angle measurements using water as a contact fluid. Then, the tribological
performance of these surfaces was analyzed using a ball-on-flat reciprocating tribometer under wet
and dry conditions. Finally, wear mechanisms were identified employing electronic and optical
microscopy techniques capable to evaluate the wear tracks on Ti surfaces and WC–Co spheres. These
analyses had determined a strong dependence between the wear behavior and the laser patterning
parameters. Wear friction effects were reduced by up to a 70% replacing conventional untreated
surfaces of Ti6Al4V alloy with laser textured surfaces
CAPACITACIÓN DE UTILLAJES FLEXIBLES PARA SU USO EN PROCESOS DE MECANIZADO DE ALTA CALIDAD: UN CASO DE APLICACIÓN DEL PARADIGMA INDUSTRIA 4.0
The incipient implementation of the Industry 4.0 paradigm has led to an increase in the machines sensoring level, in the processes optimization and, thus, in the product manufacturing with a higher added value.
In this article a new aspect is described where, through the machine monitoring, the utilization of innovative elements as fixture is enabled for high quality machining processes.
These innovative elements are characterized by the great flexibility offered by them as holding component and by their low costs. However, these elements lack the enough geometrical accuracy for applications where a high shape and surface quality product are needed.
First of all, in order to have a clear vision of the singularities of each fixture type present on the state of the art, a nomenclature and a classification has been proposed based on their geometry characteristics. Hence, based on this classification, an analysis of the different fixturing solutions provided by the market has been made, enhancing the advantages of this solution against the existing ones.
With the aim of demonstrating its suitability for certain machining applications, the behavior of these sort of flexible materials has been characterized. Besides, the sensors implementation has been analyzed in order to capacitate this solution for processes where tough tolerances on parts are demanded.
Therefore, this survey demonstrates that, through the massive information gathering, not only an optimization of the existing technologies is obtained, but it is possible to develop innovative solutions that provide improved capacities to the already existing ones in the Industry.Financial support from the Basque Government under the ELKARTEK Program (AERO3NAK project, grant number KK-2017/00033)
is gratefully acknowledged by the authors
Machining of Al-Cu and Al-Zn Alloys for Aeronautical Components
Machining operations are chosen by aircraft manufacturers worldwide to process light aluminum alloys. This type of materials presents good characteristics in terms of weight and physicochemical properties, which combined with a low cost ratio making them irreplaceable in aircraft elements with a high structural commitment. Conventional machining processes such as drilling, milling and turning are widely used for aeronautical parts manufacturing. High quality requirements are usually demanded for these kinds of components but aluminum alloys may present some machinability issues, basically associated to the heat generated during the process. Among others, surface quality and geometrical deviations are highly influenced by the condition of the cutting-tool, its wear and the cutting parameters. Consequently, the understanding of the relationship among the process parameters, the quality features and the main wear mechanism is a key factor for the improvement in the productivity. In this chapter, the fundamental issues of drilling, milling and turning are addressed, dealing with the relationship between cutting parameters, wear phenomena and micro and macro geometrical deviations