Form filling behaviour of preforms generated by laser rod end melting

Brüning, Heiko; Vollertsen, Frank

doi:10.1016/j.cirp.2015.04.129

Cited by 5 publications

(7 citation statements)

References 5 publications

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“…The heat-affected zone was found to be narrower than when directly using a wire as a filler. A high-power laser beam pulse was used to detach the drops after their generation [1]. This detachment technique was studied in depth by Kuznetsov et al (2014), where an infrared camera was used to observe the velocity and the formation of the drops.…”

Section: Introductionmentioning

confidence: 99%

Acceleration of metal drops in a laser beam

et al. 2020

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Different processes require the detachment of metal drops from a solid material using a laser beam as the heat source, for instance laser drop generation or cyclam. These techniques imply that the drops enter the laser beam, which might affect their trajectory. Also, many laser processes such as laser welding or additive manufacturing generate spatters that can be accelerated by the laser beam during flight and create defects on the material. This fundamental study aims at investigating the effects of a continuous power laser beam on the acceleration of intentionally detached drops and unintentionally detached spatters. Two materials were studied: 316L steel and AlSi5 aluminium alloy. High-speed imaging was used to measure the position of the drops and calculate their acceleration to compare it to theoretical models. Accelerations up to 11.2 g could be measured. The contributions of the vapor pressure, the recoil pressure, and the radiation pressure were investigated. The recoil pressure was found to be the main driving effect but other phenomena counteract this acceleration and reduce it by an order of magnitude of one to two. In addition, two different vaporization regimes were observed, resulting respectively in a vapor plume and in a vapor halo around the drop.

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Section: Introductionmentioning

confidence: 99%

Acceleration of metal drops in a laser beam

et al. 2020

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Section: Formabilitymentioning

confidence: 99%

“…This is possible because the material flows not only inside the cavity but also in direction of the rod. Thus, preform volumes of up to 125% of the die volume can fill the cavity completely without any burr, see [Brü15b].Finally, it is possible to mold fine surface structures after the forming stage, such as the surface roughness of the die, see [Brü14a], down to feature sizes of 500 nm which is investigated in [Brü15c]. In Fig.…”

mentioning

confidence: 99%

Micro Forming Processes

Kuhfuß¹,

Schattmann

Jahn

et al. 2019

Lecture Notes in Production Engineering

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The projects of this chapter describe micro forming processes that are studied as single processes but can also be combined as process chains. Proven examples are material accumulation and succeeding rotary swaging, or rotary swaging and extrusion.Micro forming differs from macro forming due to scaling effects, which can mean both challenges and benefits. Problems may arise from the handling of fragile parts or adhesive forces between the micro parts or friction effects.Benefits from scaling effects are made use of in the project "Generation of functional parts of a component by laser-based free-form heading". The aim is a material accumulation that is generated from short duration laser melting. This material accumulation gives the basis for succeeding cold forming operations. The first powerful application for the new technology was upsetting. In the macro range, upset ratios of about 2.3 are achievable, but this is reduced in the micro scale due to earlier buckling of the components. In the micro scale, where cohesive forces can exceed the gravitational force, the molten material forms a droplet that remains adhered to the rod. Thus, upset ratios of up to 500 were reached. The process development was accompanied by a mathematical model and allows for a deep insight into the thermodynamics of laser-induced material accumulation in the micro range.The laser molten material accumulation could, for example, be further processed by micro rotary swaging. Though rotary swaging has been known in the macro range for a long time and is nowadays an intensively used process in the automotive industry to produce lightweight components from tubular blanks, there are only a few scientific works that have addressed material characteristics like the work hardening or residual stress that are linked to the process and machine parameters and the resulting material flow. Due to micro scale specifics that follow from the kinematics, i.e. relatively smaller stiffness against part buckling and wider tool gaps in the opened state, the feed rates achievable cannot compete with high throughput technologies that produce 500 parts per minute and more. One major aim of the project "Rotary swaging of micro parts" was to increase the productivity for the main process variants, namely infeed and plunge rotary swaging. This demanded also process modeling to understand how parameter variations like friction between tools and the work in the different zones of the swaging tools affect the process.From the modeling and simulation, separate process variations were deduced and investigated. For infeed swaging, a special workpiece clamping allows for compensation of the pushback force, which results in a 10-fold increase of the maximum feed rate. For plunge rotary swaging, an approach was tested to close the tools gaps during opening using elastic intermediate elements that encapsule the workpiece against the forming dies and enable a 4-fold increase of the radial feed rate. 28 B. Kuhfuss et al.Micro rotary swaging could become a base technology ...

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“…[32] has been established and a corresponding finite element method has been developed. This simulation allows for a numerical computation of suitable parameters and process results and is used among other things to analyze the energy balance in the work-piece and the dynamics in the melt (e.g [29], [33], [34]).…”

Section: Fig 1 Laser Rod End Melting As Alternative To Upsettingmentioning

confidence: 99%

“…In [33] the influence of the cold forming stage on the eccentricity is shown. The diameter of preforms varied between 0.38 mm and 0.43 mm by constant rod diameter d0 = 0.2 mm, processed with a laser power of 102 W, a deflection velocity of 72 mm/s and a variation in thermal upset length of 0.9 mm to 1.2 mm.…”

Section: Characteristics Of Generated Preformsmentioning

confidence: 99%

Application of Cause-Effect-Networks for the process planning in laser rod end melting

et al. 2018

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In micro manufacturing, a precise configuration of manufacturing processes constitutes an essential factor for success. The continuing miniaturization of work pieces results in ever decreasing tolerances, whereas machines and processes become more and more specialized. As a result, a precise determination of each process result is important to guarantee the final product quality. Unfortunately, so called size effects often prevent the direct transfer of knowledge from the area of macro manufacturing. To cope with these effects, finite element simulations provide a suitable tool to simulate forming processes and their results in advance and to perform parameter studies in order to analyze the process and effect interdependencies. Unfortunately, these simulations usually require a rather long computing time, so that only simulations for a small subset of the available parameter range can be performed in a reasonable planning interval. In this context, this article presents an application of the method “Micro – Process Planning and Analysis” (μ-ProPlAn) for the configuration of laser rod end melting, which is used to create preforms for further forming processes. This method uses cause-effect networks, to combine expert knowledge with methods from artificial intelligence to estimate the result of laser melting processes quickly. For this purpose, the cause-effect networks are trained using a finite element simulation of the laser process using different process parameters and varying rod diameters. Results show a high accuracy for the prediction of the finite element simulation results. This article focusses on the validation of these cause-effect networks in comparison to the real laser rod end melting process and demonstrates how these models can be used to predict the resulting volume, eccentricity and the largest diameter of the solidified preform for different process configurations.

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Form filling behaviour of preforms generated by laser rod end melting

Cited by 5 publications

References 5 publications

Acceleration of metal drops in a laser beam

Acceleration of metal drops in a laser beam

Micro Forming Processes

Application of Cause-Effect-Networks for the process planning in laser rod end melting

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