Energy balance in laser-based free form heading

Vollertsen, Frank; Walther, R.

doi:10.1016/j.cirp.2008.03.028

Cited by 22 publications

(21 citation statements)

References 6 publications

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“…Scaling effects may be also benefical, e.g. when using them for new manufacturing processes [6] or they may be neutral, as they can be accounted for if they are known [7].…”

Section: Size Effect Definitionmentioning

confidence: 99%

Categories of size effects

Vollertsen

2008

Prod. Eng. Res. Devel.

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143

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Size effects play an important role in up-or downscaling of processes and the transfer of knowledge to the processing in new geometric dimensions like microand nanotechnology. A definition of size effects and a systematic order for size effects is proposed. The main categories are density, shape and microstructure size effects, which can be subdivided into further subcategories. Using the example of size effects in the strength of materials it is shown that the systematic can be used to get the different effects unambiguous into an order, which helps to avoid apparent contradictions in experimental findings.

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“…Scaling effects may be also benefical, e.g. when using them for new manufacturing processes [6] or they may be neutral, as they can be accounted for if they are known [7].…”

Section: Size Effect Definitionmentioning

confidence: 99%

Categories of size effects

Vollertsen

2008

Prod. Eng. Res. Devel.

Self Cite

143

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“…This happens due to buckling effects that occur faster because it is based on the shape inaccuracy of the specimen and of the tool as well as their perpendicularity to each other [Vol13]. To overcome these issues, a new laser-based upsetting process has been developed [Vol08].…”

Section: Generation Of Functional Parts Of a Componentmentioning

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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“…For this, the energy of a laser beam is used to heat up the lower end of a metallic rod with diameters 0.5 mm, as proposed by [7]. The molten part of the rod automatically forms spherical due to surface tension.…”

Section: Introductionmentioning

confidence: 99%