Johannes Henrich Schleifenbaum

Depositing laser-generated nanoparticles on powders for additive manufacturing of oxide dispersed strengthened alloy parts via laser metal deposition

We present a novel route for the adsorption of pulsed laser-dispersed nanoparticles onto metal powders in aqueous solution without using any binders or surfactants. By electrostatic interaction, we deposit Y2O3 nanoparticles onto iron–chromium based powders and obtain a high dispersion of nano-sized particles on the metallic powders. Within the additively manufactured component, we show that the particle spacing of the oxide inclusion can be adjusted by the initial mass fraction of the adsorbed Y2O3 particles on the micropowder. Thus, our procedure constitutes a robust route for additive manufacturing of oxide dispersion-strengthened alloys via oxide nanoparticles supported on steel micropowders.

Digital photonic production along the lines of industry 4.0

The context of future laser applications in modern manufacturing can be summarized by Digital Photonic Production (DPP). “From Bits to Photons to Atoms” describes the vision of DPP: Designing a component or product in the computer and creating it directly by additive or subtractive photon based processes or production-systems.

Influence of the material properties of a poly(D,L-lactide)/β-tricalcium phosphate composite on the processability by selective laser sintering

Complex 3D scaffolds with interconnected pores are a promising tool for bone regeneration. Such 3D scaffolds can be manufactured by selective laser sintering (SLS) from biodegradable composite powders. However, the mechanical strength of these scaffolds is often too low for medical application. We propose that the mechanical strength of laser-sintered scaffolds can be improved through composite powders with tailored properties (e.g., suitable powder particle size and melt viscosity for SLS). To prove this, two batches of a poly(D,L-lactide) (PDLLA)/β-tricalcium phosphate (β-TCP) composite powder with 50u202fwt% PDLLA and 50u202fwt% β-TCP were synthesized. The two batches differed in polymer particle size, filler particle size, and polymer molecular weight. Both batches were processed with identical SLS process parameters to study the extent to which the material properties influence how well a PDLLA/β-TCP (50/50) composite can be processed with SLS. In the SLS process, batch 2 showed improved melting behavior due to its smaller polymer particle size (approx. 35u202fµm vs. 50u202fµm) and its lower zero-shear melt viscosity (5800u202fPa∙s vs. 17,900u202fPa∙s). The better melting behavior of batch 2 led to SLS test specimens with lower porosity compared to batch 1. In consequence, the batch 2 specimens exhibited a larger biaxial bending strength (62u202fMPa) than the batch 1 specimens did (23u202fMPa). We conclude that a tailored composite powder with optimized polymer particle size, filler particle size, and polymer molecular weight can increase the achievable mechanical strength of laser-sintered scaffolds.

Local laser softening of press-hardened steel at high feed rates

The development of hot stamped manganese–boron steels established new potentials for lightweight constructions for applications in the automotive industry. This type of high strength steel allows the usage of thin sheet thicknesses resulting in low specific weight retaining the optimized performance of passive safety. The parts have a high tensile strength of about 1500u2009MPa. However, this high strength is not favorable in all sections of a part, especially those which are relevant for safety or for joining. To ensure the requirements for the crash properties or the joining areas, a high ductility is required in these areas. A way to overcome this problem is a local softening of the crash and joining zones via laser heat treatment. By means of laser radiation, the brittle martensitic microstructure is either tempered or transformed into a ferrite/perlite dominated microstructure. A fiber-coupled diode laser with a maximum laser power of 12u2009kW and rectangular laser spot is used for the laser heat treatment. The temperature is controlled by a monochromic pyrometer integrated into the optical system. Generally, the necessary process feed rate of the heat treatment process is low (about 1000u2009mm/min), as a homogeneous result of the heat treatment is pursued. As the feed rates increase (up to 8000u2009mm/min), the temperature distribution across the thickness of the material becomes more inhomogeneous. With the topside being hotter than the backside, the material is tempered with a varying intensity resulting in a hardness distribution across the thickness. The influencing parameters for this effect are being characterized, and the mechanical properties of the anisotropic material are investigated.The development of hot stamped manganese–boron steels established new potentials for lightweight constructions for applications in the automotive industry. This type of high strength steel allows the usage of thin sheet thicknesses resulting in low specific weight retaining the optimized performance of passive safety. The parts have a high tensile strength of about 1500u2009MPa. However, this high strength is not favorable in all sections of a part, especially those which are relevant for safety or for joining. To ensure the requirements for the crash properties or the joining areas, a high ductility is required in these areas. A way to overcome this problem is a local softening of the crash and joining zones via laser heat treatment. By means of laser radiation, the brittle martensitic microstructure is either tempered or transformed into a ferrite/perlite dominated microstructure. A fiber-coupled diode laser with a maximum laser power of 12u2009kW and rectangular laser spot is used for the laser heat treatment....

Mechanical properties of sheet metal components with local reinforcement produced by additive manufacturing

New technological challenges like electro-mobility pose an increasing demand for cost-efficient processes for the production of product variants. This demand opens the possibility to combine established die-based manufacturing methods and innovative, dieless technologies like additive manufacturing [1, 2]. In this context, additive manufacturing technologies allow for the weight-efficient local reinforcement of parts before and after forming, enabling manufacturers to produce product variants from series parts [3].Previous work by the authors shows that the optimal shape of the reinforcing structure can be determined using sizing optimization. Sheet metal parts can then be reinforced using laser metal deposition. The material used is a pearlite-reduced, micro-alloyed steel (ZE 630). The aim of this paper is to determine the effect of the additive manufacturing process on the material behavior and the mechanical properties of the base material and the resulting composite material. The parameters of the AM process are optimized to reach similar material properties in the base material and the build-up volume. A metallographic analysis of the parts is presented, where the additive layers, the base material and also the bonding between the additive layers and the base material are analyzed. The paper shows the feasibility of the approach and details the resulting mechanical properties and performance.New technological challenges like electro-mobility pose an increasing demand for cost-efficient processes for the production of product variants. This demand opens the possibility to combine established die-based manufacturing methods and innovative, dieless technologies like additive manufacturing [1, 2]. In this context, additive manufacturing technologies allow for the weight-efficient local reinforcement of parts before and after forming, enabling manufacturers to produce product variants from series parts [3].Previous work by the authors shows that the optimal shape of the reinforcing structure can be determined using sizing optimization. Sheet metal parts can then be reinforced using laser metal deposition. The material used is a pearlite-reduced, micro-alloyed steel (ZE 630). The aim of this paper is to determine the effect of the additive manufacturing process on the material behavior and the mechanical properties of the base material and the resulting composite material. The parameters of the AM ...

How Can Reynolds Help to Improve the Performance of Production Systems? Fluid Dynamics and its Contributions to Production Theory

Future production systems need to cope with a high degree of flexibility in terms of fluctuation of demand, product variants, etc. without loosing sight of an increasing cost pressure. For the resolution of this dilemma this work focuses on the adaption of basic principles of similitude and fluid dynamics to production theory in order to increase the production velocity while avoiding regions of instability, or turbulence, at the same time. Subsequently, an experimental setup for the verification of this analogy model is developed and discussed.