The Experts below are selected from a list of 20079 Experts worldwide ranked by ideXlab platform

Elena Kokoliou - One of the best experts on this subject based on the ideXlab platform.

Michael Schmidt - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of Laser Beam Absorption in a Polymer Powder Bed.
    Polymers, 2018
    Co-Authors: Fuad Osmanlic, Dietmar Drummer, Tobias Laumer, Michael Schmidt, Katrin Wudy, Carolin Körner
    Abstract:

    In order to understand the absorption characteristic, a ray trace model is developed by taking into account the reflection, absorption and refraction. The ray paths are resolved on a sub-Powder grid. For validation, the simulation results are compared to analytic solutions of the irradiation of the laser beam onto a plain surface. In addition, the absorptance, reflectance and transmittance of PA12 Powder layers measured by an integration sphere setup are compared with the numerical results of our model. It is shown that the effective penetration depth can be lower than the penetration depth in bulk material for Polymer Powders and, therefore, can increase the energy density at the Powder bed surface. The implications for modeling of the selective laser sintering (SLS) process and the processability of fine Powder distributions and high Powder bed densities are discussed.

  • Optical analysis of Polymer Powder materials for Selective Laser Sintering
    Polymer Testing, 2016
    Co-Authors: Tobias Laumer, Thomas Stichel, Konstantin Yu. Nagulin, Michael Schmidt
    Abstract:

    Abstract This study increases the basic understanding of optical material properties of Polymer Powders used in selective laser sintering (SLS). Therefore, different Polymer Powder materials were analyzed regarding their optical material properties with an integration spheres measurement setup. By the measurements a direct connection between the absorption behavior of the solid material and the overall optical material characteristics of the same material in Powdery form could be shown. The results were used to develop an advanced explanation model for the optical material properties of Powders. At present, existing explanation models only consider the occurring of multiple reflections in the gaps between the particles to explain the overall optical material properties of Powder materials. Thus, by also considering the absorption behavior of the single particles, the basic understanding of the beam-matter interaction and their effect on the optical material properties of Powder materials can be expanded.

Hiroaki Shimomura - One of the best experts on this subject based on the ideXlab platform.

  • Measurement of mass flow rate of Polymer Powder based on static electrification of particles
    Advanced Powder Technology, 1998
    Co-Authors: Hiroaki Masuda, Shuji Matsusaka, Hiroaki Shimomura
    Abstract:

    Measurement of mass flow rate of Polymer Powder in a gas-solids pipe flow was investigated theoretically and experimentally. The measurement was based on the static electrification of the flowing particles. In the system, two current detecting pipes made of different materials were used and mass flow rates were calculated from the two generated currents. Since Polymer Powder formed a stiff coating layer on the hard surface of metallic pipes by particle collision, several Polymer materials were examined as to the detecting pipes and the performance of the current detection was evaluated by changing the Powder flow rate. It was found that electrically conductive Polymers containing carbon had superior stability for the current detection. It was also found that the mass flow rate of Polymer Powder could be measured by use of two different conductive Polymers for the detecting pipes.

  • Measurement of the Mass Flow Rate of a Polymer Powder Based on the Static Electrification of Particles.
    Journal of the Society of Powder Technology Japan, 1997
    Co-Authors: Hiroaki Masuda, Shuji Matsusaka, Hiroaki Shimomura
    Abstract:

    Measurement of the mass flow rate of a Polymer Powder in a gas-solids pipe flow was investigated theoretically and experimentally. The measurement was based on the static electrification of the flowing particles. In the system, two current detecting pipes made of different materials were used, and mass flow rates were calculated from the two generated currents.Since the Polymer Powder formed a stiff coating layer on the hard surface of metallic pipes due to particle impaction, several Polymer materials were examined as the detecting pipes, and the performance of the current detection was evaluated by changing the Powder flow rate. It was found that electric conductive Polymers containing carbon showed superior stability in current detection. It was also found that the mass flow rate of the Polymer Powder could be measured by the use of two different conductive Polymers in the detecting pipes.

Tobias Laumer - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of Laser Beam Absorption in a Polymer Powder Bed.
    Polymers, 2018
    Co-Authors: Fuad Osmanlic, Dietmar Drummer, Tobias Laumer, Michael Schmidt, Katrin Wudy, Carolin Körner
    Abstract:

    In order to understand the absorption characteristic, a ray trace model is developed by taking into account the reflection, absorption and refraction. The ray paths are resolved on a sub-Powder grid. For validation, the simulation results are compared to analytic solutions of the irradiation of the laser beam onto a plain surface. In addition, the absorptance, reflectance and transmittance of PA12 Powder layers measured by an integration sphere setup are compared with the numerical results of our model. It is shown that the effective penetration depth can be lower than the penetration depth in bulk material for Polymer Powders and, therefore, can increase the energy density at the Powder bed surface. The implications for modeling of the selective laser sintering (SLS) process and the processability of fine Powder distributions and high Powder bed densities are discussed.

  • Optical analysis of Polymer Powder materials for Selective Laser Sintering
    Polymer Testing, 2016
    Co-Authors: Tobias Laumer, Thomas Stichel, Konstantin Yu. Nagulin, Michael Schmidt
    Abstract:

    Abstract This study increases the basic understanding of optical material properties of Polymer Powders used in selective laser sintering (SLS). Therefore, different Polymer Powder materials were analyzed regarding their optical material properties with an integration spheres measurement setup. By the measurements a direct connection between the absorption behavior of the solid material and the overall optical material characteristics of the same material in Powdery form could be shown. The results were used to develop an advanced explanation model for the optical material properties of Powders. At present, existing explanation models only consider the occurring of multiple reflections in the gaps between the particles to explain the overall optical material properties of Powder materials. Thus, by also considering the absorption behavior of the single particles, the basic understanding of the beam-matter interaction and their effect on the optical material properties of Powder materials can be expanded.

Alfonso Maffezzoli - One of the best experts on this subject based on the ideXlab platform.

  • Polymer melting and Polymer Powder sintering by thermal analysis
    Journal of Thermal Analysis and Calorimetry, 2003
    Co-Authors: A. Greco, Alfonso Maffezzoli
    Abstract:

    Sintering of Polymeric Powders is a peculiar characteristic of many processing technologies, including rotational moulding and selective laser sintering (SLS). During Polymer sintering, viscosity reduction in the melt state promotes densification of Polymer Powders, through a double stage mechanism, involving Powder coalescence and bubble removal. In particular, sintering of semi-crystalline Polymers is strongly influenced by the melting behaviour. Nevertheless, melting itself in absence of pressure is not necessarily accompanied by Powder sintering, unless low viscosities are achieved. In this work, the melting and sintering behaviour of recycled high density polyethylene (rHDPE) have been analysed through differential scanning calorimetry (DSC) and Thermomechanical Analysis (TMA). Efficient models capable of describing the melting temperature distribution and rate of sintering of rHDPE Powders have been developed, highlighting the inherent differences between the two distinct processes.