Purpose

Additive manufacturing (AM) techniques have been developed to rapidly produce custom designs from a multitude of materials. Bonded permanent magnets (PMs) have been produced via several AM techniques to allow for rapid manufacture of complex geometries. These magnets, however, tend to suffer from lower residual induction than the industry standard of injection moulding primarily due to the lower packing density of the magnetic particles and secondly due to the feedstock consisting of neodymium-iron-boron (Nd-Fe-B) powder with isotropic magnetic properties. As there is no compaction during most AM processes, increasing the packing density is very difficult and therefore the purpose of this study was to increase the magnetic properties of the PMs without increasing the part density.

Design/methodology/approach

Accordingly, this research investigates the use of anisotropic NdFeB feedstock coupled with an in-situ alignment fixture into an AM process known as selective laser sintering (SLS) to increase the magnetic properties of AM magnets. A Helmholtz coil array was added to an SLS machine and used to expose each powder layer during part fabrication to a near-uniform magnetic field of 20.4 mT prior to consolidation by the laser.

Findings

Permeagraph measurements of the parts showed that the alignment field introduced residual induction anisotropy of up to 46.4 ± 2.2% when measured in directions parallel and perpendicular to the alignment field. X-ray diffraction measurements also demonstrated a convergence of the orientation of the crystals when the magnets were processed in the presence of the alignment field.

Originality/value

A novel active alignment fixture for SLS was introduced and was experimentally shown to induce anisotropy in bonded PMs. Thus demonstrating a new method for the enhancement in energy density of PMs produced via AM methods.

中文翻译：

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使用原位对准夹具对粘合各向异性永磁体进行选择性激光烧结

目的

增材制造 (AM) 技术已经发展到可以从多种材料快速生产定制设计。粘结永磁体 (PM) 已通过多种 AM 技术生产，以便快速制造复杂的几何形状。然而，这些磁体的残余电感往往低于注塑成型的行业标准，主要是由于磁性颗粒的填充密度较低，其次是由于原料由钕-铁-硼 (Nd-Fe-B) 组成具有各向同性磁性的粉末。由于在大多数 AM 过程中没有压实，因此增加堆积密度非常困难，因此本研究的目的是在不增加零件密度的情况下增加 PM 的磁性能。

设计/方法/方法

因此，本研究调查了将各向异性 NdFeB 原料与原位对准夹具结合使用到称为选择性激光烧结 (SLS) 的 AM 工艺中，以提高 AM 磁体的磁性能。亥姆霍兹线圈阵列被添加到 SLS 机器中，用于在零件制造过程中将每个粉末层暴露在 20.4 mT 的近乎均匀的磁场中，然后再通过激光进行固结。

发现

部件的渗透率测量表明，在平行和垂直于对准场的方向上测量时，对准场引入了高达 46.4 ± 2.2% 的残余感应各向异性。X 射线衍射测量还证明了在存在对准场的情况下处理磁体时晶体取向的会聚。

原创性/价值

引入了一种用于 SLS 的新型主动对准固定装置，并通过实验证明可以在粘合的 PM 中引起各向异性。因此展示了一种提高通过 AM 方法生产的 PM 能量密度的新方法。