Abstract
One of the main issues of laser-based powder bed fusion (LB-PBF) parts is surface quality and dimensional deviations, which require post-processing. Conventional post-processing such as turning and milling cannot machine internal surfaces and therefore is not suitable for hollow components. In this paper, Ti–6Al–4 V components with different hollow shapes were printed by LB-PBF and post-processed by centrifugal barrel finishing (CBF). Samples were printed based on Taguchi L18 design of experiments (DoE) on the (L18: 21 × 33) matrix and polished in abrasive solution by porcelain triangular media 2 × 2 mm. The effect of process parameters including rotation direction, speed, time and volumetric percentage of abrasive on hardness and manufacturability, including surface quality, material removal rate (MRR) and dimensional deviation, are discussed. The novelty of this work is the application of this process to clean both the internal and external surfaces of LB-PBF parts, where previously it has only been investigated for external surfaces. This paper scrutinized the performance of the CBF on internal geometries, and it was shown for the size of the investigated components, the hexagonal hollow achieved the highest maximum removal rate over the square and circular hollows. In addition, the effect of CBF on plastic deformation and microstructural characterization has been investigated to find the effect of this process on work hardening. The results of this study also show that the rotational speed and the volumetric percentage of the abrasive directly drive the MRR. A higher rotational speed increases the slope of the sliding path and the sliding speed between printed parts and abrasive media, which causes higher cutting and grinding, MRR and media wear rate.
Highlights
The commercial application of additive manufacturing (AM) is rapidly expanding due to freedom in design, the ability to produce complex geometry in a single production process and reduction in labour costs [1–3]
This study showed that surface roughness and MRR have a non-linear correlation with the process parameters, with an almost homogeneous material removal rate obtained by centrifugal barrel finishing (CBF), making it a promising postprocess candidate to finish the surfaces of the laser-based powder bed fusion (LB-powder bed fusion (PBF)) parts
To verify the performance of the experimental results based on Taguchi design of experiments (DoE), “signal to noise ratio” (SNR) diagrams were generated (Fig. 4)
Summary
The commercial application of additive manufacturing (AM) is rapidly expanding due to freedom in design, the ability to produce complex geometry in a single production process and reduction in labour costs [1–3]. The average surface roughness (Ra) achieved by this process is approximately 15–20 times higher than for conventional machining methods such as milling and grinding This compromised surface finish of parts can cause high mechanical frictional forces and premature failure of parts during operation due to surface-initiated cracks [11–13]. Khorasani et al [15] proposed a model to predict the average areal surface roughness (Sa) and analysed the effect of laser power, scan speed, hatch space and scan pattern angle on the quality of the surface of LB-PBF of Ti-6Al-4 parts. They showed that the process parameters drive the rheology of meltpool and surface quality. Due to the brittle nature of LB-PBF parts, the chattering effect from cutting tools was observed, reducing the surface quality
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