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The conventional manufacturing chain for technical ceramics is too expensive for the production of small series or unique parts with complex designs. Hybrid machines that combine additive and subtractive processes can be an interesting solution to overcome this technology lock-in. However, despite the great interest in hybrid machines for metallic parts, there is a lack of data in the literature when it comes to ceramics. The purpose of this paper is to contribute to closing this gap. It is the first to evaluate the achievable geometrical tolerances according to ISO 2768-2 as well as the surface textures of composite zirconia parts shaped sequentially by pellet additive manufacturing (PAM, from ceramic injection molding feedstock) and finish milling. The green parts were then debinded and sintered to analyze the influence of these steps. Compared to the initial green parts, the sintered parts exhibited shiny and smooth surfaces with sharp edges. Flatness, parallelism and perpendicularity all achieved an H (fine) class, while the surface textures were significantly improved, resulting in arithmetic roughness (Ra) below 1.6 µm. [ABSTRACT FROM AUTHOR]

Knowing the tolerance interval capabilities (TICs) of a manufacturing process is of prime interest, especially if specifications link the manufacturer to a customer. These TICs can be determined using the machine performance concept of ISO 22514. However, few works have applied this to Additive Manufacturing printers, while testing most of the printing area as recommended takes a very long time (nearly 1 month is common). This paper, by proposing a novel part design called COMPAQT (Component for Machine Performances Assessment in Quick Time), aims at giving the same level of printing area coverage, while keeping the manufacturing time below 24 h. The method was successfully tested on a material extrusion printer. It allowed the determination of potential and real machine tolerance interval capabilities. Independently of the feature size, those aligned with the X axis achieved lower TICs than those aligned with the Y axis, while the Z axis exhibited the best performance. The measurements specific to one part exhibited a systematic error centered around 0 mm ± 0.050 mm, while those involving two parts reached up to 0.314 mm of deviation. COMPAQT can be used in two applications: evaluating printer tolerance interval capabilities and tracking its long-term performance by incorporating it into batches of other parts. [ABSTRACT FROM AUTHOR]

The performance assessment of additive manufacturing (AM) printers is still a challenge since no dedicated standard exists. This paper proposes a systematic method for evaluating the dimensional and geometrical performance of such machines using the concept of machine performance. The method was applied to an Ultimaker 2+ printer producing parts with polylactic acid (PLA). The X and Y axes of the printer were the most performant and led to narrower potential and real tolerance intervals than the Z axis. The proposed systematic framework can be used to assess the performance of any material extrusion printer and its achievable tolerance intervals. [ABSTRACT FROM AUTHOR]

The innovative Green Ceramic Hybrid Machining (GCHM) process sequentially combines milling with a cutting tool (GCM, Green Ceramic Machining) and laser beam machining (GCLBM) of a ceramic material (black Y-TZP in this study) at the green stage mainly to increase productivity, avoid taper angle limitations of laser beam machining, and obtain micro-features. The study focuses on the reliability and the repeatability of the properties of sintered parts obtained by three manufacturing processes (GCM, GCLBM, GCHM) to assess the performance of hybridisation. It turns out that GCHM is a compromise of both milling and laser beam processes; it increases the repeatability of the surface quality and it slightly reduces (less than 7%) the flexural strength by comparison to milling for a similar reliability. The study also highlights that the surface quality of GCLBM processed parts relies on of the surface generated by the previous operation. Milling that surface at the previous step is therefore recommended, corresponding to the sequence adopted by GCHM. [ABSTRACT FROM AUTHOR]