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Introduction
1.1Background
The quality of a product or process has several dimensions: performance, reliability, durability, serviceability, esthetics, features, perceived quality and conformance to specifications or standards (Montgomery, 2008). According to the American Society for Quality (2016), quality control (QC) includes the observation techniques and activities used to fulfill quality requirements. The seven basic tools of QC are cause-and-effect diagrams, check sheets, control charts, histograms, Pareto charts, scatter diagrams and design of experiments (DOE) (Montgomery, 2008). QC activities can also be classified into incoming QC (IQC), in-process QC (IPQC) and outgoing QC (OQC) or quality assurance, depending on when these activities are performed (Orient Semiconductor Electronics, 2016).
3D printing involves building a 3D object from a 3D model layer by layer with resin or other materials (Berman, 2012). 3D printing has been used to fabricate prototypes, mockups, replacement parts, dental crowns, artificial limbs and even bridges (Berman, 2012). With these successes, 3D printing is considered a convenient tool for producing complex internal and external porous structures (Asadi-Eydivand et al., 2016). 3D printing is also cheaper and more efficient than other rapid prototyping technologies, such as selective laser sintering (SLS) and stereolithography (Silva et al., 2008). As an extension, 3D printing has been incorporated into a convenience store chain to form a ubiquitous manufacturing network (Lin and Chen, 2017).
From a manufacturing perspective, 3D printing is a special manufacturing process in which there is no time gap between the research and development (R&D) stage and the mass production stage. In conventional manufacturing processes, a time gap is usually required for amassing the factory capacity and acquiring the raw materials.
This study investigated issues of quality and QC in 3D printing by reviewing past work and current practices. In this paper, the current practices are mapped to the stages of a QC cycle (i.e. product design, process planning, IQC, IPQC and OQC), and quality and QC activities that were either ignored or not actively performed in 3D printing are listed (Figure 1). Finally, this paper discusses possible future developments.
1.2Importance of the topic
A drug made through 3D printing was approved by the FDA in 2015 (Norman et al., 2016), which not only revolutionizes pharmaceutical manufacturing but also poses a challenge for...