System Performance and Process Capability in Additive Manufacturing: Quality Control for Polymer Jetting

Abstract

Polymer-based additive manufacturing (AM) gathers a great deal of interest with regard to standardization and implementation in mass production. A new methodology for the system and process capabilities analysis in additive manufacturing, using statistical quality tools for production management, is proposed. A large sample of small specimens of circular shape was manufactured of photopolymer resins using polymer jetting (PolyJet) technology. Two critical geometrical features of the specimen were investigated. The variability of the measurement system was determined by Gage repeatability and reproducibility (Gage R&R) methodology. Machine and process capabilities were performed in relation to the defined tolerance limits and the results were analyzed based on the requirements from the statistical process control. The results showed that the EDEN 350 system capability and PolyJet process capability enables obtaining capability indices over 1.67 within the capable tolerance interval of 0.22 mm. Furthermore, PolyJet technology depositing thin layers of resins droplets of 0.016 mm allows for manufacturing in a short time of a high volume of parts for mass production with a tolerance matching the ISO 286 IT9 grade for radial dimension and IT10 grade for linear dimensions on the Z-axis, respectively. Using microscopy analysis some results were explained and validated from the capability study.

A Design for Additive Manufacturing Strategy for Dimensional and Geometrical Quality Improvement of PolyJet-Manufactured Glossy Cylindrical Features

“…If this was the case, factor-dependent distortion models should be applied to each combination of significant factors. Since the contact between the model material and the support material causes matte finish, glossy cylindrical surfaces can only be manufactured unsupported (with the cylinder axis parallel to the Z axis) [ 5 ]. Accordingly, within the limits of the proposed example, part location in the manufacturing tray was the only processing decision left to be included in the analysis of model extension.…”

“…Some research studies [ 4 , 5 , 6 ] were focused on characterizing the process capability from a metrological point of view. Different approaches range from using a gage repeatability and reproducibility (G&R) methodology for the capacity evaluation of a polymer jetting system [ 5 ], to benchmarking comparisons of dimensional and geometrical accuracy between different polymer AM processes [ 6 ]. Other studies [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ] analyzed the influence of design, process, and production factors on part quality.…”

“…A comparative analysis [ 48 ] indicated that, for a set of circular dimensions, an average 0.74% relative error was found when manufacturing in an Objet 30, whereas this percentage increases to a 2.34% in the case of an Ultimaker MEX machine. Variability of measured sizes is also low in Polyjet; e.g., a long-term Process Capability analysis [ 5 ] found that the standard deviation value for measured sizes of a nominal 14.5 mm cylindrical glossy surfaces (n = 150) was lower than 0.010 mm. Nevertheless, quality issues are still a matter of concern up to now [ 5 , 49 , 50 ].…”

“…Variability of measured sizes is also low in Polyjet; e.g., a long-term Process Capability analysis [ 5 ] found that the standard deviation value for measured sizes of a nominal 14.5 mm cylindrical glossy surfaces (n = 150) was lower than 0.010 mm. Nevertheless, quality issues are still a matter of concern up to now [ 5 , 49 , 50 ].…”

Process–Structure–Properties in Polymer Additive Manufacturing

“…Platek et al analysed the deformation process of regular cell structures, manufactured using fused filament fabrication under quasi-static loading conditions [ 10 ]. Udroiu and Braga explored a new methodology for process capabilities analysis for material jetting AM [ 11 ]. Luis et al studied the fabrication of silicone meniscus implants using a novel heat cured material extrusion technique [ 12 ].…”