RESUMEN
The working curve informs resin properties and print parameters for stereolithography, digital light processing, and other photopolymer additive manufacturing (PAM) technologies. First demonstrated in 1992, the working curve measurement of cure depth vs radiant exposure of light is now a foundational measurement in the field of PAM. Despite its widespread use in industry and academia, there is no formal method or procedure for performing the working curve measurement, raising questions about the utility of reported working curve parameters. Here, an interlaboratory study (ILS) is described in which 24 individual laboratories performed a working curve measurement on an aliquot from a single batch of PAM resin. The ILS reveals that there is enormous scatter in the working curve data and the key fit parameters derived from it. The measured depth of light penetration Dp varied by as much as 7x between participants, while the critical radiant exposure for gelation Ec varied by as much as 70x. This significant scatter is attributed to a lack of common procedure, variation in light engines, epistemic uncertainties from the Jacobs equation, and the use of measurement tools with insufficient precision. The ILS findings highlight an urgent need for procedural standardization and better hardware characterization in this rapidly growing field.
RESUMEN
In laser powder bed fusion (LPBF) additive manufacturing, the melt pool (MP) characteristics are key indicators for process and part defects. For example, the laser scan location on the build plate can slightly change the MP size and shape due to the f-θ optics of the printer. The laser scan parameters can cause variations in MP signatures that may indicate lack-of-fusion and keyhole regimes. However, the effects of these process parameters on MP monitoring (MPM) signatures and part properties are not yet fully understood, especially during a multilayer big-part printing. In this study, our objective is to comprehensively evaluate the dynamical changes of MP signatures (location, intensity, size, and shape) under realistic printing scenarios-printing multilayer objects at different build plate locations with various print process settings. To accomplish this, we developed a coaxial high-speed camera-based MPM system for a commercial LPBF printer (EOS M290), to capture MP images continuously throughout a multilayer part. From our experimental data and results, we find that the MP image position on the camera sensor is not stationary as reported in the literature and is partly subjected to scan location. Its correlations to process deviation or part defect need to be determined. Also, the MP image profile can significantly reflect the changes in print process conditions. The developed system and analysis method can be used to establish a comprehensive profile of MP image signatures for online process diagnosis and part properties prediction, thus ensuring quality assurance and control in LPBF.
RESUMEN
OBJECTIVE: To analyze the clinical effect of Zhuang medicine tendon therapy combined with chiropractic manipulation in treating sacroiliac joint dislocation. METHODS: From January 2017 to May 2018, 60 patients with sacroiliac joint dislocation were divided into treatment group and control group according to the order of admission. There were 19 males and 11 females in the treatment group, aged from 23 to 52 (38.97±3.23) years old, with a course of 2 h to 5.1 months, with an average of (2.19±1.12) months. There were 14 males and 16 females in the control group, aged from 26 to 50 (39.07±3.30) years old, with a course of 3 h to 6 months, with an average of(2.41±1.05) months. The treatment group was treated with Zhuang medicine tendon therapy combined with chiropractic manipulation, while the control group was treated with conventional acupuncture and massage. Before treatment, the main clinical symptoms of the patients were lumbosacral pain, posterior superior iliac spine not at the same level and accompanied with dyskinesia. The pelvic separation test and the "4" test were positive. After treatment, the curative effect was evaluated according to the improved Macnab standard and the "score of treatment of lumbar diseases". RESULTS: Sixty patients were followed up for an average of 8 months. At the latest follow-up, the clinical effect of modified Macnab was better in the treatment group than in the control group(P<0.01). After treatment, the treatment group was better than the control group on lumbar function score (P<0.01). CONCLUSIONS: The treatment of sacroiliac joint dislocation by Zhuang medicine tendon therapy combined with chiropractic manipulation has good clinical effect and is worth further application and development.
