January 1, 2019 by admin 0 Comments

Additive Manufacturing of Polyaryletherketones

Authors
Manuel Garcia-Leiner Ph.D. *, Oana Ghita †, Robert McKay M.B.A., M.S.F. ‡, Steven M. Kurtz Ph.D. §
Abstract
Additive manufacturing (AM), otherwise known as three-dimensional printing (3DP), is a growing technology area comprising a spectrum of processes that allow production of solid objects of virtually any shape from information obtained from a digital object. These days, AM processes drive major innovations in engineering, manufacturing, art, education, and medicine. However, most AM processes are not necessarily new. Introduced commercially in the 1990s mainly through prototyping efforts for the manufacture of complex metal parts, AM processes have almost a 30-year history for plastics, and have driven the development of multiple commercial products through manufacturing techniques ranging from stereo-lithography to laser-based powder fusion processes. A growing number of polymeric resins intended for AM have become available in recent times due to developments of new processes and technological advancements. Of these, high-performance thermoplastics such as the polyaryletherketones (PAEKs) are perhaps the most promising candidates for demanding engineering applications. Polymers such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), and polyetherketoneetherketoneketone (PEKEKK), could revolutionize and enable the use of additively manufactured plastic parts in critical environments. However, despite their similarity in terms of chemistry and composition, commercially available PAEK resins show varying physical properties due to their molecular size-dependent structural differences that make them function differently in common AM processes. This chapter describes some of the advancements and opportunities for PAEK polymers in AM processes, as well as the relationships between structure and property and the morphological changes observed in these materials when subjected to conditions typically found in common AM processes.

January 1, 2018 by admin 0 Comments

Design, fabrication and evaluation of a hybrid biomanufacturing system for tissue engineering

Authors
Fengyuan Liu
Abstract
Plasma-assisted Bio-extrusion System (PBS System) is an innovative hybrid bio-manufacturing system to produce complex multi-material and functionally graded scaffolds combining multiple pressure-assisted and screw-assisted printing heads and plasma jets. This approach, which represents a step forward regarding the current state of the art technology in the field of biomanufacturing, enables to design and fabricate more effective scaffolds matching the mechanical and surface characteristics of the surrounding tissue, enabling the incorporation of high number of cells uniformly distributed and the introduction of multiple cell types with positional specificity. The system requires complex control software to manipulate different materials, scaffold designs and processing parameters. This software, developed using MATLAB GUI, is detailed in this paper. It provides high freedom of design allowing the users to create single or multi-material constructs with uniform pore size or pores size gradients by changing the operation parameters, such as geometric parameters, lay-down pattern, filament distance, feed rate and layer thickness. Functionally graded scaffolds can also be designed considering different layer-by-layer coating/surface modification strategies using the multi-jet plasma system. Based on the user definition, G programming codes are generated enabling fully integration and synchronization with the hardware of the PBS system. Examples will be provided describing the design of single, multi-material and functionally graded scaffolds.

October 17, 2016 by admin 0 Comments

The effects of moisture and temperature on the mechanical properties of additive manufacturing components: fused deposition modeling

Authors
Eunseob Kim, Yong-Jun Shin, Sung-Hoon Ahn
Abstract
Purpose This paper aims to investigate the water absorption behaviors and mechanical properties, according to water absorption and temperature, of components fabricated by fused deposition modeling (FDM) and injection molding. The mechanical properties of FDM and injection molded parts were studied under several environmental conditions. Design/methodology/approach FDM components can be used as load-carrying elements under a range of moisture and temperature conditions. FDM parts show anisotropic mechanical properties according to build orientation. Components were fabricated from acrylonitrile-butadiene-styrene in three different orientations. The mechanical properties of parts fabricated by FDM were compared to injection molded components made from the same material. Water absorption tests were conducted in distilled water between 20 and 60°C to identify the maximum water absorption rate. Both moisture and temperature were considered as environmental variables in the tensile tests, which were conducted under various conditions to measure the effects on mechanical properties. Findings The water absorption behavior of FDM components obeyed Fickian diffusion theory, irrespective of the temperature. High temperatures accelerated the diffusion rate, although the maximum water absorption rate was not affected. The tensile strength of FDM parts under dry, room temperature conditions, was approximately 26-56 per cent that of injection molded parts, depending on build orientation. Increased temperature and water absorption had a more significant effect on FDM parts than injection molded components. The tensile strength was decreased by 67-71 per cent in hot, wet environments compared with dry, room temperature conditions. Originality/value The water absorption behavior of FDM components was investigated. The quantitative effects of temperature and moisture on tensile strength, modulus and strain were also measured. These results will contribute to the design of FDM parts for use under various environmental conditions.