Abstract
Initially developed as a rapid prototyping tool for project visualization and validation, the recent development of additive manufacturing (AM) technologies has led to the transition from rapid prototyping to rapid manufacturing. As a consequence, increased attention has to be paid to the mechanical, chemical and physical properties of the printed materials. In mechanical engineering, the widespread use of AM technologies requires the optimization of process parameters and material properties in order to obtain components with high, repeatable and time-stable mechanical properties. One of the main problems in this regard is the anisotropic behavior of components made by additive manufacturing, determined by the type of material, the 3D printing technology, the process parameters and the position of the components in the printing space. In this paper the influence of the printing orientation angle on the tensile behavior of specimens made by material jetting is investigated. The aim was to determine if the positioning of components at different angles relative to the X-axis of the printer (and implicitly in relation to the multijet printing head) contributes to anisotropic behavior. The material used was a photopolymer with a mechanical strength between 40 MPa and 55 MPa, according to the producer. Four sets of tensile test specimens were manufactured, using flat build orientation and positioned on the printing table at angles of 0˚, 30˚, 60˚ and 90˚ to the X-axis of the printer. Comparative analysis of the mechanical behavior was carried out by tensile tests and microscopic investigations of the tensile test specimens fracture surfaces.
Highlights
Additive manufacturing technologies have developed exponentially in recent years, as they offer a number of advantages over conventional manufacturing technologies, as follows:-the rapid manufacturing of components with high geometric complexity; -the optimization of the inner geometry of parts so as to obtain a material distribution correlated to the stress state; -the manufacturing of lighter parts with various lattice infill patterns [1, 2]; -the manufacturing of a part by use of several materials simultaneously; -the use of shape memory materials and 4D materials [3,4,5]
The differences between the six categories are given by the additive manufacturing principle, by the material feedstock, by the material distribution system and by the state of fusion of material
After a layer is deposited, its height and quality are leveled by a rotating cylinder, positioned next to the printing head and it is cured by an ultraviolet light lamp. 3D printers for material jetting technology are usually equipped with at least two printing heads
Summary
Additive manufacturing technologies have developed exponentially in recent years, as they offer a number of advantages over conventional manufacturing technologies, as follows:-the rapid manufacturing of components with high geometric complexity; -the optimization of the inner geometry of parts so as to obtain a material distribution correlated to the stress state; -the manufacturing of lighter parts with various lattice infill patterns [1, 2]; -the manufacturing of a part by use of several materials simultaneously (obtaining variable compositions and variable mechanical properties in the same part); -the use of shape memory materials and 4D materials (components resulting from 4D printing have the property of changing their shape under the action of external factors: temperature, humidity, electricity, light) [3,4,5]. The ISO/ASTM 52900:2015 standard [6] defines six process categories: material extrusion, material jetting, powder bed fusion, binder jetting, vat photo-polymerization and sheet lamination. The differences between the six categories are given by the additive manufacturing principle (extrusion of melted material, multi-jet material printing, selective fusion of material in a powder bed, reactive curing, light reactive photopolymer curing, fusion of stacked sheets), by the material feedstock (filament, melted material, powder, liquid, sheet material), by the material distribution system (deposition nozzle, print head, powder bed, vat with liquid, sheet stack) and by the state of fusion of material (thermal reaction bonding, chemical reaction bonding). In material jetting manufacturing technology, photosensitive polymers in liquid state are disposed on a printing table using multi-jet printing heads. Printers with more than two printing heads allow the combination of several model materials, as to obtain multi-material components
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