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Stereolithography (SLA) is becoming a more and more popular 3D-printing method. Improvement in material properties encourages makers and engineers to embrace this technology even for load-bearing applications. Mechanical properties of 3D-printed materials are difficult to obtain from technical datasheets and, even when available, these data are often unreliable, since they depend strongly on the specific printing parameters applied. Therefore, it is often necessary to perform an in-house mechanical characterization. In this work, tensile tests are performed with a basic in-house-designed tester on SLA 3D-printed specimens; these are printed at different orientations on a Formlabs™ Form 2™ using Clear V4™ resin. The ultimate tensile strength, Young’s modulus, strain at maximum stress and strain at break are calculated. No relationship is found between printing angle and mechanical characteristics; therefore, this 3D-printed material can be considered isotropic. Results are compared with the manufacturer’s datasheet: the measured maximum stress is slightly lower than that stated by Formlabs™, while the modulus is nearly the same. Strain at maximum stress and strain at break were also measured but were not reported in the available datasheet.

Due to its building process, the mechanical properties of a 3D-printed object are substantially different from those of the same object, made of the same material, but obtained by a different manufacturing process. Tensile tests were carried out on standard specimens, which were 3D-printed with a Builder Premium™ FDM printer. Three different plastic and composite materials were tested and their stress-strain curves were obtained; significant parameters such as ultimate tensile strength and Young’s modulus were calculated and compared.

Additive manufacturing is gaining greater and greater popularity in recent years: thanks to a dramatic reduction of costs and increasing print quality, more and more people are attracted to 3D printing, even for the production of end-use load-bearing parts. Today, there are no universally accepted norms that guide the engineer through the uncertain task of predicting the mechanical behavior of 3D-printed parts. Even though there are numerous reports and articles in literature regarding this topic, the designer will have to rely mostly on his own mechanical tests. This paper describes the design of an in-house-built machine for 3D-printed material tensile testing. The accuracy of this test-rig has been verified through comparison of results on different 3D-printed specimens: these were realized through fused deposition modelling (FDM) and were divided into four distinct sets, based on the material and their orientation on the buildplate. Some samples were printed in PLA, others in XTCF-20™: a composite material made of a matrix of Amphora™ polymer reinforced with 20% in weight carbon short fibers. PLA samples were printed flat on the buildplate, on one side and standing: this affects directly the orientation of the plastic fibers. Tensile tests were performed both on ours and on a high-end commercial testing machine, following the ISO 527 norm. Maximum stress, strain at maximum stress and Young’s modulus were calculated for each tested specimen: these measures allowed to compare the results of the two testers. Results proved coherent, thus validating the in-house machine, which was realized for a fraction of the cost of an equivalent commercial model.

Additive manufacturing offers several advantages when compared to conventional manufacturing technologies, especially where large scale customization is requested. In this article, a procedure for the design of a fully-customized 3D-printed ankle-foot orthosis (AFO) is described, with reference to a case study regarding a 21-year-old woman with an injured ankle. The first step is the acquisition of the geometrical data from the patient’s foot: this is done using photogrammetry. The second step is the data conversion and import in a CAD modeler; SolidWorks™ is chosen for this purpose. The AFO is modelled parametrically around the foot mesh and optimized in order to resist the predicted mechanical stresses. Finally, the device is 3D-printed on an FDM printer and tested on the patient. An excellent geometrical correspondence between the AFO and the patient’s foot is highlighted: this leads to great comfort and enhances medical functionality. The described procedure can be easily automated, further reducing the lead time and costs of the whole process