Over the past few decades, additive manufacturing (AM) has become a reliable tool for prototyping and low-volume production. In recent years, the market share of such products has increased rapidly as these manufacturing concepts allow for greater part complexity compared to conventional manufacturing technologies. Furthermore, as recyclability and biocompatibility have become more important in material selection, biopolymers have also become widely used in AM. This article provides an overview of AM with advanced biopolymers in fields from medicine to food packaging. Various AM technologies are presented, focusing on the biopolymers used, selected part fabrication strategies, and influential parameters of the technologies presented. It should be emphasized that inkjet bioprinting, stereolithography, selective laser sintering, fused deposition modeling, extrusion-based bioprinting, and scaffold-free printing are the most commonly used AM technologies for the production of parts from advanced biopolymers. Achievable part complexity will be discussed with emphasis on manufacturable features, layer thickness, production accuracy, materials applied, and part strength in correlation with key AM technologies and their parameters crucial for producing representative examples, anatomical models, specialized medical instruments, medical implants, time-dependent prosthetic features, etc. Future trends of advanced biopolymers focused on establishing target-time-dependent part properties through 4D additive manufacturing are also discussed.

Introduction: Traumatology of the maxillofacial region represents a wide range of different types of facial skeletal injuries and encompasses numerous treatment methods. Application of computer-aided design (CAD) in combination with rapid prototyping (RP) technologies and three-dimensional computed tomography techniques facilitates surgical therapy planning for efficient treatment. Objective: The purpose of this study is to determine the efficiency of individually designed implants of poly-DL-lactide (PDLLA) in the reconstruction of blowout fractures of the orbital floor. Methods: In the course of a surgical treatment, individually designed implants manufactured by CAD/RP technologies were used. Preoperative analysis and postoperative monitoring were conducted to evaluate the successfulness of orbital floor reconstruction using customized PDLLA implants, based on: presence of diplopia, paresthesia of infraorbital nerve, and presence of enophthalmos. Results: In 6 of the 10 patients, diplopia completely disappeared immediately after surgical procedure. Diplopia gradually disappeared after 1 month in 3 patients, whereas in 1, it remained even after 6 months. In 7 patients, paresthesia disappeared within a month after surgery and in 3 patients within 2 months. Postoperative average Orbital volume (OV) of the injured side (13.333 ± 3.177) was significantly reduced in comparison with preoperative OV (15.847 ± 3.361) after reconstruction of the orbital floor with customized PDLLA implant (P < 0.001). Thus, average OV of corrected orbit was not different compared with the OV of the uninjured orbit (P = 0.981). Conclusions: Reconstruction of blowout fractures of the orbital floor by an individually designed PDLLA implant combined with virtual preoperative modeling allows easier preoperative preparation and yields satisfactory functional and esthetic outcomes.

One Contribution to the Friction Investigation in Bulk Metal Forming: Friction is resistance to relative motion when one body slides over another. In metal forming operations, both sheet metal and bulk metal forming, friction is undesirable but also unavoidable occurrence. It has negative impact on main process parameters as well as on workpiece quality. In order to obtain accurate results in metal forming experiments or simulations, the precise value of friction has to be known. In this paper several methods for friction evaluations, such as ring test, forward bar extrusion, backward - forward hollow extrusion, twist extrusion are presented and analyzed. A new double backward extrusion model is proposed.

Narrow layers of severe plastic deformation are often generated near frictional interfaces in deformation processes as a result of shear deformation caused by friction. This results in material behavior that is very different from that encountered in conventional tests. To develop models capable of predicting the behavior of material near frictional surfaces, it is necessary to design and carry out tests that account for typical features of deformation processes in a narrow sub-surface layer. In the present paper, upsetting of steel specimens between conical and flat dies is used as such a test. The objective of the paper is to correlate the thickness of the layer of severe plastic deformation generated near the friction surface and the die angle using a new criterion for determining the boundary between the layer of severe plastic deformation and the bulk.

Diabetic foot ulcer patients are usually unaware of excessive pressure on their feet due to lost pressure sensitivity. Offloading insoles are used to alleviate foot pain. This study investigated the effect of infill pattern and infill density on plantar pressure reduction for 3D-printed insoles while walking. The study involves five infill patterns: grid, honeycomb, triangle, cubic, and gyroid, along with several infill densities ranging from 14% to 20%. The test 3D-printed thermoplastic polyurethane specimens were assessed for mechanical properties to identify suitable infill patterns for creating prototypes of insoles. The results indicated that the honeycomb infill pattern exhibited the highest maximum compression load at 50% compressive strain and has a significant area under the loading-unloading curve, signifying high energy absorption. Conversely, the gyroid infill pattern exhibited the lowest maximum compression load at 50% compressive strain and minimal energy absorption. Both infill patterns with 20% infill density were applied in 3D-printed insoles and tested on the foot plantar pressure of healthy male volunteers during walking. No statistically significant differences in plantar pressure were observed between the two infill patterns compared to walking without insoles. A reduction in plantar pressure at hindfoot was observed when using the insoles, although this change was not statistically significant.