Development of an Innovative 3D-Printing Process for Reinforced Concrete – AMoRC Method

This article deals with the adjustment of a 3D printer for laser engraving and material cutting. The print head can be fitted with a solid laser diode module, which achieves a compact size while retaining its useful power. Two paths lead to the use of such a concept. It is possible to equip the existing print head with a module, which also brings a number of disadvantages such as, for example, the reduction of the printing space or the need for a suitable mounting design. A more elegant solution is to consider this in the design of a 3D printer and design a system to exchange the print heads for 3D printing and laser engraving. Such a solution allows full utilization of the workspace and simple installation of the effector for the required type of work. According to the installed power of the laser diode, it is possible not only to engrave but also cut material such as thin wood, veneer or acrylic glass. The use of such a machine is not only for graphic elements but for the creation of various stencils, boxes or simple models, which can be made up of plastic-burning pieces. The laser module is controlled by a driver, which is designed for the device. This is connected to a 3D printer control board. It is, therefore, necessary for the control board to have at least two pins, which can be controlled after adjusting the control firmware. Most laser modules are normally equipped with an adjustable lens, which is used to concentrate the focus of a laser for the given distance against the worktop. Thus, the modified 3D printer can perform its function as a multi-purpose CNC machine, while a basic platform similar for both devices is used.

Fracture behavior of intact and defected 3D-printed parts

From commercial pellets of recycled polyethylene terephthalate glycol (R-PETG), 1.75 mm diameter filaments for 3D printing were produced. By varying the filament’s deposition direction between 10° and 40° to the transversal axis, parallelepiped specimens were fabricated by additive manufacturing. When bent at room temperature (RT), both the filaments and the 3D-printed specimens recovered their shape during heating, either without any constraint or while lifting a load over a certain distance. In this way, free-recovery and work-generating shape memory effects (SMEs) were developed. The former could be repeated without any visible fatigue marks for as much as 20 heating (to 90 °C)-RT cooling–bending cycles, while the latter enabled the lifting of loads over 50 times heavier than the active specimens. Tensile static failure tests revealed the superiority of the specimens printed at larger angles over those printed at 10°, since the specimens printed at 40° had tensile failure stresses and strains over 35 MPa and 8.5%, respectively. Scanning electron microscopy (SEM) fractographs displayed the structure of the successively deposited layers and a shredding tendency enhanced by the increase in the deposition angle. Differential scanning calorimetry (DSC) analysis enabled the identification of the glass transition between 67.5 and 77.3 °C, which might explain the occurrence of SMEs in both the filament and 3D-printed specimens. Dynamic mechanical analysis (DMA) emphasized a local increase in storage modulus of 0.87–1.66 GPa that occurred during heating, which might explain the development of work-generating SME in both filament and 3D-printed specimens. These properties recommend 3D-printed parts made of R-PETG as active elements in low-price lightweight actuators operating between RT and 63 °C.

Novel multi-axial alveolar distractor — Part I: Design, manufacture, and mechanical/functional tests

A scientific base for optimising energy consumption and performance in 3D printing

Robotic arms have increasingly been applied to onsite building construction (e.g., bricklaying, welding, and 3D printing).However, engineers should make a great effort to customize different mobile platforms (e.g., quadruped, hexaploid, tracked robot) for robotic arms in the complex ground environment of the construction site.The cable-driven platform under the existing crane system has the potential to address this problem.Nevertheless, the robotic arm operation would cause the swing of the cable-driven platform.Therefore, this paper aims to propose a novel structure for the robotic arm, namely the center of gravity control margin (CoG-CM) robotic arm and its control algorithm to reduce the CoG movement in a cable-driven platform.Compared with the conventional robotic arm, the main contribution of the proposed one is that the arm consists of four parallel joints, which could provide the control capability of the system's CoG.This structure has infinite solutions for a determined target, and conventional control algorithms are unsuitable for this system.So, we formulate its CoG, and the robotic arm CoG pose control (ArmCoG-PC) is proposed to solve the kinematics of the CoG-CM robotic arm.Finally, the experiment on CoG-CM and typical 6degree-of-freedom robotic arms validate our proposal.

Biocompatibility is important for the 3D printing of resins used in medical devices and can be affected by photoinitiators, one of the key additives used in the 3D printing process. The choice of ingredients must be considered, as the toxicity varies depending on the photoinitiator, and unreacted photoinitiator may leach out of the polymerized resin. In this study, the use of ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (TPO-L) as a photoinitiator for the 3D printing of resin was considered for application in medical device production, where the cytotoxicity, colour stability, dimensional accuracy, degree of conversion, and mechanical/physical properties were evaluated. Along with TPO-L, two conventional photoinitiators, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), were considered. A total of 0.1 mol% of each photoinitiator was mixed with the resin matrix to prepare a resin mixture for 3D printing. The specimens were printed using a direct light processing (DLP) type 3D printer. The 3D-printed specimens were postprocessed and evaluated for cytotoxicity, colour stability, dimensional accuracy, degree of conversion, and mechanical properties in accordance with international standards and the methods described in previous studies. The TPO-L photoinitiator showed excellent biocompatibility and colour stability and possessed with an acceptable dimensional accuracy for use in the 3D printing of resins. Therefore, the TPO-L photoinitiator can be sufficiently used as a photoinitiator for dental 3D-printed resin.

3D-Printed specimens as a valuable tool in anatomy education: A pilot study

The need for creating realistic body parts and anatomical models using additive printing was long ago recognised. The paper "Rapid prototyping approaches for anatomical modelling in medicine" by M. McGurk et al. in Ann. R. Coll. Surg. Engl. 1997; 79; 169-174, which discussed 3-D printing of models, summarised the state of the art in this subject some years ago. Models were made by sprinkling liquid over a layer of precursor powder using inkjet printer nozzles to form a solid, thin slice. For each additional slice, the printing procedure was repeated until the item was finished as a "green state" component, which was then burned in a furnace to sinter it. The product was then subjected to further processing to create a full density portion. Large item 3D printing has been simpler than in previous years because to the development of software for computer controlled robotic XY motion systems used in the semiconductor and optical sectors. Layered building of 3D things is now a comparatively cheap and quick operation for 3D printing equipment thanks to software applications like SolidWorks, AutoCAD 360, and similar software products. Larger things may be 3D printed by either attaching rails above the print nozzles for X-Y motion directed from above the nozzles, or by positioning the object to be created on an X-Y table with motion supplied below the nozzles. The current work attempts to construct a 3D printing setup that utilises two robotic arms to print a single component. Here, the bed will be swivelled to a specific angle to prevent the robotic arms from becoming entangled, and the robotic arms will also move 180 degrees from their mean positions. Additionally, the related software will be developed locally in our lab, resulting in a shorter printing time and higher level of accuracy.

3D printing or Additive Manufacturing (AM) is significant in various applications. The authors’ previous research indicates that higher-degree-of-freedom (DOF) 3D printers have the potential for curved layer printing and multi-direction AM. Hence, this paper focuses on designing a novel 2T2R FDM 3D printer. Performance-chart-based design methodology (PCbDM) has been used for multiple parameters optimization problems due to its reliability, globality, and intuition. While its limitation is the number of optimization parameters less than four. The printer’s print head is attached to a planar parallel 1T1R mechanism (4R1P, 3R1P, and passive P). Objectives and requirements require the print head to move over a more considerable distance with a constant swing range and proper pressure angle. So, the 4R1P five-bar (virtual double-rocker, crank-rocker, and rocker-crank) has been investigated to facilitate PCbDM. Meanwhile, one DOF remote center of motion (RCM) mechanism has been integrated for decoupling motion control. Finally, the selected parameters are verified by comparing the numerical and simulation results and experiments. Besides, this novel 3D printer’s initial feasibility of flat and curved layer printing is studied with several printed parts to give qualitative analyses. This early-stage work generally intends to investigate the dimension synthesis and show the resulting 2T2R-type rotary 3D printer’s initial feasibility for curved printing. The research can help people understand how to carry out the dimension synthesis of 4R1P and a novel mechanism with multi-chain with the help of Grashof criteria to reduce the design space dimensionality.

Advances in 3D printing have enabled the use of this technology in a growing number of fields, and have started to spark the interest of biologists. Having the particularity of being cell friendly and allowing multimaterial deposition, extrusion-based 3D printing has been shown to be the method of choice for bioprinting. However as biologically relevant constructs often need to be of high resolution and high complexity, new methods are needed, to provide an improved level of control on the deposited biomaterials. In this paper, we demonstrate how microfluidics can be used to add functions to extrusion 3D printers, which widens their field of application. Micromixers can be added to print heads to perform the last-second mixing of multiple components just before resin dispensing, which can be used for the deposition of new polymeric or composite materials, as well as for bioprinting new materials with tailored properties. The integration of micro-concentrators in the print heads allows a significant increase in cell concentration in bioprinting. The addition of rapid microfluidic switching as well as resolution increase through flow focusing are also demonstrated. Those elementary implementations of microfluidic functions for 3D printing pave the way for more complex applications enabling new prospects in 3D printing.

We describe the design of the multi-finger anthropomorphic robotic hand for small-scale industrial applications, called AISRA (Anthropomorphic Interface for Stimulus Robust Applications), which can feel and sense the object that it is holding. The robotic hand was printed using the 3D printer and includes the servo bed for finger movement. The data for object recognition was collected using Leap Motion controller, and Naive Bayes classifier was used for training and classification. We have trained the robotic hand on several monotonous objects used in daily life using supervised machine learning techniques and the gesture data obtained from the Leap Motion controller. The mean accuracy of object recognition achieved is 92.1%. The Naive Bayes algorithm is suitable for using with the robotic hand to predict the shape objects in its hands based on the angular position of its figures. Leap Motion controller provides accurate results and helps to create a dataset of object examples in various forms for the AISRA robotic hand, and can be used to help developing and training 3D-printed anthropomorphic robotic hands. The experiments in object grasping experiments demonstrated that the AISRA robotic hand can grasp objects with different size and shape, and verified the feasibility of robot hand design using low-cost 3D printing technology. The implementation can be used for small-scale industrial applications.

Additive manufacturing, such as the 3D printing of composite materials for electronics is rapidly evolving, enabling the production of advanced electric and magnetic composites with tailored properties. These materials require special printing conditions and advanced control to maintain the desired material properties during the 3D printing process and in the final product design. Hence, determining the heating and energy consumption and estimating the efficiency of 3D printing is essential. This work modeled the fused filament fabrication 3D printing of composite materials with a polymer carrier matrix. A 3D time-dependent thermal model of a 3D printer extruder was developed and implemented using the finite element method to study and improve the efficiency of 3D printing. As the filler content influences the operational parameters and process energy consumption of the 3D printing process, the transient heating process parameters were estimated using different composite modifier contents. Two types of modifiers were considered: Fe2O3 and CaO, both mixed in a PLA carrier material. The volumetric fill ratio of the two modifiers did not exceed 45%, as the mixing dependency of the material properties is linear in this range. The power fluxes and power efficiency were estimated. The results provide new possibilities for better control methodologies and advanced additive manufacturing for new materials in electronics. Operational control can accelerate the 3D printing process, speeding up the heating of 3D-printed composite materials and reducing the printing time and total energy consumption. Furthermore, this research provides directions for new advanced 3D printing extruder designs with better power and energy heating efficiency.

In this paper, we improve an underactuated finger mechanism, design a robot palm, and a three finger robot hand with the finger designed. Solidworks simulation is used to verify the rationality of the design. The parts of the hand are modified for 3D printing, and the prototype of hand is produced by 3D printing which can reduce the production process with low cost, designing flexibility and other advantages. Finally, we make some grasping experiments for the prototype. The results show that the robot can grasp the objects with different sizes, and verify the rationality of the design and the feasibility of making the robot hand by 3D printing.

The subject matter of this paper is a smart design, control and security of a consumer-grade 3D printed robotic hand that replicates the hand movements controlled by a user-glove. The hand is controlled wirelessly through a secure server-client model. It also incorporates a simple but real-time signal processing and filtering to reduce noise and anomalies. In terms of materials used for 3D printing, a conscious decision was taken to use Polylactic acid (PLA) or PLA based wood filament which is recyclable and biodegradable. This paper also outlines the framework of Computer-Aided Design (CAD) models, 3D printing, programming, encryption, and testing. Overall, this paper presents a unique design of building a robotic hand using 3D printing and commonly used microcontroller to minimise costs and to maximise bespoke designs to individual needs.