articles+ search results

Mechanical engineering and machinery and TJ1-1570

A rapid prototyping technique is demonstrated which uses a red femtosecond laser to produce a metallic mould which is then directly used for the replica moulding of PDMS. The manufacturing process can be completed in less than 6 h making it a viable technique for testing new designs quickly. The technique is validated by creating a microfluidic device with channels of height and depth of 300 µm, with a ramp test structure where the height and width of the channels reduces to 100 µm to demonstrate the techniques 3D capabilities. The resulting PDMS device was easily removed from the metallic mould and closely replicated the shape aside the expected shrinkage during thermal curing. As the technique uses a single replica process, the surface roughness at the base of the channels corresponds to the un-ablated polished metal mould, resulting in a very low surface roughness of 0.361 nm. The ablated metallic mould surface corresponds to the top of the PDMS device, which is bonded to glass and does not affect the flow within the channels, reducing the need for optimisation of laser parameters. Finally, the device is validated by demonstrating laminar flow with the no-slip condition.

thermal insulation, rapid prototyping, heat transfer, thermal barrier, thermal conductivity, Mechanical engineering and machinery, and TJ1-1570

Nowadays, 3-D printing technology is very often applied in industry due to design cycles shortening and surface quality improvement when comparing to conventional manufacturing technologies. In order to adapt 3-D printed materials as thermal barriers, it is necessary to determine its thermophysical properties. As far as thermal insulation is concerned, the lowest thermal conductivity is required and therefore the crucial parameter of the material is the porosity. This paper presents the results of experimental investigation of effective thermal conductivity of thermal barriers with variable porosity fabricated by the fused filament fabrication technology. Also the numerical study was presented. The commercial code - COMSOL multiphysics was used to model the coupled heat transfer. The model was than validated by comparing the numerical and experimental results. For each sample the density and thermal conductivity were determined experimentally. The influence of the size and shape of the cell on the formation of free convection was investigated in particular. The effect of the conduction and radiation on temperature and velocity profiles within the enclosure has been analyzed. In addition, the dominant heat transfer mechanisms as a function of density have been identified.

Mechanical engineering and machinery and TJ1-1570

Digital prototyping is an innovative design method. With digital product prototyping techniques that are designed with the concept of Generative Design and Topology Optimization, the designer able to visualize and simulate the product start from the design, stress analysis to the product manufacturing process. The aim of this research is to optimization the topology of the product model results of generative design, determine the strength of the model through Stress Analysis used topology optimization 50%, 60%, and 70% of the product model results of generative design and figure the results of the product 3D printing in made prototype models as a result of generative design. This research is conducted in 3 steps, that is the preparation of made models with computing Autodesk Inventor Professional 2020, the analysis with generative design, and the printed with 3D printing. This 3D printed product is made in 2 models. Model 1 with a material reduction of 70% topology optimization was better than 50% or 60% material lighting. Model 2, the maximum of 50% Von Mises Stress reduction is smaller than the 60% and 70% reduction. Keywords: Digital prototyping, generative design, topology optimization

wrist orthosis, 3d printing, fused deposition modelling, multi-material, fdm, abs, tpu, Technology, Environmental technology. Sanitary engineering, TD1-1066, Mechanical engineering and machinery, TJ1-1570, Engineering (General). Civil engineering (General), TA1-2040, Manufactures, and TS1-2301

The paper presents design and manufacturing process of an individualized wrist orthosis. The patient’s upper limb was 3D scanned and the orthosis was design using a CAD system. Each part of the orthosis consists of two different materials, that fulfill different functions. By using the double-head Fused Deposition Modelling machine it was possible to produce theses parts in a single process without the need for additional assembly operations. The orthosis has been tested for mutual fit of parts, strength and comfort of use.

Friction coefficient, Tribological properties, Wear, Temperature in the contact area, Rapid prototyping technologies, 3D printing settings, Universal friction machine, Mechanical engineering and machinery, and TJ1-1570

This paper deals with the research of friction coefficient in tribopairs made of the polymers that are the most commonly used in rapid prototyping technologies. Parts manufactured with the use of a 3D printer with different settings of printing were chosen as samples for the experimental research. Friction coefficient and the temperature in the contact area during the runtime were measured using a universal friction machine MTU-1. The machine allows us to carry out tribological experiments using different contact schemes with or without lubricants. For this research, the scheme "plate-on-plate" was chosen. No lubricants were used. Wear of the samples was estimated after the experiments. Analysis of the experimental data has shown that changing of 3D printing settings has significant influence not only on the strength and stiffness of the parts, but also on the quality of the surface that affects the tribological properties of the tribopairs. The results of this research allow us to choose optimal settings for 3D printing depending on the required tribological properties of the parts, such as friction coefficient and wear.

Mechanical engineering and machinery and TJ1-1570

This research aims to explore a better kinematic performance and design scheme for a novel mechanical leg using parameter optimization method. Serial structural mechanisms are widely employed in anthropomorphic mechanism legs but with significant disadvantages of the complex structure and large inertia, particularly, for the multi-objective parameter optimization it is hard to select good parameters to achieve excellent performance. In this article, the plane model of the solution space for multiple parameters and a novel statistics parameter optimization method were proposed for a novel mechanical leg. In the position analysis, the structure and workspace for the novel mechanical leg were developed with simple structure, small inertia, and large workspace; and several kinematic performance evaluation indices were also proposed in the kinematics analysis. In the parameter optimization process, the design scheme and prototyping of the mechanical leg have shown a better kinematic performance by considering the assembly technique as compared with the conventional models. The proposed research provides the basis for the applications of the novel mechanical leg, which can be applied in the modern humanoid robot fields to meet the requirements of high stiffness, lower inertia, and good technological efficiency.

mechanic-electronic-hydraulic control system, fault diagnosis, virtual prototyping, simulated knowledge, pattern recognition, ensemble classifier, Mechanical engineering and machinery, and TJ1-1570

For the fault diagnosis of mechanic-electronic-hydraulic control system (MEHCS), the main barrier that restricts the application of knowledge-based methods is the lack of historical fault data. Aiming at this problem, this paper proposed a hybrid fault diagnosis method based on simulated knowledge from virtual prototyping. As a special form of mathematical model, virtual prototyping of MEHCS under faulty and nominal condition was established, validated, fault-injected and simulated to obtain simulation data. Fault features of different fault types were extracted, which were then trained by three pattern recognition methods to build the knowledge database for diagnosis. Threshold test and ensemble classifier constituted by the three pattern recognition methods were employed respectively to realize fault detection and isolation. To verify the proposed methodology, a case study of vessel steering system was presented. Fault types of stuck rudder and steady state error were studied. Probabilistic neural network (PNN), naive Bayes (NB), and k-nearest neighbor (kNN) were employed to constitute ensemble classifier based on majority voting. The diagnosis results showed that the accuracy of fault detection and isolation of both fault types were highly acceptable. The ensemble classifier performed better on comprehensiveness and smoothness than any individual pattern recognition method for the overall diagnosis. The proposed method might be an available choice for the fault diagnosis of MEHCS, especially for large-scale and complicated cases.

rapid prototyping, micro sensor chip, ITO, oxygen, pH, picosecond laser, cell monitoring system, top-down approach, Mechanical engineering and machinery, and TJ1-1570

We developed a confined microfluidic cell culture system with a bottom plate made of a microscopic slide with planar platinum sensors for the measurement of acidification, oxygen consumption, and cell adhesion. The slides were commercial slides with indium tin oxide (ITO) plating or were prepared from platinum sputtering (100 nm) onto a 10-nm titanium adhesion layer. Direct processing of the sensor structures (approximately three minutes per chip) by an ultrashort pulse laser facilitated the production of the prototypes. pH-sensitive areas were produced by the sputtering of 60-nm Si3N4 through a simple mask made from a circuit board material. The system body and polydimethylsiloxane (PDMS) molding forms for the microfluidic structures were manufactured by micromilling using a printed circuit board (PCB) milling machine for circuit boards. The microfluidic structure was finally imprinted in PDMS. Our approach avoided the use of photolithographic techniques and enabled fast and cost-efficient prototyping of the systems. Alternatively, the direct production of metallic, ceramic or polymeric molding tools was tested. The use of ultrashort pulse lasers improved the precision of the structures and avoided any contact of the final structures with toxic chemicals and possible adverse effects for the cell culture in lab-on-a-chip systems.

micropumps, microvalves, rapid prototyping, CO2 laser ablation, microdroplets, Mechanical engineering and machinery, and TJ1-1570

The fabrication of microdevices for fluidic control often requires the use of flexible diaphragms in a way that requires cleanroom equipment and compromises performance. We use a CO 2 laser to perform the standard ablative techniques of cutting and engraving materials, but we also apply a method that we call laser placement. This allows us to fabricate precisely-positioned and precisely-sized, isolated diaphragms. This in turn enables the rapid prototyping of integrated multilayer microfluidic devices to form complex structures without the need for manual positioning or cleanroom equipment. The fabrication process is also remarkably rapid and capable of being scaled to manufacturing levels of production. We explore the use of these devices to construct a compact system of peristaltic pumps that can form water in oil droplets without the use of the non-pulsatile pumping systems typically required. Many devices can be fabricated at a time on a sheet by sheet basis with a fabrication process that, to our knowledge, is the fastest reported to date for devices of this type (requiring only 3 h). Moreover, this system is unusually compact and self-contained.

Bimetal, Thermal deformation, Environmental heat, Passive dynamic walker, Thermal, Walker, Technology, Mechanical engineering and machinery, TJ1-1570, Control engineering systems. Automatic machinery (General), TJ212-225, Machine design and drawing, TJ227-240, Technology (General), T1-995, Industrial engineering. Management engineering, T55.4-60.8, Automation, T59.5, Information technology, and T58.5-58.64

Abstract This article reports on a newly designed thermal walker that can walk on a hot horizontal surface without any motor or battery. The walker converts heat energy from the hot surface into mechanical motion by using bimetal sheets. The prototype developed in the previous study successfully demonstrated walking, but its gait was not ideal; a leg swings forward and backward a few times to achieve one step. This article designs a new walker to realize more natural walking, in which a leg simply swings forward once in each step. For this purpose, the article introduces a new design process to better estimate the swing period. Also, material used for the feet of the walker is reconsidered to realize stable continuous walking. The newly fabricated prototype has aluminum feet and can walk on a hot horizontal surface with the simple gait. The surface temperature required for walking was 110 °C, which was considerably lowered from that in the previous study, which was 170 °C.

microfluidics, microfabrication, organ-on-a-chip, trans-epithelial electrical resistance, multi-culture, Mechanical engineering and machinery, and TJ1-1570

Microfluidic devices are gaining increasing popularity due to their wide applications in various research areas. Herein, we propose a two-layer multi-channel microfluidic device allowing for direct-contact cell-vessel co-culture. Using the device, we built a co-culture model of the outer blood-retina barrier (oBRB), mimicking the in vivo retinal pigment epithelial cells-Bruch membrane-fenestrated choroids. To demonstrate the versatility of the design, we further modified the device by inserting platinum electrodes for trans-epithelial electrical resistance (TEER) measurement, demonstrating the feasibility of on-chip assessment of the epithelial barrier integrity. Our proposed design allows for direct-contact co-culture of cell−cell or cell−vessel, modifiable for real-time evaluation of the state of the epithelial monolayers.

Mechanical engineering and machinery and TJ1-1570

Recently, the demand for designing mechanism-embedded artifacts has increased in personal digital fabrication. However, it is difficult for nonexperts without engineering knowledge to design and build a prototype with a kinetic mechanism. We present M.Sketch, a prototyping tool that helps nonexperts to design and build linkage-based kinetic mechanisms. It enables the user to easily configure the linkage-based mechanism with a simple interface applying a geometry drawing metaphor. The tool features computational support, including interactive visualization, top-down optimization, and connection to digital fabrication, to obtain and build the desired movement. In order to support science–art integrated science, technology, engineering, the arts, and mathematics (STEAM) education related to digital fabrication of interactive artifacts, we deployed M.Sketch in design workshops and student contests of walking robot design. The participants in the contests were able to successfully design and build walking robots with the Theo-Jansen mechanism using various support features of M.Sketch. Based on the development and deployment in science, technology, engineering, the arts, and mathematics educational domains, we figured out several implications, and further improvement points of prototyping tools supporting nonexperts in designing mechanism-embedded interactive artifacts.

upper limb, additive manufacturing, cosmetic prosthesis, medical prototype, Technology, Environmental technology. Sanitary engineering, TD1-1066, Mechanical engineering and machinery, TJ1-1570, Engineering (General). Civil engineering (General), TA1-2040, Manufactures, and TS1-2301

This paper describes prototyping of an individualized cosmetic arm prosthesis. Aim of the studies was to obtain an anatomically correct, lightweight prosthesis. It was accomplished using additive manufacturing technology of fused deposition modeling. The data was obtained by 3D scanning. An experimental concept of dual extrusion of two different materials was applied – the prosthesis was divided into an elastic shell and a rigid core, manufactured in one process. Obtained results were positive.

ankle orthosis, additive manufacturing, reverse engineering, Technology, Environmental technology. Sanitary engineering, TD1-1066, Mechanical engineering and machinery, TJ1-1570, Engineering (General). Civil engineering (General), TA1-2040, Manufactures, and TS1-2301

The paper presents design and manufacturing process of an individualized ankle orthosis using additive manufacturing technologies and reverse engineering. Conventional processes of manufacturing of orthosesareexpensive and time consuming -an alternative method was proposed. The patient’s leg was 3D scanned and the orthosis was designed using a CAD system. It was then manufactured using the Fused Deposition Modelling technology, assembled and fully tested. Positive results were obtained.

bevel gears, gear design, Tredgold, numerical simulations, Mechanical engineering and machinery, and TJ1-1570

This paper presents a semi-automated design algorithm for computing straight bevel gear involute profiles. The proposed formulation is based on the Tredgold approximation method. It allows the design of a pair of bevel gears with any desired number of teeth and relative axes inclination angles by implementing additive manufacturing technology. A specific case study is discussed to calculate the profiles of two straight bevel gears of a biomedical application. Namely, this paper illustrates the design of the bevel gears for a new laparoscopic robotic system, EasyLap, under development with a grant from POR Calabria 2014−2020 Fesr-Fse. A meshing analysis is carried out to identify potential design errors. Moreover, finite element-based tooth contact analysis is fulfilled for determining the vibrational performances of the conjugate tooth profiles throughout a whole meshing cycle. Simulation results and a built prototype are reported to show the engineering feasibility and effectiveness of the proposed design approach.

prototyping technique, microfluidics, soft lithography, ultraviolet (UV) laser direct writing, Mechanical engineering and machinery, and TJ1-1570

In microfluidic device prototyping, master fabrication by traditional photolithography is expensive and time-consuming, especially when the design requires being repeatedly modified to achieve a satisfactory performance. By introducing a high-performance/cost-ratio laser to the traditional soft lithography, this paper describes a flexible and rapid prototyping technique for microfluidics. An ultraviolet (UV) laser directly writes on the photoresist without a photomask, which is suitable for master fabrication. By eliminating the constraints of fixed patterns in the traditional photomask when the masters are made, this prototyping technique gives designers/researchers the convenience to revise or modify their designs iteratively. A device fabricated by this method is tested for particle separation and demonstrates good properties. This technique provides a flexible and rapid solution to fabricating microfluidic devices for non-professionals at relatively low cost.

dry photoresist, soft lithography, microfluidics, Mechanical engineering and machinery, and TJ1-1570

Fabrication of microfluidic devices by soft lithography is by far the most popular approach due to simplicity and low cost. In this approach PDMS (polydimethylsiloxane) is cast on a photoresist master to generate replicas that are then sealed against glass slides using oxygen plasma. In this work, we demonstrated fabrication of soft photolithography masters using lamination of ADEX dry film as an alternative to the now classic SU-8 resist masters formed by spin coating. Advantages of using ADEX dry film include the easily-achievable uniform thickness without edge bead; simplicity of the process with significant time savings due to non-sticky nature of the film; and fewer health concerns due to less toxic developing solution and antimony-free composition. As we demonstrate, the process can be performed in a low-cost improvised fabrication room in ambient light, in place of a conventional yellow-light cleanroom environment. We believe this approach holds the promise of delivering state-of-the-art microfluidic techniques to the broad field of biomedical and pharmaceutical research.

prototype fabrication, roll-to-roll (R2R) processing, polymeric thin film, microfluidic heat transfer, curved channels, Mechanical engineering and machinery, and TJ1-1570

This work presents the simple and rapid fabrication of a polymer-based microfluidic prototype manufactured by rolling up thin films of polymer. The thin films were fabricated via a casting method and rolled up around a center core with the aid of plasma activation to create a three-dimensional (3D) spiral microchannel, hence reducing the time and cost of manufacture. In this work, rolled-up devices with single or dual fluidic networks fabricated from a single or two films were demonstrated for heat sink or heat exchanger applications, respectively. The experimental results show good heat transfer in the rolled-up system at various flow rates for both heat sink and heat exchanger devices, without any leakages. The rolled-up microfluidic system creates multiple curved channels, allowing for the generation of Dean vortices, which in turn lead to an enhancement of heat and mass transfer and prevention of fouling formation. These benefits enable the devices to be employed for many diverse applications, such as heat-transfer devices, micromixers, and sorters. To our knowledge, this work would be the first report on a microfluidic prototype of 3D spiral microchannel made from rolled-up polymeric thin film. This novel fabrication approach may represent the first step towards the development of a pioneering prototype for roll-to-roll processing, permitting the mass production of polymer-based microchannels from single or multiple thin films.

Mechanical engineering and machinery and TJ1-1570

By far there is lack of research on different working conditions between rigid and flexible dynamics of truck mounted concrete pump booms. First a 3D model has been established by using virtual prototyping technology of a 37 m long boom in Pro/Engineering software. Then the rigid body simulation model has been built. Next modal superimposition method is adopted to change the 4 rigid body booms into flexible ones. Kinematics law and dynamic characteristics of 4 common working conditions had been studied then. Next tip displacement and the first boom hydraulic cylinder force of the 4 working conditions between rigid and flexible models have been researched. Furthermore the first natural frequencies of the structure have been calculated. The results show that the frequency of the horizontal condition has the lowest of all and the roof condition has the largest of all. Besides the cylinder forces of the flexible model are larger than the corresponding rigid ones because of the flexible boom vibration. Finally an experiment has been done on a boom test rig which proved that the established simulation model is reasonable and the frequency results are correct. All of these provide design reference to mechanical manipulator as well as reducing product development cost of such mechanism.

lab-on-a-chip, micro-injection-molding, femtosecond laser micromachining, fluorescent cytometry, cell phone, Mechanical engineering and machinery, and TJ1-1570

We have introduced a new hybrid fabrication method for lab-on-a-chip devices through the combination of femtosecond laser micromachining and removable insert micro-injection molding. This method is particularly suited for the fast prototyping of new devices, while maintaining a competitive low cost. To demonstrate the effectiveness of our approach, we designed, fabricated, and tested a completely integrated flow cytometer coupled to a portable media device. The system operation was tested with fluorescent plastic micro-bead solutions ranging from 100 beads/μL to 500 beads/μL. We demonstrated that this hybrid lab-on-a-chip fabrication technology is suitable for producing low-cost and portable biological microsystems and for effectively bridging the gap between new device concepts and their mass production.