Qualification of the Low-pressure Cold Gas Spraying for the Additive Manufacturing of Copper–Nickel–Diamond Grinding Wheels

Grinding wheels are usually manufactured by powder metallurgical processes, i.e., by molding and sintering. Since this requires the production of special molds and the sintering is typically carried out in a continuous furnace, this process is time-consuming and cost-intensive. Therefore, it is only worthwhile for medium and large batches. Another influencing factor of the powder metallurgical process route is the high thermal load during the sintering process. Due to their high thermal sensitivity, superabrasives such as diamond or cubic boron nitride are very difficult to process in this way. In this study, a novel and innovative approach is presented, in which superabrasive grinding wheels are manufactured by thermal spraying. For this purpose, flat samples as well as grinding wheel bodies were coated by low-pressure (LP) cold gas spraying with a blend of a commercial Cu-Al2O3 cold gas spraying powder and nickel-coated diamonds. The coatings were examined metallographically in terms of their composition. A well-embedded superabrasive content of 12 % was achieved. After the spraying process, the grinding wheels were conditioned and tested for the grinding application of cemented carbides and the topographies of both the grinding wheel and the cemented carbide were evaluated. Surface qualities of the ground surface that are comparable to those of other finishing processes were reached. This novel process route offers great flexibility in the combination of binder and hard material as well as a cost-effective single-part and small-batch production.

Study of Machine Characteristics During Rotary EDM Machining using Tools Made of Aluminium Alloy 6061

Electro discharge machining (EDM) is an unconventional machining process that uses spark energy to remove material from the workpiece. EDM process is extensively being used in die/mould making industries, automobile industry, aerospace industry etc. for generating complex and intricate shape on hard material. Numbers of research works have been carried out using EDM process in order to improve the performance. Further, different variant of EDM process like dry EDM, orbital EDM, powder mixed EDM, ultrasonic assisted EDM and rotary EDM etc. have also been studied. Rotary EDM process is very promising process that helps to improve surface finish, overcut as well as out of roundness. In the present paper, a extensive review has been presented on rotary EDM process. Significance of several input parameters has been observed on output characteristics like overcut and out of roundness.

Simulation of the Vibrations Produced to the Human Body During Operation of the Bucket Wheel Excavators. A Case Study of ERc 1400-30/7 Type Excavator

The paper deals with the analysis of the dynamic response over time of the excavator boom during operation. For a start, we determined the variation in time of the forces acting on the rotor shaft, due to the excavation. These forces have high values and a slow variation over time, which depends on the rotation speed of the bucket wheel and the number of buckets installed on it. A virtual model of the BWE boom was proposed, for which the dynamic response in time due to the excavation forces was determined, for a point in the main cabin of the BWE. A virtual sensor has been attached to this point corresponding to seat of the operator. The simulation of the dynamic response over time was performed taking into account a global damping of 2% of the critical damping. The simulation was performed both for the excavation of a homogeneous material and for the case of a shock (a sudden appearance of an inclusion of hard material during the cutting of the homogeneous material).

Auxetic Structures for Tissue Engineering Scaffolds and Biomedical Devices

An auxetic structure utilizing a negative Poisson’s ratio, which can expand transversally when axially expanded under tensional force, has not yet been studied in the tissue engineering and biomedical area. However, the recent advent of new technologies, such as additive manufacturing or 3D printing, has showed prospective results aimed at producing three-dimensional structures. Auxetic structures are fabricated by additive manufacturing, soft lithography, machining technology, compressed foaming, and textile fabrication using various biomaterials, including poly(ethylene glycol diacrylate), polyurethane, poly(lactic-glycolic acid), chitosan, hydroxyapatite, and using a hard material such as a silicon wafer. After fabricating the scaffold with an auxetic effect, researchers have cultured fibroblasts, osteoblasts, chondrocytes, myoblasts, and various stem cells, including mesenchymal stem cells, bone marrow stem cells, and embryonic stem cells. Additionally, they have shown new possibilities as scaffolds through tissue engineering by cell proliferation, migration, alignment, differentiation, and target tissue regeneration. In addition, auxetic structures and their unique deformation characteristics have been explored in several biomedical devices, including implants, stents, and surgical screws. Although still in the early stages, the auxetic structure, which can create mechanical properties tailored to natural tissue by changing the internal architecture of the structure, is expected to show an improved tissue reconstruction ability. In addition, continuous research at the cellular level using the auxetic micro and nano-environment could provide a breakthrough for tissue reconstruction.

Complex shaped micro-channels generation using tools fabricated by AWJ milling process

Fabrication of complex shape micro-channels is a major challenge for manufacturing industries. Currently in commercial applications, lithography and non-conventional machining processes like lasers, electro-discharge machining (EDM) and chemical etching are commonly used for fabrication of these channels. In the present work, a novel Abrasive water jet (AWJ) milling based tool fabrication strategy has been proposed and implemented to make micro-tools (die/ electrode). The path strategy for jet movement is considered in a manner to selectively remove metal from a piece of material such that the resulting three-dimensional features become the required die shape that can be used as tool for the texturing process. Micro-tool of complex shape as fabricated on hard material (EN 31) sheet of 12 mm thickness and its geometry were analysed by controlling the step over (SO) distance. Hydraulic control based hard press contact texturing setup was developed to analyse the performance of such fabricated tools. Experiments were conducted on soft materials like, PMMA, Copper, Brass, aluminium and Nylon. Taper along the depth of the channels was observed because of the taper of the tool during fabrication. During fabrication, width of the tool less than 200 μ m was found wavi in nature as there was not enough backing material present to bear the side wise jet pressure of impinging jet. Buckling on the tools was observed with tool height greater than 1 mm.

Optimization of in-Process Conditioning Parameters During Face Plunge Grinding of PcBN

Polycrystalline cubic boron nitride (PcBN) is an extremely hard material. Machining of the material is performed by grinding with diamond tools. Due to its high hardness, the grinding tools underlie a severe microscopic and macroscopic tool wear. This wear leads to a short tool life and results in high effort in conditioning the abrasive layer. Contrary to the usual conditioning of diamond grinding wheels with diamond dressing tools, this study investigates a conditioning process based entirely on the use of white corundum cup rolls. These conditioning tools allow the in-process face plunge conditioning of vitrified bond diamond grinding tools. The circumferential speed of the conditioning tool and the average grain diameter of the corundum are identified as the main factors influencing the topography of the generated grinding layer. To describe the performance of the conditioning process, a specific conditioning removal rate Q’sd is derived. This parameter represents a cumulated variable that allows a comparison of different conditioning strategies. It is shown that an increase in Q'sd significantly counteracts microscopic wear on the abrasive layer. Therefore, optimized process parameters enable the process of in-process conditioning to significantly reduce the wear on the grinding tool without increasing the process time or the non-productive time.

The Design of Individual Orthopedic Insoles for the Patients with Diabetic Foot Using Integral Curves to Describe the Plantar Over-Pressure Areas

Identification of over-pressure areas in the plantar side of the foot in patients with diabetic foot and reduction of plantar pressure play a major role in clinical practice. The use of individual orthopedic insoles is essential to reduce the over-pressure. The aim of the present study is to mark the over-pressure areas of the plantar part of the foot on a pedogram and describe them with high accuracy using a mathematical research method. The locally over-pressured areas with calluses formed due to repeated injuries were identified on the patients’ pedograms. The geometric shapes of the over-pressure areas were described by means of the integral curves of the solutions to Dirichlet singular boundary differential equations. Based on the mathematical algorithm describing those curves, the computer programs were developed. The individual orthopedic insoles were produced on a computer numerical control milling machine considering the locally over-pressured areas. The ethylene vinyl acetate polymers of different degrees of hardness were used to produce the individual orthopedic insoles. For the over-pressure areas, a soft material with a hardness of 20 Shore A was used, which reduces the pressure on the plantar side of the foot and increases the contact area. A relatively hard material with a hardness of 40 Shore A was used as the main frame, which imparts the stability of shape to the insole and increases its wear life. The individual orthopedic insoles produced by means of such technology effectively reduce the pressure on the plantar side of the foot and protect the foot from mechanical damage, which is important for the treatment of the diabetic foot.

PERANCANGAN PROGRAM EKOWISATA KERAJINAN TANGAN KOTA PALEMBANG PROVINSI SUMATERA SELATAN

ABSTRAKKota Palembang memiliki keanekaragaman sumberdaya budaya. Kesenian merupakan salah satu unsur budaya yang mencerminkan ciri khas suatu daerah asal kesenian. Kerajinan tangan merupakan salah satu kesenian Kota Palembang yang berpotensi sebagai daya tarik wisata. Ekowisata kerajinan tangan memiliki pengaruh dalam melestarikan produk kerajinan, meningkatkan perekonomian dan mensejahterakan para pengrajin tradisional di Kota Palembang. Tujuan penelitian ini adalah menginventarisasi dan mengindentifikasi sumberdaya kerajinan tangan di kota Palembang agar dapat dijadikan objek dalam rancangan program ekowisata di Kota Palembang Provinsi Sumatera Selatan. Metode yang digunakan yaitu studi literatur, wawancara, observasi langsung dan penyebaran kuisioner. Sumber daya wisata kerajinan tangan yang diinventarisasi terbagi menjadi dua klasifikasi yaitu kerajinan bahan keras dan bahan lunak. Terdapat empat kerajinan tangan di Kota Palembang yaitu terdiri dari satu kerajinan bahan keras dan tiga kerajinan bahan lunak. Sumber daya kerajinan tangan dianalis berdasarkan tujuh indikator penilaian Avenzora (2008) untuk mendapatkan hasil penilaian potensi sumber daya kerajinan tangan unggulan. Potensi kerajinan unggulan di Kota Palembang yaitu kerajinan Laker, Kain Songket, Kain Jumputan dan Ukir Kayu. Berdasarkan hasil identifikasi menunjukkan bahwa stakeholders setuju dan siap jika kerajinan tangan kota Palembang dimasukan ke dalam objek program ekowisata. Program Ekowisata dirancang dengan konsep eksplorasi kerajinan tangan yang melibatkan interaksi antara wisatawan dengan para pengrajin. Adanya program ekowisata kerajinan tangan ini diharapkan dapat merangsang pertumbuhan ekonomi kawasan dengan kapasitas masyarakat untuk mengelola sumberdaya. ABSTRACTPalembang City has the diversities of cultural resources. Art is the cultural element that reflects the characteristics of an area. The Handicraft is one of Palembang City's arts which has the potential as a tourist attraction. Handicraft ecotourism has the influences in preserving the handicraft products, improving the economy, and the welfare of traditional craftsmen in Palembang City. This research purpose is to inventory and identify the handicraft resources in Palembang city so that they can be used as objects in the ecotourism program design in Palembang City, South Sumatra Province. The method used is literature study, interview, direct observation, and the questionnaire distribution. The handicraft tourism resources that are inventoried are divided into two classifications, namely the handicrafts with hard materials and soft materials. There are four handicrafts in Palembang City, consisting of one hard material handcraft and three soft material handicrafts. The handicraft resources were analyzed based on the seven assessment indicators from Avenzora (2008) to get the results of the superior handicraft resources potential assessment. The superior handicrafts potentials in Palembang are Laker, Songket, Jumputan, and the wood carving. Based on the identification results, it shows that the Stakeholders agree and are ready if Palembang handicrafts are included in the ecotourism program object. The Ecotourism program is designed with the handicraft exploration concept that involves interaction between the tourists and the craftsmen. The handicraft ecotourism program is expected to stimulate regional economic growth through the resource arranged by the community.