In Slovenia, there is widespread use of structural drilling along with classical core drilling. Recently, however, the need has arisen for a highly effective core drilling method with the aid of which high-quality core might be obtained. In order to achieve this aim, one among several Slovenian companies dealing with geological surveying has decided to implement structural drilling using a high-frequency drilling method. The following article presents the theoretical foundations for such a high-frequency method, as well as the manner of its implementation. In the final part of the article, a practical comparison between the conventional and the high-frequency core drilling methods is also provided.
J. Shanafield, A. Otieno, R. Tatara, D. Schroeder and K. Rosentrater
Surface roughness and diametral consistency of holes drilled into DDGS/phenolic resin blends
In this study, corn-based distillers dried grains with solubles (DDGS) has been utilized as a filler and blended with phenolic resin. The blends were compression molded into rectangular test specimens, into which holes have been machined using a standard 9.52 mm (3/8 in) diameter, two-fluted twist drill. A series of tests was then conducted to examine the effects of DDGS content, cutting speed, and feed rate upon the surface finish (roughness) of the interior hole slot, as well as the consistency of the drilled hole diameter. DDGS content was 0, 25, 50, and 75%, by weight. Cutting speed was 17, 30, and 46 m/min (55, 100, and 150 ft/min). Feed rate was 0.025, 0.152, and 0.279 mm/rev (0.001, 0.006, and 0.011 in/rev). Results indicate that as the DDGS content increased, roughness exhibited a weak but statistically significant decrease. When the cutting speed increased, roughness increased slightly. However, when feed rate increased, roughness increased at a greater rate than that due to cutting speed. In terms of diametral consistency, the effect of adding DDGS resulted in holes with diameters less than the nominal drill size. As cutting speed increased, the holes tended to be oversized. Based on the cutting speed and feed rate levels used, optimal machining conditions which would reduce roughness occurred for 75% DDGS, cutting speed of 17 m/min (55 ft/min), and feed rate of 0.025 mm/rev (0.001 in/rev). However, to maintain consistent hole diameter, optimal conditions were found to be 40% DDGS, 30 m/min (100 ft/min), and 0.152 mm/rev (0.006 in/rev) and would produce a drilled hole with a diameter of 9.52 mm (0.375 in). As the use of biofillers in plastic composites evolves, it will become increasingly important to examine the machinability of these novel materials.
Background/Aim: The drilling process for insertion of an implant should be as conservative as possible, as not to damage the future implant bed. If this drilling is conservative additional bone can be obtained to be used afterwards, during the same surgery, as bone graft particulate if needed. The objective of this study was to evaluate the efficiency of a biological low-speed drilling and to analyse the bone obtained in order to ascertain viability and vitality of the contained bone cells. Also, the bone obtained from the low-speed drilling was compared with bone obtained with high speed drilling and irrigation, collected through a filter in aspiration system.
Material and Methods: In this pilot study, samples of biological drilling (low speed without irrigation) were collected in five patients undergoing implant surgery. In the same patients a high speed drilling with irrigation was also used. Bone of the drilling was collected through a filter in the aspiration system. Subsequently the samples were analysed by conventional histology and cultivated in order to observe cell growth.
Results: The samples of bone obtained by biological drilling showed live cells in the conventional optical microscopy and cell growth after cultivation. The bone obtained with drilling at high revolutions showed no living cells and no cell growth after cultivation.
Conclusions: The biological drilling at low speed offered two advantages compared to drilling at high speed with irrigation. The first of these is the perfect control of the drilling depth as the marks of the burs are visible during drilling; the second is possibility of collection of a large number of viable particulate bone grafts without increasing time and complexity of the surgery, which allows immediate augmentation of bone if needed.
George Boiadjiev, Ivan Chavdarov, Kamen Delchev, Tony Boiadjiev, Rumen Kastelov and Kazimir Zagurki
This paper represents the development of a prototype robotic system for automatic bone drilling in orthopaedic surgery. A new design of the mechanical structure is proposed, answering the surgical requirements for the robot dimensions and weight to be as small as possible. The new structure design is based on idea of parallelism of the axis of the linear actuator and the axis of the rotary one. The control system is improved by using a new micro-controller. A new type of linear drive and a new force sensor (load cell) are built in, so that the quality characteristics of the “Orthopaedic bone Drilling Robot” (ODRO) are not only the same as previous its two versions, but becomes better.
An experimental setup is arranged and experiments are executed to test and to verify the robot quality features and functional capabilities.
Abdelkader Hadidi, Boualem Remini and Mohamed Habi
This article discusses the various water harvesting techniques used in the oases of Boussemghoun, Moghrar and Tiout for more than nine centuries. Several hydrological assessments have been conducted in the three oases since 2002 including surveys and investigations with the local communities. The results obtained showed that after the decrease in discharge of the sources, the population had resources to various ancestral hydraulic infrastructures such as: well, foggara, and small dams (Essad). The water harvesting technique is specific to the region and depends on the hydrogeology and the topography. Traditional low-flow water-saving technologies preserve the environment, modern hydraulic techniques give more water but have a negative impact on the environment. The drying up of springs and lowering of water tables are the result of the population growing and the socio-economic development. They require more and more water. A compromise between traditional and modern techniques (or types of management) can solve this problem.
Andrej Czan, Anton Martikan, Jozef Pustay, Viktor Kuzdak and Jozef Mrazik
The article deals with drilling of titanium alloys, which are becoming more widely used in aerospace and automotive industry as well as in other sectors for its specific properties such as hardness, corrosion resistance, biocompatibility, etc. The aim of this article is basic research with focus on drilling conditions of titanium alloy using HSS drill bits with diameter ø2,3 mm with PVD coating and without coating on CNC turning machine Polygim Diamond 12 series. This research can support problem solutions in small diameter drilling.
This article deals with the use of a multi-function system for complete machining. It compares the use of conventional tools with multi-function system on the basis of main indicators of the quality of machining.
Václava Pokorná, Jan Roub, Jan Řehoř and Jaroslava Fulemová
The topic of producing accurate holes (IT6 and better) has been often discussed these days. Many research projects have started under the Department Technology of Machining, Faculty of Engineering at the University of West Bohemia in Pilsen. These projects are focused on measuring the influence of defined factors of machining on required quality, i.e. integrity of the hole surface. The first phase of the research was focused on issues of parameters of drilling technology, which almost always comes before the reaming technology. This text explores this study, which serves as a core resource for related experiments. The main aim was to gather and sort the information from authors, who discuss in their publications questions of key factors to drilling and lathing technology, with regards to evaluating accuracy of produced holes. Foreign publications were used for this research as well as Czech information sources.
The laser processing of materials which are highly reflective at laser wavelengths is problematic. We have to take into account that only a small part of the energy is absorbed, the main part being reflected. In this article we examine the laser processing of highly reflective copper and silver at 1070 nm wavelength. In laser drilling of printed circuit boards it is necessary to drill copper layer as well. In highly reflecting materials we can drill smaller holes because of the low energy efficiency. Naturally in single pulse laser drilling the focus position plays a key role: at the focal spot of the laser beam smaller diameter holes are produced, further from the focal spot, higher diameter holes are produced.
Eva Buranská, Ivan Buranský, Michaela Kritikos, Kristína Gerulová and Ján Líška
The paper is focused on the experiment where the effects of the cutting environment and feed of drilling on the bores roughness and cylindricity were evaluated. Dry drilling of aluminium alloys (without using cutting fluids) is an environmentally friendly machining process but also an extremely difficult task, which is due to the tendency of aluminium to adhere to the drills made of conventional materials such as high-speed steel; and therefore three cutting environments (namely two different emulsions and compressed air) were used in the experiment. The article demonstrates multicriterial optimization of input factors (cutting environment, feed) for two defined target functions: roughness and cylindricity). The measured values were subjected to mathematico–statistical Analysis of Variance (ANOVA). ANOVA was used for examining the effects of machining parameters and their contribution to the surface roughness and bores cylindricity. The optimal cutting parameters were evaluated for “Smaller-the-Better” quality characteristics of both output responses, as can be seen in our article published previously. Based on the ANOVA, we determined that cutting environment exhibited higher percentage of contribution on bores quality than feed of machining. The results show 77.37 % impact of cutting environment and 8.13 % impact of feed on quality of machined bores.