Volume 12, Issue 1, 2017/Journal Proceedings in Manufacturing Systems

Abstract: This paper presents a methodology for calculating the horizontal feed drives in heavy duty machines tools. Mathematical models presented allow statically and dynamically sizing or verification for heavy duty machine tools such as lathes, vertical lathes, milling machines of Gantry, AFP, AF types, etc. The calculations herein are of a general nature but can accommodate to different constructive variants chosen by the machine tool designer. The paper presents some technological and constructive aspects coming from authors’ experience. Taking into account that currently the feed drives have in most of the cases independent driving, it shows the calculation only for this variant of driving specific to CNC machine tools.

Key words: horizontal feed drive, heavy machine tools, mathematical models.

pp. 9-16 View full text

Eco-design of heat sinks based on CAD/CAE techniques

Tudor-George ALEXANDRU^1,*, Cristina PUPĂZĂ²

¹⁾ Eng., Machines and Manufacturing Systems Department, University "Politehnica" of Bucharest, Romania

²⁾ Prof., PhD, Machines and Manufacturing Systems Department, University "Politehnica" of Bucharest, Romania

Abstract: In the context of industry 4.0, the overall performance of manufacturing systems largely depends on the performance of embedded electronics. Such devices are responsible for conditioning information between machines and equipment such that desired input / output actions can be achieved. To be competitive, manufacturers are harnessing their products by performing several design decision loops based on the product’s overall performance during their lifecycle. Even so, due to new developing technologies such products become soon obsolete. Thus, high demands for new products cause large streams of electronic waste. To overcome this issue new design principles have emerged. Eco design together with the development of sustainable technologies help manufacturers to conceive their products in order to meet both environmental and customer requirements. Such interdisciplinary approaches maintain a balance between environmental costs and material necessities having a major impact on all lifecycle stages of a product. As a consequence, landfill is lowered and more value is added to the final product. Valuable knowledge is also achieved and transferred to new products by means of guidelines, check list and software extensions. Power electronics embedded in manufacturing systems requires proper thermal design to withstand high temperatures and perform according to the design specifications. Heat sinks are one of the most common devices used for cooling electronics. This paper deals with the lifecycle stages of heat sinks, discussing about the traditional CAD/CAE design tools extended to meet eco-design criteria. A case study illustrates the given concepts for the design of a variable speed drive passive cooler.

Key words: heat sinks, design tools, eco-design, variable speed drives.

pp. 17-22 View full text

Creep testing of epoxy resin-flax fiber composites

Constantin STOCHIOIU^1,*, Stéphane FONTAINE², Horia Miron GHEORGHIU³

¹⁾ Assistant Prof., Department of Materials Strength University "Politehnica" of Bucharest, Bucharest, Romania

²⁾ PhD, Prof., Department of Materials and Structures, Drive Laboratory, Superior Institute of Automotive and Transports, Nevers, France,

³⁾ PhD, Prof., Department of Materials Strength University "Politehnica" of Bucharest, Bucharest, Romania

Abstract: The present study proposes an experimental approach into determining the viscoelastic characteristics of a composite made out of an epoxy-resin matrix with long flax fiber reinforcement. In a first instance, the fabrication process will be discussed in detail, which consists of resin impregnation in the dry fiber and a thermo-compression. Afterwards, creep-recovery tests are performed at room temperature on the obtained samples in two sets of cyclic ramp loadings by varying, for the first one, the ramp load whilst keeping the creep time constant for each loading step and for the second one, a fixed load and a variable creep time. Reading of the elongation is made with the help of strain gages glued on the tested specimens for the entire duration of the experimenting session. Acoustic emission tests were performed during the creep phase for each load step in order to verify that there are no internal failures which might introduce plastic deformations. The samples are unidirectional, 0°, 90° and ±45° strips cut from the fabricated composite plates.

Key words: Creep, Flax Fiber, Fabrication, Composites, Epoxy, Bio-Material.

pp. 23-28 View full text

Measuring current discharge stored energy in capacitors welding

Victor POPOVICI^1,*, Delicia ARSENE², Claudia BORDA³

¹⁾ Assoc. Prof., PhD, Materials Technology and Welding Department, University “Politehnica” of Bucharest, Romania

²⁾ Lecturer, PhD, Materials Technology and Welding Department, University “Politehnica” of Bucharest, Romania

Abstract: This paper presents an alternative for measuring the discharge current welding with stored energy in capacitors. Spot welding equipment with stored energy electrostatic allow very harsh regimes that ensure very short times and high currents. These regimes welding allow precise metering of energy at welds and heat concentration in the desired region. Welding stored energy in capacitors is applied to welding materials and alloys with high thermal conductivity, welding special steels, where thermal cycling tough being put steel in the short time of welding restrict minimal heat affected zone and does not lead to formation of structures fragile at welding materials and alloys of different nature which occurs at the point where alloy weld is very small homogeneous. In the case of thin parts at the welding energy cannot be dispensed to produce apertures. The discharge current measurement (kA) in phase can be done with a coil-type transducer Regowski. Magnetomotive voltage provided by the Rogowski coil is taken by an integrator amplifier circuit. Chain calibration is shown for measuring the discharge current using Rogowski coil transducer and the experimental results regarding the variation of discharge currents according to the charging voltage and stored energy equipment and without turned to welding. Experiments are presented on the phenomenon of welding transformer core saturation. Disclosed is a method for measuring current discharge stored energy welding using a Hall transducer.

Key words: discharge current, stored energy in capacitors, weld current measurement, Rogowski coil.

pp. 29-34 View full text

Laparoscopic robotized instrument

Veronika IVANOVA^1,*, Ivan CHAVDAROV², Vesselin PAVLOV³

¹⁾ PhD, Department of Robotized Executive Mechanisms and Intelligent Systems, Institute of Systems Engineering and Robotics,

Bulgarian Academy of Sciences, Sofia, Bulgaria

²⁾Assoc. Professor, PhD, Department of Robotized Executive Mechanisms and Intelligent Systems, Institute of Systems Engineering and

Robotics, Bulgarian Academy of Sciences, Sofia, Bulgaria

³⁾Professor, PhD, Faculty Automatics, Technical University,”K. Ohridsky” av. #8, Sofia, , Bulgaria

Abstract: Robot-assisted surgery has many advantages over conventional surgery: greater spatial accuracy, dexterity and precision reliability, reproducibility and ultimately better patient outcomes. Investigations of current instruments for robot-assisted surgery such as daVinchi and ZEUS are indicated to have some technological deficiencies which must be overcome. The main objective of this work is focused on improving some technical deficiencies of existing robotized surgical instruments. For this reason we design a novel robotized instrument for laparoscopic surgery with better mechanical characteristics. In contrast to EndoWrist technology by Intuitive Surgical Incorporation – USA for daVinchi instruments (three orthogonal rotations) we offer other decision of the construction. The laparoscopic robotized instrument that was designed provides a kinematic structure with R ┴ R ║ R, which avoids additional rolls. As a consequence of the limitations by the operating environment - the manipulation is performed in a narrow working space inside the patient’s body through small surgical instruments, the motors are situated in the base of the instrument, which is disposed outside of the troacar, respectively, outside the human body. The model allows obtaining the optimal working area of this instrument and force feedback control. By developing of a novel type of specialized instrument for robots we have created more compact, simple, cheaper and easier robotic instruments than before. The paper includes a structure of a laparoscopic robotized instrument and describes the basic movements in the wanted working area. A kinematic-structural analysis of a novel construction with autonomous and dependent movement will be presented. Transfer functions are determined through a control system which provides control by the operator movements. In this case we have also developed a simulation program that outlines the workspace and the possible actions there. This program is not an object of present paper.

Key words: mechatronics, robotics, surgical robots, robot-assisted surgery, instruments, laparoscopy.

pp. 35-42 View full text

NC parameterization in rail wheel set re-profiling machining

Florea Dorel ANANIA^1,*, George CONSTANTIN², Claudiu-Florinel BÎȘU³, Andra Elena PENA⁴,

¹⁾ Lecturer, PhD, Machines and Production System department, University Politehnica from Bucharest, Romania

²⁾ Prof., PhD, Machines and Production System department, University Politehnica from Bucharest, Romania

³⁾ Assoc. Prof., PhD, Machines and Production System department, University Politehnica from Bucharest, Romania

⁴⁾ Lecturer, PhD, Machines and Production System department, University Politehnica from Bucharest, Romania

Abstract: The paper deals with Computer Aided Maufacturing (CAM) in the processing by turning on a lathe machine tool type, which is subject to a process of remanufacturing. The feed drives of the lathe are redesigned being associated with numerical control equipment. Moreover, on the machine tool is adapted a specific measurement system. The paper presents the most common defects and necessity of reshaping the wheel, which have suffered a process of wear, by turning on specialized machines. The paper presents a methodology and a case study for parameterization of a NC program for automation of a re-profiling turning process for a rail wheel set. The NC parameters are defined based on the nominal profile and the real damaged profile. The algorithm calculates the machining offset, depth of cut and number of passes based on the coordinates of the measured points.

Key words: Rail Wheel, Defects, Re-profiling, Turning, NC Parameterization.

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