Volume 17, Issue 3, 2022/Journal Proceedings in Manufacturing Systems

²⁾ Lecturer, PhD., Eng., Robots and Manufacturing Systems Department, University "Politehnica" of Bucharest, Romania
³⁾ Student, Robots and Manufacturing Systems Department, University "Politehnica" of Bucharest, Romania

Abstract: For some models of industrial robot arms, due to the motors located inside or internal mechanisms that can generate heat, after a working period from the start of the robot, structural elements can heat up causing slight deformations of the robot. Because of the serial structure of the kinematic chain, expansions and torsions of structural elements lead to errors that cumulate towards the endpoint of the robot. This paper proposes the usage of a modified virtual model of a robot that is modeled closed to the actual deformed model to compute the right angular values for the joints of the deformed robot in order to still reach the initial programmed targets.

Key words: industrial robot, heating, errors, compensation

pp. 89-96 View full text

Finite element analysis of metal structures based on elongated Johnson cupola

Patricia Isabela BRAILEANU ^1,*, Sorin Cananau ², Tiberiu Gabriel Dobrescu ³, Nicoleta-Elisabeta Pascu ⁴

1) Lecturer, PhD, Department of Machine Parts and Tribology, University "Politehnica" of Bucharest, Romania

2) Prof., PhD, Department of Machine Parts and Tribology, University "Politehnica" of Bucharest, Romania

3) Prof., PhD, Department of Robots and Manufacturing Systems, University "Politehnica" of Bucharest, Romania

4) Assoc. Prof., PhD, Department of Robots and Manufacturing Systems, University "Politehnica" of Bucharest, Romania

Abstract: Nowadays, metal structures occupy an important segment in the field of buildable space due to the execution speed of the construction, easy assembly, the possibility of creating a modular structure, durability, etc. We find them most often in the construction of industrial halls, metal bridges, certain footbridges or overpasses, we can even find the metal structures either as urban furniture as recreation spaces, public transport waiting spaces, greenhouse structures or even in the form of furnished domes intended for various activities. This article aims to analyse the metallic structures that follow the geometry of Johnson's elongated cupola made of different metallic materials under different external static forces to observe the mechanical behavior of the three variants of elongated cupola characterized by Johnson Norman.

Key words: metal structures, elongated Johnson cupola, dome structures.

pp. 97-102 View full text

Laser cladding as repairing method for parts made of stainless steel

Sabin MIHAI ¹^,*, Diana CHIOIBASU ², Cristina MOHORA ³, Dana TILINA ⁴, Andrei C. POPESCU ⁵

¹⁾ PhD Student, Eng., Doctoral School of Industrial Engineering and Robotics, University "Politehnica" of Bucharest, Romnaia

²⁾ PhD, Eng., National Institute for Laser, Plasma and Radiation Physics (INFLPR), Magurele, Romania

³⁾ Prof., PhD Eng., Robots and Manufacturing Systems Department, University "Politehnica" of Bucharest, Romania

⁴⁾ Assoc. Prof., PhD, Robots and Manufacturing Systems Department, University "Politehnica" of Bucharest, Romania

⁵⁾ PhD, Scientific Researcher, National Institute for Laser, Plasma and Radiation Physics (INFLPR), Magurele, Romania

Abstract: This research study aims the rectification by coating of channels with depths of 0.5 mm, 1 mm and 2 mm, respectively. The experiments were carried out using the coating method by laser cladding with additive material in the form of 304 stainless steel powder particles. In a graphical engineering program were designed the technical drawings needed to create the channels by milling, which represent the macroscopic defects. In order to obtain homogeneous structures without internal defects, 600 W laser power, 0.6 m/min processing speed and 10 g/min powder flow assisted by a He gas mixture (4 slpm, carrier gas) – Ar were used (7 slpm, protective gas) process parameters were used. The width of a single line drawn using the optimal processing parameters was 1.9 mm and the optimal scanning strategy for the channel depth of 0.5 mm was 0.6 mm the distance of the hatch that forms the meander and in case of the other 2 different depths (1 mm and 2 mm) the horizontal distance was 1 mm and the vertical distance was 0.6 mm. Using these parameters, the rectification of macroscopic defects by laser cladding with additive material was achieved and the exceed material was kept at minimal values. The process proved to be thermally stable, the temperature varying between 1030–1100 °C. The lack of thermal fluctuations can be an indicator of the quality of the deposited structures. The cross-sectional microscopic analysis of the samples validated this theory, because all the structures proved to be free of internal defects.

Key words: laser melting deposition, stainless steel, laser cladding, macroscopic defects, rectification.

pp. 103-108 View full text

Stiffness parameters evaluation of panels hinge for Cardsat microsatellite deployment

Claudiu BÎŞU ^1,*, Tudor George ALEXANDRU ², Cristina PUPĂZĂ ³, Luminiţa GEORGESCU ⁴

¹⁾ Assoc. Prof., PhD, Robots and Manufacturing Systems Department, University "Politehnica" of Bucharest, Romania

²⁾ Lecturer, PhD, Robots and Manufacturing Systems Department, University "Politehnica" of Bucharest, Romania

³⁾ Prof., PhD, Robots and Manufacturing Systems Department, University "Politehnica" of Bucharest, Romania

⁴⁾ PhD Msc. Eng., Faculty of Industrial Engineering and Robotics, University "Politehnica" of Bucharest, Romania

Abstract: Self-opening panels are employed in the design of small satellites for extending their mission capabilities. Such solutions comprise an array of mechanical or electromechanically actuated joints that can deploy solar panels, communication antennas or scientific instruments in their operating position. Various sizing methodologies are depicted throughout the literature for deciding the optimal parameters of the deployment mechanisms. However, an accurate description of the loads that act on self-opening panels can only be achieved with the support of experimental and simulation procedures. The present paper studies the stiffness characteristics of laminar spring type joints in a new approach. Experiments are conducted on a laboratory scale prototype. An incremental pressure is applied normal to the spring surface. A displacement sensor captures the radial deflection of the specimen. Afterwards, a FEM simulation model is developed by taking into account the geometric and material characteristics of the assembly. The same loads and boundary conditions that are employed in the test platform are considered for completing the numeric study. A good match was noticed between the stiffness characteristics derived by means of experiments and simulations. The results achieved can be further used for replicating the linear elastic behavior of MAEVA joints.

Key words: small satellite, self-opening, laminar spring, stiffness, FEM simulation.

pp. 109-116 View full text

Modular design and modeling for qualification of small satellite deployers

Cosmin GOGU^1,*, Cristina PUPĂZĂ²

¹⁾ Ph.D. Student, Eng, Politehnica University of Bucharest, Robots and Manufacturing System Department, Romania

²⁾ Prof, Ph.D., Eng, Politehnica University of Bucharest, Robots and Manufacturing Systems Department, Romania

Abstract: Upcoming space missions depend essentially on the launch system development and its qualification. The paper presents a small satellite deployer benchmark and new trends in the domain. Integrators on the market only offer deploying services, and not much data is available regarding deployers' development. Cost savings and technology improvements may be achieved, but more research is still required. From this perspective the Cube-Sat's deployer design is a relevant example. The authors analyze the qualification requirements and related standards for the assessment of novel deployers applicable to the new generation of small satellites employed in upcoming space missions. The design of a new deployer and model preparation for FEA are described, and a preliminary dynamic verification is provided. Model validation methods are also presented. The gained knowledge from this study will be employed in future industrial projects.

Key words: small satellite deployer, modular design, model preparation, FEA, design qualification.

Electronic mail: orgcom@icmas.eu