This paper presents a study of 2D roughness profiles on a flat surface generated on a steel workpiece by ball nose end milling with linear equidistant tool paths (pick-intervals). The exploration of the milled surface with a surface roughness tester (on the pick and feed directions) produces 2D roughness profiles that usually have periodic evolutions. These evolutions can be considered as time-dependent signals, which can be described as a sum of sinusoidal components (the wavelength of each component is considered as a period). In order to obtain a good approximate description of these sinusoidal components, two suitable signal processing techniques are used in this work: the first technique provides a direct mathematical (analytical) description and is based on computer-aided curve (signal) fitting (more accurate); the second technique (synthetic, less accurate, providing an indirect and incomplete description) is based on the spectrum generated by fast Fourier transform. This study can be seen as a way to better understand the interaction between the tool and the workpiece or to achieve a mathematical characterisation of the machined surface microgeometry in terms of roughness (e.g., its description as a collection of closely spaced 2D roughness profiles) and to characterise the workpiece material in terms of machinability by cutting.

Designing an industrial robot gripper suitable for today’s industry is a challenging task due to the rapid evolution of products. Industrial robots are involved in machining, the transfer of parts, control and assembly, and the number of tasks performed by robots are increasing. Robots need to have the capability to adapt to new jobs consisting of new parts and new trajectories, and in most cases the preferred end effectors are grippers. In turn, grippers need to be flexible enough in order to cope with these changes. For this research, the authors propose a new gripper design which is capable of handling a large variety of parts with different sizes and shapes. In this research, an electrically actuated four-jaw gripper, with the capability of parallel movement of its jaws, is presented that also has the capability to fold the clamping jaws two by two and become a two-jaw gripper. Since the design is most suitable for additive manufacturing techniques, different additive techniques are analyzed for the manufacturing of the gripper. In the second part of the paper, different setups of the 3D printers are considered, such as infill percentage, raster angle and layer height. The main material on focus is a PET with grinded carbon-fiber reinforcement, but different materials are used for a better comparison of the rigidity of the system. This comparison is also presented in this article. The analysis of the material and 3D printing parameters are tested with Standard D638-14 probes used in a traction testing machine. After performing the traction test, the results are compared with FEA analysis. An optimal solution based on the experimental tests is proposed for the manufacture of the proposed gripper design.

For reduced mechanical stress, some chains with links made of metallic materials could be replaced by chains made of polymeric materials. A lower weight and a higher corrosion resistance would characterize such chains. From this point of view, research on the behavior of chain links made of polymeric materials under the action of tensile stresses can become important. Modeling by the finite element method highlighted some specific aspects of the behavior of a chain link subjected to tensile stresses. Later, we resorted to the manufacture by 3D printing of some chain links from four distinct polymeric materials, with the modification of the size of the chain link and, respectively, of the values of some of the input factors in the 3D printing process. The tensile strength of the chain links was determined using specialized equipment. The experimental results were processed mathematically to determine some empirical mathematical models that highlight the influence of the values of the input factors in the 3D printing process on the tensile strength of the samples in the form of chain links. It thus became possible to compare the results obtained for the four polymeric materials considered and identify the polymeric material that provides the highest tensile strength of the sample in the form of a chain link. The results of the experimental research showed that the highest mechanical resistance was obtained in the case of the links made of polyethylene terephthalate glycol (PETG). According to experimental results, when tested under identical conditions, PETG links can break for a force value of 40.9 N. In comparison, polylactic acid links will break for a force value of 4.70 N. Links printed in the horizontal position were almost 9-fold stronger than those printed in the vertical position. Under the same test conditions, according to the determined empirical mathematical models, PETG links printed in a horizontal position will break for a force of 300.8 N, while links printed in a vertical position will break for force values of 35.8 N.

This paper presents a study of the 2D roughness profiles on a flat surface generated on a steel work piece, by ball nose end milling, with linear equidistant tool paths (pick-intervals). The milled surface exploration with a surface roughness tester (on pick and feed directions) produces usually 2D roughness profiles having periodical evolutions. These evolutions can be seen as time-dependent signals, describable as a sum of sinusoidal components (the wavelength of each component being regarded as a period). In order to detect a well approximated description of these components, two appropriate signal processing techniques are used in this work: first technique provides a direct mathematical (analytical) description and is based on computer aided curve (signal) fitting (more accurate), the second technique (providing an indirect and incomplete description) is based on the spectrum generated by fast Fourier transform (less accurate). This study can be seen as a way for a better understanding the interaction between the tool and the work piece or to achieve a mathematical description of the machined surface microgeometry in terms of roughness (e. g. its description being a collection of closely spaced 2D roughness profiles).

The paper consists in analyzing some of the researches on specialized literature regarding to gripping systems and proposing a new solution for a gripping mechanism that can fulfill the increasing requirements imposed by the flexible manufacturing systems regarding the orientation and positioning of parts with variable shape and dimensions. Some general consideration on state of the art in the field of gripping mechanism are presented and main development direction are indicated. The second part of the paper contains in the development of new gripper constructive solution. From the literature analysis the main requirement for a gripping system is the multi-tasking ability. The proposed designed solution uses four parallel open-close jaws/fingers controlled by two electric motors. The actuation of the jaws/fingers for clamping the part is accomplished by a primary motor. The main contribution/improvement refers to the introducing of a second/supplementary motor that is used for the movement of the position of the jaws in order to transform the gripper clamping system from a four-jaw construction to a two-jaw gripper construction and vice versa, thus increasing range of clamped parts.