Margareta Coteaţă

Drilling of Difficult-to-Cut Steel by Electrochemical Discharge Machining

In the case of workpieces made of difficult-to-cut materials, the small-diameter holes (1 mm diameter below) can be obtained by means of various nonconventional machining methods, one of these being the hybrid electrochemical discharge machining (ECDM). In the literature they researched, the authors could not find enough information that would allow them to establish adequate work conditions for the ECDM of small diameter holes by using an electrolyte. The use of a spring in order to obtain the work motion required to drill thin workpieces, and the need to remove the insulating film appearing on the workpiece, including in the last stage of the machining, were considered. The experimental research ended in the development of a power type function, which emphasizes the influence of the electrode tool diameter, of the voltage applied to the electrodes, of the capacity of the electric circuit involved in obtaining the electrical discharges, and of the density of the electrolyte upon the absolute axial wear of the electrode tool.

Electrospark Deposition by Using Powder Materials

Electrical discharges can be used to improve the operational properties of the surface layer of parts by using the phenomena of tempering, alloying, and deposition. Various techniques of alloying or deposition have been studied so far and sometimes even applied in the industry. The systemic approach of the deposition process shows which input and output factors can be taken into consideration. This article presents the experimental results obtained by using the deposition process based on the introduction of additional material such as powders put directly in the plasma channel corresponding to the electrical discharge. The established empirical mathematical models emphasize the influence exerted by the work gap value between the electrode and the workpiece, the powder flow, the delivered energy, and the specific energy on the quantity of added material.

Machinability of a Stainless Steel by Electrochemical Discharge Microdrilling

Due to the chemical elements included in their structure for ensuring an increased resistance to the environment action, the stainless steels are characterized by a low machinability when classical machining methods are applied. For this reason, sometimes non‐traditional machining methods are applied, one of these being the electrochemical discharge machining. To obtain microholes and to evaluate the machinability by electrochemical discharge microdrilling, test pieces of stainless steel were used for experimental research. The electrolyte was an aqueous solution of sodium silicate with different densities. A complete factorial plan was designed to highlight the influence of some input variables on the sizes of the considered machinability indexes (electrode tool wear, material removal rate, depth of the machined hole). By mathematically processing of experimental data, empirical functions were established both for stainless steel and carbon steel. Graphical representations were used to obtain more sugges...

Requirements statement in product design

One of the activities corresponding to the product design and development refers to clarifying the requirements necessary to be fulfilled by the final product. There are distinct opinions concerning the ways in which these requirements could be formulated and applied. The paper presents the results of a succinct analysis aiming to highlight the developing of product requirements in the case of applying the value analysis method and the axiomatic design method, respectively. The way in which the requirements are formulated in the case of a patent application is also considered. Results of the study were applied in the cases of designing some mechanical products.

Kerf generation during the plasma cutting process

The plasma beam cutting is a machining method applied in order to detach parts or workpieces from plate type workpiece. Essentially, a plasma jet is sent to workpiece, determining melting, vaporizing and removing of the material from the workpiece. If there is a relative movement between the plasma jet and the workpiece, a kerf gradually appears. Many factors exert influence on the kerf characteristics. A full factorial experiment with three independent variables at two levels was designed, in order to highlight the influence exerted by the cutting speed, workpiece thickness and arc current on the kerf width in the superior and inferior zones and on the kerf taper angle, respectively. Power type empirical mathematical models were determined by mathematical processing of the experimental results.

ECDM Drilling Process Analysis via Taguchi Method

Electrochemical discharge machining (ECDM) is based on synergetic action of anodic dissolution with erosive effect of electrical discharges in material removal process. Drilling by ECDM can be applied for hard to be cut materials, when no drilling by cutting or no EDM machine is available.

Machining of External Cylindrical Surfaces on a RAM Electrical Discharge Machine

As other nonconventional machining methods, the electrical discharge machining is applied when the workpieces materials are difficult to be machined by classical machining methods or the surfaces could not be obtained in efficient conditions by classical machining methods. Such a situation could appear, for example, when test pieces must be separated from materials whose machining by classical methods is difficult. Taking into consideration the necessity to detach a cylindrical test piece from a workpiece made of a high resistance metallic alloy, the problem of using the electrical discharge machining was formulated. An initial experimental test by using the common work motion of the tool electrode from up to down highlighted high shape errors, due to the accumulation in the work zone of the particles detached from the workpiece and from the tool electrode, as a consequence of electrical discharge machining process. A second set of experiments were developed, placing the test piece over the electrode tool and ensuring a work motion of workpiece from up to down; in this situation, a diminishing of the shape error was noticed. The second set of experiments highlighted a relatively reduced conicalness of the machined surface and a low decrease of the machining speed. as the penetration depth of the tool electrode in the workpiece increases, too.

Laser marking as a result of applying reverse engineering

The elaboration of a modern manufacturing technology needs a certain quantum of information concerning the part to be obtained. When it is necessary to elaborate the technology for an existing object, such an information could be ensured by using the principles specific to the reverse engineering. Essentially, in the case of this method, the analysis of the surfaces and of other characteristics of the part must offer enough information for the elaboration of the part manufacturing technology. On the other hand, it is known that the laser marking is a processing method able to ensure the transfer of various inscriptions or drawings on a part. Sometimes, the laser marking could be based on the analysis of an existing object, whose image could be used to generate the same object or an improved object. There are many groups of factors able to affect the results of applying the laser marking process. A theoretical analysis was proposed to show that the heights of triangles obtained by means of a CNC marking equipment depend on the width of the line generated by the laser spot on the workpiece surface. An experimental research was thought and materialized to highlight the influence exerted by the line with and the angle of lines intersections on the accuracy of the marking process. By mathematical processing of the experimental results, empirical mathematical models were determined. The power type model and the graphical representation elaborated on the base of this model offered an image concerning the influences exerted by the considered input factors on the marking process accuracy.The elaboration of a modern manufacturing technology needs a certain quantum of information concerning the part to be obtained. When it is necessary to elaborate the technology for an existing object, such an information could be ensured by using the principles specific to the reverse engineering. Essentially, in the case of this method, the analysis of the surfaces and of other characteristics of the part must offer enough information for the elaboration of the part manufacturing technology. On the other hand, it is known that the laser marking is a processing method able to ensure the transfer of various inscriptions or drawings on a part. Sometimes, the laser marking could be based on the analysis of an existing object, whose image could be used to generate the same object or an improved object. There are many groups of factors able to affect the results of applying the laser marking process. A theoretical analysis was proposed to show that the heights of triangles obtained by means of a CNC marking eq...

Surface roughness at vibroburnishing

Vibroburnishing is a finishing method of metallic surfaces based on plastic deformation of workpiece surface layer under the action of a ball which is pressed and rolls on the workpiece surface. As main process results, the surface roughness and the thickness of the layer affected by the burnishing tool pressure are considered. Some theoretical considerations highlighted some groups of process input factors able to affect the size of roughness corresponding to burnished surface. An experimental research was designed and developed in order to highlight the influence exerted by some vibroburnishing process input factors (frequency and amplitude of vibratory motion, radius of spherical surface corresponding to ball burnishing tool and the force exerted by the ball on the test piece surface) on the size of the Ra surface roughness parameter. Empirical mathematical models were established and analyzed.Vibroburnishing is a finishing method of metallic surfaces based on plastic deformation of workpiece surface layer under the action of a ball which is pressed and rolls on the workpiece surface. As main process results, the surface roughness and the thickness of the layer affected by the burnishing tool pressure are considered. Some theoretical considerations highlighted some groups of process input factors able to affect the size of roughness corresponding to burnished surface. An experimental research was designed and developed in order to highlight the influence exerted by some vibroburnishing process input factors (frequency and amplitude of vibratory motion, radius of spherical surface corresponding to ball burnishing tool and the force exerted by the ball on the test piece surface) on the size of the Ra surface roughness parameter. Empirical mathematical models were established and analyzed.

Nanoreliefs Obtained by Various Machining Methods

The nanoreliefs could be defined as surface asperities having height characteristics lower than one micrometer, in order to be expressed in nanometers. There are various applications that need nanoreliefs and this aspect determined the investigation of the possibilities offered by distinct manufacturing processes of obtaining nanoreliefs. A research concerning the manufacturing methods based on the material removal from workpiece was developed. The analysis revealed that there are machining methods by traditional cutting and nonconventional machining methods that use thermal or electrochemical phenomena in order to remove the material from workpiece. Some essential aspects of such machining methods were highlighted. The factors able to affect the asperities heights were showed. Experimental researches facilitated the identification of mathematical empirical models able to offer supplementary information concerning the influence exerted by some of the process input factors on the surface roughness parameter Ra. Surfaces profiles or images were obtained by means of instruments for investigation of the machined surfaces.