Applied Mechanics and Materials Vols. 809-810

Abstract: From practical experience is well known that the establishment of the right values for the cutting regime parameters (without taking into consideration the cutting schematics) is requiring a large volume of work, thorough calculations and accurate input information regarding the process to be conducted. The high competition from the market is generating increased requirements concerning the productivity of processes, quality of the products as well as the production costs. There it is a strong correlation between these issues and the accurate determination of the cutting regime parameters. This article presents the methods of calculation for the cutting regime parameters for drilling process by using analytical method (classical) and automated method (by using specialized software packages) and the analysis of the results obtained with the goal of establishing which of them are providing the best results in the shortest period of time.

Abstract: Starting with the necessity to identify the optimum values of the cutting parameters which are affecting the surface quality, it is appropriate to use the design of experiment techniques to conduct the experiments. Previous researches [1] focused on the investigation of the effects of machining parameters on surface roughness. In this paper, the experiments were conducted based on the established Taguchi’s technique, L8 orthogonal array using Minitab-17 statistical software. Three machining parameters are chosen as process parameters: Cutting Speed, Feed per tooth and Depth of cut. The orthogonal matrix includes these three factors set for analysis, each with 2 levels associated. The level of influence that the process parameters exert on the surface roughness is analyzed by Taguchi method data analysis. In this case the signal to noise ratio was tacked into account. Also, the recommended configuration regarding the optimum values of these parameters was determined as well as the interactions between them, in order to obtain better surface roughness for 7136 aluminum alloy machining. The final results will be used as data for future research.

Abstract: Surface quality is affected by various processing parameters and inherent uncertainties of the metal cutting process. Therefore, the surface roughness anticipation becomes a real challenge for engineers and researchers. In previous researches [1] I have investigated the feed rate influence on surface roughness and manufacturing time reduction. The 7136 aluminum alloy was machined by end milling operation using standard tools for aluminum machining. The purpose of this paper is to identify by experiments the influence of cutting speed variation on surface roughness. The scientific contribution brought by this research is the improvement of the end milling process of 7136 aluminum alloy. This material is an aluminum alloy developed by Universal Alloy Corporation and is used in the aircraft industry to manufacture parts from extruded profiles. The research method used to solve the problem is experiment. A range of cutting speeds was used while the cutting depth and the feed per tooth were constrained per minimum and maximum requirements defined for the given cutting tool. The experiment was performed by using a 16 mm End milling cutter, holding two indexable cutting inserts. The machine used for the milling tests was a HAAS VF2 CNC. The surface roughness (response) was measured by using a portable surface roughness tester (TESA RUGOSURF 20 Portable Surface Finish Instrument). Following the experimental research, results were obtained which highlight the cutting speed influence on surface roughness. Based on these results we created roughness variation diagrams according to the cutting speed for each value of feed per tooth and cutting depth. The final results will be used as data for future research.

Abstract: In the last years there has been an increased demand to lower the impact of industrial activities on environment quality. Cutting fluids, among other products, are an important pollutant but they have often been associated with the need for a higher productivity of machining processes. Cutting fluids are a mean of reducing temperature in the cutting area, friction and tool wear but they also represent 7% to 17% of the production costs. Other problems raised by cutting fluids are: microorganism infestation, which can cause pulmonary and dermatological diseases and poor lubrication or corrosion caused by some of the chemicals. Dry cutting is regarded as the cleanest cooling method, but it has a reduced heat dissipation efficiency and practically there is no lubrication. Other relatively new green solutions concern the use of minimum quantity lubrication (MQL) and cryogenic machining.

Abstract: During cutting processes, due to the multiple causes which they have their error sources into the technological system, appears a series of processing errors. Depending by the source of influence, the radial deflection error will affect the accuracy of work piece processed. This paper proposes an experimental study under the aspects which follow the elimination of the radial deflection of a processed work piece. For that, it will be applied the principle of removing the excess material, by multiple processing passing over the processed surface, in order to eliminate the radial deflection. This research supposes that the radial deflection could be studied by measuring the relative distance between a transducer and the considered work piece, considering the machine tool as experimental stand.

Abstract: The knowledge about machinability indices for distinct machining processes allows finding the most appropriate values of the relevant factors for definite machining operations. Several criteria can be used to characterize machinability, such as the tool wear, the magnitude of the cutting forces, the roughness of the machined surfaces, or the shape of the chips that are formed during the machining process. One of the methods for studying the machinability is based on the analysis of drilling operations that are made under constant feed force. A drill press is probably the most readily available device to implement an experimental setup for drilling machinability tests. In normal operation, however, the chip accumulation at the dead end of the machined hole has a detrimental impact on the results of machinability tests, so that an improved setup was designed. A two-level, full factorial experiment with three independent factors (the drilling tool diameter, the rotational speed of the spindle and the feed force) has proven the suitability of the new experimental setup. Using it, we could find a power-type empirical model that explains the impact of the input factors in the depth of a hole that is machined in a pre-defined time interval.

Abstract: Optimization of cutting parameters in finish turning of medical stainless steel 316LVM with coated carbide tools using Taguchi method is proposed in this paper. Four cutting parameters namely, insert radius, depth of cut, feed and cutting speed are optimized with considerations of surface roughness as performance characteristic. The effects of cutting parameters on the surface roughness were experimentally investigated. Experimentation was conducted as per Taguchi's orthogonal array. Four cutting parameters with three levels are arranged in L₂₇ orthogonal array. The orthogonal array, measured values of surface roughness, signal-to-noise ratios and analysis of variance are employed to study the surface roughness. Based on the analysis, the optimal cutting parameter settings were determined. Through the confirmation test with optimal cutting parameter settings the effectiveness of the optimization approach are validated. The obtained results have shown that Taguchi method is suitable for optimizing the cutting parameter levels with the minimum number of experiments.

Abstract: The existing manufacturing technology of small mechanisms elements (gears, gear racks, displacers, bushings, precise mechanical parts, implants) is based on standard material removal techniques (turning, milling etc.). The problem is a variety of a polyamide materials chemical composition. Each additive has a significant influence to the material machinability in technological process. In a result it changes also resistance for melting of material in heat influence area. The method is based on automatically adaptation of parameters with author GRIP NC software and repeatable check of outer layer surface quality in various conditions and cutting strategies. Siemens NX Manufacturing module was used as a tool for operation simulation, parameters correction and G-code post processing tool. Fast G-code Generations gives possibility not only of parameters correction (that can be easily made in G-code itself) but also to optimize trajectory. Iterative comparison of surface roughness and chip flow monitoring were the main criteria that decided of cutting speed modification. On the output of the proposed method the proper cutting parameters table was prepared as well as a set of manufacturing recommendations. The case study is oriented to three polyamide modified materials: ERTHALON 6 PLA PA 6G, ERTALON LFX PA 6G (oil additive) NYLATRON GSM IPA 6 (MoS2 additive). Each material has a different set of fitted cutting parameters. Achieved results could be the guidance and provide proper outer surface roughness for (rough and finish) cutting operations like: axial and radial turning, threading and cutting.

Abstract: The implementation of the Differential Evolutionary Algorithm for the solution of a multi-pass turning optimization problem is presented in this paper. The optimization of a multi-pass turning process is a highly demanding problem due to the number of constraints imposed. A specific variation of the Differential Evolutionary Algorithm appropriate for the treatment of constrained problems is used. It is based on the separation of candidate solutions into those that satisfy all constraints and those that do not and the simultaneous execution of two optimization algorithms. Numerical results from the minimization of the production cost of a popular multi-pass turning problem with six degrees of freedom, namely cutting speed, feed rate and depth of cut of rough machining and finishing, validate the methodology. The selected problem is characterized by a number of equally stepped roughing passes and a final finishing pass of the cutting tool in order to obtain the desired metal part removal from the initial workpiece.

Abstract: Throughout my doctoral study I have encountered the problem of milling vulcanized rubber in a company specialized in the production of V-belts, which uses milling to generate the final surface of an assortment of V-belts. In this process I have encountered difficulties starting from fastening up to milling the rubber. At vulcanized rubber any error makes the workpiece to be rejected without the possibility to fix it, or not even to reuse the material. The reject rate at milling this assortment of V-belts is almost 40%. After we studied the literature from domain, we observed that the cutting issue of flexible polymeric materials is not well defined from some points of view, for this reason we made an experiment to observe the behavior of rubber at cryogenic and conventional milling, with a cutting speed of 2355m/min at a feed range between 0.0025 mm /tooth and 0.02 mm/tooth. As a result of the experimental study of milling vulcanized rubber type 3540, we observed that for the workpieces that were cooled with liquid nitrogen, the reject rate was reduced down to 20%. We also observed that, for the workpieces which were cooled with liquid nitrogen, feed milling had a small influence on the obtained surface quality.