S. Plaza

Computer simulation of wire-EDM taper-cutting

Wire electro discharge machining (WEDM) has become one of the most popular processes for producing precise geometries in hard materials, such as those used in the tooling industry. Since it is recognized as a precision process, optimization of different aspects related to dimensional accuracy is a classic research topic. The so-called taper-cutting involves the generation of inclined ruled surfaces, and it is especially important in the manufacturing of tooling requiring draft angles. In this paper a computer simulation software for the analysis of error in wire EDM taper-cutting is presented. The software is based on previous research work, but it includes the effect of friction to model adequately the cutting of large angles. Experimental tests have been carried out to establish the limits of application of the software, and the results compared with those obtained by the classical trial-and-error method. Although this latter approach is more precise, computer simulation dramatically reduces experimental work and the degree of accuracy can be acceptable for many applications, one of which is presented in the current paper.

Computer simulation of performance of electrical discharge machining operations

The electrical discharge machining (EDM) process is optimum for accurate machining of complex geometries in hard materials, as those required in the tooling industry. It has become by far the most popular among the non-conventional machining processes. However, although a large number of EDM machines are sold every year, available knowledge of the process is still very empirical. Experimental trials are required in many cases to set up the optimum conditions for an EDM operation, resulting in increases in lead-time and cost for the final part. The reason for this is the complex nature of the process, highly stochastic, that involves simultaneous interaction of thermal, mechanical, chemical and electrical phenomena. Therefore, research efforts must be directed towards process modelling in order to reduce the experimental cost associated to the technology. In this work, an original computer simulation model of the EDM process is presented. The model is based on the numerical calculation of temperature fields within the workpiece, from which the amount of part material removed per discharge can be estimated. The objective is to theoretically predict material removal rate (MRR) and the final surface finish of the machined part using as input variables the EDM process parameters and the properties of the work material. The model has been validated by carrying out tests on an industrial EDM machine, showing that it can adequately predict MRR and surface roughness with errors below 9%.

Analysis of Micro-Pin Manufacturing Using Inverse Slab Electrical Discharge Milling (ISEDM) Process

Abstract. This paper analyses the technological capabilities of a novel rotary (EDM) electrical discharge machining process for the manufacturing of high aspect ratio cylindrical micro-components. The process is called Inverse Electrical Discharge Grinding (ISEDM). An experimental analysis has been carried out on high speed steel (tool steel Vanadis 23), using a conventional EDM machine and graphite electrode. The effect of pulse off-time, work piece final diameter and machining length on material removal rate, electrode wear ratio, radial accuracy and surface roughness has been quantified. From the study, optimum strategies that involve the use of different EDM regimes for achieving the optimum requirements can be defined. Micro-pins of 0.3 mm diameter with aspect ratio as high as 100:1 have been successfully manufactured.

Modeling recast layer and surface finish in the manufacturing of high–aspect ratio micro-tools using the inverse slab electrical discharge milling process

Electrical discharge milling–based processes are a good alternative for the manufacturing of micro-tools. However, some limitations must be considered both on the fields of process cost and control of surface characteristics. The inverse slab electrical discharge milling (ISEDM) process is an economic alternative to other high-precision high-cost machining processes because a conventional slab electrical discharge milling (SEDM) machine can be used to produce high–aspect ratio cylindrical tools with diameters as low as 200 µm. In this article, the influence of process variables on the surface integrity generated by the ISEDM process is presented. An experimental model aiming at the prediction of both surface finish and thickness of the recast layer as a function of the spark characteristics is developed. The influence of process variables is then analyzed. The model was validated with a high degree of agreement by carrying out experimental tests on submicron sintered high-speed steel micro-pins. Micro-tools with a diameter 335 µm and an aspect ratio as high as 90:1 can be manufactured using this novel technique with a surface finish below Ra 0.7 µm and thickness of recast layer below 3 µm.

Characterization of the Response of Embedded Thermocouples in Grinding

Temperature measurement in grinding has been a widely analyzed field in the study of the process. Temperatures in grinding are too difficult to measure due to the high gradients in the ground workpiece. A lot of different methods have been employed by many researches in the last years. In this paper the use of thermocouples is analyzed attending to the mathematical characterization of their response. It will be shown that correct modeling of the thermocouple’s response permits the avoidance of the problem of thermal inertia, making thus possible the use commercial thermocouples for temperature measurement in grinding.

Unexpected Event Prediction in Wire Electrical Discharge Machining Using Deep Learning Techniques

Theoretical models of manufacturing processes provide a valuable insight into physical phenomena but their application to practical industrial situations is sometimes difficult. In the context of Industry 4.0, artificial intelligence techniques can provide efficient solutions to actual manufacturing problems when big data are available. Within the field of artificial intelligence, the use of deep learning is growing exponentially in solving many problems related to information and communication technologies (ICTs) but it still remains scarce or even rare in the field of manufacturing. In this work, deep learning is used to efficiently predict unexpected events in wire electrical discharge machining (WEDM), an advanced machining process largely used for aerospace components. The occurrence of an unexpected event, namely the change of thickness of the machined part, can be effectively predicted by recognizing hidden patterns from process signals. Based on WEDM experiments, different deep learning architectures were tested. By using a combination of a convolutional layer with gated recurrent units, thickness variation in the machined component could be predicted in 97.4% of cases, at least 2 mm in advance, which is extremely fast, acting before the process has degraded. New possibilities of deep learning for high-performance machine tools must be examined in the near future.

Industrial Application of the MCG (Minimum Coolant Grinding) Technology

The use of fluids in grinding is necessary to carry out an optimized process that avoids any kind of damage in the ground workpieces. However, the use of fluids in machining processes presents some problems as the economic one and the environmental one. The present work analyzes the industrial viability of a new solution to avoid the use of fluids in grinding, the MCG system. This system combines the use of a MQL (Minimum Quantity Lubricant) commercial system and a gas supplied at low temperatures. In this case the grinding of a component of the engine of a competition motorcycle with the MCG (Minimum Coolant Grinding) system is compared with the classic fluid flow system.

Implementation of Simulation Software for Better Understanding of Manufacturing Processes

The adaptation of universities to the European Higher Education Area (EHEA) plays an essential role in society, creating new knowledge, transferring it to students by means of new and more active methodologies aimed at learning that will enable students to put everything they learn into practice. However, such methodologies are not equally applicable in all subjects. Subjects such as Manufacturing Technology, taught at different levels in both undergraduate and graduate levels, are descriptive to a great extent. This descriptive nature must be supported by new technologies if these subjects claim to be more attractive to students. In this paper some examples of successful case studies are presented. They represent the new way of understanding the teaching replacing the old concept of traditional classroom lecture by more interactive ones and, therefore, more attractive to students.

Electrodischarge dressing (EDD) applied to contour grinding

Superabrasive grinding is a high efficiency process used in special applications such as high speed grinding, creep feed grinding, and Quick-Point. Although the maximum efficiency is obtained by metallic bonded wheels due to their wear resistance, their hardness makes almost impossible to dress them properly. Vitrified bonded wheels are now being used instead of metallic bonded ones since they have superior self-dressing capability. With the aim of obtaining maximum efficiency of these special grinding processes, in the last years a number of non-conventional dressing processes have been developed allowing the use of metallic bonded wheels. In this work, a methodology to introduce the electro-discharge dressing (EDD) of superabrasive conductive metallic bonded wheels is presented. The efficiency of EDD process to regenerate shaped wheels applied in Quick-Point or peel grinding has been studied by grinding hard metal rollers. Results show that EDD is able to remove the run-out and regenerate cutting capability.

Aeronautics Advanced Manufacturing Center, the Bet to Surpass the Valley of Death between University and Company

The present times are changing and need new formulas that satisfy the need for effective transfer between universities and companies. In the Basque Country, attending to this demand the Aeronautics Advanced Manufacturing Center (CFAA) has been founded. This center belongs to the University of the Basque Country (UPV/EHU) and has several companies related to this strategic sector as partners. The CFAA, equipped with the latest machinery and technology, born to be a catalyst for research activity in the field of advanced manufacturing for aeronautical sector, focusing its activity on the called Pillar 2 of the MRL scale (Manufacturing Readiness Level) as the proximity to the final application. Belonging to the UPV/EHU, this center allows stays of doctoral students, students for performing their master and bachelor’s degree projects. This implies a high quality training, and closer to reality, in manufacturing technologies.