Advanced Materials Research Vol. 498

Abstract: This paper presents a method to detect tool wear and surface roughness during steel dry turning. It is important to note that the objective of the proposed method is to fulfill the needs in the development of these monitoring systems according with the research community in this area, and they are: 1) A trade-off between the number of sensors used and their cost, and the performance of the monitoring system, 2) A sufficiently reduced computing time that allows to change the tool before the wear exceeds the fixed threshold and/or stop the machining process before the surface roughness exceeds its threshold, and 3) The use of sensors that do not disturb the machining process. The monitoring signals are the feed motor current and the vibrations. The results show that the proposed system can be used for this purpose due to its high accuracy and reliability.

Abstract: Boring operations of deep holes with a slender boring bar are often hindered by the precision because of their low static stiffness and high deformations. Because of that, it is not possible to remove much larger depths of cuts than the nose radius of the tool, unlike the case of turning and face milling operations, and consequently, the relationship between the cutting force distribution, tool geometry, feed rate and depth of cut becomes non-linear and complex. This problem gets worse when working with a rotating boring head where apart from the cutting forces and the variation of the inclination angle because of shape boring, the bar and head are affected by de centrifugal forces. The centrifugal forces, and therefore the centrifugal deflection, will vary as a function of the rotating speed, boring bar mass distribution and variable radial position of the bar in shape boring. Taking in to account all this effects, a load and deformation model was created. This model has been experimentally validated to use as a corrector factor of the radial position of the U axis in the boring head.

Abstract: Titanium and nickel-based alloys belong to the group of difficult-to-cut materials. The machining of these high-temperature alloys is characterized by low productivity and low process stability as a result of their physical and mechanical properties. Major problems during the machining of these materials are low applicable cutting speeds due to excessive tool wear, long machining times, and thus high manufacturing costs, as well as the formation of ribbon and snarled chips. Under these conditions automation of the production process is limited. This paper deals with strategies to improve machinability of titanium and nickel-based alloys. Using the example of the nickel-based alloy Inconel 718 high performance cutting with advanced cutting materials, such as PCBN and cutting ceramics, is presented. Afterwards the influence of different cooling strategies, like high-pressure lubricoolant supply and cryogenic cooling, during machining of TiAl6V4 is shown.

Abstract: Minimizing downtime in machine tools is one of the factors that determine the performance increase of the production processes involved. This increase can be considered from different points of view: economic, energetic and environmental. Machining processes can be stopped by needing to change the tool as a consequence of the loss of their initial properties due to the wear process that suffer during machining. One of the wear processes which takes place in a wider range of temperatures in the machining of metal alloys is the adhesion wear, and specially in the case of light alloys, secondary adhesion wear, which can be placed in the tool rake face as a layer (Built-Up Layer, BUL) and in the tool edge (Built-Up Edge, BUE). This paper analyzes the influence of cutting parameters on the secondary adhesion wear effects in the dry turning of UNS A92024 (Al-Cu) alloy.

Abstract: The main objective of this paper is to analyze the behaviour of cold formed steel cross section respect to mechanical characteristics, such as deflection, mainly. A cold formed steel profile with thickness of 1 mm regards is studied to determine its viability as reinforcement of timber upgrading. Thus, temperatures, stresses and strains have been analysed during the manufacturing process of these profiles, and also, the deflection supported, comparing between unreinforced and reinforce pieces. The analysis has been carried out by means of Finite Element Method, using DEFORM 2D software, during the simulation of manufacturing process and COPRA software during the final static computations. Results provide information about the integrity and good behavior of these profiles for timber upgrading.

Abstract: Surgical procedures that affect the human bone structure often entail drilling operations of bone. The post-operative evolution of these interventions is conditioned largely by the damage generated during the operation. The aim of this study was to determine clearly the influence of the cutting conditions on temperatures and forces when drilling bovine cortical bone, in the interests of further optimization of cutting conditions to minimize the generated damage. The infrared thermography technique and a piezoelectric dynamometer were employed as measurement devices. It was observed that the main parameter affecting temperatures was the feed per tooth. The temperatures obtained were lower when drilling with high feed per tooth, even though an opposite effect was noticed on the feed force and torque, with an increase of them. From the experimental results, prediction models of temperature rise, feed force and cutting torque were created, in order to predict the response based on the selected cutting conditions.

Abstract: Different techniques of volumetric verification for long range machines are presented in this paper. Its working principle is based on captured points that can be distributed or not, through laser tracker (LT) or a measurement instrument that is generally of large scale. The developed model allows us to characterize the different errors in the machine tool to study, depending on its kinematics and geometry. Obtaining the transformation matrices that define the kinematics of the machine tool (MT) including the measurement system in the kinematic model, it is possible to relate the coordinates of the tool with the coordinates of LT. The best combination of parameters, techniques and models were obtained through the realization of a large number of synthetic tests based on non linear optimisation techniques

Abstract: The primary aim of this study was to design and develop an on-line control system of finished surfaces in automated machining process by CNC turning. The control system consisted of two basic phases: during the first phase, surface roughness was monitored through cutting force signals; the second phase involved a closed-loop adaptive control system based on data obtained during the monitoring of the cutting process. The system ensures that surfaces roughness is maintained at optimum values by adjusting the feed rate through communication with the PLC of the CNC machine. A monitoring and adaptive control system has been developed that enables the real-time monitoring of surface roughness during CNC turning operations. The system detects and prevents faults in automated turning processes, and applies corrective measures during the cutting process that raise quality and reliability reducing the need for quality control.

Abstract: This work proposes a mechanistic model to predict the cutting forces during machining of low machinability materials such as austempered ductile irons (ADI). For these cases, commonly used models are not accurate due to high rates of wear and a new coefficient is necessary to correctly estimate the cutting forces against time. As well, ceramic inserts are applied for the first time in dry turning of ADI.

Abstract: For understanding todays metrology a brief historical review is given, starting with the definition of units for trade and construction of buildings. Later on, industrial metrology is needed for the development of modern production processes and interchangeable manufacturing. In order to support the international exchange of goods and the development of precise manufacturing processes traceability of measurement results had to be established. Global trade as well as international companies profited from the standards to achieve lower costs for products from all over the world and simultaneously new measurement techniques were developed. The firstly defined two point-size-tolerances and measurements with simple measurement devices like calipers became soon insufficient. Together with the improvement of manufacturing processes and increasing demands for an economical way of production, advanced measurement techniques were found. In this overview, the development from tactile to optical measurement techniques with some important examples is shown in parallel with the development of standards. The requirements for todays manufacturing metrology methods as well as the role of measurement of geometrical quantities in industry and trade are derived and future trends are pointed out.