November 2019
In grinding the use of coolants is inevitable to achieve high precision surface properties under the need of high process performance and under reasonable material removal rates. In conventional grinding typically a significant share of the total production energy refers to the delivery and conditioning of the coolants due to the use of flood cooling, which contributes a significant portion to the produ (…)
Because of its unique material properties, Ti6Al4V is used for components in the aerospace industry which are subject to high mechanical and thermal loads. Due to that, this material is considered as difficult to cut from a machining point of view. In order to improve productivity in machining Ti6Al4V the use of an effective cooling and lubrication strategy is necessary. This challenge can be managed wi (…)
The improvements of robust optical 3D metrology and robot systems are opening new possibilities of inline optical geometry measurements. The combination of these two facts allows measurements using the robot as manipulation system to increase the measurement area beyond a single field of view. By examining the sample from different angles using the robot to obtain high-resolution 3D datasets also from (…)
In this paper a technique to compute the 3-axis toolpath for a thin-wall component is presented aiming at maximizing the engagement conditions, keeping the geometry in tolerance. The toolpath generation is based on the static deflection of the component, predicted by coupling a mechanistic model of the cutting forces with a FE model of the workpiece, including, at each machining step, material removal m (…)
Micro structure with arrayed slots has excellent performances, including friction, lubrication and diffraction, because of their arrayed features. Numerous fields are concentrating on this structure, attributed to its excellent properties. In this paper, the conventional micro end milling tool was analyzed, and the drawbacks in micro slot milling were discussed. A micro slotting tool with a novel struct (…)
The measurement of cutting forces using highly sensitive piezoelectric force sensors is significant in the optimization of the machining process. In this study, the modelling and optimization of the cutting forces during the milling process of Ti6Al4V was carried out using the Response Surface Methodology (RSM) and the dynamometer. The ranges of the process parameters are: cutting speed (250-280 mm/min (…)
Brass is known for excellent machinability, but its ultimate productivity potential with high speed machining requires further study. An extensive testing program was conducted in laboratory and production settings on representative brass rod alloys using modern machine tools. Machinability data collected for turning, drilling and milling offers new insights on the effects of increasing speed, feed rate (…)
The importance of the 3D metal printing parts still increases in many branches of production not only for prototyping. The metal prints need machining very often to obtain specific shape, accurate dimensions as well as superior surface roughness. Internal structure of 3D metal prints differs from workpiece made by conventional processes like a rolling process. That leads to different mechanical properti (…)
Additive manufacturing (AM) is a fast growing innovative technology with attractiveness to transform the manufacturing segment of the aerospace industries due to its ability to produce final usable parts. However, the surface finish of AM produced parts usually fall short of desires when compared to the conventional manufacturing method. Therefore, post-processing is often required for surface finishing (…)
The paper focuses on the issue of controlling the cutting conditions in finishing machining of compliant workpieces, such as typically thin blades, in order to eliminate undesirable vibration and achieve high quality machined surfaces while also increasing productivity in machining processes. Workpiece vibration along the toolpath results from excitation of the workpiece by cutting forces. A strategy of (…)
This article presents a new design for setting up high speed synchronous reluctance motors (SynRM) in motor spindle applications for up to 30,000 rpm. The transversal laminated SynRM rotor package is supported by thin steel sheets and a shaft nut to exert a constant axial clamping force. Both, numerical and practical investigations are carried out using FEM-analysis and a test bench for centrifugal forc (…)
Deep hole drilling is a metal cutting method for producing primary cylindrical deep bores with a length-to-diameter ratio larger than l/D = 10. Due to the increasing interest of different branches of the industry in inner contoured workpieces, the Institute of Machining Technology (ISF) and the BGTB GmbH developed a chamber boring system, which allows to contour boreholes in axial and radial directions. (…)
Knowledge of the tool wear state in machining has become an important issue in research and industrial application. Current systems use the spindle power or cutting force as measured variable and refer it to a taught set point. However, this method lacks the ability to adapt to new work piece geometries. This new approach focusses on the tool instead of the workpiece, and uses a sensory tool holder with (…)
From the point of view manufacturer, machine tools fulfill technological requirements of manufacturing processes for part geometrical dimensions, shaping, and material property change. Main machine tool functions are axis motions with sufficient power reserve drives to technological process loads, consuming energy. The participation of manufacturing systems and processes for sustainable life in industri (…)
Nickel-based alloys are known to be difficult to cut material, which can cause high cutting forces and temperature rise which always leads to excessive tool wear. Traditional views hold the opinion that cutting temperature rise could lead to negative effects. However, milling under high temperature, cutting material can get a thermal softening effect. In this research, the monolithic ceramic end mill wa (…)
This paper presents the modal control applied to motion systems, in particular for machine tools. This control approach is particularly suitable for over-actuated systems that have more actuators than degrees of freedom. By using the modal approach, the parameterisation of the control loops is simplified since each control loop corresponds to a specific eigenmode. A four-variable modal control of a lin (…)
Improving the accuracy, reliability and performance of high-speed technological systems is one of the most pressing challenges in modern industry. The process of improvements in machine tools is permanent because of growth in requirements for the parts quality. The HSM process progress may depends on specific characteristics of particular machine. In this connection, there is a need to carry out investi (…)
The needs of increase in accuracy, quality and shape complexity of parts manufactured in high-speed equipment is a trend of industry. Problems of ensuring the accuracy at high velocities of machine organs motions are formulated. Machine organs movements accuracy is determined by smoothness of their motions and depends on the smoothness of the trajectory and the law of velocity changing along the traject (…)
Components produced and repaired by the Laser Metal Deposition (LMD) process require finish-machining steps in order to improve the poor geometrical tolerance of the functional surfaces. In this work, the LMD process was conducted to build up samples from Ti-6Al-4V powders. The effect of the face milling process on surface roughness of the Ti-6Al-4V parts was studied in different build directions. The e (…)
Specific cutting force is a key parameter that is important for estimating cutting forces that occur during machining. This information is important for various applications. The most important application is estimation of the stability limit valid for the specific configuration of the machine tool, tool and workpiece. There are a number of procedures used to predict the specific cutting force through v (…)
The tendency of substantially increasing the cutting speeds in the cutting processes of metallic materials leads to an increase in the productivity of the machining processes. In order to ensure such increase, the regularities of the cutting characteristics at the high cutting speeds should be examined more closely. For the analysis of chip formation at high cutting speed, cutting simulations were used (…)
Diamond wire is a relatively new abrasive tool technology used in wire sawing of hard and brittle materials i.e. Si, SiC, sapphire or ceramics in general. Process characteristics such as the undeformed chip thickness, abrasive wear and material removal regime heavily depend on the wire properties. However, manufacturers only provide data on the abrasive grain size range, relative grain density and core (…)
This paper deals with methods to reduce the influence of gravitational force on machine tool vertical feed axes. It provides an overview of existing counterbalancing mechanisms that are used in industrial applications. The main focus is on an existing solution that uses a rotary piston hydromotor, which has a number of advantageous properties. However, its significant torque ripple limits the practical (…)
Cylinder linings of lightweight combustion engine blocks made from aluminium cast alloys are typically coated with thermally sprayed layers to enhance the chemical resistance. Finish machining of the cylinder linings is currently done by honing. A substitution of this process by machining with geometrically defined cutting edges would have significant advantages, especially concerning ecological aspects (…)
A significant influencing factor that determines the strength, lifetime and reliability of a component after machining is the residual stress state in the boundary zone. A reliable adjustment of this condition during machining is currently not possible. It is desired to control the milling process using a model-based approach in order to generate defined geometries and residual stresses in titanium comp (…)
Ball screws and linear guides are among the key components of machine tools. Abrasive wear causes a loss in stiffness of these components over time affecting the attainable manufacturing precision and, eventually, leads to failures and costly down-time. In order to control these effects, the condition of the crucial feed drive components needs to be monitored. This paper shows, how the feed drive condit (…)
High-pressure cutting fluid supply is widely used in rough turning of difficult-to-cut materials to ensure chip breaking. The acting force of the cutting fluid jet on the back of the chip causes chip breaking. The broken chips are accelerated by this force and can damage the workpiece surface on impact. Consequently, high-pressure cutting fluid supply is not suitable for finish turning mostly, especiall (…)
Today, an operator performs experiments to adaptively select grinding process parameters using observations, expert knowledge, and rules of thumb. Self-optimizing grinding machines cannot use operator observations and must, therefore, extract enough information out of the grinding process. In this study, a holistic sensor set-up as foundation for self-optimizing machines are presented exemplarily for cu (…)
Resulfurized steels are commonly used in the industry due to its good machinability, which can be related to the formation of microstructural manganese sulfide (MnS) inclusions. On the downside, MnS inclusions cause a high steel anisotropy due to its elongated form. Within this paper, the effect of a MnS reduction and the influence of different countermeasures on the machinability is investigated. The a (…)
Milling parts for watch, medical, aircraft or molds industries is a compromise between time and precision or surface quality. The latter is very often related to machine vibrations during the process. This paper summarizes results obtained with two approaches aiming at reducing machine vibrations caused by axes accelerations. Both are control model based, taking into account the machine's modal behavior (…)
Numerical modeling of machining processes exhibits a high potential for shortening process development times. When modeling the machining process, an accurate material model is essential for the success and reliability of the simulated results. Especially, the simulation results depend largely on the material model and on the material parameters. To identify the parameters for machining conditions, inve (…)
This paper presents a prediction and compensation approach for thermal errors of 5-axis machine tools, based on supervised online machine learning. Process-intermittent probing is used to identify and update a thermal autoregressive with exogenous input (ARX) model. The approach is capable of predicting and compensating thermal displacements of the tool center point based on changes in the environmental (…)
Achieving high workpiece accuracy is a long-term goal of machine tool designers. There are many causes of workpiece inaccuracy, with thermal errors being the most dominant. Indirect compensation (using predictive models) is a promising strategy to reduce thermal errors without increasing machine tool costs. A modeling approach using thermal transfer functions (a dynamic method with a physical basis) has (…)
A digital process twin unifies information from planning and manufacturing of a machining process. Calculation and technological models allow the prediction of further information, which normally is not provided. The work shows the recording of both data sources and creation of a digital process twin for a milling application. Further the usage of technological models is shown at the example of cutting (…)
The machining of large dimension part presents issues of accuracy and of part handling. Machine-tools of large capacity are classically used, but they are very expensive. The paper investigates original solutions with mobile milling machines. A comparative study of a machining robot and of a portable milling machine is performed. Instrumented experiments of face milling operation were carried out and th (…)
Milling structural components from aluminum under enormous requirements of productivity and quality from the aerospace perspective is still the subject of extensive research. The assessment strategies of the surface quality are a big challenge for the surface measurement technique, since only a fraction of the manifesting surface topography can be described with the help of two-dimensional measured va (…)
The Micro5 5-axes milling machine was specifically developed for micro, or mini, technical productions and focused on simplicity and efficiency. It provides functional, qualitative and economical performances. Designed for low cutting forces (HSC technology), it has an excellent dynamics. The first vibration modes and compliances being very high, the machine is insensitive to axes accelerations. It ther (…)
This work presents a holistic approach for monitoring machining processes of an industrial deep drilling machine. For that purpose, a machine tool was equipped with a multi-sensory monitoring system with the objective to detect and assess dynamic disturbances during the machining process. Disturbances are key characteristics of deep drilling processes and are intensified due to the high length to diamet (…)
This study mainly focuses to investigate the machining performances of variety of metal working fluid (MWF) strategies such as cryogenic (CO2), minimum quantity lubrication (MQL) and emulsion, into rake and flank face application during the face milling of titanium (Ti-6Al-4V grade 5) alloy. Modified CoroMill600 milling cutter with internal channels to inserts rake face and flank face delivery, and PVD (…)
Deep hole drilling processes are relevant for various applications where bore holes with high length-to-diameter-ratios (L/D) and good surface qualities are necessary, carried out mostly at the end of the (machining) process chain. Therefore, the avoidance of tool breakage and the resulting process stability is mandatory. One of the main causes for the failure of single-lip drills in the machining of lo (…)
Robotics is increasing its presence in the machine tool sector. One interesting application for robot assisted machining involves a robot locally increasing the stiffness of a thin walled part to suppress regenerative vibrations and minimize part deformations during machining. Simulating the dynamics improvement achieved when coupling the robot and the part is of high concern, in order to guarantee th (…)
Manufacturing improvements are becoming a real need in industry. In order to satisfy these industrial requirements, they should be targeted in two different directions: new manufacturing processes and surface optimization through algorithms. On the one hand, Super Abrasive Machining (SAM) is presented as a new manufacturing process combining benefits from milling and grinding technologies. On the other (…)
An active method for boring bar vibration attenuation and chatter suppression is presented through the introduction of a nonlinear control force within a tuned mass damper. Its effects on process stability and its control options are discussed in detail. The effectiveness of the active damping system and the optimal control parameters are determined through numerical simulations carried out on a simplif (…)
A common approach for the experimentally estimation of modal parameters is the Experimental Modal Analysis (EMA). EMA takes place in the standstill of the machine, consequently neglecting effects that only occur during the cutting process. Alternatively the Operational Modal Analysis (OMA) makes possible to investigate structures under operational loads and conditions. In this paper, a machine tool is i (…)
This study investigates the influence of cutting conditions on surface integrity in the milling of Ti-6Al-4V using various cooling methods: soluble oil coolant; supercritical carbon dioxide; and supercritical carbon dioxide with Minimum Quantity Lubrication. A Design of Experiments approach was used to evaluate a change in direction and interactions between the input factors and the responses. The resul (…)
Global production is in a state of change, with multiple challenges. One challenge is the digitization of production processes in the aerospace industry, due to the high requirements regarding the reliability of the transportation vehicle. It is a premise to record the manufacturing processes using sensors and to analyze them by means of process data management. Therefore, approaches regarding the predi (…)
Detailed manufacturing process data and sensor signals are typically disregarded in production scheduling. However, they have strong relations since a longer processing time triggers a change in schedule. Although promising approaches already exist for mapping the influence of manufacturing processes on production scheduling, the variability of the production environment, including changing process cond (…)
Ultrasonic machining (USM) is known for its ability of processing brittle and hard materials such as silicon, glass and quartz. Usually, material removal in conventional USM is in brittle mode. The machined surface is covered with sharp tips and edges. In micro USM, the size of machined feature is less than 1 mm. Different from the conventional USM, in micro USM, it was found that the machined surface i (…)
The article discusses the ability of multilayer composite nano-structured coatings based on the Cr-CrN-(Ti,Cr,Al,Si)N system to resist wear factors activated with increasing temperature, such as diffusion and oxidation processes, as well as spinodal decomposition of the coating material. Investigators were carried out in turning C45 steel at the following cutting conditions: f = 0.2 mm/rev, ap = 1.0 mm, (…)
Machining is one of the stochastic processes, in which, the work specimen is exposed to rigorous plastic deformation which, results in rapid increase in work hardening effect and affects the life of the cutting tool particularly for Inconel 718. The depth and degree at which machined surface harden depends on factors like material properties, tool composition and tool dimensions, tool condition, cutting (…)
The present article deals with the measurement methods based on experimental tests and their impact on the resultant volumetric error of CNC machine tools (MT). Volumetric error compensations represent a promising technology to increase the production accuracy of machine tools. This article studies direct and indirect methods to measure the volumetric accuracy on a MT. The assessed parameters are not on (…)
Simple cutting force models are well suited for orthogonal cutting. However, industrial processes often use oblique cutting with complicated cutting edge shapes, where simple cutting force models underestimate the forces. The new cutting force model is based on an existing model for restricted chip motion, but generic cutting edge and rake face shapes and arbitrary process kinematics are accepted to cal (…)
The productivity of machining processes is often limited by the occurrence of dynamic effects. The presented approach intends to counteract tool deflections, and thus to damp and disrupt chatter vibrations by using milling tools with defined functional structures on the flank faces at the minor cutting edges. The potential of process stabilization is evaluated by analyzing the operational behavior of th (…)
To reduce the excitation of structural oscillations machine tools’ feed dynamics are usually limited. Thus, their productivity is restricted, especially for high dynamic processes with negligible process forces. The principle of Kinematically Coupled Force Compensation (KCFC) tries to overcome this issue by combining a redundant axis configuration with the principle of force compensation. In this paper (…)
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