Tool Clamping Research Articles

Influence of constant feed per tooth via spindle speed adaption on groove quality in micro milling

Adjustments of the feed per tooth in a spindle with an asynchronous motor and mechanical clamping can lead to reduced groove quality, resulting in increased burr formation, inferior surface quality, and radial run-out during changes in spindle speed. In turn, a constant feed per tooth during milling offers advantages for tools and machining processes.This study aims to optimize groove quality during micro milling with a constant feed per tooth, achieving reduced burr formation, improved surface quality, and the elimination of radial run-out. Experiments were conducted on a tool spindle with a synchronous motor, considering both constant and non-constant feed per tooth. The influence of the toolholder type and tool clamping repeatability was considered.Using the synchronous motor and a constant feed per tooth, a length change of the tool spindle was observed during rotational speed variations due to compression/expansion. This change was absent with a non-constant feed per tooth. No adverse effects on groove quality were found with varying feed per tooth.The results demonstrate that a synchronous motor enhances groove quality during micro milling with varying spindle speeds. Employing a constant feed per tooth requires adjustments in cutting depth to compensate for the observed compression/expansion.

Process Monitoring using Digital Twin-Based Sensors integrated in Tool Clamping Surfaces

Process monitoring in forming technology can serve as a basis for transparent manufacturing and closed-loop control systems. Particularly, sensor systems associated with tool clamping interfaces offer great potential for robust inline process monitoring but are hardly investigated. In this paper, a concept to monitor a sheet metal forming process combined with a digital twin-based approach for virtual sensors is introduced. Here, sensors integrated into the T-slots of tool clamping surfaces in forming machines are enhanced by a mathematical representation of the elasto-mechanical behavior of the tool clamping interfaces. Moreover, the potential of the certain sensor system for inline process monitoring is highlighted. The resulting approach is substantiated by simulative analysis and by experimental investigation.

Characterization of tool clamping conditions in forging hammers

1. WECK M., BRECHER C., 2005, Werkzeugmaschinen 1, 6th Edition, Springer-Vieweg, Berlin Heidelberg. Google Scholar

An application system for the design of the spindle tool clamping mechanism

<p>The heart of the machining center design is the spindle design, and one of the primary functions in the spindle design is a tool clamping system mechanism. The selection of disc spring stack for a tool clamping mechanism is an iterative process that highly depends on the spindle space availability, drawbar design, tool unclamp stroke length, and standard clamping force requirements. For example, even a design space of 0.1 mm may impact one kN clamping force depending on the disc spring stack design. Hence the design of the tool clamping system for a spindle is a time- intensive process and also needed careful attention. The iterative process of disc spring stack selection may lead to an unoptimized tool clamping system, which may not be the best design. This paper explains a dynamic way to find the best spring stack selection to optimize the spindle tool clamping mechanism based on the computational application.</p>

Chatter Stability Prediction and Process Parameters’ Optimization of Milling Considering Uncertain Tool Information

Stability is the prerequisite of a milling operation, and it seriously depends on machining parameters and machine tool dynamics. Considering that the tool information, including the tool clamping length, feeding direction, and spatial position, has significant effects on machine tool dynamics, this paper presents an efficient method to predict the tool information dependent-milling stability. A generalized regression neural network (GRNN) is established to predict the limiting axial cutting depth, where the machining parameters and tool information are taken as input variables. Moreover, an optimization model is proposed based on the machining parameters and tool information to maximize the material removal rate (MRR), where the GRNN model is taken as the stability constraint. A particle swarm optimization (PSO) algorithm is introduced to solve the optimization model and provide an optimal configuration of the machining parameters and tool information. A case study has been developed to train a GRNN model and establish an optimization model of a real machine tool. Then, effects of the tool information on milling stability were discussed, and an origin-symmetric phenomenon was observed as the feeding direction varied. The accuracy of the solved optimal process parameters corresponding to the maximum MRR was validated through a milling test.

Experimental Validation of an Intelligent Hybrid Plain Bearing Active Control

Abstract The replacement of damaged journal bearings in forming machines eventuates in very high personal and material costs as well as long-term downtime. Moreover, new discontinuous forming processes (e.g., press hardening and pendulum operations) have a negative effect on the hydrodynamic pressure built up in the bearing and can lead to failure. Therefore, users and manufacturers of forming presses are looking for ways to improve the safety of this key component. In this paper, the concept of an intelligent hybrid plain bearing (IHPB) that combines hydrodynamic and hydrostatic characteristics, presented by Kurth et al., (2019, “Forming 4.0: Smart Machine Components Applied as a Hybrid Plain Bearing and a Tool Clamping System,” Proc. Manuf., 27, pp. 65–71), is detailed and validated on a test rig. The clearance state of the journal bearing is monitored through eddy current sensors and a controlled hydrostatic support is activated, when this state is evaluated as critical. The results show a strong increase in the load capacity and in the minimal lubrication gap of the IHPB within three series of tested experiments: stationary, nonstationary, and press-typical load cases.

Examination of Tool Shank Structure for the Purpose of Restraint of Chatter Vibration

In turning by engine lathe, it is empirically known that chatter vibration may be suppressed when the cutting tool is mounted upside down on the tool post (hereinafter, this method called ‘upside-down tool mounting method’). This study discusses the suppression mechanism of chatter vibration of this tool mounting in terms of the tool vibration trajectory such as vibration direction and amplitude. Because the translational motion in the height direction of the tool is dominant in upside-down tool mounting, the vibration in the tool axis direction is reduced compared to that of usual tool mounting. The effect suppresses chatter vibration in upside-down tool mounting method. Then, tool shank structures for the normal cutting operations were designed to demonstrate the similar tool vibration trajectory to the cutting opetation with the upside-down tool mounting. A parallel leaf spring structure promotes the translational component in the tool height direction to reduce the chatter vibration. The chatter vibration largely depends on the tool vibration trajectory as well as modal paramters of tool clamping.

A design method of applied voltage waveform for high-power ultrasonic monopole pulses

Our previous studies demonstrated that an ultrasonic monopole pulse with ringing suppression can be generated by utilizing a half sine voltage waveform and its generating method. The resultant vibration amplitude of the ultrasonic monopole pulse is too small for high-power ultrasonic application. However, ringing suppression provides advantages for a minimized jumping phenomenon, and can be applied to improve surface quality when machining hard and brittle material. A small displacement of vibration amplitude is suitable to reduce the finish machining margin, while suppressing microcracking and chipping. In addition, machining application using an ultrasonic monopole pulse is predominately unreported. Therefore, we design a bolt-clamped Langevin type transducer with a tool clamping system for generating a high-power ultrasonic monopole pulse with suppression ringing for the experimentation of ultrasonic burnishing and the observed effect upon the machined surface.

Forming 4.0: Smart machine components applied as a hybrid plain bearing and a tool clamping system

Abstract Higher process reliability as well as detailed information about the machine condition are necessary requirements for the manufacturing of complex geometric shapes with simultaneous increase of the machine availability and output rate. By implementing smart machine components it is possible to solve central challenges focusing on the investment-intensive field of forming technology. These components gather and evaluate machine and process data on decentralized spots with certain integrated sensors. Within this paper the potential benefits of those smart machine components are demonstrated using the example of an intelligent hybrid plain bearing and a smart tool holder. Focusing on the damage prevention of plain bearings, a load controlled journal bearing combining hydrodynamic and hydrostatic characteristics has been developed and tested by simulation. In addition, a smart hydraulic tool holder for upper dies has been successfully tested by simulations and experiments in order to investigate and demonstrate the potential for using the monitored clamping characteristics to increase the process transparency and the condition of the tool holder. As a result these smart machine components can be used additionally for a significant improvement of industry 4.0 tools such as digital twins of both process and machine.

Research on the tool holder mode in high speed machining

High speed machining technology can improve the processing efficiency and precision, but also reduce the processing cost. Therefore, the technology is widely regarded in the industry. With the extensive application of high-speed machining technology, high-speed tool system has higher and higher requirements on the tool chuck. At present, in high speed precision machining, several new kinds of clip heads are as long as there are heat shrinkage tool-holder, high-precision spring chuck, hydraulic tool-holder, and the three-rib deformation chuck. Among them, the heat shrinkage tool-holder has the advantages of high precision, high clamping force, high bending rigidity and dynamic balance, etc., which are widely used. Therefore, it is of great significance to research the new requirements of the machining tool system. In order to adapt to the requirement of high speed machining precision machining technology, this paper expounds the common tool holder technology of high precision machining, and proposes how to select correctly tool clamping system in practice. The characteristics and existing problems are analyzed in the tool clamping system.

Research on Several Tool Chuck Technology in High Speed Milling

In order to meet the requirements of high-speed precision machining technology, the paper elaborates the tool clamping technology commonly used in high-precision machining, such as the static pressure expansion chuck, CoroGrip chuck, and stress locking chuck and so on. How to correctly select the tool clamping system, the characteristics of the tool clamping system and the existing problems are analyzed.

Analysis of new, energy-efficient hydraulic unit for machine tools

In machine tools, hydraulic units are one of the main consumers of energy. Hydraulically driven functionalities of machine tools include tool clamping, tool change, work piece clamping or palette change operating. For these functions, two pressure circuits (60 bar and 200 bar) are necessary. This paper introduces a novel, energy-efficient hydraulic unit that combines a variable displacement pump with a variable speed controlled drive and hydraulic booster. The result is a lower overall energy consumption and decreased operating temperatures of the hydraulic unit. Hydraulic fluids contain up to 85% mineral oil. This paper also introduces a mineral oil-free, water-based hydraulic fluid, which will be replacing a conventional mineral oil-based hydraulic fluid (ISO-VG 46) within the novel energy-efficient hydraulic unit. The effects on the unit’s performance (operating temperature, pressure, flow rate, power consumption, efficiency) will be evaluated.

Experimental study of strain fields during shearing of medium and high-strength steel sheet

There is a shortage of experimentally determined strains during sheet metal shearing. These kinds of data are a requisite to validate shearing models and to simulate the shearing process. In this work, strain fields were continuously measured during shearing of a medium and a high strength steel sheet, using digital image correlation. Preliminary studies based on finite element simulations, suggested that the effective surface strains are a good approximation of the bulk strains below the surface. The experiments were performed in a symmetric set-up with large stiffness and stable tool clearances, using various combinations of tool clearance and clamping configuration. Due to large deformations, strains were measured from images captured in a series of steps from shearing start to final fracture. Both the Cauchy and Hencky strain measures were considered, but the difference between these were found negligible with the number of increments used (about 20 to 50). Force-displacement curves were also determined for the various experimental conditions. The measured strain fields displayed a thin band of large strain between the tool edges. Shearing with two clamps resulted in a symmetric strain band whereas there was an extended area with large strains around the tool at the unclamped side when shearing with one clamp. Furthermore, one or two cracks were visible on most of the samples close to the tool edges well before final fracture. The fracture strain was larger for the medium strength material compared with the high-strength material and increased with increasing clearance.

SMA를 이용한 공구홀더의 자동공구교환장치 개발

Micromanufacturing is a useful system for reducing energy consumption. For micromanufacturing, tool clamping and workpiece clamping are important components to realize the machining process. Therefore, a shape memory alloy (SMA) ring type tool holder is developed. In addition, this holder needs cooling and heating processes to execute the tool clamping process. This study suggests a cooling/heating device based on peltier elements. The device will be applied to the heating/cooling process of an automatic tool changer (ATC) for the SMA tool holder. This study introduces the configuration and operating principle of the proposed ATC system. The description and prototype evaluation of this system were given. Plastic bolt and aluminum block were selected to enhance the cooling performance, and the installed tool was changed in 17 s during the experiments.

Calculating the Workpiece Quality Using a Hobbing Simulation

Gear hobbing is one of the most productive manufacturing processes for cylindrical gears. The quality of the gears is a result of the tool quality, the precision of the workpiece, tool clamping and kinematics of the machine. The dry gear hobbing process allows machining of gears with a quality according to the DIN standard of up to IT 5. To evaluate which gear quality is possible to machine with a given clamping and hob it is useful to simulate the process in advance. This is also an opportunity to order the required quality of the hob according to its application.The objective presented in this paper is to simulate non-ideal gear hobbing processes and to calculate the geometry and topography of the workpiece. To achieve this goal, a simulation for continuous gear hobbing was developed. By calculating planar intersections of transverse sections of both gear and tool, the resulting gear geometry is determined. Beside it is possible to calculate different characteristic values for the hobbing process such as chip thickness and cutting volume. By an evaluation of tool and clamping tolerances these deviations can be used to modify the simulation model. Afterwards a non-ideal hobbing simulation can be performed and the resulting gear geometry can be analyzed using a virtual measurement machine. An advantage of this non-ideal simulation is also the possibility of calculating the tool load taking these deviations into account and to use the results for further process designs to reduce the risk of tool failure.The virtual measurement machine analyses the geometry according to VDI/VDE 2612/2607 and DIN 3961. The resulting measurements of the flank and lead lines can be used for a classification of the gear quality. By using this simulation program it is possible to reduce the costs and time effort of setting up a new hobbing process.

Design and evaluation of a high-speed and precision microspindle

This study presents the design and evaluation of a high-speed and precision microspindle used for micromechanical machining. A radial impulse turbine with two rows of nozzles was designed to realize the high-speed performance. A monolithic flexible coupling was used to decouple the turbine shaft and the tool, and then, the tool shank was directly supported by aerostatic bearings, which can minimize the run-out of the tool at high speeds. Additionally, a shape memory alloy (SMA)-based clamp was designed for tool clamping. It can avoid the assembly error caused by stack-up tolerances. The microspindle has simple configuration and compact design with a 30-mm outer diameter and a 95-mm length. The prototype microspindle has a maximum speed of over 240,000 rpm and a tool radial run-out of 2.79 μm. The evaluation results show the feasibility and potential application of the new design concept of the microspindle proposed in this study.

Analysis of Dynamic Characteristics of Boring Tool Holder

Machining is a complex process in which many variables can detrimental the desired results. Among them, tool vibration is the most critical phenomenon which affects the life of the cutting tool, quality of the components machined and functional behaviour of the machined tools. This familiar phenomenon is recognized in many operations including boring, milling and drilling. The causing factors are related to the machine tool itself, tool clamping, length and diameter of the tool holder and the cutting data to be used. One way to avoid vibration problem during boring process is the location of boring tool holder in the relevant position for increasing the precision of the machining process. The present investigation aims at determining the optimum position of tool shank overhang for a boring tool holder S25T PCLNR/L12 and also to study the effect of damping force on tool vibration using Analytical, computational and experimental methods.

Sensor System for Monitoring the Planar Tool Flange Contact on the Basis of Ceramic Resonators and Circular Waveguide Structures

The proposed sensor system based on ceramic resonators and circular waveguide structures offers a novel solution for controlling the quality of tool clamping in a tool-receiving socket interface. Compared to current solutions this sensor system enables both an easy, cost-effective production and a high-resolution passive distance measurement on a rotating system component. The basic element of the monitoring system are standard bores in combination with industrial ceramic pins as well as standard potting compound, through which an electromagnetic signal is transferred to the measurement location.

An Improved Design of the Manipulator on Automatic Tool Changer

The tool falling and vibration faults often occur in the process of tool changing, In order to improve the stability of the tools on automatic tool changer, a new structure of the manipulator is presented. The new manipulator contains two-point locking instead of the original one-point locking, and the tools can be clamped more tightly. When the old manipulator is slotting the tool, the forces are analyzed, and the working load and parameters is determined by calculating and analyzing the output curve of manipulator. The three-dimensional model is built in ADMS, and the validity of the new designed manipulator is verified by the simulation in a limit state. The simulation result shows that the new manipulator can increase the ability of tool clamping effectively.

Vibration Polishing Edge Preparation for Cemented Carbide Inserts

Micro-cracks on cutting edge will cause early breakages on cutting tools, accelerate tool wear and reduce cemented carbide tool life. Edge preparation can improve the cutting edge quality. Vibration polishing experiments were carried out for cemented carbide inserts edge preparation. Inserts and fixtures were put into the vibration polishing equipment which forced abrasive particles to collide and polish inserts. Edge preparation for fixed type insert and free type insert were compared with three sizes of abrasive particles. And the polishing time was changed for each testing cases. Experiments were carried out by altering polishing time, abrasive particle size and tool clamping way to determine the optimum technology of vibration polishing edge preparation. The experimental results showed that edge breakage numbers of insert significantly reduced. Smooth and round cutting edges were observed by optical microscope after edge preparation. Edge preparation experiments prove that edge preparation can change the cutting edge geometry and improve the cutting tool quality.