Smart Spindle Research Articles

Prediction, detection, and suppression of regenerative chatter in milling

In metal cutting processing, especially in the processing of low-rigidity workpieces, chatter is a key factor affecting many aspects such as surface quality, processing efficiency and tool life. The academic research on chatter mainly focuses on three directions: chatter prediction, real-time detecting, and chatter suppression. With the continuous development of machining toward intelligence, the hot spots and trends of chatter research are also constantly changing. Therefore, an in-depth and systematic summary of the current situation of chatter research is urgently needed. On this basis, it is of great significance to realize the prediction of the hot spots and trends of chatter research. This article summarizes the research status from three aspects of chatter prediction, detecting and suppression, and points out the advantages and limitations of current chatter research. After in-depth discussion, this article also looks forward to the trend of chatter research. The hot spots of chatter research will focus on the following points: (1) Chatter research methods and means based on data-driven. (2) Integrated data collection, processing and decision-making methods. (3) Chatter detecting unit and chatter suppression unit are integrated in the smart spindle. (4) The chatter mechanism and detecting research of robot milling.

Potential for smart spindles adoption as edge computing nodes in Industry 4.0

Smart spindles extend conventional electromechanical machine tool sub-systems with additional sensing and local data processing capabilities, according to the Cyber-Physical Systems paradigm, in the framework of Industry 4.0. The article investigates the possibility and advantages of performing local elaboration of spindle-specific data, which allows embedding and protecting the expertise of component creator in form of proprietary data processing algorithms and numerical models. The main elements and functionalities of a smart spindle are discussed, focusing on how they can deliver a competitive performance exploiting edge computing, the convenience of use for the end user and aspects related to data privacy.

RF–DC converter and DC–DC converter for UHF and microwave wireless power transfer (UWPT/MWPT)

In this work, we propose a UHF/microwave wireless power transfer (UWPT/MWPT) and communication module (WPT-communication module) for smart spindle. The WPT-communication module can integrate with sensors, such as force/torque, temperature, displacement or vibration sensor, to form a WPT-communication sensor module. The WPT receiver constitutes a UWPT/MWPT receiving antenna, an RF–DC converter and a DC–DC converter. A novel UWPT/MWPT RF–DC converter with power conversion efficiency (PCE) of 86.5–92.2% is demonstrated in the condition of load reistance of 20 Ω and input signal power and frequency of 0.2 W and 0.915–10 GHz, respectively. It can integrate with the 915 MHz UWPT antenna and the DC–DC converter (with the proposed high-speed phase dectector) to form a UWPT receiver, or integrate with the 10 GHz (or 2.4 GHz) MWPT antenna and the DC–DC converter to form a MWPT receiver. A UWPT-communication receiver is designed and implemented. The corresponding PCE is 70%, one of the best results ever reported for UWPT/MWPT receivers.

An experimental investigation on ultra-precision instrumented smart aerostatic bearing spindle applied to high speed micro-drilling

High speed drilling of small diameter holes ranging from 0.1 to 1mm in printed circuit board (PCB) drilling industry has been largely carried out by using tungsten carbide twist drills and high speed spindles. In high speed drilling, however, the tool wear leads to increased cutting forces and results in poor hole quality as well as the hole location inaccuracy. Both hole quality and location accuracy are further considered as significant issues in drilling multilayer and heavy copper layered PCB workpieces. This paper presents the experimental development of an instrumented smart spindle, which can examine the tool wear by measuring the axial shaft displacement (known as the axial displacement) on the fly and thus applicable to real-time drilling processes. Cutting trials using the instrumented smart spindle and a Kistler dynamometer (9345A) on the customized multilayers PCB workpiece have shown a good correlation between the axial displacement and axial drilling force measurements. The axial displacement is capable of being used to detect the drilling engagement with each copper layer. Furthermore, the instrumented smart spindle can additionally be used to prevent a thrust bearing from being over-loaded and most importantly to detect tool wear in process.

Design and Decoupled Compensation Methods of a PM Motor Capable of 6-D Force/Torque Actuation for Minimum Bearing Reaction

This paper presents a methodology to design and control a permanent magnet (PM) motor capable of 6-D force/torque actuation for real-time compensation of external loads to achieve minimum bearing reaction (MBR). Unlike conventional multiphase designs, the current inputs to the stator-electromagnets (EMs) can be flexibly configured to enable 6-D force and/or torque actuation in one motor; two common motor structures (radial and axial types) are illustrated. Both the forward and inverse force/torque models are presented in terms of coordinate-independent kernel functions that characterize the force between an EM and a PM pole pair. Two closed-form solutions to the inverse model that solves for the current-input vector minimizing the total input energy to generate a desired force/torque vector, which can be computed within 1 ms, are derived and verified numerically. A feedforward MBR compensator designed to argument the proportional-integral-derivative (PID) speed regulator has been experimentally evaluated on a structurally smart spindle system to minimize bearing reactions. Experiments show that the MBR compensation effectively reduces vibrations and improves cutting quality.

Development of Smart Tooling Concepts Applied to Ultraprecision Machining

This paper presents smart tooling concepts applied to ultraprecision machining, particularly through the development of smart tool holders, two types of smart cutting tools, and a smart spindle for high-speed drilling and precision turning purposes, respectively. The smart cutting tools presented are force-based devices, which allow measuring the cutting force in real-time. By monitoring the cutting force, a suitable sensor feedback signal can be captured, which can then be applied for the smart machining. Furthermore, an overview of recent research projects on smart spindle development is provided, demonstrating that signal feedback is very closely correlated to the drilling through a multilayer composite board. Implementation aspects on the proposed smart cutting tool are also explored in the application of hybrid dissimilar material machining.

English

Spindle system plays a very important role in CNC and milling machines; but the foremost disadvantage over these machines are - they dissipate lots of energy which affects the overall efficiency and accuracy of the process. On identifying the various causes for the energy dissipation - major factors like improper speed control and imperfections in design may cause pulsation and thermal inertia that may impart a great amount of disturbance in the system. This paper emphasis on a framework in the development of a smart spindle system innate with cutting edge Mechatronics system that aims for its intelligent and dynamic control. The proposed system is equipped with sensory feedback to understand the environmental variations and spindling processes it also has an on-board control system, intelligent enough to control the machining process effectively and efficiently.

Design methodology for smart actuator services for machine tool and machining control and monitoring

This paper presents a methodology to design the services of smart actuators for machine tools. The smart actuators aim at replacing the traditional drives (spindles and feed-drives) and enable to add data processing abilities to implement monitoring and control tasks. Their data processing abilities are also exploited in order to create a new decision level at the machine level. The aim of this decision level is to react to disturbances that the monitoring tasks detect. The cooperation between the computational objects (the smart spindle, the smart feed-drives and the CNC unit) enables to carry out functions for accommodating or adapting to the disturbances. This leads to the extension of the notion of smart actuator with the notion of agent. In order to implement the services of the smart drives, a general design is presented describing the services as well as the behavior of the smart drive according to the object oriented approach. Requirements about the CNC unit are detailed. Eventually, an implementation of the smart drive services that involves a virtual lathe and a virtual turning operation is described. This description is part of the design methodology. Experimental results obtained thanks to the virtual machine are then presented.

Real-Time Balancing Mechanism Using Magnetic Fluid for a Machine Tool Spindle

Spindle vibration of machine tools causes premature tool wear and deterioration of machining accuracy. The vibration of machine tool spindles changes depending on a used tooling system and rotational speed during various machining operations. Especially, in high speed machining, even small unbalance mass of the spindle makes large whirl. However, a real-time balancing mechanism for a machine tool spindle including a tooling system has never realized successfully. In this study, in order to reduce unbalance response of the spindle to achieve high accuracy and efficiency machining, a smart spindle with a real-time balancing mechanism using magnetic fluid is proposed. The magnetic fluid is enclosed inside the spindle, and the distribution of the circumferential mass is actively controlled. A test spindle with the real-time balancing mechanism was designed and developed in order to evaluate the control method of the magnetic fluid experimentally and to accumulate adequate information for the basic design of a machine tool spindle. The experimental results presented in this paper proved the feasibility of the proposed real-time balancing mechanism for a machine tool spindle.

3614 磁性流体による機械主軸のリアルタイムバランシングに関する基礎研究(S64 工作機械,S64 工作機械)

In order to reduce rotor vibration, a smart spindle with real-time balancing mechanism using magnetic fluid is proposed in this study. The magnetic fluid is enclosed in the spindle, and the distribution of the circumferential mass is controlled dynamically. In this paper, the characteristics of various kinds of magnetic fluid have been examined. The suitable results for the smart balancing mechanism were obtained. A test spindle for verifying the expected effects of the real-time balancing mechanism was designed and developed in order to evaluate the control method of the magnetic fluid experimentally and to accumulate adequate information for the basic design of a machine tool spindle. Moreover, the testing spindle was modeled and simulated using a software package to estimate the rotor vibration.

REAL-TIME CUTTER PATH COMPENSATION FOR HIGH SPEED PLANING

This paper presents an experimental implementation of a novel approach for producing high quality machined timber surfaces at advanced production speeds. The focus of the work is on adjusting each cutting tool tip in real-time to compensate for inherent mechanical errors in the rotary machining process. The principle of cutter inaccuracy compensation is proved on a special purpose test rig comprised of a smart spindle unit supporting a two knife cutterhead. The smart spindle unit utilises piezo-electric actuators to displace the cutterhead support bearing. The improvements in surface waviness over non-compensated cutting are a factor of two, in accordance with the number of cutters.