scholarly journals On Vibration Joint Time-Frequency Investigations of CNC Milling Machines for Tool Trajectory Task Conformity Estimation

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Silviu Nastac
Keyword(s):  
Spectral Characteristics ◽  
Experimental Tests ◽  
Vibration Monitoring ◽  
Cnc Milling ◽  
Cnc Machine ◽  
Shape Accuracy ◽  
Time Frequency ◽  
Milling Tool ◽  
Milling Machines ◽  
Acceleration Signals

This study deals with estimation of milling shape accuracy and trajectory conformity for small CNC 3D milling machines, based on vibration monitoring during the regular working cycles. The author made a large number of experimental tests, acquiring the acceleration signals, both on the milling tool-holder and on the bed frame. In order to evaluate the appropriate spectral characteristics of different machine parts and their weights on equipment dynamics, it was analyzed both the complete and the partial working cycle (such as forward tool motion, with or without effective milling, with or without tool driving, exclusively the milling cutter transitory/stabilized regime) for different basic milling shapes. The acceleration signals were jointly time-frequency investigated in order to evaluate specific spectral indicators related to the real motion characteristic of milling tool. It was used short time fast Fourier transform (STFFT) and Hough transform (HT) algorithms, along with stochastic evaluation of signal parameters, within time and frequency domains. The results reveal an accurate correlation between the specific transitory dynamics of the machine and the imposed milling shape. Main implications of the results within this analysis involve the noninvasive and facile investigation for milling errors of the CNC machine, conformity of tool head trajectory, identification of potential failure source, or damaged machine part.

APPROXIMATION ALGORITHM FOR MULTIPLE-TOOL MILLING

2001 ◽  
Vol 11 (03) ◽  
pp. 339-372 ◽  
Author(s):  
SUNIL ARYA ◽  
SIU-WING CHENG ◽  
DAVID M. MOUNT
Keyword(s):  
Approximation Algorithm ◽  
Computer Aided Design ◽  
Minimum Cost ◽  
Cnc Milling ◽  
Automated Generation ◽  
Polynomial Time Approximation Algorithm ◽  
Milling Tool ◽  
Milling Machines ◽  
Aided Design ◽  
Milling Tools

Milling is the mechanical process of removing material from a piece of stock through the use of a rapidly spinning circular milling tool in order to form some desired geometric shape. An important problem in computer-aided design and manufacturing is the automated generation of efficient milling plans for computerized numerically controlled (CNC) milling machines. Among the most common milling problems is simple 2-dimensional pocket milling: cut a given 2-dimensional region down to some constant depth using a given set of milling tools. Most of the research in this area has focused on generating such milling plans assuming that the machine has a tool of a single size. Since modern CNC milling machines typically have access to a number of milling tools of various sizes and the ability to change tools automatically, this raises the important optimization problem of generating efficient milling plans that take advantage of this capability to reduce the total milling time. We consider the following multiple-tool milling problem: Given a region in the plane and a set of tools of different sizes, determine how to mill the desired region with minimum cost. The problem is known to be NP-hard even when restricted to the case of a single tool. In this paper, we present a polynomial-time approximation algorithm for the multiple-tool milling problem. The running time and approximation ratio of our algorithm depend on the simple cover complexity (introduced by Mitchell, Mount, and Suri) of the milling region.

Generating of Worm Gears of an Arbitrary Profile

2011 ◽  
Author(s):  
Tadeusz Nieszporek
Keyword(s):  
Small Diameter ◽  
Surface Profile ◽  
Cnc Machine Tools ◽  
Geometrical Parameters ◽  
Cnc Milling ◽  
Cnc Machine ◽  
Machined Surface ◽  
Arbitrary Profile ◽  
Milling Machines ◽  
Worm Gears

The helical surfaces of worms are most often formed using rotary tools, disk-type, finger-type, cup-type, or ring-type over the whole profile height. The form of machined surface is determined not only by the geometrical parameters and profile of the tool, but also by the tool type. Due to technological reasons, the tool most often has the axial action surface profile which is rectilinear, and much more rarely circular. The increasingly wide use of modern multi-axial CNC machine tools enable the development of technologies for machining helical surfaces of an arbitrary profile. The tool in this case is a small-diameter ball finger cutter. A worm of an arbitrary profile can, however, be made on a principle similar to that of making complex-shaped mould and dies on CNC milling machines with a small-diameter finger cutter. Worm gear can be generated by the same method. In this technology universal tool, ball finger cutter, can be applied for manufacturing worms and wormwheels.

scholarly journals Study of Machining of Gears with Regular and Modified Outline Using CNC Machine Tools

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2913
Author(s):  
Rafał Gołębski ◽  
Piotr Boral
Keyword(s):  
Machine Tools ◽  
Coordinate Measuring Machine ◽  
Optical Microscope ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Cnc Milling ◽  
Cnc Machine ◽  
Cylindrical Gears ◽  
Measuring Machine ◽  
Five Axis

Classic methods of machining cylindrical gears, such as hobbing or circumferential chiseling, require the use of expensive special machine tools and dedicated tools, which makes production unprofitable, especially in small and medium series. Today, special attention is paid to the technology of making gears using universal CNC (computer numerical control) machine tools with standard cheap tools. On the basis of the presented mathematical model, a software was developed to generate a code that controls a machine tool for machining cylindrical gears with straight and modified tooth line using the multipass method. Made of steel 16MnCr5, gear wheels with a straight tooth line and with a longitudinally modified convex-convex tooth line were machined on a five-axis CNC milling machine DMG MORI CMX50U, using solid carbide milling cutters (cylindrical and ball end) for processing. The manufactured gears were inspected on a ZEISS coordinate measuring machine, using the software Gear Pro Involute. The conformity of the outline, the tooth line, and the gear pitch were assessed. The side surfaces of the teeth after machining according to the planned strategy were also assessed; the tests were carried out using the optical microscope Alicona Infinite Focus G5 and the contact profilographometer Taylor Hobson, Talysurf 120. The presented method is able to provide a very good quality of machined gears in relation to competing methods. The great advantage of this method is the use of a tool that is not geometrically related to the shape of the machined gear profile, which allows the production of cylindrical gears with a tooth and profile line other than the standard.

One Touch Workpiece Verification System for CNC Machining Using a Low-Cost Computer Vision Approach

2016 ◽  
Author(s):  
Maxwell K. Micali ◽  
Hayley M. Cashdollar ◽  
Zachary T. Gima ◽  
Mitchell T. Westwood
Keyword(s):  
Computer Vision ◽  
Low Cost ◽  
Cnc Machining ◽  
Potential Operator ◽  
Cnc Milling ◽  
Machining Processes ◽  
Loop Control ◽  
Operator Error ◽  
Verification System ◽  
Milling Machines

While CNC programmers have powerful tools to develop optimized toolpaths and machining plans, these efforts can be wholly undermined by something as simple as human operator error during fixturing. This project addresses that potential operator error with a computer vision approach to provide coarse, closed-loop control between fixturing and machining processes. Prior to starting the machining cycle, a sensor suite detects the geometry that is currently fixtured using computer vision algorithms and compare this geometry to a CAD reference. If the detected and reference geometries are not similar, the machining cycle will not start, and an alarm will be raised. The outcome of this project is the proof of concept of a low-cost, machine/controller agnostic solution that is applied to CNC milling machines. The Workpiece Verification System (WVS) prototype implemented in this work cost a total of $100 to build, and all of the processing is performed on the self-contained platform. This solution has additional applications beyond milling that the authors are exploring.

scholarly journals Modeling of Position-, Tool- and Workpiece-Dependent Milling Machine Dynamics

2016 ◽  
Vol 2 (1) ◽  
Author(s):  
Christian Brecher ◽  
Marcel Fey ◽  
Matthias Daniels
Keyword(s):  
Machine Tool ◽  
High Speed ◽  
Dynamic Properties ◽  
Major Effect ◽  
Modeling Framework ◽  
Milling Tool ◽  
Milling Machines ◽  
Engagement Process ◽  
Coupling Approach ◽  
Interpolation Strategy

AbstractDepending on the machine design, milling machines can show a significant variation of their dynamic properties with respect to the axes configurations, in particular at high speed spindle rotations and high feedrates. Moreover, the workpiece and the milling tool are critical parts of the machine tool and can have a major effect on the dynamic properties. Certain combinations of milling tool,workpiece, tool engagement, process parameters and axes configurations can come along with undesired forced or self-excited vibrations. So far, planning of milling processes usually does not account for these unwanted vibrations. The focus of this paper is to present a modeling framework, which accounts for the abovementioned influences via simulation. The dynamic properties of various workpieces and tools as well as the dynamic properties for many different axes configurations are stored in databases. Based on these databases, the dynamics of any given machine tool configuration can be simulated efficiently based on a substructure coupling approach and an interpolation strategy.

scholarly journals Enhancement of Teaching Design of CNC Milling Machines

2015 ◽  
Vol 176 ◽  
pp. 571-577 ◽  
Author(s):  
Antonín Max ◽  
Václava Lašová ◽  
Šimon Pušman
Keyword(s):  
Cnc Milling ◽  
Teaching Design ◽  
Milling Machines

Spectrum analysis of moving average operator and construction of time-frequency hybrid sequence operator

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Changhai Lin ◽  
Sifeng Liu ◽  
Zhigeng Fang ◽  
Yingjie Yang
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Moving Average ◽  
Spectral Characteristics ◽  
Complex Data ◽  
Time Data ◽  
Average Operator ◽  
Content Type ◽  
Time Frequency ◽  
Hybrid Sequence

PurposeThe purpose of this paper is to analyze the spectral characteristics of moving average operator and to propose a novel time-frequency hybrid sequence operator.Design/methodology/approachFirstly, the complex data is converted into frequency domain data by Fourier transform. An appropriate frequency domain operator is constructed to eliminate the impact of disturbance. Then, the inverse Fourier transform transforms the frequency domain data in which the disturbance is removed, into time domain data. Finally, an appropriate moving average operator of N items is selected based on spectral characteristics to eliminate the influence of periodic factors and noise.FindingsThrough the spectrum analysis of the real-time data sensed and recorded by microwave sensors, the spectral characteristics and the ranges of information, noise and shock disturbance factors in the data can be clarified.Practical implicationsThe real-time data analysis results for a drug component monitoring show that the hybrid sequence operator has a good effect on suppressing disturbances, periodic factors and noise implied in the data.Originality/valueFirstly, the spectral analysis of moving average operator and the novel time-frequency hybrid sequence operator were presented in this paper. For complex data, the ideal effect is difficult to achieve by applying the frequency domain operator or time domain operator alone. The more satisfactory results can be obtained by time-frequency hybrid sequence operator.

Current-Aided Time-Frequency Analysis of Vibration Signals for Gearbox Fault Diagnosis

2018 ◽  
Author(s):  
Xiaotong Tu ◽  
Yue Hu ◽  
Fucai Li
Keyword(s):  
Fault Diagnosis ◽  
Frequency Analysis ◽  
Vibration Signal ◽  
Vibration Monitoring ◽  
Current Signal ◽  
Reliable Technique ◽  
Time Frequency Analysis ◽  
Rotating Speed ◽  
Planetary Gearbox ◽  
Time Frequency

Vibration monitoring is an effective method for mechanical fault diagnosis. Wind turbines usually operated under varying-speed condition. Time-frequency analysis (TFA) is a reliable technique to handle such kind of nonstationary signal. In this paper, a new scheme, called current-aided TFA, is proposed to diagnose the planetary gearbox. This new technique acquires necessary information required by TFA from a current signal. The current signal is firstly used to estimate the rotating speed of the shaft. These parameters are applied to the demodulation transform to obtain a rough time-frequency distribution (TFD). Finally, the synchrosqueezing method further enhances the concentration of the obtained TFD. The validation and application of the proposed method are presented by a simulated signal and a vibration signal captured from a test rig.

CNC Milling Tool of Choice to Explore

2013 ◽  
Vol 706-708 ◽  
pp. 1246-1249
Author(s):  
Da Lin Zhang ◽  
Ji Lin Guo ◽  
Tian Rui Zhou
Keyword(s):  
Type Structure ◽  
Cnc Machining ◽  
Machining Efficiency ◽  
Processing Quality ◽  
Cnc Milling ◽  
Tool Selection ◽  
Milling Cutter ◽  
Milling Tool

The CNC tool selection is an important factor affecting the CNC machining efficiency and parts processing quality. In this paper, based on the analysis of the CNC milling cutter type, structure, diameter, angle, economy and other factors, a reasonable strategy to select the tool.

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