Chatter prediction based on frequency domain solution in CNC pocket milling

Ko, Jeong Hoon; Shaw, Kah Chuan

doi:10.1007/s12541-009-0067-3

Cited by 8 publications

(5 citation statements)

References 15 publications

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“…3, the effect of ultrasonic vibration is obviously positive for higher spindle speeds where chatter marks becomes worse without ultrasonic vibration assistnace. This phenomenon is observed because critical stable cutting depth becomes lower at higher spindle speeds than lower speeds due to process damping [10][11][12][13] .Feed per tooth also affects machining quality considering minimum chip thickness effect [14][15][16][17] , which should be investigated further in near future. Spindle axial ultrasonic vibration assisted milling can improve surface roughness values from 20% to 65% with reduced vibration marks for most tested spindle RPMs.…”

Section: Resultsmentioning

confidence: 99%

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Surface Quality Improvement in Meso-Scale Milling with Spindle Axial Directional Ultrasonic Vibration Assistance

Shaw

Tan

et al. 2012

AMR

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So far, the industrial application of ultrasonic vibration assistance has been successful in continuous machining process such as turning process where ultrasonic vibration velocity is much higher than cutting velocity. Recently, vibration assistance has been experimentally investigated to the intermittent milling process mainly for feed and cross- feed directions. This paper focuses on the effect of ultrasonic vibration assistance in spindle axial direction for improvement of machined surface. With the designed ultrasonic vibration assisted milling process with 39.7 kHz and a few micro-meter amplitudes, workpiece vibrates along spindle axial direction while different RPMs and feed rates are applied. The axial directional vibration assistance acts as additional cutting motion which further reduces the leftover surface error. Experimental results validate that surface roughness can be improved from 20 % to 65 % for the tested conditions. Apparently chatter marks of the milling process are reduced with the help of the axial ultrasonic vibration assistance.

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Section: Resultsmentioning

confidence: 99%

“…In this intermittent high speed milling process, the cutting speed is always higher than the ultrasonic vibration speed. High speed milling may cause a machining chatter marks on the machined surface based on the combinations of spindle speeds and cutting depths [10][11][12][13] .…”

Section: Spindle Axial Ultrasonic Vibration Assistance Configurationmentioning

confidence: 99%

Surface Quality Improvement in Meso-Scale Milling with Spindle Axial Directional Ultrasonic Vibration Assistance

Shaw

Tan

et al. 2012

AMR

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“…Prediction of these effects is nowadays crucial to optimize process parameters and reduce detrimental vibrations occurrence. In particular, cutting forces must be taken into account in every dynamic simulation, such as chatter vibration prediction [2], surface finish estimation [3], process time-domain evolution [4] and thin-walled machining optimization [5]. In the last decades several cutting force models have been developed [6,7,8].…”

Section: Introductionmentioning

confidence: 99%

Accurate and fast measurement of specific cutting force coefficients changing with spindle speed

Grossi

2017

Int. J. Precis. Eng. Manuf.

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Prediction of cutting forces is essential to simulate dynamic effects of the milling process, and optimize process parameters to reduce detrimental vibrations. Cutting forces are conventionally modeled by assuming a dependence on uncut chip thickness using dedicated coefficients, to be experimentally identified. These coefficients are proven to vary significantly with spindle speed, causing the need of a time-consuming experimental phase to achieve an accurate simulation of cutting forces in a wide range of spindle speeds. This paper presents a method to efficiently identify the specific cutting force coefficients in the entire speed range by a single milling test, in which spindle speed is ramped-up. During the test, the forces signals are acquired and then processed to identify the speed-varying cutting force coefficients. The method was applied to the identification of Aluminum 6082-T4 coefficients in a wide range of speeds and results were validated through traditional approach, proving the efficiency and effectiveness of the proposed technique. In addition, an application of the obtained coefficients to chatter prediction is presented and validated through chatter tests.

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“…Other important and undesired effects to take into account are chatter vibrations. 1,2 In order to decrease these malfunctions in the process the peak cutting force on the workpiece has to be maintained below a prescribed safety upper-bound. Some works have been developed in the identification of the milling forces.…”

Section: Introductionmentioning

confidence: 99%

Analysis of discrete time schemes for milling forces control under fractional order holds

Rubio

Sen

Longstaff

et al. 2013

Int. J. Precis. Eng. Manuf.

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In this paper, discrete time model reference control schemes for practical milling using different discretization of the continuous-time plant are presented. First, a basic controller scheme is addressed where a fractional order hold with pre-fixed value of the gain is used. Secondly, a multi-model scheme, which outputs different discretization in parallel with the continuous-time milling system transfer function under a fractional order hold (FROH) of correcting β ∈ [−1, 1], is dealt with. Then, an intelligent design framework is designed as a supervisory scheme with two hierarchical levels in order to find the most appropriate value for the gain β. For choosing the value of β, a tracking performance index is designed. It evaluates each pre-defined discretization of the continuous time milling transfer function and the scheme chooses the one with the smallest value of the index in order to generate the real control input to the plant. Two different methods of adjusting this value are presented and discussed. The first one selects a β-value among a fixed pre-defined set of possible values, while the second one the value of β is updated by adding or subtracting a small quantity.

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Chatter prediction based on frequency domain solution in CNC pocket milling

Cited by 8 publications

References 15 publications

Surface Quality Improvement in Meso-Scale Milling with Spindle Axial Directional Ultrasonic Vibration Assistance

Surface Quality Improvement in Meso-Scale Milling with Spindle Axial Directional Ultrasonic Vibration Assistance

Accurate and fast measurement of specific cutting force coefficients changing with spindle speed

Analysis of discrete time schemes for milling forces control under fractional order holds

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