Analysis and compensation of mass loading effect of accelerometers on tool point FRF measurements for chatter stability predictions

Özşahin, Orkun; Özgüven, H. Nevzat; Budak, Erhan

doi:10.1016/j.ijmachtools.2010.02.002

Cited by 48 publications

(16 citation statements)

References 5 publications

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“…Even using a low-weight accelerometer, the mass and the stiffness of the wire can influence the measurement of thin parts with high modal frequencies. Özsahin et al [46] obtained errors of the 10% in the natural frequency of a tool with a diameter of 12 mm and an overhang of 80 mm because of a mass of 2,5 gr from the accelerometer. This error is critical as it has a proportional effect in the stability diagram displacing the lobes horizontally and distorting the stable speeds selection.…”

Section: Discussionmentioning

confidence: 99%

Chatter avoidance in the milling of thin floors with bull-nose end mills: Model and stability diagrams

Campa

Lacalle

Celaya

2011

International Journal of Machine Tools and Manufacture

120

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The milling of thin parts is a high added value operation where the machinist has to face the chatter problem. The study of the stability of these operations is a complex task due to the changing modal parameters as the part losses mass during the machining and the complex shape of the tools that are used. The present work proposes a methodology for chatter avoidance in the milling of flexible thin floors with a bull-nose end mill. First, a stability model for the milling of compliant systems in the tool axis direction with bullnose end mills is presented. The contribution is the averaging method used to be able to use a linear model to predict the stability of the operation. Then, the procedure for the calculation of stability diagrams for the milling of thin floors is presented. The method is based on the estimation of the modal parameters of the part and the corresponding stability lobes during the machining. As in thin floor milling the depth of cut is already defined by the floor thickness previous to milling, it is proposed the use of stability diagrams that relate the tool position along the tool-path with the spindle speed. Hence, the sequence of spindle speeds that the tool must have during the milling can be selected. Finally, this methodology has been validated by means of experimental tests.

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Section: Discussionmentioning

confidence: 99%

Chatter avoidance in the milling of thin floors with bull-nose end mills: Model and stability diagrams

Campa

Lacalle

Celaya

2011

International Journal of Machine Tools and Manufacture

120

View full text Add to dashboard Cite

show abstract

“…The subscript ' m ' denotes an experimentally obtained FRF. The influence of sensor mass loading on the measured FRF was compensated using the structural modification method [12]. Figure 3 shows the measured and predicted tip FRFs for a tool holder with two 16 mm carbide blanks with overhangs of 60 mm and 100 mm.…”

Section: Joint Parameter Identificationmentioning

confidence: 99%

Efficient joint identification and fluted segment modelling of shrink-fit tool assemblies by updating extended tool models

Brecher

Chavan

Fey

2020

Prod. Eng. Res. Devel.

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In milling, the dynamic behavior of the tool center point is crucial for estimating surface quality of the workpiece as well as the process stability behavior. Experimental-analytical receptance coupling can be used for predicting the tool tip dynamics but requires accurate analytical modelling of the holder-tool assembly. This includes the reliable identification of the holder-tool joint properties as well as the correct modelling of the fluted segment of end mills. However, the modelling effort associated with accurately representing the dynamic behavior of the fluted segment is significant. In addition, the joint identification requires a reference tool tip frequency response function of the tool assembly clamped in the machine spindle. This is inefficient and can also lead to incorrect estimation of joint properties. This paper provides an efficient method for joint identification and fluted section modelling using an offline, free–free excitation approach. The objective of this paper is to enable a direct comparison of the dynamic behavior of the freely constrained analytical tool assembly model with that of the real freely constrained tool assembly. The comparison of displacement to force frequency response at certain points on the tool assembly allows for the identification of tool model parameters such as the joint properties and effective diameter of the fluted segment. The comparability is realized by extending the analytical holder-tool beam model to include the receptance model of the standard spindle-holder interface. In this study, as an example, a thermal shrink-fit holder-tool beam model is extended to include an HSK-A63 interface. Subsequently, frequency response functions at two points on the real freely constrained tool assembly are measured in order to identify the joint stiffness and effective diameter of the fluted segment using the corresponding proposed formulations. The updated holder-tool model is then coupled with a 4-axis milling machine and validated. Despite the reduced modelling effort, a good prediction accuracy could be achieved for different holder-tool combinations.

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“…In the OMA, there is a significant issue regarding "noise" (or spurious) modes, and distinguishing them from physical modes still remains to be solved. There is also a problem associated with measurement techniques and the influences of the selection of signal processing on experimental results [22][23][24]. Thus, it is necessary to consider the electrical noise sources in measurement to avoid a bad signal-to-noise ratio and complexity for data analysis, which can cause a severe error in damping estimation [13].…”

Section: Sensitivity To Noisementioning

confidence: 99%

Enhanced frequency domain decomposition algorithm: a review of a recent development for unbiased damping ratio estimates

Hasan¹,

Ahmad²,

Leong³

et al. 2018

J. vibroeng.

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Enhanced frequency domain decomposition (EFDD) is one of OMA methods and has received significant interest from the engineering community involved in the identification of the modal structure. The great attention towards this method is driven by its capability as a user-friendly and fast processing algorithm. However, this method has drawbacks in providing accurate identification of damping ratios, despite natural frequencies and mode shapes can be computed through assuredly and reasonably accurate estimates. The exact practical computation of modal damping is still an open issue, often leading to biased estimates since the errors are coming from every step in EFDD procedures and mainly due to signal processing. Thus, the computation of modal damping becomes tremendously vital in structural dynamics because modal damping is one of the critical parameters of resonance. This review aims to provide relevant essential information on modal damping for a reliable estimation, reduce uncertainties and define error bounds. A literature review has been carried out to find the best practice criteria for modal parameter identification, in particular, modal damping ratio.

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Analysis and compensation of mass loading effect of accelerometers on tool point FRF measurements for chatter stability predictions

Cited by 48 publications

References 5 publications

Chatter avoidance in the milling of thin floors with bull-nose end mills: Model and stability diagrams

Chatter avoidance in the milling of thin floors with bull-nose end mills: Model and stability diagrams

Efficient joint identification and fluted segment modelling of shrink-fit tool assemblies by updating extended tool models

Enhanced frequency domain decomposition algorithm: a review of a recent development for unbiased damping ratio estimates

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