Turning Dynamics: Part 2 — Stability at High Speed

2012 ◽  
Author(s):  
Eric B. Halfmann ◽  
C. Steve Suh ◽  
N. P. Hung
Keyword(s):  
Natural Frequency ◽  
Vibration Amplitude ◽  
High Speed ◽  
Stability Limit ◽  
Stability Diagram ◽  
Spindle Speed ◽  
Depth Of Cut ◽  
Work Piece ◽  
Highly Nonlinear ◽  
Cutting Model

A comprehensive 3D lathe cutting model is validated by comparing numerical simulations to the experimental data obtained in Part 1 using instantaneous frequency. Comparison of chatter-free cutting demonstrates that the model effectively captures the work-piece natural frequency, tool natural frequency, a nonlinear mode, and the spindle speed, which are main components of the underlying dynamics observed experimentally. The model accurately simulates chatter vibrations characterized as increased vibration amplitude and the appearance of coupled tool – work-piece vibrations at a chatter frequency. The stability diagram constructed by running the model at various spindle speeds and depth-of-cuts demonstrates a general increase in the chatter-free critical depth-of-cut as the spindle speed increased. This chatter-free limit begins to exponentially level out as the spindle speed exceeds 1500RPM. At high spindle speeds the work-piece motions dominate the cutting dynamics, resulting in cases of excessive work-piece vibration amplitude and highly nonlinear frequencies which affect the efficiency of the process. The excessive work-piece amplitude cases create a second stability limit to be considered as a result of imbalance and configuration of the work-piece. Thus, work-piece dynamics should not be neglected in mathematical and experimental analyses for the design of machine tools and robust cutting control law.

Definition of Cutting Conditions for Thin-to-Thin Milling of Aerospace Low Rigidity Parts

2008 ◽  
Author(s):  
F. J. Campa ◽  
L. N. Lopez de Lacalle ◽  
G. Urbikain ◽  
D. Ruiz
Keyword(s):  
Dimensional Stability ◽  
High Speed ◽  
Tool Path ◽  
Three Dimensional ◽  
Stability Diagram ◽  
Spindle Speed ◽  
Cutting Conditions ◽  
Depth Of Cut ◽  
Compliant Parts ◽  
Tool Position

The main drawback of the high speed milling of monolithic parts for the aerospace industry is the high buy-to-fly ratio that leads to a huge material waste. This problem is caused by the need to stiffen the part during the machining in order to avoid chatter, excessive vibration and residual stresses. The present work proposes a methodology for the milling of compliant parts based on the selection of cutting conditions free of chatter. First, the modal parameters of the part in the most problematic stages of the machining are calculated by means of the finite elements method. Secondly, a three-dimensional stability model is used in each stage to calculate a three-dimensional stability lobes diagram dependent on the tool position along the whole tool path. Given the fact that the depth of cut is defined by the bulk of material, the three-dimensional stability diagram can be reduced to a two-dimensional one, which relates tool position during the machining and spindle speed, and indicates how to change the spindle speed in order to avoid the unstable areas. What is more, the proposed methodology can also be used to dimension the bulk of material, select the proper tool or improve the fixturing of the part. Finally, the methodology is validated experimentally on a test part.

scholarly journals Influence of the Cut Axial Depth on Surface Roughness at High-Speed Milling of Thin-Walled Workpieces

2021 ◽  
Vol 20 (2) ◽  
pp. 127-131
Author(s):  
A. I. Germashev ◽  
V. A. Logominov ◽  
S. I. Dyadya ◽  
Y. V. Kozlova ◽  
V. A. Krishtal
Keyword(s):  
High Speed ◽  
End Milling ◽  
Spindle Speed ◽  
Depth Of Cut ◽  
Work Piece ◽  
Natural Vibration Frequency ◽  
High Speed Milling ◽  
Wide Range ◽  
Thin Walled ◽  
Axial Depth

The paper presents the results of research on the dynamics of end milling of thin-walled work-pieces having complex geometric shapes. Since the milling process with shallow depths of cut is characterized by high intermittent cutting, the proportion of regenerative vibrations decreases, and the effect of forced vibrations on the dynamics of the process, on the contrary, increases. The influence of  axial depth of cut on the vibrations arising during processing, and roughness of the processed surface have been studied in paper.  The experiments have been carried out in a wide range of changes in the spindle speed at different axial cutting depths.  Vibrations of a thin-walled work-piece  have been recorded with an inductive sensor and recorded in digital form. Then an oscillogram has been used to estimate the amplitude and frequency of oscillations. The profilograms of the machined surface have been analysed. Roughness has been evaluated by the parameter Ra. The results have shown similar relationships for each of the investigated axial cutting depths. The worst cutting conditions  have been observed when the natural vibration frequency coincided with the tooth frequency or its harmonics. It is shown that the main cause of vibrations in high-speed milling  is forced rather than regenerative vibrations. Increasing the axial depth of cut at the same spindle speed increases the vibration amplitude. However, this does not significantly affect the roughness of the processed surface in cases when it comes to vibration-resistant processing.

Modeling and Optimization of Vibration Amplitude in Turning of Ti-6Al-4V Using Response Surface Methodology

2012 ◽  
Vol 217-219 ◽  
pp. 1567-1570
Author(s):  
A.K.M. Nurul Amin ◽  
Muammer Din Arif ◽  
Syidatul Akma Sulaiman
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Vibration Amplitude ◽  
Desirability Function ◽  
Cutting Speed ◽  
Vibration Sensor ◽  
Experimental Investigations ◽  
Depth Of Cut ◽  
Work Piece ◽  
Inferior Surface

Chatter is detrimental to turning operations and leads to inferior surface topography, reduced productivity, dimensional accuracy, and shortened tool life. Avoidance of chatter has mostly been through reliance on heuristics such as: limiting material removal rates or selecting low spindle speeds and shallow depth of cuts. But, modern industries demand increased output and not steady operational limits. Various research efforts have therefore focused on developing mathematical models for chatter formation. However, as yet there is no existent model that meets all experimental verification. This research employed a novel technique based on the synergy of statistical modeling and experimental investigations in order to develop an effective empirical mathematical model for chatter amplitude and to subsequently find optimal machining conditions. Ti-6Al-4V, Titanium alloy, was used as the work-piece due to its increased popularity in applications related to aerospace, automotive, nuclear, medical, marine etc. A sequence of 15 experimental runs was conducted based on a small Central Composite Design (CCD) model in Response Surface Methodology (RSM). The primary (independent) parameters were: cutting speed, feed, and depth of cut. The tool overhang was kept constant at 70 mm. An engine lathe (Harrison M390) was employed for turning purposes. The data acquisition system comprised a vibration sensor (accelerometer) and a signal conditioning unit. The resultant vibrations were analyzed using the DASYLab 5.6 software. The best model was found to be quadratic which had a confidence level of 95% (ANOVA) and insignificant Lack of Fit (LOF) in Fit and Summary analyses. Desirability Function (DF) approach predicted minimum vibration amplitude of 0.0276 Volts and overlay plots identified two preferred machining regimes for optimal vibration amplitude.

Investigation of Surface Roughness and Material Removal Rate for High Speed Micro End Milling on PMMA

2015 ◽  
Vol 1115 ◽  
pp. 12-15
Author(s):  
Nur Atiqah ◽  
Mohammad Yeakub Ali ◽  
Abdul Rahman Mohamed ◽  
Md. Sazzad Hossein Chowdhury
Keyword(s):  
Surface Roughness ◽  
Material Removal Rate ◽  
Feed Rate ◽  
Material Removal ◽  
High Speed ◽  
End Milling ◽  
Removal Rate ◽  
Spindle Speed ◽  
Depth Of Cut ◽  
Micro End Milling

Micro end milling is one of the most important micromachining process and widely used for producing miniaturized components with high accuracy and surface finish. This paper present the influence of three micro end milling process parameters; spindle speed, feed rate, and depth of cut on surface roughness (Ra) and material removal rate (MRR). The machining was performed using multi-process micro machine tools (DT-110 Mikrotools Inc., Singapore) with poly methyl methacrylate (PMMA) as the workpiece and tungsten carbide as its tool. To develop the mathematical model for the responses in high speed micro end milling machining, Taguchi design has been used to design the experiment by using the orthogonal array of three levels L18 (21×37). The developed models were used for multiple response optimizations by desirability function approach to obtain minimum Ra and maximum MRR. The optimized values of Ra and MRR were 128.24 nm, and 0.0463 mg/min, respectively obtained at spindle speed of 30000 rpm, feed rate of 2.65 mm/min, and depth of cut of 40 μm. The analysis of variance revealed that spindle speeds are the most influential parameters on Ra. The optimization of MRR is mostly influence by feed rate. Keywords:Micromilling,surfaceroughness,MRR,PMMA

Comparative Study on Cutting Force Simulation Using DEFORM 3D Software during High Speed Machining of Ti-6Al-4V

2020 ◽  
Vol 856 ◽  
pp. 50-56
Author(s):  
Kundan Kumar Prasad ◽  
Santosh Kumar Tamang ◽  
M. Chandrasekaran
Keyword(s):  
Finite Element ◽  
Cutting Force ◽  
High Speed ◽  
Cutting Temperature ◽  
Experimental Result ◽  
Depth Of Cut ◽  
Work Piece ◽  
High Speed Machining ◽  
3D Software ◽  
Deform 3D

The finite element-based machining simulations for evaluation/computation of different machining responses (i.e., cutting temperature, tool wear, cutting force, and power/energy consumption) are investigated by number of researchers. In this work, finite element machining simulation was performed to obtain knowledge about cutting forces during machining of hard materials. Titanium alloy (Ti-6Al-4V) has been increasingly used in aerospace and biomedical applications due to high toughness and good corrosion resistance. The high speed machining (HSM) simulation of Ti-6Al-4V work-piece using carbide tool coated with TiCN has been conducted with different combination of cutting conditions for prediction of main cutting force (Fz). The simulated result obtained from Deform 3D software is validated with experimental result and it was found that the result found in good agreement. The parametric variation shows that depth of cut and feed are influencing parameters on cutting force.

Tool Vibration due to High Speed Micro End Milling Parameters

2013 ◽  
Vol 372 ◽  
pp. 364-368 ◽  
Author(s):  
Abdul Rahman Mohamed ◽  
Nur Atiqah ◽  
Mohammad Yeakub Ali ◽  
M.S.H. Chowdhury
Keyword(s):  
High Speed ◽  
End Milling ◽  
Signal To Noise Ratio ◽  
Cutting Parameters ◽  
Spindle Speed ◽  
Depth Of Cut ◽  
Signal To Noise ◽  
Tool Vibration ◽  
Milling Parameters ◽  
Micro End Milling

This paper presents the effect of high speed micro end milling parameters on tool vibration during machining of poly (methyl methacrylate) (PMMA). The main focus is to achieve minimum tool vibration by controlling the cutting parameters; spindle speed, feed rate and depth of cut. An empirical model for tool vibration has been developed using Taguchi method. The orthogonal array, signal-to-noise ratio and analysis of variance revealed that high spindle speed is the most influential parameter to increase the level of tool vibration.

The Effect of Multiple Dynamic Absorbers on Regenerative Chatter and Resonance in End Milling Process

2012 ◽  
Author(s):  
Yutaka Nakano ◽  
Hiroki Takahara ◽  
Kengo Yasue ◽  
Ryutaro Asaga
Keyword(s):  
Natural Frequency ◽  
Phase Difference ◽  
Forced Vibration ◽  
End Milling ◽  
Rotation Frequency ◽  
Spindle Speed ◽  
Depth Of Cut ◽  
Critical Depth ◽  
Spindle Rotation ◽  
Critical Depth Of Cut

The present study investigates the effect of multiple dynamic absorbers on regenerative chatter and resonance caused by forced vibration generated in the end milling operations. Regenerative chatter is caused by the cutting force variation due to the phase difference between the wave left by the previous cutting edge and the wave left by the current one. This phase difference is expressed as the product of the tooth passing period and chatter frequency [1]. The tooth passing period depends on the spindle rotation frequency and the number of teeth. Chatter frequency is related to the natural frequency of the tool and spindle system. If the integral multiple of the spindle rotation frequency approaches to the natural frequency, the phase difference gets smaller and the critical depth of cut at the onset of chatter is increased. Therefore the critical depth of cut varies with the spindle speed and stable cutting conditions are plotted on the chatter stability lobe, which is a chart that represents the boundary between stable and unstable cuts as a function of the spindle speed and the depth of cut. The chatter stability lobe is widely employed to find the axial depth of cut and the spindle speed in which chatter doesn’t occur. Meanwhile, the cutting force variation by the intermittent cutting with an end milling tool causes the forced vibration. The excitation frequency is determined by the spindle rotation frequency and the number of teeth. When the integral multiple of the excitation frequency approaches to the natural frequency of the tool and spindle system, resonance can be caused by the forced vibration. The resonance occurs in the spindle speed resistant to chatter. Therefore, there is a need for a countermeasure against not just the chatter but also the resonance caused by the forced vibration. In the present study, the cutting conditions which can lead to the chatter and the resonance are investigated by the direct numerical integration method. It is made clear that the optimum tuning parameters of the absorbers to maximize the critical depth of cut vary with the spindle speed. Furthermore, a significant suppression effect on the chatter and the resonance by using the absorbers mounted in a rotating collet holder with a spindle is confirmed.

Avoiding Instability on the Milling of Parts with Thin Features

2006 ◽  
Vol 526 ◽  
pp. 37-42 ◽  
Author(s):  
Francisco Javier Campa ◽  
Luis Norberto López de Lacalle ◽  
S. Herranz ◽  
Aitzol Lamikiz ◽  
A. Rivero
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Spindle Speed ◽  
Depth Of Cut ◽  
Test Device ◽  
High Speed Milling ◽  
Thin Walls ◽  
Chatter Vibrations ◽  
The Stability ◽  
Selection Of

In this paper, a 3D dynamic model for the prediction of the stability lobes of high speed milling is presented, considering the combined flexibility of both tool and workpiece. The main aim is to avoid chatter vibrations on the finish milling of aeronautical parts, which include thin walls and thin floors. In this way the use of complex fixtures is eliminated. Hence, an accurate selection of both axial depth of cut and spindle speed can be accomplished. The model has been validated by means of a test device that simulates the behaviour of a thin floor.

Machining Time Simulation in High Speed Hard Turning

2011 ◽  
Vol 264-265 ◽  
pp. 1102-1106 ◽  
Author(s):  
Erry Yulian Triblas Adesta ◽  
Muataz H.F. Al Hazza
Keyword(s):  
High Speed ◽  
Hard Turning ◽  
Rotation Speed ◽  
Cutting Speed ◽  
Depth Of Cut ◽  
Work Piece ◽  
Machining Time ◽  
Set Up ◽  
Cutting Point ◽  
Productive Time

High speed hard turning is an advanced manufacturing technology that reduces the machining time because of two reasons; reducing the manufacturing steps and increasing the cutting speed. This new approach needs an economical justification; one of the main economical factors is the machining time. The machining time was breaking down into three main parts; productive time, non productive time, and preparation time. By using matlab Simulink, a new program was developed for machining time allowing the manufacturer to find rapidly the values of cutting time parameters and gives the management the opportunity to modify the processing parameters to achieve the optimum time by using the optimum cutting parameters. Table 1: Nomenclature d Depth of cut M T total machining time pmv t Total movement time D Work piece diameter h t handling time pch t Total Tool changing time f Feed rate tc t tool changing time pre t Total preparing time z e Engagement distance on Z-axis ch t Tool changing time per piece, prg t Programming time x e Degagement distance on X-axis am t Machine allowance time su t Set up time k Number of passes ao t Operator allowance time sum t Machine set up L Tool life a t Allowance time sut t Tool set up l Work piece length o t Tool movement at the rapid speed suw t Work piece set up N Spindle speed oA t From zero point to cutting point TH Tool hardness tool n No. of tool posts in the turret p t Total productive time o X tidy of the O t point o1 p Initial position of the turret. o Z = abciss of the O t point w Work piece weigh o2 p Position of the used tool c V Cutting speed c w Width of cutting speed r Rotation speed of the turret f V Feeding speed tool n no. of tool in the turret c t Cutting time o V Rapid speed speed r : Turret rotation speed

Tool Life and Wear Mechanism when Machining LM6 Aluminium (MMC) with Coated and Uncoated High Speed Steel

2015 ◽  
Vol 761 ◽  
pp. 262-266
Author(s):  
A. Siti Sarah ◽  
A.B. Mohd Hadzley ◽  
Raja Izamshah ◽  
Abu Abdullah
Keyword(s):  
Tool Life ◽  
Feed Rate ◽  
High Speed ◽  
Adhesive Wear ◽  
Cutting Tools ◽  
High Speed Steel ◽  
Spindle Speed ◽  
Depth Of Cut ◽  
Radial Depth ◽  
Titanium Aluminium

This paper aims to study the tool life of coated and uncoated high speed steel (HSS) when machining LM6 aluminium. The experiment was carried out in dry condition with spindle speed of 5000 rpm and 6000 rpm, and feed rate of 90 mm/min and 120 mm/min. Axial and radial depth of cut remain constant at 0.5 mm and 1.0 mm, respectively during the experiment. Throughout the experiments, coated HSS showed higher tool life as compared to uncoated HSS due to the coating layer of titanium aluminium nitride (TiAlN) provides protection from rapid wear during machining. For both cutting tools, the optimum cutting parameter was recorded at 5000 rpm spindle speed, 90 mm/min feed rate, 0.5 mm axial depth of cut and 1.0 mm radial depth of cut. Some evidence of built up edge (BUE) formation were observed at most of cutting tools, showing the dominant wear mechanisms appear to be adhesive wear.

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