Mahdi Eynian

Chatter Stability of General Turning Operations With Process Damping

The accurate prediction of chatter stability in general turning operations requires the inclusion of tool geometry and cutting conditions. This paper presents regenerative chip and regenerative chip arealcutting edge contact length based dynamic cutting force models, which consider cutting conditions and turning tool geometry. The cutting process is modeled as it takes place along the equivalent chord length between the two end points of the cutting edge. The regenerative chip model is simple, and the stability can be solved directly. However, the three-dimensional model considers the effect of tool vibrations at the present and previous spindle revolutions on the chip area, chord length, and force directions and is solved using Nyquist stability criterion. The penetration of worn tool flank into the finish surface is considered as a source of process damping. The effects of the nose radius, approach angle of the tool, and feedrate are investigated. The proposed stability model is compared favorably against the experimental results.

Analytical Chatter Stability of Milling With Rotating Cutter Dynamics at Process Damping Speeds

Thispaper presents a chatter stability prediction method for milling flexibleworkpiece with end mills having asymmetric structural dynamics. The dynamicchip thickness regenerated by the vibrations ...

Cutter Exit Effects during Milling of Thin-Walled Inconel 718

During milling of thin-walled components, chatter vibrations give rise to process issues. These include dimensional inaccuracy, damaged and scrap parts, and damaged cutting tools. This, in turn, leads to loss of production time with increasing cost as a consequence. This paper identifies the force profile during a single cut milling process. It focuses on the exit and post-exit behavior of the cut and discusses the process dynamics. The force profiles of various tool-to-workpiece positions are analyzed as regards the exit and post exit phases. A standard on-the-market cutter and a specially designed zero rake cutter are used in the investigation. Finally, a time-domain simulation of the force is performed and compared to the experimental results. The study concludes that a small change in exit angle may result in a considerable improvement in cutting behavior. In addition, the tool position should be chosen so that the cutter exits in the least flexible direction possible for the workpiece.

Influence of radial depth of cut on entry conditions and dynamics in face milling application

The choice of milling cutter geometry and appropriate cutting data for certain milling application is of vital importance for successful machining results. Unfavorable selection of cutting conditions might give rise to high load impacts that cause severe cutting edge damage. Under some circumstances the radial depth of cut in combination with milling cutter geometry might give unfavorable entry conditions in terms of cutting forces and vibration amplitudes. This phenomenon is originated from the geometrical features that affect the rise time of the cutting edge engagement into workpiece at different radial depths of cut. As the radial depth of cut is often an important parameter, particularly when machining difficult-to-cut materials, it is important to explore the driving mechanism behind vibrations generation. In this study, acceleration of the workpiece is measured for different radial depths of cut and cutting edge geometries. The influence of the radial depth of cut on the dynamical behavior is evaluated in time and frequency domains. The results for different radial depths of cut and cutting geometries are quantified using the root mean square value of acceleration. The outcome of this research study can be used both for the better cutting data recommendations and improved tool design.

Process stability strategies in milling of thin-walled Inconel 718

Trends in Aerospace development have led to thin-walled, reduced-weight engine designs. The demands in manufacturing have forced production speeds and material removal rates (MRR) to increase. As component wall thickness gets thinner, the consequence oftentimes is an increase in chatter vibrations. This paper suggests that a correctly chosen tool-to-workpiece offset geometry may lead to a robust and chatter free process. The results show the differences in force response for three geometries while varying the height overhang of the workpiece. This is part of a concerted effort to develop a robust methodology for the prediction of chatter vibrations during milling operations of thin-walled Aerospace components. This paper gives guidelines on how to accomplish robust machining practices. It also answers the following questions: How critical is the choice of offset between tool and workpiece during milling setup? And what effects do the entry and exit of cut have on system vibrations?

Milling Strategies for Thin-walled Components

Recent developments in the Aerospace industry have led to thin-walled, reduced-weight engine designs. Due to demands in manufacturing, production speeds and material removal rates (MRR) have increased. As component wall thickness gets thinner, the consequence oftentimes is an increase in chatter vibrations. This paper suggests that a correctly chosen tool-to-workpiece offset geometry may lead to a robust and chatter-free process. The results show the differences in force response for three geometries while varying the overhang of the workpiece. This is part of a concerted effort to develop a robust methodology for the prediction of chatter vibrations during milling operations of thin-walled Aerospace components. This paper outlines certain robust machining practices. It also analyzes the criticality of the choice of offset between tool and workpiece during milling setup as well as the effects that the entry and exit of cut have on system vibrations.