International Journal of Machine Tool Design and Research 

About: International Journal of Machine Tool Design and Research is an academic journal. The journal publishes majorly in the area(s): Machining & Machine tool. It has an ISSN identifier of 0020-7357. Over the lifetime, 583 publications have been published receiving 9230 citations.

The prediction of cutting forces in end milling with application to cornering cuts

Abstract: This paper presents the development, verification, and implementation of a mechanistic model for the force system in end milling. This model is based on chip load, cut geometry, and the relationship between cutting forces and chip load. A model building procedure based on experimentally obtained average forces is presented and both instantaneous and average force system characteristics are described as a function of cut geometry and feed rate. A computer program developed to implement the mechanistic model provides tabular and graphical outputs which show force distributions as functions of the axial depth of cut and rotation of the cutter. Force characteristics during concerning cuts are predicted by the model and verified via a set of cornering cut experiments typical of aerospace machining operations. Force characteristics in cornering are examined as a function of axial depth of cut and feedrate.

The effect of runout on cutting geometry and forces in end milling

Abstract: Cutter runout is a universal condition affecting the performance of multi-tooth metal cutting operations such as milling operations. In end milling, the use of set screw-type tool holders causes the milling cutter to be offset in the tool holder with the offset side of the cutter experiencing higher than average chip loads leading to higher peak forces and uneven tool wear on the cutter. Mathematical models are developed for the cutting geometry, tooth radius, chip thickness and entry and exit angles for end milling with cutter offset or runout. These geometry models are merged with previously developed cutting force models to predict cutting force characteristics with cutter runout for end milling. These models are verified through the comparison of measured and predicted forces for aerospace grade 7075 aluminum. It is shown that the presence of runout increases the average chip thickness for those teeth actually engaged in the cut and increases the ratio of the maximum to average force. Runout also shifts the frequency content of the force signal away from the tooth passing frequency to the spindle rotational frequency. The ratio of the runout to the feed rate is identified as an important parameter which determines the effect of runout on the cutting force system.

Minimum zone evaluation of surfaces

Abstract: The surfaces that are obtained by various machining and finishing processes deviate from the specified geometry. The evaluation of such surfaces for straightness, flatness, circularity, etc. are given by ISO in terms of the minimum zone values. But no specific methods to obtain the minimum zone values are available. Hence an attempt has been made in this paper to present different methods developed at Central Machine Tool Institute (CMTI) for such applications. The present paper deals with the evaluation of spherical, cylindrical and flat surfaces for sphericity, circularity, flatness etc. in terms of minimum zone deviation. Monte Carlo technique, normal least squares fit, simplex search and spiral search techniques were applied. Monte Carlo, simplex and spiral search techniques were found suitable for minimum zone evaluation.

Theory of finite amplitude machine tool instability

Abstract: A non-linear theory of machine tool chatter is presented. It is shown that even when the machine tool structure is linear or only slightly non-linear (as appears to be the case), large non-linearity is introduced by two causes. Firstly, by the chatter amplitudes exceeding a certain value, dependent on the mean chip thickness and the vibrating tool leaving the workpiece. Secondly, by a non-linearity of the cutting force characteristics. By combining these non-linear effects with the linear operative receptance of the machine tool structure, non-linear stability conditions are derived which describe a surface in the three-dimensional space defined by rotational speed, depth of cut and chatter amplitude. Sections through this surface provide the traditional (linear) stability chart relating depth of cut and rotational speed, as well as non-linear charts relating chatter amplitude with depth of cut. The latter are used for discussing the mechanism of stabilisation of chatter amplitudes and the phenomenon of finite amplitude instability. It is shown that the physical cause of finite amplitude instability lies in the non-linearity of the cutting force characteristic. The theory presented leads to conclusions of practical significance. The most important of these is that when the cutting force characteristic is non-linear the cutting process may be stabilised by a large increase of the mean chip thickness. Theoretical work is supported by experiments and good correlation between these is noted.