Mathematical study of the effect of errors during oblique cutting

Dissertant

Jamil, Rahim Sadun

University

University of Technology

Faculty

-

Department

Department of Production Engineering and Metallurgy

University Country

Iraq

Degree

Master

Degree Date

2006

English Abstract

Machining accuracy is considerably affected by the deflection of the machine-tool-work piece system under the action of the cutting force.

Many key factors play an important role such as cutting tools, machining conditions, resolution of the machine tool and the type of work piece eats.

However, once these are decided upon, the consistent performance of the machine work piece dimension.

This task is largely constrained by errors either built into the machine or occurring on a periodic basis on account of temperature changes or variation in cutting forces.

In this work, a procedure is described in order to estimate the work piece errors in bar turning due to cutting forces.

During the turning process, the part is subjected to three components of cutting force, namely the radial Fry, axial Fad and tangential F, components.

This cutting force causes the tool system, the machine as well as the work piece deflection, to deflect.

The cross-section deflection 8xy of the work piece, which can be resolved into directional component 8X and 5V due to respectively to components of the cutting forces (Fr, Fa) and Ft respectively.

The prediction is based on a geometric analysis of the part cross- section where the cutting tool is in position of machining in order to obtain the predicted workpiece diameter Dp(z) and depth of cut dp (z) along the Z-axis after machining.

The work piece cross-section deflection 5xy at the position of the tool is of interest because it affects the part quality directly.

This deflection is obtained from 8X and Sy which are determined by using two methods, first DEM and second FEM.

The numerical results are compared with these obtained by the experiments tests carried out through on a (Harrison M300) lathe .The results show that in case the deflection is neglected in the machine (tailstock, chuck) from influence of cutting force have large effect on the diameter errors and depth of cut.

This effect causes the curve of both the diameter error and depth of cut to change from convex shape to a concave shape.

Also the peaks of deflection do not occur exactly at the Centre of the part length to be machined, since the chuck-Centre mounting type causes more compliant deflection increasing towards the support, which is the tailstock.

The resulting error of manufacturing bar seems to be higher than that obtained by finite element method.

Those effects are due to reflectance of the influence of chuck and tailstock stiffness, vibration, chatter and backlash error in lead screw.

Also the value of the maximum diameter error moves from the tailstock to middle of chuck by increasing the work piece length.

This is due to the tool-machine-work piece system that, for the considered values of work piece length, spindle and tailstock stiffness.

Increasing the work piece length, the shift of maximum diameter error is caused by work piece length; therefore, the work piece deflection is large due to the machine-tool structure.

Main Subjects

Engineering & Technology Sciences (Multidisciplinary)

Topics

• Mathematical models

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305690