CHATTER OF PLASTIC MILLING CNC MACHINE

AUTHOR: OZOEGWU CHIGBOGU GODWIN

DEPARTMENT: MECHANICAL ENGINEERING

AFFILIATION: NNAMDI AZIKIWE UNIVERSITY, AWKA

The desire to carry out this work arose from an observation during a practical work on a typical plastic end milling CNC machine (C-501). It was noticed that under certain conditions of cutting, the operation of the machine became noisy with increasing depth of cut and eventual perforation of workpiece. Therefore the basic aim is to unravel and explain the reason for this behaviour. As a prerequisite to modelling the dynamics of milling, the simpler turning dynamics was modelled and various stability conditions derived in the form of stability charts and response histories of the tool system. Dynamical modelling of milling was conducted and the resulting periodic delay differential equation of motion solved with the help of MATLAB. Based on the graphical solutions several deductions were made about the sensitivity and readiness of bifurcation in tool motion as a result of variations in cutting parameters. Stability charts were generated on the parameter plane on which stable and unstable domains were separated. Results of the MATLAB time domain analysis were used in the validation of the charts. Also the resulting charts were validated by a milling stability chart found in literature and the result that in conformity with theory the boundary curve of the chart reflects only the two types of possible bifurcation in milling process which are Secondary Hopf and Flip bifurcations. Based on the charts, various recommendations were made for the studied system having the parameters; tool mass m = 0.0431kg, tool natural frequency ω􀭬 = 5700 rad⁄sec, damping factor ξ = 0.02 and workpiece cutting coefficient C = 3.5 × 10􀬻Nm 􀰷􀰳 􀰰 . The recommendations made include that the depth of cut should be below 1􀝉􀝉 while the machine runs within operational spindle speed range of (0 − 3000􀝎􀝌􀝉). Though this work has practical roots, it is entirely theoretical with the modal and material parameters used chosen judiciously from literature. That notwithstanding this work resulted in the understanding of the performance of the reference plastic milling CNC machine (C-501). 

TO VIEW THE FULL CONTENT OF THIS DOCUMENT, PLEASE VISIT THE UNIZIK LIBRARY WEBSITE USING THIS LINK, http://naulibrary.org/dglibrary/admin/book_directory/Thesis/11053.pdf

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One Response to “CHATTER OF PLASTIC MILLING CNC MACHINE”

  1. Thermoformed plastic company Says:

    Great post!

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