| Author | Kawin Sonthipermpoon |
| Call Number | AIT Diss. no. ISE-98-02 |
| Subject(s) | Machine-tools--Numerical control
|
| Note | A dissertation submitted in partial fulfillment of the requirement for the degree of Doctor
of Engineering, School of Advanced Technologies |
| Publisher | Asian Institute of Technology |
| Abstract | Innovations in the field of manufacturing system engineering have enhanced the employment
of milling machines in various manufacturing processes. Guided by computers, they can
produce free-shape surfaces to supply the needs of the mass manufacturing industries of
automobiles, airplanes, ships, etc. Five-axis machines have become capable of handling
geometrically complex workpieces. Moreover, the most modern machines are characterized by
high material removal rates and excellent surface finish.
Unfortunately, several physical phenomena, such as: machine kinematics, thermal effects,
static and dynamic loading, common-cause failures, clamping and spindle of cutting devices
tend to affect the quality of surfaces. Kinematic machine errors - the most significant
impediments of their employment - are the main objective of this research.
Traditionally the tool path generated by a computer aided manufacturing system approximates
the surface as a piecewise linear curve. On a three-axis CNC machine the curve followed by
the cutter location point and the cutter contact point will be the same piecewise linear curve.
However in 5-axis milling the path between two successive cutter location or cutter contact
point will be curved due to the simultaneous linear interpolation in rotary and linear machine
axes. Instead 6f conecting this "tool path curvature" error in the post-processor, the cutter
location tool path will be generated so that this curved tool path approximates the surface with
in the required tolerances. The results of this are smoother and more accurate surface quality
and a considerable smaller number of cutter location points for the same surface.
This new algorithm for the optimization of the tool-paths of five-axis machines is based on
global approximation of the desired surface by a virtual surface comprising tool trajectories. In
order to construct a suitable grid generator, let the global spatial error be defined as the
difference between the required surface and the surface generated by non-linear trajectories.
The elliptic grid techniques [Thompson J.F. 1993 and Ivanenko S.A. 1993], [Brackbill J.U.
1982], based on the optimization of the following properties, is modified: Smoothness of the
grid, adaptively to regions of large milling errors and a particular constraint related to the
prescribed tool diameter and scallop height. A numerical solution of the constrained
minimization problem is developed employing the iterative algorithm which penalizes large
scallop height and maximum difference between the real surface and toolpaths surface. The
capability of the algorithm to generate tool-paths for sculptured surfaces with complex,
boundaries is increased by introduction of zigzag-adaptive patterns. |
| Year | 1998 |
| Type | Dissertation |
| School | School of Advanced Technologies |
| Department | Department of Industrial Systems Engineering (DISE) |
| Academic Program/FoS | Industrial Systems Engineering (ISE) |
| Chairperson(s) | Bohez, Ir. Erik L.J. ; |
| Examination Committee(s) | Tabucanon, Mario T. ;Batanov, Dencho N. ;Makhanov, Stanislav S. ;Kruth, Ir. Jean-Pierre; |
| Scholarship Donor(s) | Royal Thai Government; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1998 |