On the effect of fixture layout on part stability and flatness during machining: A finite element analysis

Abstract

Deflection during machining can potentially introduce inaccuracies into the machined part geometry ultimately reducing its functionality. The traditional approach used in industry for fixture layout and configuration is mainly a trial and error scheme, which involves online examination of different combinations of fixture positions and clamping force magnitudes based on previous experience. Thus to be relevant, physics-based simulations of cutting processes must include the dynamics of the machine tool, fixture element, and part. In the current paper a developed simulation system is used to analyse and modify the fixture layout a priori to the metal removal process. This work analyses the effect of cutting forces, part features, and location of the fixture elements on the flatness and stability of the part. A typical industrial flexible part is used as a case study and its dynamic behaviour is analysed under different fixturing scenarios. The cutting forces are modelled using a mechanistic approach. The finite element method is used to model and analyse the dynamic behaviour of the fixtured part. Modal analysis was carried out using the finite element method and then results were verified experimentally.

Keywords

fixture layout machining dynamics finite element analysis

References

Deiab

I. M.

Elbestawi

M. A.

Effect of workpiece/fixture dynamics on machining process output. Proc. Instn Mech. Engrs, Part B: J. Engineering Manufacture, 2004, 218(11), 1541–1553.

Melkote

S. N.

Devor

Kapoor

Burkey

Prediction of reaction force system for machining fixtures based on machining process simulation. In Transactions of the North American Manufacturing Research Conference, Michigan Technical University, MI, 1995, Vol. 23, pp. 207–214.

Deiab

I. M.

Effect of fixture dynamics on the face milling process. PhD Thesis, McMaster University, Hamilton, Canada, 2003.

Siebenaler

S. P.

Melkote

Prediction of workpiece deformation in a fixture system using the finite element method. Int. J. Machine Tool Mf., 2006, 46, 51–58.

Raghu

Melkote

Modeling of workpiece location error due to fixture geometric error and fixture-workpiece compliance. Trans. ASME, J. Mfg Sci. Engng, 2005, 127, 75–83.

Deng

Melkote

S. N.

Modeling of fixturing dynamic stability accounting for material removal effect. In Transactions of the 33rd North American Manufacturing Research Conference, Columbia University, New York, May 2005, Vol. 33, pp. 289–296.

Chou

Y.-C.

Barash

M. M.

Automatic configuration of machining fixtures: A methodology. In Proceedings of the Integrated Systems Conference and Society for Integrated Manufacturing Conference, Atlanta, GA, 1989, pp. 390–397.

Chou

Y.-C.

A methodology for automatic layout of fixtures elements based on machining forces considerations. In ASME Winter Annual Meeting, Advances in product design and manufacturing, Dallas, Texas, 1990, pp. 181–189.

Hamedi

Rogers

R. J.

Nadkarni

G. R.

Bonham

D. J.

On realistic modeling of workpiece-fixture interaction. In Proceedings of the 31st MATADOR Conference, Manchester, 1995.

10.

Dokainish

M. A.

Subbaraj

A survey of direct time-integration methods in computational structural dynamics - I. Explicit methods. Computers Structs, 1989, 32(6), 1371–1386.