KINEMATIC MODELING OF QUASI-STATIC ERRORS OF 3-AXIS MACHINING CENTERS

Quasistatic error sources, which include thermal, mechanical loading a nd geometric error sources, are responsible for a very large proportio n (typically, 70%) of the volumetric errors of a numerically controlle d machine-tool. This paper, the first in a set of three, discusses the development of a very general model for the effects of geometric erro rs of the components of the kinematic chain (structural members and ax es) of a machine on the volumetric errors in the work space. The effec ts of the other two sources are modeled as changes in the geometric er ror. The generality of the model arises from the fact that the errors along an axis of the machine can be characterized by any polynomial fu nctions and the model is recursive in the order of these polynomials. This model can be used as the basis of a compensation scheme as well. as in budgeting of errors on a machine-tool.