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The factors that influence the machining accuracy of
Computer Numerical Control (CNC) machine tool mainly come from
the geometric errors and structural thermal deformation during
cutting. Hence, people pay attention to thermal error
compensation technology on a CNC machine tool recently.
Although real-time thermal error compensation techniques have
been successfully demonstrated in both research laboratories and
industrial sites, there are still some major barriers before
widespread application are possible such as optimal thermal
sensor placement, the long period time required to build the
thermal error model, and expensive. In this thesis, a stand-
alone hardware with INTEL 8051 single chipmicrocomputer is built
in for real-time thermal compensation technology. The face
milling cutter with indexable insert throw away tip is used to
create faster temperature rising than end miller. An IC type
digital thermometer is designed to detect the temperature
variation. These thermal errors of Z axis are measured on-line
by the touch trigger probe and a standard bar. A mathematical
model is then derived ,based on the sensed temperature variation
and the errors by multi-variable regression analysis. And
thermal error compensation command is send to CNC controller to
shift the zero point of the machine coordinate system in real-
time phase. The experimental results show that the technology
can successfully improve machining accuracy from 60 um to ±10
um in real cutting condition.
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