Abstract:
Grinding and polishing of engineered components are critical aspects of the precision
manufacturing of high performance, quality assured products. Elevated process
temperatures, however, are a common and for the most part undesirable feature of
the grinding process. High process temperatures increase the likelihood of
microstructural change within the immediate subsurface layer and are detrimental to
the strength and performance of the manufactured products. Increasing processing
costs and tighter environmental legislation are encouraging industry to seek innovative
fluid application techniques as significant savings in production can be achieved.
In this context, and with sponsorship from three industrial partners, namely; Fives
Cinetic, Fuchs Lubricants plc and Southside Thermal Sciences Ltd, and also from the
Engineering and Physical Science Research Council (EPSRC), this research aimed to
develop an understanding of Minimum Quantity Solid Lubrication (MQSL) as a method
for abrasive machining, with particular reference to the control of surface
temperatures.
Improving the lubricity of Minimum Quantity Lubrication (MQL) fluids reduces the
frictional source of process heat and controls the finish surface temperature. The
application of effective solid lubricants is known as Minimum Quantity Solid
Lubrication (MQSL). Molybdenum Disulphide (MoS2), Calcium Fluoride (CaF2), and
hexagonal Boron Nitride (hBN) were compared against a semi-synthetic water soluble
machining fluid (Fuchs EcoCool). A series of Taguchi factorial experimental trials
assessed their performances through ANOVA (ANalysis Of VAriance) statistical method.
The hBN produced the lowest grinding temperatures of the solid lubricants tested,
although they still remained higher than those achieved using the EcoCool control.
The reduction of the machining fluid enabled a Charged Coupled Device (CCD) sensor
to be fitted into the grinding machine. The recorded movement in the emitted
spectrum from the grinding chips was compared to experimental and modelled
process temperatures. This showed that the wavelengths of the chip light correlated to
the temperature of the finish grinding surface. This greatly contributed to determining
the feasibility of constructing a non-destructive, non-invasive, thermally-adaptive
control system for controlling grinding surface temperatures.