the combined effect of vacuum level and effective vacuum pocket area reached a maximum due to leakage from the clearance between the shoe and workpiece to the vacuum pocket 24 the measured vacuum retaining force was smaller than the ideal force of 32 7 n experiments were carried out to obtain a correlation between the external load and the vacuum hydrostatic shoe workpiece clearance at various fluid supply pressures inflow resistances and design clearances for the vacuum hydrostatic shoe in the experiments step or multi step loading was generated by the piezoelectric actuator 42 the external load was measured by the piezoelectric force transducer 38 while working clearance was the average value from the two capacitance sensors 40 the results shown in fig7 a and 7 b were obtained under the following conditions design clearance of the shoe 0 0015 in 37 5 u03bcm fluid supply pressure 37 5 psi 0 26 mpa and resistance ratio 2 72 at the design clearance the stiffness of the vacuum hydrostatic shoe 10 was also be verified by examining the dynamic behavior of the shoe 10 under impulse input fig8 shows an impulse input to the shoe 10 and fig9 shows the associated output power spectrum density of the shoe 10 excited by the.