In this study, varied cooling oil volume (VOV) control was developed for the oil coolant of a machine tool. This allows adjustment of the oil circulation flow rate in terms of the machining loads and rotational speeds of the spindle to remove the generated heat effectively from the spindle. A mathematical model of the cooling oil flow rate in terms of the rotating speed and torque of the spindle for VOV method is developed. From the thermal deformation experiments with the VOV method, the thermal deformations in both the Y-axis and Z-axis can be greatly reduced, by 70.1 % and 73.5 %, respectively, in variable rotational speed operation with a short operational period (10 minutes). Moreover, the VOV method was applied to shorten the required warm-up time of the spindle. The required warm-up time of the spindle can be shortened by 50 %, while the three axes of the spindle attain stable thermal conditions. In practical machining experiments, the machining accuracy with the VOV method can be greatly enhanced by 34 % to 62 % in comparison with the current case of constant cooling oil volume (COV). The VOV control system in the machine tool spindle can effectively reduce the thermal deformation and shorten the required warm-up time. In addition, the machining accuracy can be greatly enhanced. INDEX TERMS Thermal deformation, thermal suppression, varied cooling oil volume, machining accuracy.

In this study, a series of aliphatic-aromatic poly(butylene terephthalate-co-e-caprolactone) (PBTCL) copolyesters were synthesized from various monomeric compositions of terephthalic acid (TPA), 1,4-butanediol (BDO), and e-caprolactone (CL) in the presence of tetrabutyl titanate (Ti(Obu) 4 ) and stannous octoate (Sn(Oct) 2 ) as catalysts through a combination of polycondensation and ring opening polymerization. A significant increase in the melting temperature (T m ) of copolyesters was observed by increasing the TPA/(CLþTPA) molar ratio, starting from the low end (T m 66.2 C) of pure poly-e-caprolactone PCL upward. We found that PBTCL-50, which has a TPA/(CLþTPA) 50% molar ratio and polycondensation at 260 C for 1.5 h, resulted in a proper T m of 139.2 C that facilitates thermal extrusion from biomass or other biodegradable polymers of similar T m . The number-average molecular weight (M n ) of 7.4 Â 10 4 for PBTCL-50 was determined from the intrinsic viscosity [g] by using the Berkowitz model of M n ¼ 1.66 Â 10 5 [g] 0.9 . Good mechanical properties of PBTCL-50 have been shown by tensile stretching experiment that indicates tensile strength, elongation, and Young's modulus are 11.9 MPa, 132%, and 257 MPa, respectively. Polymers with aforementioned properties are suitable for manufacturing biodegradable plastic films for downstream agricultural applications or merely for trash bag. This article reveals that the PBTCL-50 contains all five monomers with different molar ratios and characteristical linkages between each other. The novel structure was furthermore analyzed by 1 H-and 13 C-NMR spectroscopy.

The aliphatic-aromatic copolyesters are becoming more important due to their desirable mechanical properties and biodegradability. In this study, a series of Poly(butylene succinate-co-terephthalate) (PBST) of various monomer compositions were synthesized from succinic acid (SA), dimethyl terephthalate (DMT), and 1,4-butanediol (BDO) in the presence of tetrabutyl titanate (Ti(Obu) 4 ). The experiment was divided into three parts. The first part is a 2 3 factorial design with permutations of three factors, namely, temperature, molar ratio of BDO/DMT, and molar ratio of SA/ DMT in polycondensation. Our statistical analysis showed that the temperature has a more significant effect on the intrinsic viscosity ([Z]) of PBST than the other two factors. The number-average molecular weight (M n ) of the PBST was determined from the intrinsic viscosity by using the Berkowitz model of M n = 1.521 Â 10 5 [Z] 1.5 . The second part of the experiment is a time course investigation of polycondensation under various temperatures, molar ratios of BDO/ (DMT + SA), and concentrations of Ti(Obu) 4 . Our results showed the best polycondensation occurred at 1.5 hr with [Z] reaching 0.49 dL/g when the temperature was held at 250 C, BDO/(SA + DMT) = 1.2 mol/mol with SA/(SA + DMT) = 50 mol%, and 0.97 mmol of Ti(Obu) 4 per mol of SA + DMT. The third part of the experiment involves searching for the best molar ratio of SA/(SA + DMT) in obtaining desirable polymer properties and biodegradability. The results showed that the highest melting point of PBST can be as high as 177 C at SA/(SA + DMT) = 30 mol%. The maximum tensile strength of 25.6 MPa is obtained at SA/(SA + DMT) = 30 mol%. The maximum elongation at break of 269.3% and the maximum Young's modulus of 754.8 MPa are reached at SA/(SA + DMT) = 60 mol% and at SA/(SA + DMT) = 30 mol%, respectively. The fastest lipase-decomposition rate of PBST reached 100 % at day six for samples with molar ratio SA/(SA + DMT) = 80 mol%.

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