The effects of process parameters in rapid heat cycle moulding （RHCM） on parts warpage were investigated. A vehicle-used blue-tooth front shell （consisting of ABS material） was considered as a part example manufac...The effects of process parameters in rapid heat cycle moulding （RHCM） on parts warpage were investigated. A vehicle-used blue-tooth front shell （consisting of ABS material） was considered as a part example manufactured by RHCM method. The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the Jll-W-160 type precise temperature controller was proposed. During heating/cooling process, the mould was able to be heated from room temperature to 160 ~C in 6 s and then cooled to 80 ~C in 22 s. The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory. Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage, thus improving mouldability and enhancing part quality, whereas the overheated of mould temperature will lead to defective product. The feasible mould temperature scope in RHCM should be no higher than 140 ~C, and the efficient mould temperature scope should be around the polymer heat distortion temperature. Melt temperature as well as injection pressure effects on warpage can be divided into two stages The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend. But others affect the warpage as a V-type fluctuation, reaching to the minimum around the heat distortion temperature. Under the same mould temperature condition, the effects of process parameters on warpage decrease according to the following order, packing time, packing pressure, melt temperature, injection pressure and cooling time, respectively.展开更多
3D microstructures of Fe–6.5%Si(mass fraction) alloys prepared under different cooling conditions were simulated via finite element-cellular automaton(CAFE) method. The simulated results were compared to experimental...3D microstructures of Fe–6.5%Si(mass fraction) alloys prepared under different cooling conditions were simulated via finite element-cellular automaton(CAFE) method. The simulated results were compared to experimental results and found to be in accordance. Variations in the temperature field and solid-liquid region, which plays important roles in determining solidification structures, were also examined under various cooling conditions. The proposed model was utilized to determine the effects of Gaussian distribution parameters to find that the lower the mean undercooling, the higher the equiaxed crystal zone ratio; also, the larger the maximum nucleation density, the smaller the grain size. The influence of superheat on solidification structure and columnar to equiaxed transition(CET) in the cast ingot was also investigated to find that decrease in superheat from 52 K to 20 K causes the equiaxed crystal zone ratio to increase from 58.13% to 65.6%, the mean gain radius to decrease from 2.102 mm to 1.871 mm, and the CET to occur ahead of schedule. To this effect, low superheat casting is beneficial to obtain finer equiaxed gains and higher equiaxed dendrite zone ratio in Fe–6.5%Si alloy cast ingots.展开更多
基金Project(20122BAB206014)supported by National Natural Science Foundation of ChinaProject(51365038)supported by the Natural Science Foundation of Jiangxi Province,ChinaProject(GJJ13068)supported by the Science and Technology Program of Educational Committee of Jiangxi Province,China
文摘The effects of process parameters in rapid heat cycle moulding （RHCM） on parts warpage were investigated. A vehicle-used blue-tooth front shell （consisting of ABS material） was considered as a part example manufactured by RHCM method. The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the Jll-W-160 type precise temperature controller was proposed. During heating/cooling process, the mould was able to be heated from room temperature to 160 ~C in 6 s and then cooled to 80 ~C in 22 s. The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory. Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage, thus improving mouldability and enhancing part quality, whereas the overheated of mould temperature will lead to defective product. The feasible mould temperature scope in RHCM should be no higher than 140 ~C, and the efficient mould temperature scope should be around the polymer heat distortion temperature. Melt temperature as well as injection pressure effects on warpage can be divided into two stages The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend. But others affect the warpage as a V-type fluctuation, reaching to the minimum around the heat distortion temperature. Under the same mould temperature condition, the effects of process parameters on warpage decrease according to the following order, packing time, packing pressure, melt temperature, injection pressure and cooling time, respectively.
基金Project(2012AA03A505)supported by the High-Tech Research and Development Program of ChinaProject(51474023)supported by the National Natural Science Foundation of China
文摘3D microstructures of Fe–6.5%Si(mass fraction) alloys prepared under different cooling conditions were simulated via finite element-cellular automaton(CAFE) method. The simulated results were compared to experimental results and found to be in accordance. Variations in the temperature field and solid-liquid region, which plays important roles in determining solidification structures, were also examined under various cooling conditions. The proposed model was utilized to determine the effects of Gaussian distribution parameters to find that the lower the mean undercooling, the higher the equiaxed crystal zone ratio; also, the larger the maximum nucleation density, the smaller the grain size. The influence of superheat on solidification structure and columnar to equiaxed transition(CET) in the cast ingot was also investigated to find that decrease in superheat from 52 K to 20 K causes the equiaxed crystal zone ratio to increase from 58.13% to 65.6%, the mean gain radius to decrease from 2.102 mm to 1.871 mm, and the CET to occur ahead of schedule. To this effect, low superheat casting is beneficial to obtain finer equiaxed gains and higher equiaxed dendrite zone ratio in Fe–6.5%Si alloy cast ingots.
