Laser Sintering Characteristics Of Bamboo Flour/Thermoplastic Composite Powders And Properties Of Sintered Parts

Selective Laser Sintering (SLS) is an important powder layered manufacturing methods in Additive Manufacturing. At present, the suitable kinds of powder materials for the SLS process mainly include polymer powder, metal powder, ceramic powder and polymer-coated metal powder. SLS is applied extensively to fabricating the pattern of investment casting, plastic parts, metal parts, dental model, aerospace and automotive parts and so on.China is a major bamboo producer. Bamboo products enterprises produce 300-500 million tons of bamboo waste every year. It is an urgent problem that needs to be solved to make full use of bamboo waste. Bamboo flour is a kind of cheap reproducible natural plant powder, easily made at a low cost, by collecting bamboo products factory waste. The polyester hot melt adhesive (polyester), polyamide hot melt adhesive (polyamide) and epoxy resin are good wood adhesives. Laser sintering materials of bamboo flour/thermoplastic resin composite powder was prepared through mechanical mixing method. Bamboo waste was used in Addtive Manufacturing, which expands the forest engineering in the application of advanced manufacturing technology.The powder bed preheating temperature of the laser sintering processing and the laser processing parameters of bamboo flour/polyester composite powder are determined through the thermal differential scanning heat method(DSC method) and single layer sintering experiment. Different mass mixing ratio of bamboo flour/polyester composite powders are prepared by high speed mixer. The mechanical properties of SLS parts fabricated by different mass mixing ratios of bamboo flour/polyester are studied using experimental methods. Influence of direction of fabricating of SLS parts, laser scanning methods, laser sintering process parameters on mechanical properties of SLS parts fabricated by bamboo flour/polyester composite powder are also investigated. The process of wax infiltration and epoxy resin infiltration of SLS parts fabricated by bamboo flour/polyester composite powder are studied. The mechanical properties of wax-infiltrated parts and epoxy-infiltrated parts of bamboo flour/polyester are also investigated. The mechanical properties of SLS parts of bamboo flour/polyester composite powder were improved after postprocessing. This paper also studies the laser sintering characteristics and the mechanical properties of SLS parts of bamboo flour/birch flour/polyester composite powder.Microstructure analysis of fracture surfaces and sintered surfaces of the SLS parts fabricated by bamboo flour/polyester composite powder is carried out by micrograph of Scanning Electron Microscope(SEM). The fracture surfaces of wax-infiltrated and epoxy-infiltrated parts of bamboo flour/polyester are also analyzed using the SEM micrograph.The adhesive effect between bamboo flour and polyester and the effect of wax and epoxy resin infiltrating of SLS parts are observed in the SEM micrograph of the wax-infiltrated and the epoxy-infiltrated parts. The mechanical properties enhancements mechanism of wax-infiltrated and epoxy resin-infiltrated of SLS parts of bamboo flour/polyester are also analyzed. The preheating temperature of powder bed is simulated by ANSYS and measured by infrared thermometer. In order to study the influence of the temperature distributions of powder bed on properties of layer sintering, the mechanical properties of SLS parts of different areas of processing area of powder bed are investigated.The laser sintering characteristics of blend of bamboo flour/polyamide composite powder is studied based on the research results of bamboo flour/polyester composite powder. The infiltrated process and mechanical properties of wax-infiltrated parts and epoxy-infiltrated of SLS parts of bamboo flour/polyamide composite powder are also studied. Since the melting process of polyamide is different from the polyester, a large polyamide matrix in SLS parts are formed on the surface and internal of the SLS parts. The mechanical properties of SLS parts of bamboo flour/polyamide composite powder were also superior to the SLS parts of bamboo flour/polyester composite powder. The density of SLS part fabricated by bamboo flour/polyamide composite powder is relatively higher, which is not easy to infiltrate resin using post-processing technology. Using scanning electron microscopy images of cross-section and laser sintered surface of specimens, the laser sintering forming mechanism of bamboo flour/polyamide composite powder in the laser sintering process was analyzed based on the SEM micrograph of SLS specimens.Epoxy resin is a good adhesive for plant fiber. The bamboo flour/epoxy resin/(polyester or polyamide) are prepared using high speed mixer by adding some amount of mixed powder of thermoplastic epoxy resin, latent curing agent and accelerator into the bamboo flour/polyester blend and bamboo flour/polyamide blend. The laser sintering forming characteristics and mechanical properties of SLS specimens fabricated by bamboo flour/polyester/epoxy resin blend and bamboo flour/polyamide epoxy resin blend are studied in the experimental process. Further SLS parts is curing through the process of constant temperature of 120℃ for 60 minutes, and after the constant temperature process, the mechanical properties and dimensional accuracy of constant temperature processed specimens are investigated. The fracture surfaces of before and after heat treatment of SLS parts of bamboo flour/polyester/epoxy and bamboo flour/polyamide/epoxy are also analyzed using the SEM micrograph.The surfaces processing of wax-infiltrated parts fabricated by bamboo flour/polyester and bamboo flour/polyamide composite powder for investment casting process were done. The investment casting experiments were done based on thermogravimetric analysis and the ash content material of the bamboo flour/polyester and bamboo flour/polyamide composite powder.The relatively high dimensional accuracy of castings is obtained through investment process.