Development Of Curved Bamboo Strip Softening Equipment And Study On Flattening Process

As a novel processing technology emerging in the bamboo industry,the no-groove flattening technique for flattened bamboo sheet has attracted widespread attention in recent years.This study focuses on flattened bamboo sheet and flattened bamboo sheets,aiming to develop a new automatic feeding and discharging softening equipment for the production of no-groove flattened bamboo sheets.Based on this new softening equipment and taking the initial moisture content,softening temperature,and softening time of flattened bamboo sheet as three variables,15 different softening processes were formulated.The mechanical properties,physicochemical properties,and microstructure of flattened bamboo sheet after softening and flattening using different processes in the new softening equipment were tested and analyzed.The optimal softening process for flattened bamboo sheet was determined using the grey relational analysis method.Furthermore,the performance of the softening equipment was comprehensively evaluated from multiple aspects,such as production efficiency,production cost,and product quality,to verify the effectiveness of the automatic feeding and discharging softening equipment in actual production,providing strong technical and theoretical support for industrial production in enterprises.The main research contents are as follows:(1)Development of an automatic feeding and discharging softening equipment for flattened bamboo sheet.The dimensions of the transport device for this softening equipment are designed to be 130×130×1200 mm;the tank dimensions are 200×200×2500 mm,and the material is 5mm thick stainless steel;the overall machine dimensions are 3000×200×1040 mm,with a distance of1270mm between the two support brackets and their arc diameter being 205.6 mm and thickness2.8 mm;the cylinder is selected as the SC50-160 type,with a diameter of 32 mm,thrust of164.04 N,operating speed of 140mm/s,and piston rod travel of 150cm.Based on previous research and the characteristics of the new softening equipment,a PLC is chosen as the control system,and 11 softening step processes are customized.Finally,CAD and SOLIDWORKS are used to establish the model and complete the manufacturing of key components of the new softening equipment,as well as the design and installation of the overall machine.(2)The study of the optimal softening process for the new softening equipment involved testing the microstructure and chemical composition of flattened bamboo sheet under different saturated steam softening processes.This revealed the mechanism of crack-free flattening of flattened bamboo sheet and provided a theoretical basis for the changes in the physical and mechanical properties of flattened bamboo sheets.The experimental results showed that,from the microstructural perspective,the thin-walled cell tissues of the bamboo cross-sections underwent wrinkling deformation during the softening process,while the radial sections did not show significant changes,and some breakage appeared in the tangential sections.From the perspective of chemical composition changes,the cellulose and hemicellulose in the softened bamboo degraded,while lignin remained relatively stable.The characteristic peaks of the samples weakened as the softening temperature increased,with the hemicellulose and cellulose groups degrading faster.After the softening treatment,the cellulose 002 crystal plane diffraction peak positions of the bamboo material remained relatively stable and were concentrated between21.86°and 22.03°,with their relative crystallinity greatly affected by the softening temperature.(3)As an important parameter for studying the optimal softening process,the physical and mechanical properties of flattened bamboo sheets were further tested under different softening processes.The experimental results showed that an appropriate softening process could improve the material’s MOR and MOE.At a softening temperature of 175°C,the MOR reached 111.64MPa and the MOE reached 8571.81 MPa,increasing by 8.8%and 27.8%respectively compared to untreated materials.As the softening temperature increased,the density of the flattened bamboo sheets decreased.At a softening temperature of 165°C,the overall dry density and air-dry density of the bamboo material were 0.72g/cm~3and 0.67g/cm~3,respectively,decreasing by 6.5 and 7.5%compared to untreated materials.Softening treatment also reduced the tensile and compressive strength of flattened bamboo sheets along the grain,and the mechanical properties decreased with the increase in treatment temperature.When the softening temperature was 165°C,the tensile and compressive strength along the grain were 153.53 MPa and 46.51MPa,decreasing by 8.6%and 1.5%compared to untreated materials.The main reason for these changes was the degradation of cellulose and hemicellulose in the bamboo material during the softening process,leading to a decrease in physical and mechanical properties.From a micromechanical perspective,the elastic modulus and hardness of the cell walls increased with the increase in softening temperature,reaching up to 20.8 GPa and 0.77 GPa,which were 35.1%and 26.2%higher than untreated materials,respectively.This was because the lignin content increased during the softening process,and the lignin condensation reaction could enhance the mechanical properties of the bamboo cell wall.(4)Using the flattened bamboo sheet surface quality evaluation standard,we compared the effects of different saturated steam softening processes on the surface quality of flattened bamboo sheets.The experimental results showed that when the initial moisture content of the flattened bamboo sheet was 60%,the softening temperature was 175°C,and the softening time was 350s,the surface quality was optimal,with a smooth and crack-free surface.Considering the softening and flattening effects and the physicochemical properties of the flattened bamboo sheet,the grey relational analysis method was used to measure the degree of correlation between the various indicators.The optimal process parameters were found to be an initial moisture content of 60%,a softening temperature of 175°C,and a softening time of 350s,with the total evaluation correlation degree reaching a maximum value of 0.6.Through actual production,it was found that the flattened bamboo sheets prepared under this process demonstrated excellent physical and mechanical properties,with a complete,crack-free surface and bright,vibrant colors.Based on this process,the calculated production cost of flattened bamboo sheet using the automatic infeed and outfeed softening equipment was approximately 2.15 yuan per piece,a26%reduction compared to traditional softening equipment.Although the softening efficiency of the automatic infeed and outfeed softening equipment was 20 seconds per piece,which was not as fast as traditional equipment,it had the advantage of continuous automation,significantly reducing labor costs.In summary,the new softening equipment has high application feasibility and effectiveness.