# Design and 3D Printing of Interbody Fusion Cage Based on TPMS Porous Structure
## 3 Experiment and Discussion
### Discussion  
The corresponding TPMS porous structure was obtained by pretreatment, and the porous structure with optimal spatial distribution was obtained. For the optimal TPMS variable pore porous structure entity, non-TPMS uniform porous structure entity, TPMS uniform porous structure entity, we carry on the corresponding compression analysis, according to the numerical value, to judge whether these structures meet the actual needs of the human body. Through the detailed data of the above simulation analysis chapter, we get the following information: the P structure with variable pore size is better than the G structure, in terms of porosity and mechanical properties. It not only meets the corresponding better mechanical properties, but it also takes into account the large porosity. It can further ensure the transport of nutrients, and further promote the wound healing and rapid connection of implanted instruments with surrounding bone tissue. The maximum equivalent stress and porosity of the TPMS-based uniform porous structure are basically better than those of the non-TPMS uniform porous structure, indicating that the applicability of the TPMS-based uniform porous structure is higher than that of the non-TPMS uniform porous structure. Considering that the porosity is 10-95%, and the range of compressive strength in 0.5-350 MPa can meet the mechanical properties and medical requirements, the TPMS porous structure entity with variable pore sizes designed in this paper is reasonable [26]. To judge whether the designed porous structure meets the actual needs, we constructed the L3-L4 vertebral body model by reverse engineering, carried out the corresponding compression analysis, and gave the corresponding parameters according to different bone tissues to obtain the stress-strain state of different bone tissues under the actual motion state of the human body. Through the comparison of the relevant data in the fourth chapter, we can judge whether the TPMS porous structure, with variable pore sizes designed above, meets the needs of the actual human body. Finally, it can be found that the TPMS porous structure with variable pore sizes can meet the actual needs. Finally, we analyzed the performance of bone tissue engineering scaffolds. We used Ti6 Al4V powder for SLM printing, and then carried out corresponding SEM analysis and compression experiments. For the specific phenomenon of bone tissue engineering scaffold: spheroidization. Through the analysis, we found that it was due to the fact that the substrate was not preheated, which led to the occurrence of this phenomenon. Spheroidization will make the metal powder \"not solidified\" to form a continuous and smooth molten pool, which makes the printed products loose and porous, resulting in a decline in quality. We adopted the method of preheating the substrate to heat the printed substrate, so that when the temperature of the substrate reached 80 \({}^{\circ}\)C, we began to print. By comparing the pictures of the two SEM analyses, we found that the occurrence of spheroidal decreased significantly. As a result, it was proven that the pre-heating treatment of the substrate could effectively reduce the formation of spheroidization. The purpose of the compression experiment was to confirm whether the performance of the bone tissue engineering scaffold met the requirements of the practical application environment. According to the compression test data, it was confirmed that the compressive yield strength of the P structure with variable pore sizes was smaller than that of the G structure, which could better meet the actual needs of the human body. In summary, the porous implant constructed by Pvariable pore could effectively reduce the \"stress shielding\" effect between the implant and bone tissue, and could well meet the mechanical properties and medical needs. Then compression experiments were carried out on the porous implant. The unidirectional compression experiment was carried out on a microcomputer controlled electronic universal testing machine.