Recently, the innovation patent of 'Method of dimensional alignment of parts for additive manufacturing' applied by DPR New Materials Technology CO., LTD has been granted by China National Intellectual Property Administration. The Chinese patent number is 201711348280.5 and the international patent number is CN108168483A. The inventors are Zhihui Wang, Shuze Xu and Xin Jiang.
The innovation patent presents an inventive method for dimensional alignment of denture products for additive manufacturing, by taking a full-mouth crown bridge as a prototype. The parts are standardized for easy printing, measured and calculated. It is mainly used to improve the problem of long bridged crowns that do not comply with the required dimensional accuracy of the profile caused by solidification shrinkage and melt pool size. It mainly includes the following steps: creation of a calibration model of the part; printing of the calibration model and performing the required post-processing; measurement of the corresponding dimensions of the printed calibration model and calculation; calibration based on the results of the above calculation; reprinting of the calibrated calibration model and measurement to verify that the critical dimensions meet the requirements.
The use of selective laser melting technology (3D printing) for the manufacturing of fixed prosthetic denture can improve the material utilization, reduce the use of human resources, simplify the production process and shorten the production cycle, it is the future trend of manufacturing fixed prostheses. However, 3D printing technology also has its limitations. 3D printing technology is a thermoforming technology. The dimensional accuracy of the part profile prepared is influenced by two main factors: the solidification shrinkage of the material and the size of the melt pool (the mutual influence of the laser spot diameter and the material properties, the spot compensation is required, which could be corresponding to tool compensation in machining). The two factors are independent of each other and produce superimposed effects mutually. In order to achieve highly accurate crown printing, two aspects should be corrected accordingly.
Based on the design of a calibrated model that is similar to the actual shape of a human tooth, combined with a theoretical analysis, the invention could calculate the shrinkage rate from the difference between the calibrated model dimensions and the wall thickness of calibrated model. Calibrating the equipment or modifying the model based on the calculated shrinkage and spot compensation data can effectively improve the dimensional accuracy of 7-14 long bridges after 3D printing, reduce the rework rate and improve production efficiency.
Calibrated models and calculation methods (Please refer to the patent documents published by the China National Intellectual Property Administration for details).
Calculation of spot compensation: By measuring the wall thickness of multiple crown, the theoretical wall thickness value of the model are calculated as below:
Calculation of shrinkage rate: By measuring the center distance of any two coronal simulators, the theoretical values of the model are calculated as below:
About the inventor - Zhihui Wang: Zhihui Wang graduated from the School of Materials of Beihang University, obtaining a master's degree in 2016. He has been engaged in the metal 3D printing industry for many years, with a solid theoretical foundation and rich practical experiences. He is currently working as a senior technical expert in DPR New Materials Technology CO., LTD.
About DPR:
Relying on the team from the School of Materials of Beihang University, with the combination of many years of accumulation in 3D printing materials, equipment and processes, DPR New Materials Technology CO., LTD focuses on the development, production and application of new medical materials used in 3D printing processes. At present, the original results in Cobalt Chromium alloy, titanium alloy, biodegradable materials, ceramics and others have been achieved. Moreover, DPR make great efforts to promote the industrialization.
The company has completed the registration application of Cobalt Chromium alloy material for dentistry, with good mechanical properties and bio-compatibility, which is a Class III medical device and can be used for 3D printing of oral prostheses, which is the first registration certificate at this field in China.Homepage of the company: www.dprmat.com