超音波輔助磨削氧化鋯及其應用於牙冠製作之研究

Study of the Ultrasonic Vibration Assisted Grinding of Zirconia and its Application in Fabricating Dental Crown

賴森奎(Sen-Kui Lai)

指導教授 ： 廖運炫

國立臺灣大學/工學院/機械工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202002916

摘要

近年來，陶瓷材料越來越興盛，尤其是氧化鋯陶瓷，其有優良的機械性質，更有安全的生物相容性，故常用於製作人工假牙。假牙製作過程中，首先加工氧化鋯粉塊，再將加工完的氧化鋯粉塊拿去烤爐做燒結，但因為各種環境濕度、溫度、壓力、水份、時間，因此不好掌控材料各部位的收縮率，導致形狀精度與原本有差異，還需要牙技師再做修飾，再上一層釉料，最後再燒結一次，即可完成牙冠假牙。為了避免收縮率的變異，因此有一種方法是直接加工已燒結的氧化鋯陶瓷，其硬度非常高，直接對其加工，雖然可以很好的掌握形狀精度，但因為材料太硬，會導致刀具磨耗嚴重，因此用超音波輔助磨削加工，可以用來加工硬度很高的氧化鋯陶瓷。在加工牙冠時，比起傳統加工，超音波輔助磨削不但可以減少軸向切削力24.4%，亦可減少進給方向切削力10.7%，鑽孔切削力下降20.5%。除了切削力的下降，在加工牙冠的過程中，換刀次數從原本的3次，減少為只換1次。磨棒的嚴重受損情況也不會出現，磨棒壽命得到提升。以超音波輔助磨削加工，會對工件表面形成一層加工變質層，表面硬度從原本未加工的1463HV上升到1620HV。其局部抗應變能力是上升的。但因為超音波振動會對表面造成較多且較深的凹坑，因此對於整體的抗彎強度是下降的，傳統磨削的工件抗彎強度為1670Mpa，以超音波輔助加工，抗彎強度降為1498.5Mpa。整體的抗應變能力是降低的。在加工表面時，超音波輔助加工下，因為切削力的下降，使得表面碎裂情況是比傳統磨削還要小且其表面有起伏較大的表面特徵，因此工件表面和釉料的接觸面積較大，故對於釉料的抓附力也比起傳統加工出來的表面還要強。

關鍵字

超音波輔助磨削 ； 氧化鋯 ； 牙冠 ； 切削力 ； 微克氏硬度 ； 四點抗彎試驗

並列摘要

In recent years, ceramic materials have become more and more prosperous, especially zirconia ceramics, which have excellent mechanical properties and safer biocompatibility, so they are often used as materials for artificial dentures in dentistry. In the process of making dentures, the zirconia powder block is processed first, and then the processed zirconia powder block is taken to the oven for sintering, but because of various environmental humidity, temperature, pressure, moisture, time, so the shrinkage rate of each part of the material is not easy to control, resulting in a difference in shape accuracy from the original. It also requires the dental technician to make appearance size modification, then apply a layer of glaze, and finally sinter once to complete the crown denture. However, in order to avoid the variation of shrinkage, there is a method to directly process the sintered zirconia ceramics, which has a very high hardness, and directly processing it can well control the shape accuracy, but because the material is too hard, it will cause the grinding rod wears too seriously, so the ultrasonic grinding process can be used to process zirconia ceramics. When machining, compared with traditional machining, ultrasonic assisted grinding can not only reduce the axial cutting force by 24.4%, but also reduce the cutting force in the feed direction by 10.7%, and the drilling cutting force is 20.5%. In addition to the decrease in cutting force, the number of tool changes during the crown processing in the experiment was reduced from the original 3 times to only 1 time. Serious damage to the grinding rod will not occur, and the life of the grinding rod will be improved. Ultrasonic-assisted grinding processing will cause processing deterioration layer on the surface of the workpiece, and the surface hardness will increase from the original unprocessed 1463HV to 1620HV. Its local resistance to strain is rising. However, because ultrasound will cause more and deeper troughs on the surface, the bending strength of the workpiece is reduced. The bending strength of the traditionally grinding workpiece is 1670Mpa. With ultrasonic assisted processing, the bending strength is reduced to 1498.5 MPa. The overall strain resistance is reduced. When machining the surface, under ultrasonic-assisted machining, due to the reduction of cutting force, the surface chipping is smaller than that of traditional grinding and the glaze gripping force of the ultrasonic-assisted machining surface is stronger than the conventional one.

並列關鍵字

Ultrasonic Assisted Grinding ； Zirconia ； Crown ； Cutting Force ； Micro Vickers Hardness ； Four Point Bending Test

參考文獻

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