Abstract Almost all major medical implant OEMs are actively exploring the feasibility of making a variety of common implants from ceramic materials. Ceramics are particularly suitable for making implants. Compared with metal and plastic polymers, this material has high strength, wear resistance, smoothness and...
Almost all major medical implant OEMs are actively exploring the feasibility of making a variety of common implants from ceramic materials. Ceramics are particularly suitable for making implants. Compared to metal and plastic polymers, this material has exceptional strength, abrasion resistance, smoothness and biocompatibility. However, ceramics lack a very important quality - processability.
Speaking of ceramics, most people think of falling onto a plate or coffee cup that is hard to break on a hard floor. In fact, industrial and medical ceramics are not the case. These ceramics are very tough and dense, so they are not brittle, but they are difficult to process by traditional methods. However, this deficiency can be compensated for by means of a laser beam.
Several carefully selected ceramic implants are currently in production. However, they are manufactured using a grinding machine, which has a very limited shape in terms of its proximity to contours, its strength and its ability to machine other complex workpiece shapes. In addition, due to the slow grinding speed, the manufacturing cost is high, making the implant extremely expensive. In view of this, ceramic implants are used in a limited number of patients compared to affordable metal implants.
Most implants currently produced are made of titanium alloy, cobalt chrome or stainless steel. The most commonly used implants are used to replace the knee and hip joints, but are also widely used as femoral, joint, and tibial prostheses.
The average life of a metal implant depends on the specific application. The more frequently the implant accepts the activity, the faster the implant wears. In some cases, the service life is only about 10 years, and for people with less activity, the implant life may be as long as 25 years. This means that for young people receiving metal implants, the initial implant is likely to need to be replaced an additional one or two during its lifetime. It should be noted that the healing process of orthopedic surgery such as knee and hip replacement is painful and lengthy.
Compared to ceramic implants, the average lifespan is 75 years, which is roughly equal to one's life. The implant recipient only has to undergo one operation and one recovery period. In addition, no foreign matter is generated in the body due to wear like a metal implant.
On the other hand, the advantages of ceramic implants can only become a reality when ceramic materials can be processed cost-effectively, making them easy to purchase and reasonably priced. It is for this reason that manufacturers, universities and other research institutions have been exploring and experimenting with different manufacturing methods in order to successfully process ceramics using traditional tools. As of now, there is a laser processing method that has achieved some good results.
The key to this economical ceramic processing process is the specially designed inserts and the bold use of lasers mounted on multi-function machines. The machine accurately positions the laser beam in front of the blade to plasticize the workpiece material, making it easy to cut.
Cost-effective ceramic processing tool technology has been developed, including polycrystalline diamond (PCD) and cubic boron nitride (CBN) tools. Among them, CBN tools show extraordinary potential in a variety of ceramic applications. In addition, superhard carbide tools are used to process ceramics.
To date, laser-assisted machining has enabled manufacturers to successfully turn, mill, and thread ceramic materials such as silicon nitride, zirconium, and aluminum oxide. But most importantly, the system extends tool life, shortens the processing time of these materials, and produces workpieces that were previously impossible to produce.
These institutions that develop laser-assisted processing technology will continue to deepen their understanding of the ceramic cutting process and will greatly advance the use of ceramics in the medical industry as well as in other areas such as automotive and aerospace engine components and bearings. However, more tests are currently required to better understand the edge treatment of the tool and the chemistry between the tool and the particular ceramic material. Further testing also helps to increase the efficiency of the laser, thereby heating the ceramic material more quickly and improving the precision of the part to be heated.
If laser-assisted machining is still developing at the current rate, as with hard turning instead of grinding 20 years ago, cutting of ceramics is likely to replace diamond grinding in the future. Although the method is still in its infancy, milestones have been achieved in reducing the cost of manufacturing medical implants and industrial ceramic parts. (The author is Don Graham, Seco Education and Technical Services Manager)
