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What Is the Difference between CNC Processing in the Medical Device Industry and Other Mechanical Industries?

Date: Mar 18 2021 | By:LC Rapid
Tag:CNC Machining,

In recent years, the parts and components used in the medical device industry in CNC machining have shown a dynamic growth trend. Medical device manufacturers are also continuously looking for better turning centers and good tools to enhance their competitive advantages in the industry. But what's the difference between CNC processing in the medical industry and other mechanical industries like aerospace cnc machining?


CNC Machining - Medical parts.jpg


Ⅰ. CNC machining and difficult-to-process materials


The difficult-to-process titanium alloy material 90% of the medical device implant components are made of Ti6Al4V titanium alloy, which is derived from the light weight, high strength and high biocompatibility. Because of these characteristics, the titanium alloy 6AL-4V becomes the most commonly used material of medical implant. Titanium alloy 6AL-4V is commonly used in the production of hip joints, bone screws, knee joints, bone plates, dental implants, and spinal connection components.


One of the characteristics of titanium alloy is CNC work hardening. In the CNC machining process, the shear angle is large, the chips produced are thin, and a relatively small contact area is formed on the tool.


In addition, the high cutting force in the CNC machining process, combined with the frictional force during chip flow, will cause the local cutting heat of the tool to be too high. However, the poor thermal conductivity of titanium alloys results in that the generated heat cannot be conducted well. As a result, a large amount of cutting heat is concentrated on the cutting edge and the tool surface. High cutting force and cutting heat will comprehensively cause crater wear, as well as rapid tool failure. The poor product quality caused by these factors and the high wear and tear of tools are all issues that companies have to consider.


Titanium alloys have better elastic properties than steel because of their relatively low modulus of elasticity. Therefore, in order to ensure that the rebound of the workpiece is small, excessive cutting force should be avoided. Thin-walled parts usually have a tendency to deform under tool pressure, and problems such as chatter, friction and even tolerances will also occur.


Therefore, the key to solving these problems is to ensure the rigidity of the entire system. It is very necessary to use sharp cutting edges and correct geometry tools! In addition, titanium alloys have a tendency to chemically react and alloy with cutting tools at high temperatures, and their chips have a tendency to be welded to the surface of the tool. These are all factors that have to be considered!


Reliable and compact machine tool fixtures, medical equipment processing equipment, small and complex parts made of difficult-to-process materials (such as titanium alloy or stainless steel) and high precision requirements, such as CNC machining bone and joint replacement parts are quite complicated.


Due to the poor cutting performance of the CNC machined materials, bars are usually used as blanks - which means that a large amount of metal needs to be removed. Some parts are also cast into a shape close to the finished product, but this also adds some trouble - in this case, it is necessary to manufacture complex and expensive fixtures.


Another factor that increases the complexity of CNC machining is the narrow tolerance range. The requirements for the material, processing accuracy, and surface finish of medical equipment parts and components are very high, which require high reliability of the processing system. Therefore, extremely high requirements are put forward on machine tools, fixtures, cutting tools, and software.


Workpieces are usually processed on internationally advanced medical equipment processing equipment such as Swiss automatic lathes, multi-spindle machine tools and rotary tables. These machine tools are mostly characterized by very small size and very compact structure.


The characteristics and requirements of medical device parts processing have undoubtedly promoted the development of CNC processing technology and solutions to improve the competitiveness and production efficiency of small and medium-sized enterprises in processing CNC machining medical devices.


Ⅱ. The medical device industry is different from other mechanical CNC machining industries in three points:


1. The requirements for machine tools are relatively high. Advanced medical equipment processing equipment such as Swiss automatic lathes, multi-spindle machine tools and rotary tables are completely different from the commonly seen CNC machining centers and lathes. Their structure is very compact and the size is also very small.


In order to meet these requirements, the structure of the tool also needs to have a special design, the size of the tool is also required to be small, and the rigidity of the tool must be ensured.


2. High requirements for CNC processing efficiency. For medical equipment, the most important thing is CNC processing efficiency, that is, the processing pace, which requires that the blade can be replaced in the shortest time.


3. As for the CNC machining workpiece itself, it is quite different from other mechanical parts. Medical devices implanted in the human body first require very good surface finish, very high precision, and no deviations. This has strict requirements on the blade structure of the knife and the coating of the blade.


In addition, there are strict requirements on the accuracy of the repeated positioning of the blade, so that it can ensure the efficiency improvement while not neglecting the high quality!

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