Changzhou Longfu Knitting Co., Ltd. , http://www.circularmachine.com
Analysis of the demand for processing technology in the development of artificial joints
Artificial joint replacement technology has undergone nearly a century of development, progressing from its early exploratory stages to the relatively advanced phase we see today. The continuous collaboration between the medical and engineering fields has driven significant advancements in design concepts, medical materials, manufacturing techniques, and testing methodologies. These developments have greatly benefited countless patients.
With the support of clinical statistics and scientific analyses, particularly in the manufacturing process, modern technologies like reverse engineering, computer numerical control (CNC) machining, rapid prototyping, and high-energy beam processing (such as laser and electron beam applications) have made many previously challenging design concepts feasible. This has ushered in a new era of transformation and growth within the artificial joint industry. Accompanying these changes, new demands and expectations for manufacturing processes have emerged.
(1) Despite the steady stream of innovative design concepts for artificial joints over recent years, one aspect remains relatively stable and evolves gradually: the materials used. Artificial joints are medical devices implanted in the human body, requiring a lifespan of 10 to 20 years or more. Consequently, selecting materials for artificial joint manufacturing is approached with extreme caution. After years of rigorous screening and industry recognition, the most commonly used materials include titanium and titanium alloys, cobalt alloys, and ultra-high molecular weight polyethylene. Bioceramics and animal-derived materials are less commonly used for machining purposes and are not covered here. These materials share the characteristic of being difficult to machine. For instance, titanium and titanium alloys, despite their widespread usage, exhibit poor mechanical cutting properties, largely due to their low thermal conductivity. At higher cutting speeds, excessive heat accumulates at the cutting edge, accelerating tool wear. Titanium's chemical reactivity poses a fire risk at elevated temperatures, while its tendency to cause severe surface hardening affects both surface roughness and dimensional accuracy. Additionally, the continuous formation of long chips presents a significant challenge. Cobalt alloys, known for their high hardness, also present difficulties in machining. While ultra-high molecular weight polyethylene offers lower hardness and strength compared to metallic materials, its high viscosity complicates chip breaking, and the localized heating during cutting can lead to softening or even melting, severely impacting surface quality.
These challenges impose considerable obstacles on the production processes of enterprises. Finding suitable tools has become a top priority for artificial joint manufacturers. Ideal tools should possess satisfactory hardness, heat resistance, minimal wear, and excellent guidance and chip-breaking capabilities. Managing the tangled chips has long been a source of frustration, often necessitating interruptions in processing and manual intervention to resolve issues. Collaboration among machine tool builders, software developers, and tool manufacturers could significantly alleviate these burdens. For example, integrating an automated chip-handling device into the machine, developing corresponding programs within the operating system, and utilizing tools with superior guidance and chip-breaking functions could dramatically reduce the energy and labor required for these tasks.
(2) As economic conditions improve and the medical profession’s demand for surgical precision grows, there is an increasing expectation for personalized and quasi-personalized products tailored to individual patient needs. To address this trend, artificial joint designs are increasingly focusing on personalization and rapid manufacturing. However, due to constraints such as manufacturing methods, processing cycles, cost considerations, and security validation, achieving full-scale personalization remains challenging. As an alternative, multi-specification and multi-type products have entered the market, offering solutions that closely align with the anatomical requirements of individual patient joints (see Figures 1 and 2).
A side effect of multi-specification design is that when the total production volume remains constant over a given period, the output of each product type decreases, leading to frequent changes in processes and tools. This results in increased downtime for tool replacement and program debugging, negating the efficiency gains from the rapid performance features of modern machines, such as fast movement and quick tool changes.
Consider, for example, the general-purpose CNC lathes and slitting lathes commonly used by artificial joint manufacturers. While these machines typically include positioning devices between the tool holder and tool post, their accuracy is insufficient. During product changes, when different types and grades of tools are exchanged, it is often impossible to quickly return to the previous processing state. If an accurate positioning mechanism were implemented between the tool holder and tool post, tool parameters could be fixed in the machining program. Pre-calibrating the external tool would allow the installation of positioning parameters, ensuring accuracy. Once the tool holder is quickly mounted, the original program could be directly called for trial cutting. After inspection and appropriate tool compensation, regular processing could commence. Achieving this concept would greatly enhance production efficiency for small-batch, multi-variety operations.
In summary, while artificial joint technology continues to evolve, addressing the challenges in material processing and customization remains crucial for future advancements.