In this article, Dr. Humphrey Carter of CompoTech explains why CFRP tools are a feasible option for machinery manufacturers.
The use of carbon fibre-reinforced plastics (CFRPs) is very widespread in motorsports and the aerospace industry. The exceptional stiffness and lightweight of these materials make them ideal for enhancing the performance of Formula 1 cars and high-speed jet aircraft.
Less widespread is the use of CFRPs for the production of machine tools. The same properties that make these materials so popular in high performance applications can impart significant benefits in this arena too, especially for load-bearing and structural components, or for precision movements.
In particular, the use of CFRP parts can help to improve the speed and acceleration and deceleration of a machine tool, especially over extended distances. The accuracy and repeatability with which, for example, a tool set can be returned to exactly the same location, operation after operation, can have a significant impact on productivity and, through a reduction in weight, operating life.
Steel-composite Hybrid Milling Tool
To highlight the benefits of the use of CFRPs in such applications, CompoTech recently developed a steel-composite hybrid milling tool that, in testing, has been shown to perform faster and machine more accurately than conventional options. The tool also imparts improved surface roughness meaning that, in certain circumstances, it can perform the job normally requiring two steel tool sets, for rough and final machining. This increases milling productivity, decreases machining time and reduces machining cost.
The hybrid milling tool is produced by depositing carbon and graphite fibre onto a steel part using a process called robot assisted filament laying (RAFL). The steel body acts both as a mandrel and as a means of connecting the tool to the tool holder and the tool holder to the spindle. It also provides a means for the attachment of the tool to the milling teeth.
After fibre placement, the part is cured at room temperature to reduce the likelihood of any thermally induced stress. It is later machined to its final shape.
The reduction in weight, up to 40 percent, and the increased stiffness provided by the use of graphite and carbon fibres enhances the damping properties. As well as increasing the natural frequency of the tool, reducing unwanted vibrations in the machining process, it gives the tool greater stability.
The low weight of the milling tool means that less energy is used in non-loaded positioning, while the lower inertia reduces peek energy in acceleration. Fortunately, this can also reduce wear on parts of the machine, meaning that the lifetime of the machine and the durability of the tool tip can be increased.
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