Machining of CFR TP shapes
The machining of continuous fiber reinforced thermoplastics offers opportunities to add functionality to your products, for instance to connect to other parts/components during the assembly of the final product.
The process of machining can be compared to machining of metal parts. Each type of metal requires tooling with cutting parameters, which are optimized for the properties of the metal, to achieve optimal cutting conditions. For CFR thermoplastics this is similar with the fiber and the type of thermoplastics have an impact on the cutting tool and parameters, yet the most important factor is the fiber type. Carbon fiber is very hard material to cut and causes high wear of conventional cutting tool materials. It requires specials high cost tools with polycrystalline diamond (PCD) to cut (carbon) fiber reinforced materials in order to obtain good quality and longer tool life time.
When applying the right cutting tools, all type of machining (lathe and milling) or simply cutting with sawing machines can be executed. While cutting thermoset composite materials is typically done with high cutting speeds and low feed rates because of the brittle material, thermoplastic composite material has a much better machinability. That means also that the cutting speed is lower and the feed rate is higher compared to machining of thermoset composites.
Machining of thermoplastic composite material offers, as said before, additional opportunities yet it is important to understand the effect of machining with regard to the strength and stiffness when removing/cutting the fibers. If you have optimized your CFR thermoplastic product with the lay-up (number of layers and angles), the machining of your product can cause a local weakening of the properties.
Therefore we always recommend to design the connections if possible without the need to remove material. For example reshaping (thermoforming) of thermoplastic composite material allows to maintain the material characteristics without the need to remove material. Please refer to the blog about “connections” on our website.
Written by Theo Mimpen (April 2023)