an improved cutting method with additional technological coating for clean finishing of fibrous composites

Due to specifics of structure and properties of some kinds of polymer fibrous composites (organoplastics, hybrid materials containing organofiberes etc.), when cutting, a hairiness of cut fibrous material and a property damage of surface appear on the machined surface, thereby substantially restricting achievable classes of surface quality, i.e. surface roughness, material condition of the surface layer, dimensional accuracy, etc. These features of polymer composite materials (PCM) allow their referring to a special group of hard-to-cut materials, which requires creation and use of unconventional machining methods and tools to provide high-quality treatment and desirable engineering and economic indicators.

The BMSTU has developed a clean finishing method of PCM, i.e. cutting with an additional technological coating (ATC). A principle of the method is that the two-pass machining in the finish size is provided. The first cutting tool pass provides processing in the pre-finish size of the product surface; then the hairiness appeared after machining is bound by applying a curing technological coating, and the second (finishing) pass in the final size removes a tightly binderheld hairiness together with cured temporary coating. This allows us to reduce roughness, significantly reduce dimensions and number of defects of the surface layer. However, the time required to cure the temporary coating before the second (final) pass of a cutting tool results in lower production rates of finishing with ATC, reduced performance rate, and higher product cost. Increased performance rate in ATC cutting, with the same high quality of the processed surfaces of fibrous composites, has been achieved by reducing the curing time of coating that can be realized in different ways.

It has been experimentally established that under optimum processing conditions high quality of surface (roughness class of 7-8) and substantially reduced curing time of coating, i.e. the time interval between preliminary and final tool passes are achieved through the temperature control of ATC curing. Thus, the coating heated from 20 °C to 120 °C provides 18 times reduction of its curing time. Time of ATC cutting operation can be lessened more through pre-curing of technological coating on the site where components are mixed before applying it on the product to be cut. Changing weight ratio between the epoxide compound and the curing agent also has a significant impact on the curing time.

The study has shown that the quality of the machined surface when cutting with ATC is also dependent on processing conditions such as the thickness of the coating layer (0.8 ... 1 mm at least), the surface crispness after preliminary pass of a tool before applying the temporary coating, and the wear rate of a cutting tool. To ensure the economic efficiency of the ATC cutting process and high quality of treatment it is necessary to take into account all abovementioned factors that affect the machined surface.