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Современные технологии и автоматизация в машиностроении
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the optimal cutting conditions, require the further study of technological methods to increase the efficiency
and operating characteristics of cutting tools while composites machining.
With blade processing of composite materials the major difficulty is to ensure the quality of products
surfaces. This is due to the anisotropy properties of composites, the presence of a layered structure, high
strength characteristics, low thermal conductivity and high hardness of the filler [2, 3].
In the rocket and aerospace technology the technological support providing surface layer quality
there is paid more attention to the products manufacturing of fibrous composites by mechanical processing
(cutting and abrasive as well), perforating fibers of the filler in the cutting process where the pile is formed
[1].
The mentioned specifications do not allow to use the technologies used in traditional cutting (metal
and non-metallic structural materials). The composites machining differs significantly from the traditional
materials cutting. A prerequisite is the sharpness of the cutting tool edge designed to reduce, greatly, the
friction between the tool and the workpiece. The probability of tool wear must be minimized, as any change
of the geometric shape of the cutting edge causes a rapid temperature rise in the cutting zone and critical tool
wear [4]. One of the most important requirements to the processing of composite materials is to select
rational geometrical parameters of tools and cutting data. They should provide the specified surface finish to
meet the performance criteria of processing and the wear resistance of cutting tools [5].
When processing composite materials the operating parameters and, first of all, the cutting speed are
prescribed according to the deficiency of thermal oxidative break-down material, which is considered to be
one of the mandatory requirements ensuring the quality of the product surface layer. Initial low temperature
of thermal degradation of composite materials (250...350°C) together with their extremely low thermal
conductivity (100...600 times less than that of structural steel) necessitate, despite the relatively small unit
pressure on the tool, to specify the machining operations, small cutting speed [1, 6]. This, in many cases,
limits the performance productivity significantly.
The research works of the authors [1, 6, 7] showed that at high cutting speeds (25...100 m/s) at the
temperatures much (up to 2...4.5 times) greater than the critical temperature of thermal degradation of
composite materials, there is a wide range of processing conditions, which ensures the high quality of the
surface layer. This takes short time at high speed machining, deficit for the thermal-oxidative processes, the
contact duration temperature impacts on the workpiece. The obtained research results allow to recommend
the high speed machining as an effective way to increase the process intensity of composite materials
machining by 50...100 times. The application of the method may be limited by the engineering
specifications of equipment, large size (inertial forces) or insufficient rigidity of the workpiece.
Only individual approach to each particular operation for composite materials machining can,
eventually, provide reliable productive process of articles production of this complex material. The
achievement of the designed quality for individual operations and, at the same time, a reasonable cost of its
implementation can greatly affect the performance efficiency. Ensuring the required quality at the primary
operation excludes the need in finishing manipulations that would reduce the overall operation time. Under
continuous development of the manufacturing techniques of composite parts the need in specialized tools
increases taking into account individual peculiarities of machining process [4].
One of the most common ways of the surface formation of the articles made of composite materials
by cutting is milling, which allows to obtain both linear and shaped profile details. This is the rational usage
of prefabricated cutters which give a chance to select the cutting material and to replace the cutting elements
if they wear or break [7].
Both the selection of optimal parameters for machining operations and the suitable adjustment can be
keys to improve the composite materials competitiveness.
Analysis of scientific publications, reference books, and the research patents, concerning the subject,
results in the conclusion that today there are no clear recommendations about composites processing modes
and conditions. In this connection much additional research is required to determine the optimal modes for
the composites processing using an edge cutting tool of a specific geometry, and it must be made of high-
strength tool materials. This factor will optimize the production processes of composite parts of designed
precision and high quality machined surfaces in conjunction with maximum productivity; determine the
optimal cutting modes, thereby, increase the efficiency of blade processing of composite parts (articles,
products).