Purpose -The purpose of this paper is to analyze machinability of CFRP, GFRP, GLARE-type composites in drilling process taking into account their features and properties (the geometric characteristics, the volume fraction and the mechanical properties of the individual components of the composite). Drilling in non-plan surfaces and slope drilling. Design/methodology/approach -The tests were carried out in two stages: perpendicular drilling of materials such as GLARE with special drill bits, and drilling of composite structures with non-planar surfaces made of unidirectional carbon fiber prepregs, using the modified special drill. Measurement of cutting forces and torque, stress distribution (photoelastic method) and a visual assessment of defects occurring during drilling allowed to determine the relationship between the type and geometry of the composite drill. Findings -Identified great effect of kind of composite on the machinability of these materials has substantiated modification of the standard geometry of drills and matching this geometry to specific properties of the various type of composites. Practical implications -Drilling of assembly holes for aerospace parts. Originality/value -New type of drill geometry for different type of composite.

Purpose -The purpose of this paper is to investigate the concept of new drill bit geometry adjusted to a given composite type. This paper explores the possibility of drilling in composites without negative effects such as: delamination, rapid tool wear, matrix burns, pulling out of fibers, etc. Design/methodology/approach -Appropriate modification of drill bit geometries applied to composite materials include, among other things: modifications of point angles, reduction of chisel edge width, modification of drill margins and proper preparation of drill bit corners. Findings -Description of tool geometry for drilling of different types of composites, in particular drilling in parts included free grain surfaces but also drilling at a different angle than 90°. Research limitations/implications -Geometrical details of the tool for drilling are depended on the type of composite. Practical implications -Making of montage holes in parts made of composites without negative effects during drilling. Originality/value -Analysis of the current state of knowledge shows that there are insufficient solutions in terms of new drill geometry for drilling of composites. Existing solutions do not guarantee adequate stability and repeatability of the cutting process. It is necessary to create new geometry drills permit the elimination of negative phenomena during drilling.

The paper presents an investigation of results on an additive manufactured drill base body. Due to the technological and strength limitations, conventional drills with inner coolant ducts may not be smaller than 13 mm diameter. The novel idea was to keep the strength of small diameter drills making spiral coolant ducts. Drills were fabricated using a 3D laser printer to obtain the designed geometry in a way not affecting its stiffness and strength. The tensile strength of samples was between R m = 1287 and 1603 MPa, and microhardness of drills was between 606 and 627 HV5. The sintered material revealed a very small porosity rate (below 1%) and very few discontinuities. Thus, it was demonstrated that the 3D laser printing enabled the production of advantageous drill base bodies.

In the paper, the researches on sleeves made out of maraging steel 1.2709 using selective laser melting (SLM) technology are presented. This additive technology is recognized as favorable for the environment, due to 100% use of material and durability of manufactured details. The fabricated sleeves underwent subsequent tests, in particular, microhardness, porosity and homogeneity of the material was examined before and after heat treatment and salt bath nitrocarburizing process. Two kinds of fatigue tests were performed. The first consisted of the typical sinusoidal alternating load, the other was the high pressure pulse load test close to the real work conditions. It is of high importance that the fatigue strength of the tested sleeves is considerably higher than that of the similarly produced details shaped as a standard samples for tensile stress. The Mössbauer spectrometry analysis of hyperfine magnetic field distributions proved that SLM did not change considerably the martensite structure at atomic level.

Precision milling of free (curved) surfaces with the use of monolithic milling cutters is used in the production of hardened steel elements such as dies, molds, or press tools. Precision milling processes are carried out with the following milling parameters: axial cutting depth ap <0.3 mm, cutting width ae <0.5 mm and the required machining accuracy below 40 µm. The quality of the obtained surfaces in injection molds is directly transferred to the quality of the molded part. One of the key criteria for the manufactured elements is the surface quality which is mainly assessed by the roughness parameters. Due to the use of carbide tools high reliability and quality of machining is obtained which allows to eliminate the grinding process. In precision milling processes, due to the very small radius of the cutting edge and the cross-sections of the cutting layers, the conditions that must be met for the decohesion process to occur are fundamentally diff erent from macro-scale. The minimum value range of ap and ae parameters was determined in a carried-out experiment, which allows for stable and repeatable machining. The tests were carried out with double-edge shank cutters with a diameter of 6 mm on a workpiece made out of WCVL hardened steel 45-47 HRC. Recommended machining conditions have been defi ned to ensure the required technological quality of the surface layer. The research was fi nanced under the research project POIR.01.01.01-00-0890/17 co-fi nanced by the European Union from the European Regional Development Fund.