Journal of Engineering Sciences / Журнал інженерних наук
Permanent URI for this collectionhttps://devessuir.sumdu.edu.ua/handle/123456789/34326
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Item Stabilization of contour milling on CNC machines(Sumy State University, 2025) Petrakov, Y.V.; Myhovych, A.V.Contour milling processes are characterized by a quasi-stationary nature, which leads to the need to assign a cutting mode for the entire contour based on the most unfavorable cutting conditions in a particular area. Simultaneously, CNC machines allow for selecting different cutting modes for contour sections, stabilizing cutting conditions along the entire contour, and stabilization is advisable based on the material removal rate (MRR) criterion. The research deals with contour milling on a CNC machine. Since the process is quasi-stationary, the problem arises of stabilizing it by controlling the feed rate and spindle speed. Therefore, the MRR as the main process parameter was considered the research subject. This parameter determines the cutting intensity and is responsible for forming the required surface quality of the part. A computer program was developed to simulate the contour milling process by determining the main characteristic of the MRR process. At the first stage of the developed technology, using the created modeling program and a G-code control program, a digital file of the MRR dependence was created for the part’s contour. Such a file was used in a developed authors’ program to generate a G-code control file, which ensures stabilization of the cutting process according to the MRR criterion. Moreover, control was realized when changing the feed rate to discretize the resulting array with a specified percentage of the change step. This reduced the number of frames for the new control program while maintaining the positive effect of stabilizing the process in terms of MRR. The developed technology was tested for machining the contour with convex and concave sections in the trajectory. Experimental studies were conducted on a CNC milling machine with the workpiece mounted on a dynamometer table. This made it possible to record the cutting force during milling. As a result, the high efficiency of the developed technology was confirmed. Overall, process stabilization increased productivity approximately 3.0 times compared to the process designed in a CAM system at a constant feed rate and spindle speed.Item Determination of chatter-free cutting mode in end milling(Sumy State University, 2024) Petrakov, Y.V.; Ohrimenko, O.A.; Sapon, S.P.; Sikailo, M.O.; Fedorynenko, D.Y.Chatter accompanies the cutting process and is the main obstacle to achieving precision and productivity in milling operations. To reduce the amplitude of vibrations, it was proposed to use a stability lobes diagram (SLD) when assigning cutting modes. The machining system in end milling was represented by a two-mass dynamic model in which each mass has two degrees of freedom. The behavior of such a system was described by a structure with two inputs, in-depth and cutting feed, and a delay in positive feedback on these inputs. A new criterion was applied to design the SLD based on an analysis of the location of the machining system Nyquist diagram on the complex plane. The algorithm for designing a stability chart was developed into an application program, a tool for the technologist-programmer when assigning cutting modes. A method for parameter identification necessary for designing the dynamic system “tool – workpiece” was proposed. The effectiveness of the developed method was proven experimentally when the choice of spindle speed during end milling allows one to reduce the roughness parameter Ra from 3.2 µm to 0.64 µm at the same feed rate of 650 mm/min.Item Cutting forces simulation for end milling(Sumy State University, 2023) Petrakov, Y.V.; Ohrimenko, O.A.; Sikailo, M.O.; Myhovych, A.V.The cutting force in end milling is the essential perturbation of the machining system that limits the productivity of the process. Therefore, forecasting the cutting force when assigning the processing mode and the geometry of the allowance layer to be cut is an urgent task that requires an operational tool for its solution. The method of calculating the cutting force is presented, based on a mechanistic approach, when the geometric ratios of the cutter blades’ positions on the sweep determine the thickness of the undeformed chip. The developed algorithm calculates the cutting force by double integration, first by the length of the cutting edge and then by the number of such edges. The algorithm also allows the simulating of the outrun of the mill on the cutting force and its components. The created application program visualizes the simulating process by oscillograms of the cutting force components for both up and down milling. Experimental studies, in general, proved the adequacy of the developed modeling method. The created program is a tool for operational forecasting of the cutting force during the technological preparation of the end milling process in production.