Desenvolvimento e avaliação de estratégias trocoidais para o fresamento do aço AISI 4340 temperado e revenido
Trochoidal trajectory shows to be efficient for rough machining of grooves in materials with low machinability index, since it decreases the engagement angle and reduces the cutting load on the cutting edges. The trochoidal trajectories have variations of their path which mainly influences the ma...
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| Formato: | Dissertação |
| Idioma: | por |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/25785 |
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| Resumo: | Trochoidal trajectory shows to be efficient for rough machining of grooves in
materials with low machinability index, since it decreases the engagement angle
and reduces the cutting load on the cutting edges. The trochoidal trajectories have
variations of their path which mainly influences the machining time. Information on
the influence of this tool path variations are scarce in the literature. This research
presents the influence of trochoidal strategy and the tool helix angle on the milling
of AISI 4340 steel (40 HRC) using coated carbide tools, considering the machining
time, the cutting force and wear mechanism. A methodology for the creation of
trochoidal strategies (circular and ellipsoidal), based on parametric equation, was
developed and applied to the experiments. Variations of the trochoidal trajectory
suggesting the machining time reduction were created with this methodology. The
results showed that the ellipsoidal trajectory promoted a reduction of 23% in the
theoretical machining time, as compared to the circular trajectory. Higher cutting
force was obtained using of the ellipsoidal trajectory and the increase of the helix
angle tends to reduce it, regardless of the type of trajectory. The mathematical
definition of the trajectories of the cutting edges in the trochoidal paths, circular and
ellipsoidal, allowed to determine the thickness of the undeformed chip as a function
of time. It was possible to modify the cutting force model, developed by Altintas,
which presented similarity between the experimental and simulation data. By
comparing the experimental and simulated data, =110 N/mm, = 200 N/mm
e = 23 N/mm values were obtained for the material adopted in this research.
Tool life is a complex variable to estimate for the machining conditions adopted in
this study due to the wear type and mechanisms on the cutting edges: mechanical
and thermal cracks, notch wear and chipping. |
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