Dependency of The Technological Quality of Elements Made From An Aluminum Alloy on Their Shape in The Water Jet Machining
Treść / Zawartość
The problem of the technological quality of elements is one of the primary problems of modern machine production. In many cases, elements are made from new construction materials with specific properties considered to have poor machinability in cases where conventional technologies are applied. Thus, there is a need to identify the capabilities of new technologies, including the technology of cutting with a high-pressure abrasive water jet for the production of elements made of Al alloys, while observing qualitative machining requirements. This paper presents the results of studies of the accuracy of production of elements with a complex shape made of a 2017A alloy (PA6) and of studies of the coarseness of obtained surfaces depending on the pressure of the water jet, cutting advance rate, and the amount of dosed abrasive for a constant thickness of the element. The measure of the accuracy of production, independent of dimensional accuracy, was assumed to be the size of chamfering on the side surface of the cut element caused by a specific mechanism of material decohesion occurring under the influence of water jet technology. In cases where Al alloys are cut, depending on assumed conditions, it is possible to shape the side surface of an element with a positive, negative, or neutral (zero) wall inclination (side of the element). In the process of cutting, specific errors in the shape of the element occur and appear on curved fragments of the object or in discontinuous areas of the profile (e.g. transition from a straight fragment to an arc fragment); this is caused by a shift in the exit of the high-pressure abrasive water jet from the object relative to the point of entry. Consequently, selection of cutting parameters for the water jet method for elements with complex shapes is, in essence, a compromise between the obtained inclination of the wall of the processed element and the required surface coarseness, and between the required (acceptable) inclination of the wall of the element or lack thereof and the obtained coarseness of the elements surface. Thus, in the outlined problem, it is not possible to simultaneously obtain two satisfactory criteria quantities of element quality, that is, accuracy of shape and requisite coarseness of the surface of the machined element, if the water jet method is applied for the purpose of machining Al alloys.
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