Analysis of the Differences between Force Control and Feed Control Strategies during the Honing of Bores

Abstract

Honing is a machining process that can economically produce very exact bores regarding form, geometry and surface quality. It is mainly used as the final finishing operation for ready made parts and typically conducted on the inner surface of a cylinder. Due to their specific surface structure which has a good ability to keep lubricants and a high wear resistance, honed parts usually serve as functional surfaces to guide moved parts. Today, the main fields for applications of honing technology can be found in most sectors of the metal working industry, e.g. the automotive industries, hydraulic and pneumatic manufacture and aircraft industries. During the long-stroke honing process the tool, equipped with one or several abrasive honing stones, is performing three overlaying movement components. These are a rotational movement, an oscillating stroke movement in axial direction and the radial feed movement of the honing stone. This feed movement is one of the decisive factors for the results of the honing process. It can be realized through feed control or, in a more recent approach, through force control strategies. By feed controlled honing, the position of the honing stone is changed in defined invariable steps in certain time intervals. In contrast, by force controlled honing the force of the honing stone against the wall of the workpiece is measured indirectly by a force sensor, which is located within the feed unit of the honing machine. A required force value is given and, if necessary, the honing stone is fed outwards to reach and maintain a constant cutting force throughout the honing process. This constant force is supposed to produce better results of the honing process in terms of geometric and form accuracy as well as surface structure. The presented research studies aim at improving process know-how to further increase the production accuracy and process repeatability. In a comparison between parts honed with the two different feeding strategies for the honing stone, force components and moments were analyzed and correlated to the phases of the process and several influencing parameters. In addition to the forces and moments measured during the honing process, the quality parameters of the honed parts have also been analyzed and compared.