Robert J. Stango

Morphology of metal surface generated by nylon/abrasive filament brush

Abstract Nylon/abrasive brushing tools are used in surface finishing processes for a wide range of applications, including blending, polishing and edge-radiusing of both ductile and brittle materials. In this paper, the surface topography and machined materials that are generated during orthogonal brushing of a flat 6061-T6 workpiece are examined using scanning electron microscopy. Also, the microscopic morphology of nylon/SiC filaments is examined in as-received and steady-state configurations. This information is used to postulate a qualitative model for material removal mechanisms and the wear/attrition characteristics of the filament material system.

On the frictional response of a filamentary brush in contact with a curved workpart

Abstract Filamentary brushes are used widely for both manual and automated deburring and surface finishing operations. However, insufficient information is available to manufacturing engineers concerning guidelines for the selection, use, and anticipated performance of such tools. In this paper, a formulation for the quasi-static, finite displacement mechanics analysis of constrained filament deformation is developed which includes frictional forces generated at the interface of the brush/workpart system. The constrained path along which the filament tip traverses corresponds to a workpart surface having variable curvature. The problem is formulated in terms of curvilinear coordinates, which facilitate the development of a filament-tip “kinematic trace”. The kinematic trace, in turn, provides a rational basis for evaluating the approximate final position for filament/workpart contact. For illustrative purposes, the results for filament force, overall brush force and brush torque are reported in non-dimensional form for several different constant workpart curvatures and friction coefficients. Additionally, discussion is provided concerning the relationship between the friction coefficient used in this study, and the actual filament machining forces that are generated during the material removal process.

Contact Zone Force Profile and Machining Performance of Filamentary Brush

Filamentary brushing tools are used in a wide range of surface finishing processes, such as deburring, edge radiusing, polishing, and surface decontamination applications. Moreover, these tools are easily adapted to automation because the filament tips, which perform the machining operation, readily conform to the workpart surface without the need for sophisticated control systems technology. However, little is known about the material removal mechanics of filamentary brushes and, therefore, trial-and-error experimentation is often necessary before the tool is implemented in a production environment. This uncertainty of performance can be traced to a lack of understanding of the actual forces that are generated within the contact zone, that is, along the interface of the filament tip and workpart surface. Although previous experimental research has focused on the overall (i.e., resultant) brush force exerted onto the workpart, no information exists in the literature regarding the variation of force within the contact zone. Such information is essential for understanding the material removal profile within the contact zone, and could provide valuable information regarding the most active machining site along the contact surface. In this paper, a novel experiment is proposed for evaluating the force profile of filament tip forces that are generated within the contact region of a brushed surface. A specially designed workpart fixture is constructed and used in conjunction with a multiaxis force sensor for measuring the detailed force variation within the contact zone. The experiment is conducted using a wire brush at several different rotational speeds, which enables one to ascertain the role of filament inertia in the material removal process. Findings are reported which suggest that a significantly enhanced material removal rate can be achieved at a selective location within the contact zone at moderately elevated spindle speeds.

Automated Deburring with a Filamentary Brush: Prescribed Burr Geometry

In this paper, a dynamic model for removal of edge burrs with a compliant brushing tool is reported. Description of the burr geometry is assumed to be known through on-line measurement methods such as a computer vision system in the flexible manufacturing cell. Dynamic response of the brush/workpiece system is evaluated on the basis of experimentally obtained data. Master Curves are introduced as machining descriptors which characterize the incremental burr removal performance of the brush/workpiece system, leading to the development of an analytical dynamic model for orthogonal burr removal using a finite-width brushing tool. Based upon the dynamic model for material removal, a control strategy for automatic deburring is presented for burr configurations having constant height as well as variable height. A closed-form solution for transverse brush feed rate is obtained which is applicable for removal of burrs having variable height, as described by suitable geometry functions. For illustrative purposes, simulations are carried out for a straight-edge burr profile and sinusoidal burr geometry. Results are reported which identify important relationships among brush feed rate, brush penetration depth, and brush rotational speed. In order to help assess the validity of the proposed analytical model and control strategy, experimental results are reported for a combination ramp/straight-edge burr configuration. The results demonstrate generally good correlation between the predicted and actual profile for the edge burr that has been machined. In addition, some important observations include; (1) burr removal is most rapidly carried out by using the highest brush speed and deepest brush/workpiece penetration depth, subject to the condition that the brush fiber is not damaged, (2) Currently available polymer abrasive brushing tools exhibit very slow machining characteristics and must be improved in order to be used in a production environment where burr size is appreciable, (3) Material removal characteristics of the leading and trailing edge of brushes may be a source of error which merits further investigation.