Laboratory for Manufacturing and Sustainability

One of the major concerns in deburring technology is centered on how to predict the size and shape of burrs to insure uniform removal and, if this is possible, how to design the process or product in advance to minimize or control the burr size. This paper reviews some of the research done over the past several years on this important topic. The paper includes a discussion of burrs in conventional machining, process planning for burr minimization as well as micromachining applications.

Increasing demands on function and performance call for burr-free workpiece edges after machining. Since deburring is a costly and non-value-added operation, the understanding and control of burr formation is a research topic with high relevance to industrial applications. Following a review of burr classifications along with the corresponding measurement technologies, burr formation mechanisms in machining are described. Deburring and burr control are two possible ways to deal with burrs. For both, an insight into current research results are presented. Finally, a number of case studies on burr formation, control and deburring along with their economic implications are presented.

In the past few years, cleanability of mechanical components became a new engineering constraint in the automotive and aerospace industry due to a rapid increase in the complexity of engines, transmissions, suspension components, etc. Cleaning processes currently used in industry are quite inefficient as they incur significant energy and consumable costs and, in many cases, cannot achieve the degree of cleanliness necessary to meet performance and service life requirements of the components. There is a good amount of scope to improve the existing technology with analytical and computational tools that can help predict and control cleaning effect at design and process planning stages. On the other hand, an improvement in the understanding of the mechanics of chip cleanability which involves interactions between the cleaning fluid and the chip critical and workpiece bottleneck dimensions can help us investigate the development of new technologies that enhance the phenomenon that aid in the cleanability of these solid particle contaminants. This work discusses the potential of using a two-phase air-water mixture for the internal cleaning of complex automotive components like the cylinder heads of internal combustion engines, by selectively exploiting specific properties of the mixture, different from its individual components.

Effective cleaning with high pressure waterjets requires direct impact of jets and sufficiently high impact pressure. The objective of this research is to find all such cleanable regions, given a CAD model of a workpiece, by means of geometric accessibility analysis. We use a configuration space (C-space) approach for addressing the problems of both optimum surface proximity for effective cleaning and collision avoidance between the cleaning lance and the workpiece. Minkowski sums are used to compute the C-spaces and cleanable regions are then found by visibility analysis. Implementations and results for 2D examples are shown to validate the approach.

The presence of solid particle contaminant chips in high performance and complex automotive components like cylinder heads of internal combustion engines is a source of major concern for the automotive industry. Current industrial cleaning technologies, simply relying on the fluid transport energy of high pressure or intermittent high impulse jets discharged at the water jacket inlets of the cylinder head, fail to capture the dynamics of interaction between the chip morphology and the complex workpiece landscape. This work provides a preliminary insight into an experimental investigation of the mechanics of chip transport at play, and how it can be used to build an effective chip optimization model that significantly aids in improving the cleanability of contaminant chips. The objective is to relate the mechanics of chip transport with the chip form parameters as much as possible, which makes the objective and constraints in the optimization model quantifiable. The end objective is of course to transmit this information upstream of the manufacturing pipeline in the form of a Design for Cleanability (DFC) feedback, which highlights the industrial cleaning problem as a design centric issue.

We developed computer-aided planning tools for waterjet cleaning processes incorporating experimental results. We designed experiments to determine the influence of key waterjet parameters on cleaning effect and devised a computer-aided visualization and optimization scheme incorporating these parameters. In addition, we developed a particle dynamics model to simulate local waterjet interaction with target surfaces. Finally, we developed a model to predict water traps inside the workpieces based on layered volume segmentation. Our tools will aid designers and process planners in achieving efficient cleaning of geometrically complex workpieces in a high volume manufacturing environment.

In order to advance understanding of the burr formation process, a series of finite element models are introduced. First a finite element model of the burr formation of two-dimensional orthogonal cutting is introduced and validated with experimental observations. A detailed and thorough examination of the drilling burr forming process is undertaken. This information is then used in the construction of an analytical model and, leads to development of a three-dimensional finite element model of drilling burr formation. Using the model as a template, related burr formation problems that have not been physically examined can be simulated and the results used to control process planning resulting in the reduction of burr formation. We highlight this process by discussing current areas of research at the University of California in collaboration with the Consortium on Deburring and Edge Finishing (CODEF).

The research describes part of a "Pipeline of De-sign and Manufacturing Tools" for product de-signers who are driven by short delivery-times. The overall project has been called CyberCut be-cause the modules can interoperate in a distrib-uted, Internet-based environment. This particular paper focuses on tool path generation of sculp-tured surfaces using 3-axis CNC machines. Im-portance is given to generating cutter location points that will meet the tolerance requirement while maintaining a certain surface finish. Sec-tions of the paper describe: a) the offset-generation method, b) the tool path generation scheme and c) the tool holder collision detection algorithm. The algorithms that have been devel-oped are used to machine sample parts.

Accurate models of twist drills are needed for Finite Element simulations of the drilling process. Existing drill designing methods rely extensively on discretized analytical equations to describe the drill and different sets of equations need to be formulated as the drill design changes. This paper presents a method to create accurate models of two-flute conical twist drills using solid-modeling techniques which addresses some of these shortcomings. Boolean operations are used to mimic the drill manufacturing steps and generate the fully designed drill. The drills generated by this method have been used in Finite Element simulations to study the effect of drill point geometry on burr formation in drilling.

The quality of machined components in the aerospace and automotive industries has become increasingly critical in the past years because of greater complexity of the workpieces, miniaturization, usage of new composite materials, and tighter tolerances. This trend has put continual pressure not only on improvements in machining operations, but also on the optimization of the cleanability of parts. The paper reviews recent work done in these areas at the University of California-Berkeley. This includes: Finite element modeling of burr formation in stacked drilling; development of drill geometries for burr minimization in curved-surface drilling; development of a enhanced drilling burr control chart; study of tool path planning in face-milling; and cleanability of components and cleanliness metrics.