Design of a Flexible and Agile Centering Preprocessing System

Precise machining of bearing rings is integral to finished bearing assembly quality. The output accuracy of center-based machining systems such as lathes and magnetic chuck grinders relates directly to the accuracy of part centering before machining. Traditional tooling for centering on such machines is subject to wear, dimensional inaccuracy, setup time (hard tooling) and human error (manual centering). A flexible system for initial part centering is proposed based on a single measurement system and actuator. In this system, the part is placed by hand onto the machine table, automatically rotated and measured to identify center of geometry offset from center of rotation, then moved by a series of controlled manipulations to align the centers. Such a system eliminates the need for part-specific tooling or the inconsistency of manual centering by a skilled operator, reduces the lifetime cost, and creates agility for varied part acceptance with minimal setup effort. Results in both time and accuracy are currently equivalent to the manual process

Application of a Linear Center Identification Scheme to Deterministic Polar Positioning

In a number of manufacturing applications, parts of circular cross-section must be centered for optimal processing or measurement. However, part form is never perfect, making accurate determination of the “centered” state of a part difficult. Imperfect inputs to the manufacturing process such as rough-processed parts, deformation due to heat treatment, or raw formed materials present difficulty in centering by the traditional manual method. This paper presents a filtering and quantification technique for identifying the true center of an imperfect round part through isolation of the lowest polar frequency component. A low-cost device is presented that centers parts based on this frequency domain identification of center

Real-time identification of sliding friction using LabVIEW FPGA

Friction is present in all mechanical systems, and can greatly affect system stability and control in precision motion applications. In this paper, we present application of a frictional model to trajectory planning of a part centering system with real-time identification of model parameters through system force and position response. This identification is carried out using LabVIEW motion control software and digital signal processing (DSP) and field-programmable gate array (FPGA) hardware. A comparison of hardware performance for force measurement is also made

Experimental Studies in Stereolithography Resolution

As we move towards micron-scale rapid manufacturing, it is critical to understand build resolution of Stereolithography technology. In order to determine the resolution limitations, positive and negative features on Stereolithography parts were built and analyzed. Results from several experiments were compared to an analytical model and important resolution issues are highlighted. Based on these experimental results, parameters that will maximize build resolution for a number of well-understood shapes are suggested in the paper. Build resolution experimental results, analysis, and measurement techniques are discussed. Conclusions are drawn related to feature shape as resolution limits are approached.We gratefully acknowledge the support from the RPMI member companies and the George W. Woodruff School of Mechanical Engineering at Georgia Tech. This work was partially funded by the National Science Foundation under Grant Number DMI-9988664.Mechanical Engineerin

Volumetric Flank Wear Characterization for Titanium Milling Insert Tools

Machining wear models are useful for the prediction of tool life and the estimation of machining productivity. Existing wear models relate the cutting parameters of feed, speed, and depth of cut to tool wear. The tool wear is often reported as changes in flank width or crater depth. However, these one-dimensional wear measurements do not fully characterize the tool condition when tools wear by other types of wear such as notching, chipping, and adhesion. This is especially true when machining difficult-to-machine materials such as titanium. This paper proposes another approach for characterizing tool wear. It is based on taking measurements of the retained volume of the cutting tool. The new wear characterization approach is used to demonstrate the progression of volumetric wear in titanium milling

Quality and inspection of machining operations: Review of condition monitoring and CMM inspection techniques 2000 to present

In order to consistently produce quality parts, many aspects of the manufacturing process must be carefully monitored, controlled, and measured. The methods and techniques by which to accomplish these tasks has been the focus of numerous studies in recent years. With the rapid advances in computing technology, the complexity and overhead that can be feasibly incorporated in any developed technique has dramatically improved. Thus, techniques that would have been impractical for implementation just a few years ago can now be realistically applied. This rapid growth has resulted in a wealth of new capabilities for improving part and process quality and reliability. In this paper, overviews of recent advances that apply to machining are presented. Moreover, due to the relative significance of two particular machining aspects, this review focuses specifically on research publications pertaining to using tool condition monitoring and coordinate measurement machines to improve the machining process. Tool condition has a direct effect on part quality and is discussed first. The application of tool condition monitoring as it applies to turning, drilling, milling, and grinding is presented. The subsequent section provides recommendations for future research opportunities. The ensuing section focuses on the use of coordinate measuring machines in conjunction with machining and is subdivided with respect to integration with machining tools, inspection planning and efficiency, advanced controller feedback, machine error compensation, and on-line tool calibration, in that specific order and concludes with recommendations regarding where future needs remain

An OSSE Search for the Binary Radio Pulsar 1259-63

We have searched data from the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory (GRO) for evidence of low‐energy γ‐ray emission from the binary radio pulsar PSR1259−63. This 47 ms pulsar is in a long‐period, highly eccentric orbit around a Be stellar companion and was observed by OSSE approximately 400 days after periastron. The period derivative allowed by the published radio ephemeris (Johnston et al. 1992) suggests that the pulsar might be relatively young, and therefore a γ‐ray source. However, the ephemeris is not sufficiently accurate to allow the traditional epoch‐folding technique over the full OSSE observation. Instead, the OSSE data were analyzed using Fourier transform spectral techniques after applying trial accelerations to correct for a range of possible orbital accelerations. We searched 48 accelerations; each FFT was 2 ^2^9 points sampled at 2 ms, spanning ∼106 seconds of observation time. There was no evidence of pulsed emission in the 64–150 keV band, with a 99.9% confidence upper limit of 6×10^(−)3 photons cm^(−2) s^(−1) MeV− 1 or ∼40 m Crab pulsars, which suggests that the pulsar’s intrinsic period derivative is small and its magnetic field weak. This work was performed on the Concurrent Supercomputing Consortium’s Intel Touchstone Delta parallel supercomputer as part of a GRO Phase 1 Guest Investigation

Inspection strategy for LIGA microstructures using a programmable optical microscope.

The LIGA process has the ability to fabricate very precise, high aspect ratio mesoscale structures with microscale features [l]. The process consists of multiple steps before a final part is produced. Materials native to the LIGA process include metals and photoresists. These structures are routinely measured for quality control and process improvement. However, metrology of LIGA structures is challenging because of their high aspect ratio and edge topography. For the scale of LIGA structures, a programmable optical microscope is well suited for lateral (XU) critical dimension measurements. Using grayscale gradient image processing with sub-pixel interpolation, edges are detected and measurements are performed. As with any measurement, understanding measurement uncertainty is necessary so that appropriate conclusions are drawn from the data. Therefore, the abilities of the inspection tool and the obstacles presented by the structures under inspection should be well understood so that precision may be quantified. This report presents an inspection method for LIGA microstructures including a comprehensive assessment of the uncertainty for each inspection scenario

Electronic Enterprise Support

We are designing a long-term research project to develop a standard-based, customizable, integrated tool set called the Support Environment for Enterprise Engineering (SEEE), enabling organizations to manage and evolve all technological and organizational processes effectively; integrate and manage all enterprise information electronically; and empower knowledge workers at all levels with broad decision support capabilities. This paper presents the SEEE architecture and shows how it supports these goals