John A. Patten

Construction and testing of a nanomachining instrument

This paper presents a nanomachining instrument that was developed for conducting nanocutting, nanoscratching, and nanoindentation experiments. A piezoelectric tube scanner (PZT) is employed to generate three-dimensional machining motions. The sample is moved by the PZT, and the tool is kept stationary during machining. The machining forces are measured by force sensors with a resolution of sub-milliNewtons. The instrument is compact and can be used inside optical microscopes and scanning electron microscopes. In this paper, depth-sensing indentation experiments were performed to test the basic performance of the instrument. The indentation displacement was measured by a capacitance probe situated inside the PZT tube. An experimental system was constructed to locate and image indentations. The system consists of a high magnification microscope to measure coordinates of the indentation relative to a reference corner point on the sample, and an AFM equipped with an on-axis optical imaging system for locating the indentation. A technique was also employed to establish the tool-sample contact to nanometer accuracy. Indentation experiments were carried out on three kinds of materials with different hardness. Experimental results demonstrated the instrument has the ability of performing depth-sensing indentations. The frame compliance was also evaluated from the indentation results.

Extreme negative rake angle technique for single point diamond nano-cutting of silicon

Experiments were conducted to evaluate cuts made with the rake face of the tool and the clearance face. The technique involved cutting in the corresponding opposite directions, i.e., forward with the rake face and backward with the clearance face. Cutting of single crystal silicon with both the rake and the clearance face resulted in a smooth ductile cut, with no evidence of fracture. This cutting technique may prove useful for furthering our understanding of the ductile machining of brittle materials.

NUMERICAL SIMULATIONS OF DUCTILE MACHINING OF SILICON NITRIDE WITH A CUTTING TOOL OF DEFINED GEOMETRY

Recent experiments involving machining of silicon nitride at the micrometer scale has shown that silicon nitride behaves in a ductile fashion under high pressures and when the depth of cut is small. In this paper, a preliminary study of ductile machining of Silicon Nitride (Si3N4) using numerical simulations is reported. The commercial software package ADVANTEDGE is used to model the cutting process. The numerical simulations involve a parametric study carried out to understand the effects of cutting speed, feed, rake angle and tooltip radius to evaluate conditions that are conducive to brittle-to-ductile phase transition. The feed, tooltip radius and depth of cut are of the order of tens of micrometers and the cutting speeds range from 0.5 m/min to 300 m/min. The results indicate that machining of silicon nitride may be carried out in a ductile fashion for small tooltip radii, high negative rake angles and small depths of cut.

Force measurement in a nanomachining instrument

Two miniature, high sensitivity force transducers were employed to measure the thrust force along the in-feed direction and the cutting force along the cross-feed direction in a nanomachining instrument. The instrument was developed for conducting fundamental experiments of nanocutting especially on brittle materials. The force transducers of piezoelectric quartz type can measure machining forces ranging from 0.2 mN to 10 N. The submillinewton resolution makes it possible to measure the machining forces in the cutting experiments with depths of cut as small as the nanometer level. The stiffness and resonant frequency of the force transducers are 400 mN/nm and 300 kHz, respectively, which meet the specification of the instrument. A force transducer assembly is designed to provide a mechanism to adjust the preload on the force transducer and to decouple the measurement of forces. The assembly consists of three dual-axis circular flexures and a subframe. The axial stiffness of the flexures is designed to be ...

Automatic vision inspection and measurement system for external screw threads

Abstract Production of threaded parts in some manufacturing environments requires high-precision thread measurement and a reliable inspection method. This paper describes considerations and techniques used in the development of a vision system for measurement and inspection of male screw threads. A two-stage process was developed to calibrate the imaging system. This procedure uses a calibration gauge pin to calibrate the vision systems pixel scale and two pitch standards (max, min) to correct for lighting and image distortion. New and enhanced imaging techniques were used to determine outer and inner diameters for each thread pair. These techniques enable the system to determine the maximum, minimum, and average inner and outer diameters of each part. Pitch measurements were obtained using cross sections of each thread pair in the image. The dark and light (crest and root) areas were examined to deduce pitch diameter very precisely. Measurement techniques for overall thread length and full thread length were found to be beneficial to the part inspection process. Lab results as well as production line measurement results using the vision system are compared to optical comparator, micrometer, and gauge measurements. Overall accuracy was within ± 0.0005″ of gauge measurements. Some measurements exceeded this accuracy in lab tests and on the production line. The thread measurement system was demonstrated to be extremely beneficial during the manufacturing process.

Thermal imaging with near-field microscopy

Optical microscopy is an important measurement tool in many industries. This importance is primarily due to the ease-of-use and nondestructive characteristics of optical microscopes. Unfortunately, the far-field optics of conventional microscopes limit their resolution to approximately 200 nm. An imaging technique called near-field microscopy uses a subwavelength aperture to circumvent this limit to obtain images with enhanced resolution without many of the destructive consequences of other techniques. Visible microscopes based on this technique have produced images that demonstrate 10–15 nm resolution. This article describes the extension of these techniques to the infrared regime. A description of an infrared microscope capable of imaging the thermal emissions from micron scale conductors using optical techniques has been given. The microscope has been designed to operate in both the collection mode using an external infrared radiation source and in the self-illumination mode using thermally activated objects. Several infrared images of 2-μm-wide conductors have been provided to demonstrate the resolution capabilities of the microscope. These images clearly show the presence of the conductors and represent a significant increase in resolution over conventional infrared imaging devices.

A man-machine interface software system for the design, modeling and simulation of robotic and automation systems

This paper describes the development and use of a man-machine interface software package used to demonstrate and develop robot control programs. These programs are used to integrate an industrial robot into various automation systems for laboratory investigations. The software package is a menu driven, user friendly, interactive and real time development and training system. The software program, and associated hardware, allows a novice user to develop robot control programs without prior knowledge of the specific robot system software. At the same time the program allows the more experienced user to develop sophisticated robot control programs using many of the standard features provided for in the man-machine software package. The system is configured around a Unimation PUMA 560 robot with the VAL II operating system[4]. VAL II versions 1.4b and 2.0 are used for this application. Standard PUMA hardware used for this project consists of a VAL II controller, CRT terminal and keyboard, floppy disk drive, teach pendant and digital I/O interfaces[5].