Precision Processes Research Articles

Evaluating the relationship between use phase environmental impacts and manufacturing process precision

The environmental impact of most consumer products is dominated by their use phase. However, these impacts tend to be driven by the manufacture of the product's components since components fabricated with higher precision typically allow the product to operate at higher efficiencies. This paper investigates the relationship between precision and life cycle environmental impacts by extending the traditional LCA methodology to evaluate the impact of manufacturing process precision on the functional performance of a product during its use phase. The implications of this relationship to manufacturing decision-making are also discussed as sustainability concerns may support the use of higher precision processes.

Mechatronics Design Methodology applied at manufacturing companies

New mechatronic products require integration of novel methods and tools to be developed. Mechatronics is becoming the basis for high-tech products, such as autonomous systems, high precision processes or adaptive devices. The complexity derived from integrating effectively its components may mislead and produce confusion during its design. This paper presents a new methodology to obtain a mechatronic design and will show some of the available virtual tools to design, evaluate and integrate the different parts of it. The methodology was applied to 40 different mechatronic projects creating good university-manufacturing companies links with satisfactory results.

Characteristics of Residual Stress Profiles in Hard Turned Versus Ground Surfaces With and Without a White Layer

Hard turning and grinding are precision processes in many cases for manufacturing various mechanical products. Product performance is highly dependent on the process induced residual stress. However, the basic differences in residual stress profiles generated by hard turning and grinding with and without the presence of a thermal white layer have not been well understood. This study aims to compare basic characteristics of the residual stress profiles using an extensive residual stress measurement for five surface types: hard turned fresh, hard turned with a white layer, ground fresh, ground with a white layer, and as heat treated. The X-ray diffraction data revealed distinct differences in the residual stress profiles for the five surface types. Hard turning with a sharp cutting tool generates a unique “hook” shaped residual stress profile characterized by compressive residual stress at the surface and maximum compressive residual stress in the subsurface, while “gentle” grinding only generates maximum compressive residual stress at the surface. The depth of compressive residual stress in the subsurface by hard turning is much larger than that by grinding. The high hertz pressure induced by the cutting tool in turning is the determining factor for the differences in residual stress. High tensile residual stress associates with the existence of a turned or a ground white layer. The coupled effects of high hertz pressure and rapid temperature change induced by tool wear play an important role in the resultant tensile residual stress. In addition, residual stress by grinding is more scattered than that by turning. Compared with the deterministic influence of machining process on the magnitudes and profiles of residual stress, the effect of heat treatment is minor.

Uniform Nonspherical Colloidal Particles with Tunable Shapes

Colloidal particles are ubiquitous for a broad spectrum of applications. Many current applications require nonspherical particles. They have been used for modifying optical properties and as a building block for self-assembled biomaterials. They are also beneficial for controlling suspension rheology and for engineering colloidal composites. In general, synthesizing uniform nonspherical particles is difficult because surface tension favors spherical shapes in overall length scales. This limitation may be overcome with advanced techniques such as microfluidics and clusterization separations; these precision processes generally produce small yields, severely limiting their utility for practical applications. Recently, several methods that can produce nonspherical particles such as dimers and higher-order clusters have produced larger yields. These methods all rely on random coagulation of single particles or on the formation of clusters by using emulsification techniques. However, a common limitation of these synthesis techniques is that a single batch contains many particle types, requiring a sorting process to produce homogeneous samples, thus limiting the yield for any given sample type. Thus, there exists a need for flexible and robust techniques to generate nonspherical particles with well-defined shapes and high yields. One method of controlling particle shapes is to use a controlled phase separation in the seeded polymerization technique. This technique can produce extremely high yields of uniform particles. In the typical technique, seed particles are first swollen with a polymerizable monomer-based solution, and subsequent polymerization induces phase separation. Depending on thermodynamic and kinetic factors, the phase separation results in a variety of particle shapes. Shapes of higher aspect ratio may be obtained by crosslinking the seed particles before the phase separation. The crosslinking makes the seed particles more elastic. The elastic forces can impart greater directionality to the formation of the newly polymerizing phase. This suggests that seed particle crosslinking might be used to control the shapes of nonspherical particles. In this Communication, we introduce a new seeded-polymerization technique that uses the crosslinking forces to synthesize a variety of uniform nonspherical particles in large synthesis scales. Our technique involves controlling the directionality of phase separations in the seeded-polymerization technique by manipulating the crosslinking density gradients of the seed particles. This enables us to generate a variety of particle shapes, including “rod”, “cone”, “triangle”, and “diamond” particles (Fig. 1). The uniform placement of the individual bulbs in nearly all of the particles in each batch is achieved solely by tuning the crosslinking properties of the seed particles. To illustrate how crosslinking controls particle morphology, we compare the synthesis of two different types of trimer particles: “rods” and “triangles” (Fig. 1a and b, respectively). Rods and triangles both result from the seeded polymerization performed on dimers. The difference is the degree of crosslinking in the two bulbs of the seed dimer. Dimers that contain two bulbs with slightly different degrees of crosslinking become rods when swollen and polymerized. By contrast, dimers that contain two bulbs with equal crosslinking become triangle particles (Fig. 2). This is demonstrated by a series of experiments in which we synthesized trimers from different types of dimers. First, we synthesized spherical crosslinked polystyrene (PS) particles from linear PS template particles by swelling them with styrene monomers containing a crosslinker, divinylbenzene (DVB). In this swelling step, step a, the concentration of DVB, [DVB]a was fixed at 1 vol % relative to the total monomers. After polymerizing the spherical particles, we performed another swelling step, step b, to produce dimers. In step b, [DVB]b was varied from 0.5 to 1.1 vol %. Polymerization after swelling step b resulted in symmetrical phase-separated PS dimers. The size and appearance of the dimers produced were identical for all samples. Finally, in step c, the dimers were again swollen with a similar mixture, and polymerized following the same procedure. This resulted in trimer particles of various shapes. The shape of the trimers depends only on [DVB]b. High values of [DVB]b produced triangle particles, intermediate values of [DVB]b produced triple rod particles, and the lowest value of [DVB]b gave rise to snowman particles. To understand this behavior, we examine how changing [DVB]b changes the internal network properties of the seed C O M M U N IC A IO N

Femtosecond Fiber Laser and Machining Applications

Ultrafast lasers are ideal for material processing that requires high precision on the micron and sub-micron order. Many researchers have intensively pursued this topic over the last ten years. High precision processes include direct-writing of features such as channels or waveguides at or below the surface of various materials, as well as surface texturing, glass welding, and nanoparticle production. Here, we present the first industrially qualified ultrafast lasers based upon optical fiber technology that produce light pulses in the femtosecond to picosecond range with micro Joule pulse energy levels at repetition rates higher than 100 kHz. We also present new applications realized with the laser's unique performance. The performance and reliability of these laser systems opens new possibilities in commercial laser processes. This technology base, coupled with highquality engineering, provides a laser tool that can meet the demands of new, high-precision, industrial applications today.

Microwear of cutting tool in ultraprecision single-point diamond machining of polymers for optical and bioengineering application

This paper is a continuation of a long duration research and it reports new results in the investigation of wear of natural monocrystalline diamond cutting tool in single-point precision and ultraprecision machining processes of vitreous thermoplastic amorphous polymeric materials for various applications, for example, for photon-optical and bioengineering applications. In these investigations, we have been using up-to-date methods and devices, including Atomic Force Microscopy, interferometers and optical profilers, 3D Topographic Analysis Systems, optical-polarisable microscope, etc. Wear criteria were chosen as the technological criterion of the diamond tool cutting wedge clearance face wear, criterion of temperature rise and criterion of cut surface deterioration. The compulsory replacement of cutting tools on reaching of appointed value of wear allows to provide high quality level of the machined surfaces of the articles from polymers and their long durability.

Seeking the Finer Light

Manufacturers, engineers, architects, and researchers are using the precision, speed, and noncontact processes and achieve more control. Riegl Laser Systems of Horn, Austria, designed its 3-D LMS-Z210 imaging scanner to generate 240,000 laser measurement points within 30 seconds to create highly accurate images of complex structures without the need for conventional surveying. The National Institute of Standards and Technology in Gaithersburg, Maryland, is designing a laser-based system to track the myriad of tools, materials, and equipment on construction sites. Riegl Laser Measurement designed its LMS-Z210 3-D Imaging Scanner to serve in three-dimensional measurement applications that are too complex for traditional theodolites to survey, including shipyards, quarries, vineyards, and crime scenes. Riegl USA expects to begin several projects using the 3-D scanner to continuously monitor bulk material piles in the wood and corn processing industries to improve process management and control.

The Role of Precision Engineering in Manufacturing of the Future

High precision manufacturing, and thus the development of new and improved high precision processes and machines, has gained much greater prominence in the last decade. Many advanced technology products depend entirely on one or more components being manufactured to tolerances or dimensions in the micro-or even nanotechnology range. The paper gives a few examples and summarises today's state-of-the-art in dimensional measurement and servo motion control for instruments and ultra precision machine systems needed to meet this growing demand. A forward look is made at ‘atomic-bit’ engineering based on scanning tunnelling microscopy.

The effect of temperature and strain rate on the super-plastic behaviour of P/M in-100 superalloy

IN-100 is a very important superalloy, used in such industrial high-temperature, high-strength, applications as gas turbine blades, nozzles and wheels. Such parts are normally produced from cast alloy and complex heat-treatment is required to obtain the desirable fine-grained structure. An alloy of superior microstructure can be produced by powder metallurgy techniques. This greatly simplifies subsequent processing and enhances the hot ductility of the alloy within a certain range of temperature and strain rate. This paper reports the results of an investigation designed to establish the optimum range of conditions within which a low-carbon P/M IN-100 superalloy is superplastic. Enhanced hot ductility of the alloy is of considerable practical importance since it extends the range of possible manufacturing techniques to such precision processes as pressing, extrusion and forging.