Current challenges and potential directions towards precision microscale additive manufacturing – Part I: Direct ink writing/jetting processes

This paper is the first in a series of articles which comprehensively discuss the state-of-the-art in microscale additive manufacturing processes and present solutions to challenges impeding their scalability. In this paper, a class of additive manufacturing techniques known as Direct Ink Write/Jet Processes are explored which have been used by researchers for fabrication of microscale parts with varying geometric freedom. The paper identified the key challenges to high throughput 3D microfabrication using these processes, by analyzing the material constraints, geometric constraints, feature-size resolution limits and throughput limits. While some of these challenges can be overcome by novel precision engineering approaches, there are several others which need an acute understanding of material systems, process parameters and critical components. This paper identifies these challenges and suggests potential approaches to eliminate them with the goal of fabricating true-3D parts at high throughputs.     

Current challenges and potential directions towards precision microscale additive manufacturing – Part III: Energy induced deposition and hybrid electrochemical processes

The Part III of the four-part series of articles discusses the challenges and opportunities in microscale additive manufacturing processes, specifically focusing on energy-induced deposition and electrochemical processes. Compared to the direct ink write (DIW) and laser-based processes, the energy-induced deposition methods can fabricate high-resolution, high aspect ratio and complex parts, while the hybrid electrochemical process can be used to fabricate complex parts using a wide range of conductive and photoactive materials. However, the volumetric throughput of these processes is lower than their DIW and laser-based counterparts. The processes that have been explored in this process are Focused-ion Beam Induced Deposition (FIBID), Laser Chemical Vapor Deposition (LCVD), Menicus-confined Electrodeposition (MCED) and Laser-Enabled Electrochemical Printing (LECP). The range of processable materials, feature-size resolution, geometry and volumetric throughput are used as factors to evaluate the current state-of-the-art for these processes. Novel approaches have been proposed in the article to address these challenges associated with microscale AM processes.     

Technology and system of constraint programming for industry production scheduling — Part I: A brief survey and potential directions

The use of techniques and system of constraint programming enables the implementation of precise, flexible, efficient, and extensible scheduling systems. It has been identified as a strategic direction and dominant form for the application into planning and scheduling of industrial production. This paper systematically introduces the constraint modeling and solving technology for production scheduling problems, including various real-world industrial applications based on the Chip system of Cosytec Company. We trend of some concrete technology, such as modeling, search, constraint propagation, consistency, and optimization of constraint programming for scheduling problems. As a result of the application analysis, a generic application framework for real-life scheduling based on commercial constraint propagation (CP) systems is proposed.     

Analysis of Double-Row Tapered Roller Bearings,Part II – Results: Prediction of Fatigue Life and Heat Dissipation

The model developed to predict the performance of double-row tapered roller bearings (DRTRB) and described in the first part of the paper is now exemplified. For a given example results on the internal load distribution, bearing fatigue life and hear generation are presented and discussed for various operating conditions including the mounting preload. It is revealed that some sliding occurs at the contact between the rollers and the cone that contributes significantly to the total power dissipated within the bearing. It is also shown that an optimum axial compression (or mounting preload) may be found in terms of fatigue life and heat dissipated. As the main conclusion the initial compression between bearing rows was found to play a major role upon the bearing behavior and therefore should be considered carefully for each application.     

Effects of Gas Composition,Humidity and Temperature on the Tribology of the Head/Disk Interface—Part II: Model and Analysis

A qualitative model for the effect of water condensation on the frictional behavior of unlubricated and lubricated carbon-overcoated disks is presented. The model suggests that for unlubricated disks adsorbed water acts as a lubricant, protecting the unlubricated disk surface from direct solid/solid contact and direct exposure to the environment. For lubricated disks, the interaction between adsorbed water and lubricant molecules seems to be responsible for the effect of humidity on the frictional behavior of lubricated disks. The effect of temperature on the frictional behavior of the head/disk interface is discussed in terms of surface energy, lubricant viscosity and mobility.     

Antiwear Film Formation by ZnDTP,Detergent, and Dispersant Components of Passenger Car Motor Oils—Part II: Effects of Low-Molecular-Weight Dispersant on Film Formation

Passenger car motor oils (PCMOs) are undergoing a rapid evolution. Studies have found that some exhaust emission catalysts may be deactivated by phosphorus, largely derived from zinc dialkyldithiophosphate (ZnDTP), the mainstay antiwear and antioxidant agent in PCMO formulations for the past 50 years. Consequently, future engine oils will contain significantly reduced phosphorus levels. Since ZnDTP is the dominant antiwear and antioxidant in current PCMOs, lower phosphorus content will impact engine oil formulation strategies.

To better understand the effects of ZnDTP reduction on wear control, electrical contact resistance (ECR) studies have been carried out on blends containing ZnDTP, detergent, and low-molecular-weight (LMW) succinimide dispersant. In contrast to previous results obtained with high-molecular-weight (HMW) dispersant, the combination of ZnDTP and LMW dispersant gave an ECR trace closely resembling that of ZnDTP alone. Thus, the chemical structure of the succinimide dispersant can have a profound effect on ZnDTP antiwear film formation. ECR experiments on three-way combinations of ZnDTP + LMW succinimide dispersant + overbased phenate detergent provided a much better film than that from a similar formulation using an HMW succinimide dispersant. This study demonstrates that the ECR experiment is sensitive to the chemical structures of components controlling the function of modern PCMOs, making ECR a convenient tool to optimize the performance of the remaining ZnDTP in lower phosphorus PCMO formulations.