On MBS Constraints and Projections

Constraints in multibody systems are usually treated by a Lagrange I - method resulting in equations of motion together with the constraint forces. Going from non-minimal coordinates to minimal ones opens the possibility to project the original equations directly to the minimal ones, thus eliminating the constraint forces. The necessary procedure is described, a general example of combined machine-process dynamics discussed and a specific example given. For a n-link robot tracking a path the equations of motion are projected onto this path resulting in quadratic form linear differential equations. They define the space of allowed motion, which is generated by a polygon-system.

A Framework for Measuring Relevancy in Discovery Environments

Discovery environments are ubiquitous in academic libraries but studying their effectiveness and use in an academic environment has mostly centered around user satisfaction, experience, and task analysis. This study aims to create a quantitative, reproducible framework to test the relevancy of results and the overall success of Washington State University’s discovery environment (Primo by Ex Libris). Within this framework, the authors use bibliographic citations from student research papers submitted as part of a required university class as the proxy for relevancy. In the context of this study, the researchers created a testing model that includes: (1) a process to produce machine-generated keywords from a corpus of research papers to compare against a set of human-created keywords, (2) a machine process to query a discovery environment to produce search result lists to compare against citation lists, and (3) four metrics to measure the comparative success of different search strategies and the relevancy of the results. This framework is used to move beyond a sentiment or task-based analysis to measure if materials cited in student papers appear in the results list of a production discovery environment. While this initial test of the framework produced fewer matches between researcher-generated search results and student bibliography sources than expected, the authors note that faceted searches represent a greater success rate when compared to open-ended searches. Future work will include comparative (A/B) testing of commonly deployed discovery layer configurations and limiters to measure the impact of local decisions on discovery layer efficacy as well as noting where in the results list a citation match occurs.

Defining an Optimized Machine Process Sequence to Address Broken Wafer Phenomenon on Semiconductor Products

Silicon wafer as a direct material is one of the vital parts of a semiconductor product. Wastages on manufacturing plants that pulls the yield down should be addressed innovatively and accurately. This paper focused on the phenomenon of broken wafers at wafer taping process during wafer preparation. Using a wafer taper machine, silicon wafers are covered by an industrial tape as preparation for the next process. During processing and wafers are placed on wafer boat, unexpected phenomenon of broken wafers due to unwanted falling was encountered. Findings was due to the unintentional dragging of the machine’s robot arm after wafer processing. The problem is resolved through simulation and experiments using statistical analysis. As a result, an optimized machine parameter setting was defined to eliminate the said rejection. Statistical analysis was of a big help in resolving the said phenomenon and improved the process yield of the manufacturing.

GPU accelerated voxel-based machining simulation

The simulation of subtractive manufacturing processes has a long history in engineering. Corresponding predictions are utilized for planning, validation and optimization, e.g., of CNC-machining processes. With the up-rise of flexible robotic machining and the advancements of computational and algorithmic capability, the simulation of the coupled machine-process behaviour for complex machining processes and large workpieces is within reach. These simulations require fast material removal predictions and analysis with high spatial resolution for multi-axis operations. Within this contribution, we propose to leverage voxel-based concepts introduced in the computer graphics industry to accelerate material removal simulations. Corresponding schemes are well suited for massive parallelization. By leveraging the computational power offered by modern graphics hardware, the computational performance of high spatial accuracy volumetric voxel-based algorithms is further improved. They now allow for very fast and accurate volume removal simulation and analysis of machining processes. Within this paper, a detailed description of the data structures and algorithms is provided along a detailed benchmark for common machining operations.

The Development of Efficient Contaminated Polymer Materials Shredding in Recycling Processes

Recently, a dynamic increase in the number of polymer elements ending their life cycle has been observed. There are three main ways of dealing with polymer waste: reuse in an unchanged form, recycling (both material and energy), and disposal (mainly in the form of landfilling or incineration). The legislation of European countries promotes in particular two forms of waste management: reuse and recycling. Recycling processes are used to recover materials and energy especially from contaminated waste, which are structurally changed by other materials, friction, temperature, machine, process, etc. The recycling of polymers, especially of multi-plastic structural elements, requires the use of special technological installations and a series of preparatory operations, including crushing and separating. Due to the universality and necessity of materials processing in recycling engineering, in particular size reduction, the aim of this study is to organize and systematize knowledge about shredding in the recycling process of end-of-life polymeric materials. This could help properly design these processes in the context of sustainable development and circular economy. Firstly, an overview of the possibilities of end-of-life plastics management was made, and the meaning of shredding in the end-of-life pathways was described. Then, the development of comminution in recycling processes was presented, with special emphasis given to quasi-cutting as the dominant mode of comminution of polymeric materials. The phenomenon of quasi-cutting, as well as factors related to the material, the operation of the shredding machine, and the technological process affecting it were described. Research conducted on quasi-cutting as a phenomenon when cutting single material samples and quasi-cutting as a machine process was characterized. Then, issues regarding recycling potentials in the context of shredding were systematized. Considerations included the areas of material, technical, energy, human, and control potentials. Presented bases and models can be used to support the innovation of creative activities, i.e., environmentally friendly actions, that produce specific positive environmental results in the mechanical processing of recycled and reused materials. The literature survey indicates the need to explore the environmental aspect of the shredding process in recycling and connect the shredding process variables with environmental consequences. This will help to design and control the processes to get the lowest possible environmental burdens.

Glue Voids Reduction on QFN Device through Material and Process Improvement

The paper is focused on the glue voids reduction on critical semiconductor quad-flat no-leads (QFN) device processed on a stencil printing type of die attach machine. Process optimization through material preparation improvement was done to mitigate the silver lumps of the sintering glue which is a main contributor on the voids occurrence. Eventually, the glue voids were reduced to less than the allowed 5% limit. For future works, the learnings and configuration could be used on devices with similar requirement.