Ding Yucheng

A new hollowing process for rapid prototype models

A new method of hollowing rapid prototype models based on STL models and their cross‐sectional contours is presented to meet the demands of hollowed prototypes in casting and rapid prototype manufacturing. Offsetting along the Z‐axis and cross‐sectional contour offsetting are employed to perform the hollowing operation. The process performs two‐dimensional Boolean operations on the polygons made by the offset contours of cross‐sectional contours instead of three‐dimensional offsetting of the STL models. This hollowing operation is especially suitable for hollowing STL models with free‐form surfaces. Detailed algorithms are described to generate the correct offset contours of an STL model. Adopting this method, the hollowing process is dramatically simplified and becomes more efficient. This method has been verified by practical case studies, and it is proved that this simplified hollowing operation can reduce the prototype build time and cost.

Theory and simulations of peel demolding for large-area nanoimprint lithography

Nanoimprint lithography (NIL) is an emerging nanopatterning approach for producing large-area micro/nano scale structures with low cost, high throughput and high resolution. Demolding has now been considered as one of the most challenging issues for large area NIL, and a bottleneck hindering the industrialization of full wafer NIL. Peel demolding mode has been proven to be an effective way implementing large area nanoimprinting. This paper investigated the theoretical model and numerical simulation of peel demolding for large are NIL. A general model estimating demolding force was established based on the combination of the strain energy method and the conservation of energy in demolding stage. The required separating force for vertical demolding of grating patterns was achieved using the proposed model. Furthermore, the influence of the properties of mold materials and the aspect ratio of feature patterns for peel demolding was revealed by numerical simulation using ABAQUS software. These findings are valuable in providing a theoretical basis for large area NIL, optimizing demolding process and further enhancing the performance of full wafer NIL tool.

Nanopositioning and Nonlinearity Compensation for Step Imprint Lithography Tool

In this paper, the motion mode and nanopositioning accuracy in the step imprinting lithography process are presented, and the positioning errors different from the traditional errors, such as the gap error existing in the hinges of the stage structure and the random error produced during the process of the stage position adjustment, are analyzed. To avoid and eliminate these nonlinearity errors, radial basis function-proportional integral derivative and position control algorithms are introduced into the macro- and microdriving processes, respectively. The innovation of this driving method is that the motion locus is monotone, nonoscillatory, and a multistep approaching target, which eliminates the root of the random error by single direction driving mode and avoids the backlash error through preloading function. Driving experiments of different motion ranges prove that this nonlinearity compensation is very effective and the positioning accuracy during the step imprinting process can be improved up to 10-nm.

A cross-sectional image measuring system based on NC milling machine

It is especially difficult to capture both exterior and interior shape data of a complex part with high accuracy and low cost by using the current reverse engineering measuring methods. This paper presents a novel cross-sectional imaging measurement system for reverse engineering based on existing NC milling machine, which can simultaneously acquire the full cross-sectional contours of a part with complex external and internal surfaces. The principle and architecture of the system are described. Furthermore, some key issues to implement the measuring system are discussed in detail. Finally, a real case is employed to illustrate the applications of the system. As a result, this system provides a feasible and useful scheme for many enterprises to construct their own reverse measuring system based on existing equipments to aid rapid product development and extend the function of existing equipments. It will potentially find widespread application in industrial reverse measurement due to its advantages including high accuracy, rapid construction and low cost.