Study on High-Performance Computing for Simulation of End Milling Force

Milling Process Simulation is one of the important re search areas in manufacturing science. For the purpose of improving the prec ision of simulation and extending its usability, numerical algorithm is more and more used in the milling modeling areas. But simulative efficiency is decreasin g with increase of its complexity. As a result, application of the method is lim ited. Aimed at above question, high-efficient algorithm for milling process sim ulation is studied. It is important for milling process simulation’s applicatio n. Parallel computing is widely used to solve the large-scale computation question s. Its advantages include system flexibility, robust, high-efficient computing capability and high ratio of performance to price. With the development of compu ter network, utilizing the computing resource in the Internet, a virtual computi ng environment with powerful computing capability can be consisted by microc omputers, and the difficulty of building hardware environment which is used to s upport parallel computing is reduced. How to use network technology and parallel algorithm to improve simulative effic iency for milling forces simulation is investigated in the paper. In order to pr edict milling forces, a simplified local milling forces model is used in the pap er. End milling cutter is assumed to be divided by r number of differential elem ents along the axial direction of the cutter. For a given time, the total cuttin g forces can be obtained by summarizing the resultant cutting force produced by each differential cutter disc. Divide the whole simulative time into some segmen ts, send these program’s segments to microcomputers in the Internet and obtain the result of the program’s segments, all of the result of program’s segments a re composed the final result. For implementing the algorithm, a distributed Parallel computing framework is de signed in the paper. In the framework, web server plays a role of controller. Us ing Java RMI(remote method interface), the computing processes in computing serv er are called by web server. There are lots of control processes in web server a nd control the computing servers. The codes of simulative algorithm can be dynam ic sent to the computing servers, and milling forces at the different time are c omputed through utilizing the local computer’s resource. The results that are ca lculated by every computing servers are sent to the web server, and composed the final result. The framework can be used by different simulative algorithm. Comp ared with the algorithm running single machine, the efficiency of provided algor ithm is higher than that of single machine.

3D阶梯模板在SMT特殊制程及器件上的应用技术

在当前的SMT生产制程中，由于某些电子产品SMD凹腔电路板（CarityPCB）设计、元器件高密度组装与特殊构造需要，以及通孔回流焊（Through—HoleReflow）器件、混合制程器件（HybridProcessComponent）、正反表面焊接连接器（DoubleSurfaceReflowSolderingDevice）等问题，令焊锡膏或胶的印刷与涂覆工艺，变得日益复杂与多样化。而一直来最具主流的普通平面型印刷模板（2DScreenStencil），便难以满足日新月异复杂工艺需求，于是非共面性阶梯模板（3DStencil）应运而生，它为解决SMT特殊制程及异型器件的焊锡或胶的印刷涂覆问题，正发挥着日益重要的作用。3DStencil的设计多种多样且用途广泛，它适宜各种较为复杂的PCBA组装工艺需求，可用在各种较为前端的特殊而复杂的工艺产品上。传统的非共面性3D模板，通常有局部减薄模板（Step—downstencil）、局部加厚模板（Step—upstencil）或两种工艺同时在一块模板上应用，模板的局部加厚或减薄的阶梯高度，通常需依据PCB板面的凹陷或凸起高度以及元器件的特点灵活应对，且加厚或减薄的阶梯既可放在模板装锡膏的印刷面，也可放在模板的底面。而时下的精密特制3D阶梯型模板，其模板钢片厚度与普通2D模板无异，但阶梯高度可达N20mm它足以避让底部多数己组装的SMD器件或AI器件剪脚后的高度。这种模板通常称之为VectorGuard3DStencil，由于它能够对己贴片组件展示出全方位的立体屏蔽保护而得名。3D阶梯模板在设计制作过程中，需重点关注其脱模性能与模板的使用寿命，力求使其既有良好的印刷效果又能经久耐用。在各种模板的制作工艺中，电铸成形模板和激光切割／电抛光模板的印刷性能较好，而以激光切割加电抛旋光性价比最高；对于印刷工艺的优化，模板的设计是关键的一环。为了使焊锡膏的脱模性能达到最好，模板上的开孔尺寸比率以及开孔性能应当按照行业标准设计，其开口的宽厚比、面积比、开孔梯度、开口侧壁的光洁度等方面都有严格要求。多半情况下，通过3D阶梯模板能够解决的SMT特殊制程及器件的工艺难题，也能通过非接触式喷印（JetPrinting）或针头点涂（Dispenser）的工艺方式解决。不过机器喷印或点涂的方式，不仅前期设备投资巨大，而且它们对于高密度设计的PCB和精细间距器件（FinePitchTechnology），在组装精度、质量和效率等诸多方面都还受到限制，很多时候还不及3D模板实用有效。