In Jet Interferometry for Ultra Precise Electrolyte Jet Machining

超精密加工技术允许制造最高价值的部件。部件复杂性不断发展，研究人员面临的挑战是以更精确的方式去除更小体积的材料，同时保持工件的完整性。微加工、微放电/电化学加工和高速激光加工现在通常用于微电子、生物医学和航空航天工业的微元件制造。电解液射流加工（EJM）是一种较新的工艺，尚未被这些行业以有意义的方式所接受。该工艺本身有几个吸引人的能力，例如加工难以加工的材料的能力，而不会产生零件的热负荷，也不会产生残余应力。该技术的一个特别有趣的方面是，通过简单的修改，该过程也可以反向运行，作为一种增材制造技术来精确沉积材料。在这里进行的工作将使用诺丁汉大学定制的MkI原型EJM工具，该工具最近由调查员完成。除了能够进行材料表面加工外，它还具有独特的功能，代表了最先进技术的重大进步。研究人员在计算机控制的信号生成方面展示了一种新的功能，这种功能能够创建所谓的“拨号表面”或根据表面纹理/形态规范进行表面制造，而不仅仅是表面粗糙度。众所周知，加工过程中的表面纹理控制很难实现，因为表面状况通常决定了性能，因此高价值部件的价格很高。通常情况下，微观表面纹理是工程以外的几个研究小组感兴趣的。其中包括研究细胞/表面相互作用的生物医学研究人员，以及希望提高表面与流体相互作用性能的空气动力学家。为了释放EJM的全部潜力，必须创建新颖的机器仪表。该仪器必须能够快速、准确、高精度地收集过程数据，以支持实时自适应过程控制。它还应该允许进行机器表面测量，这是成功工业过程日益重要的要求。为了在研究环境中成功地利用EJM，并且作为一种可行的生产技术，必须对这一套新颖的过程仪表进行调查，然后开发，以便在过程进行时对机器进行准确和及时的计量。这里要研究的仪器将分为两个关键领域。首先，将设计并优化一种新型的射流激光干涉仪，用于EJM。该传感器将提供高速、高精度的过程控制测量数据。这将允许材料的去除率的过程和形式的材料去除面积直接符合射流被测量。此外，光纤装置将包括允许光束传输。由于EJM内的距离很短，因此可以使用高亮度光源（激光）向工件提供光斑。除了射流激光器外，两个额外的传感器将部署到机器头部，位于射流外部。这些将是定制设计的单线相干扫描干涉仪设备，配置为单线检测（以提高采集率）。这些技术将允许实时收集不同的数据集，这些数据集将通过控制算法进行操作，以执行在线加工和自适应加工。这代表了生产复杂和高价值零件的工艺可行性的一个步骤变化。

Ultra-precision machining techniques permit the manufacture of the most high value components. Component complexity continues to develop and researchers are challenged to remove smaller volumes of material in a more precise manner while maintaining work piece integrity. Micro-machining, micro electrical discharge/electrochemical machining and high speed laser processes are now commonly used for micro component manufacture for the microelectronics, biomedical and aerospace industries. Electrolyte Jet Machining (EJM) is a newer process which is yet to be embraced in a meaningful way by these industries. The process itself has several attractive capabilities, such as the ability to process difficult to machine materials with no resulting thermal loading of parts and no induced residual stress. A particularly interesting aspect of the technology is that, with simple modifications, the process may also run in reverse as an additive manufacturing technique to precisely deposit materials. The work to be undertaken here will make use of a custom built MkI prototype EJM tool at the University of Nottingham which was recently completed by the Investigators. As well as being able to perform material surface machining, this has unique capabilities and represents a significant advancement in terms of the state-of-the-art. The investigators have demonstrated a new functionality in terms of computer controlled signal generation which is capable of creating so called 'dial-up-surfaces' or surface manufacture against a specification for surface texture/morphology as opposed to surface roughness alone. Surface texture control within a machining process is notoriously difficult to achieve, commanding a premium price for high value components since surface condition often dictates performance. Typically, micro surface textures are of interest to several groups of researchers outside of engineering. These include biomedical researchers who study cell/surface interaction and aerodynamicists who look to enhance the performance of surfaces interacting with fluid flow. To unlock the full potential of EJM, novel on machine instrumentation must be created. This instrumentation must allow fast, accurate, high precision process data to be collected to support real-time adaptive process control. It should also allow for on-machine surface metrology to be undertaken which is increasingly an essential requirement for successful industrial processes. For EJM to be successfully exploited in both a research environment, and critically as a viable production technology this novel set of process instrumentation must be investigated and then developed to allow accurate and timely metrology to be undertaken on the machine while the process is under way. The instrumentation to be investigated here will be split into two key areas. Firstly, a novel form of in-jet laser interferometer will be designed and optimised for use with EJM. The sensor will provide high speed, high precision process control measurement data. This will allow the material removal rate of the process and the form of the material removal area directly in line with the jet to be measured. In addition a fibre optic arrangement will be included to allow beam delivery. Since stand-off distances are short within EJM this will be possible with a high brightness source (laser) to deliver a spot to the work piece. In addition to the in-jet laser two additional sensors will be deployed to the machine head, external to the jet. These will be custom designed single line coherence scanning interferometer devices, configured for single line based detection (to allow increased acquisition rates).These techniques will allow the collection of disparate data sets in real-time which will be manipulated through control algorithms to perform online processing and adaptive machining. This represents a step change in the viability of this process for the production of complex and high value parts.