Development of novel abrasive finishing process to achieve final net shape of complex metal additive manufactured components

5.技术方法：该项目旨在开发用于精加工金属增材制造部件的新型机械转换工艺，以实现1）表面抛光达到所需标准（M1：第6个月）2）精加工增材制造部件以纠正公差（M2：第9个月）3）去除内部支撑结构（M3：第12个月）（M3dixB）。CAM将设计和制造一种新颖的磨料流抛光工艺，该工艺采用泵驱动磨料介质的可逆流动，用于多个AM部件。流量将由工业尺寸的蠕动泵或气动泵通过定制的腔室提供，腔室具有分隔批次中每个AM部件的隔室，以防止部件之间的碰撞，同时保持360度自由旋转。由于AM部件中的小孔，目前可用的抛光介质可能必须以新的组合混合以实现期望的效果。CAM将调查旋转抛光机中的时间和研磨介质，以产生不同的抛光效果。CAM将研究新型再生玻璃抛光介质（Vibraglaz）在振动碗中去除内部支撑结构。合适的增材制造试件将在内部设计和制造。将记录抛光介质和时间的逐步变化，并通过光学（内部）和SEM（STFC）显微镜、摄影和外表面光洁度评价人员测量结果。项目主任将管理进度和报告。CAM将通过由学术界、设备公司和最终用户组成的咨询委员会寻求外部技术支持。这将包括来自利物浦约翰摩尔大学和STFC的成员。人们一直在寻找替代技术，但目前还没有标准工艺可用于为金属AM部件提供指定的形状或测量。虽然液体抛光和电解抛光可以提供表面光洁度，但它们强调AM部件的不均匀表面（附录B）。一些增材制造公司使用CNC加工来生产最终形状，但是这种方法无法进入增材制造零件的内表面。6.创新：3RTP为英联邦运动会创造了钛AM女王接力棒，他们将外表面抛光到高镜面光洁度，并将内部保持为自然光洁度作为艺术效果。这种方法不能用于许多工业过程，因为对于食品生产，所有表面都需要按照相同的规格进行精加工。其他AM公司使用CNC加工来完成他们的AM零件，这对于具有外部可加工表面的零件是可能的。其他增材制造用户，如航空航天公司正在追求更复杂的零件的精加工，但通过文献检索尚未发现有关这些工艺的信息。对网格AM部件的机械精加工进行的CAM测试确定了对工具和劳动力的需求，因此可能效率低下（图3）。因此，该项目是创新的，因为它旨在开发新的精加工工艺，通过操作新的介质组合，并通过在自由旋转的零件批次上设计磨料流工艺来抛光内表面，以提供高规格的精加工和某些工业标准所需的公差。在专利搜索中没有发现类似的磨料流设计。此外，去除内部构建结构允许AM部件设计有更多的内部复杂腔室，这些腔室由于保留的构建支撑结构而目前无法使用。这些创新将通过金属AM开发最终零件形状生产，减少劳动力并提高该技术的能力，以提供高规格零件和额外的复杂性。7.在此阶段识别的一些风险见附录B。已识别的风险包括：低风险：小孔径所需的小尺寸研磨介质可能无法充分通电以抛光金属AM部件。通过改变介质的速度、方向和组合可以提供更多的能量。AM部件边缘因过度暴露于介质而产生的研磨毛刺：时间和类型。解决方案是在短时间间隔内进行检查，以确定这种影响，然后改变测试参数，即时间，介质类型。中等风险：金属AM部件的外表面可能在内部部件之前进行抛光，导致所需的外部尺寸减小。这可以通过将超声波能量引入磨损介质来增加能量来降低。抛光不均匀：可能需要引入夹具来固定零件并旋转零件。由于记录保存和审查不充分，项目可能无法顺利进行。CAM和外部顾问将监控所有实验，整理结果，并确保及时交付项目。高风险：磨损流处理器可能无法工作，管路可能因逆流而磨损。CAM工程师有能力评估问题，提供解决方案并调整策略以实现预期结果，从而降低定制处理器可能无法实际工作的风险。然而，磨料抛光实现金属AM部件的最终形状的能力是未知的，但初步测试表明可以进行改进。

5. Technical Approach: This project aims to develop novel mechanical conversion processes for finishing metal AM parts to achieve 1)surface polish finish to required standards (M1: month 6) 2)to finish AM parts to correct tolerances (M2 month 9) 3) remove internal support structures (M3: month 12)(AppendixB). CAM will design and fabricate a novel abrasive flow polishing process with pump energised reversible flow of abrasive media for multiple AM parts. Flow will be provided by an industrial sized peristaltic or pneumatic pump through a customised chamber with compartments to separate each AM part in the batch, to prevent part on part collisions whilst retaining 360 free rotation. Due to the small apertures in the AM parts currently available polishing media may have to be mixed in new combinations to achieve the desired effect. CAM will investigate timings and abrasive media in a rotational polisher to produce different finishes. CAM will investigate novel recycled glass polishing media (Vibraglaz) in a vibratory bowls to remove internal support structures. Suitable AM test pieces will be designed and built inhouse. Stepwise changes in polishing media and timings will be recorded and results measured by light (inhouse) and SEM (STFC) microscopy, photography and external surface finish evaluators. A project director will manage progress and reporting. CAM will seek external technical support through an advisory board formed from academia, equipment companies and end users. This will include members from Liverpool John Moores University and STFC. Alternative techniques have been sought, but currently there are no standard processes available that deliver specified shape or measurement for metal AM parts. Whilst liquid finishing and electro-polishing can provide a surface finish, they emphasise the uneven surface of AM parts (Appendix B). Some AM companies use CNC machining to produce final shape however this method cannot access internal surfaces of AM parts. 6. Innovation: 3RTP created the titanium AM Queen's Baton for the Commonwealth Games, they polished the external surfaces to a high mirror finish and left the inside as natural finish as an artisitic effect. This method cannot be used in many industrial processes as for food production all surfaces would be required to be finished to the same specification. Other AM companies use CNC maching to finish their AM parts, this is possible for parts with external machineable surfaces. Other AM users eg aerospace companies are pursuing finishing on more complex parts however as yet no information on these processes has been identified through literature search. CAM tests on mechancal finishing for latticework AM parts identified a need for tooling and labour, therefore potentially inefficient (AppendixB). This project is therefore innovative as it aims to develop novel finishing process that would allow internal surfaces to be polished by the manipulation of new combinations of media, and by the design of abrasive flow process over freely rotating batches of parts to deliver high specification finishes and tolerances required for certain industrial standards.No similar abrasion flow designs were found in patent searches. In addition the removal of internal build structures allows AM parts to be designed with more internal complex chambers that currently would not be employable due to the retained build support structures. These innovations would develop final part shape productionby metal AM, decrease labour and advance this technology's capabilities to deliver high specification parts and additional complexity. 7. Some Risks identified at this stage are shown in Appendix B. Identified risks include: Low Risk: The small sized abrasion media required for small apertures may not be energised sufficiently to polish metal AM parts. More energy could be supply by altering speed, direction and combination of medias. Abrasive burring of AM part edges through over exposure to media: time and type.Solution is to examine at short time intervals to identify this effect then change test parameters ie time, media type. Medium Risk: While external surfaces of metal AM parts may be polished before the internal parts leading to decreases in desired external dimensions. This may be decreased by increasing energy by the introduction of ultrasonic energy to abrasion media. Uneven polishing: may have to introduce jigs to hold parts in place and rotate parts. Project may not progress well due to inadequate record keeping and review. CAM and external advisors will monitor all experiments, collate the results and ensure that timely delivery keeps project on track. High Risk: Abrasion flow processor may not work, tubes might be worn away due to reverse flow. CAM engineers have the ability to assess problems, provide solutions and adapt strategies to achieve the desired result thus decreasing the risk that the customised processor may not physically work. However the ability of abrasive polishing to achieve final shape for metal AM parts is unknown, but preliminary tests suggest that improvements can be made .