I-POLISH is a computational fluid dynamic (CFD) platform to predict material removal distribution from two different surface enhancement processes - abrasive flow machining processes and robotic stream finishing processes. Abrasive Flow Machining Simulator
(AFMSIM) is used for the internal polish process while the Robotic Stream Finishing Simulator (RSFSIM) is for external polish. The platform is developed based on an open-source package - OpenFOAM, with Graphical User interface (GUI) for targeting
additive manufacturing (AM) engineers for easy adoption.
Fig 1. Illustration of I-POLISH CFD platform
For the development of I-POLISH, IHPC collaborated with the A*STAR's Institute of Materials Research and Engineering (IMRE), Advanced Remanufacturing and Technology Centre (ARTC), Singapore Institute of Manufacturing Technology (SIMTech), and the Nanyang
Technological University in the 2.5-year "Advanced Post-processing and Non-Destructive Evaluation for Additive Manufacturing" project funded by the AME Industry Alignment Fund. The project aggregates capabilities across the local ecosystem to address
the identified technology gaps and leverage IHPC's expertise in modelling surface enhancement processes and NDE techniques. IHPC also contributes to our "Digital Manufacturing Processes & Design" initiative that focuses on applying advanced simulation
and modelling and AI to design and manufacturing processes.
Fig 2. Demonstration of AFMSIM with GUI
Features
- Predict final AM products after internal (AFM) and external (RSF) surface finishing processes
- Optimise control parameters used in AFM and RSF through the CFD platform to reduce trial-and-error tests experimentally
- Integrate built-in graphical user interface (GUI) for AM engineers with basic CFD knowledge
- Build viscoelastic models into the AFMSIM with different types of wall slip boundary conditions
- Implement log-conformation tensor representation (LCR) approach for high Weissenberg number (We=λṙ, λ: relaxation time, ṙ : shear rate) to stabilise the simulations in AFMSIM
The Science Behind
Additive manufacturing (AM) has enabled the design and fabrication of components with complex internal geometry such as closed impellers, nozzles and mold inserts. However, rough as-printed
surfaces (Ra 5 µm – 15 µm for laser sintering and Ra 30 µm – 100 µm for electron beam melting) may cause problems such as carbon deposition, corrosion, and poor fatigue life, rendering the components unfeasible
for actual applications. Additive manufacturing exacerbates this problem, as components have complicated internal and external geometry that is not encountered previously due to limitations of traditional manufacturing methods. To meet the stringent
surface roughness requirements (e.g. Ra < 0.8 µm) in the respective industries, post-process surface finishing of AM components is required.
The methods to polish these AM products internally and externally are abrasive flow machining (AFM) and robotic stream finishing (RSF), respectively, as illustrated in Figs. 3 and 4. However, there are challenges when applying AFM and RSF on AM components.
Due to the high initial roughness of AM surfaces, the thickness of the material that needs to be removed is significant (typically 5 to 10 times the initial Ra). As a result, there could be a loss of dimensional accuracy after AFM and RSF processes.
Furthermore, the material removal (MR) distribution depends on the media flow field during AFM and RSF and typically not uniform. Thus, the final geometry after AFM and RSF is hard to predict and quantify.
 Fig 3. AFM Process
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Fig 4. Robotic Stream Finishing Setup |
IHPC develops a process model to simulate some processes and design iteration in a virtual environment. The model can predict local material removal across an AM surface would be a huge enabler of AFM and RSF technology. With predictable material
removal by I-POLISH, AM engineers can conduct material compensation during the AM design phase to ensure the dimensional accuracy of the final product after AFM or RSF. As there are currently no methodologies or commercial solutions to simulate
the AFM and RSF processes, I-POLISH seeks to address these problems and support AM engineers to minimise product iterations via trial and error.
Industry Applications
With the development of I-POLISH, we could establish excellent research and capability in post-processing for AM components and related fields for advanced manufacturing. Besides, innovative scientific excellence and industrial applicability are fundamentally
linked through I-POLISH. Moreover, potential AM end-users in Aerospace, Marine and Offshore and other AM related industries would be compelled to conduct AM R&D in Singapore. AM service bureaus can tap on IHPC’s expertise to become more
competitive and better able to attract new business. The potential industry applications for I-POLISH could be in Aerospace Engineering, Marine & Offshore and heavy machinery sector.
Reference
- Wu C.H., Kum, C.W., Wan, S. Y. M., Abu Bakar, A. M., (2020) Numerical and experimental investigation of abrasive flow machining of branching channels. International Journal of Advanced Manufacturing Technology. 108, pages 2945–2966(2020) DOI 10.1007/s00170-020-05589-z
- Kum, C.W., Wu C.H., Wan, S. Y. M., Kang, C.W. (2020) Prediction and compensation of material removal for abrasive flow machining of additively manufactured metal components. Journal of Materials Processing Tech. 282.
- IHPC-TD-FD-2017-021. Method, apparatus and system for measuring the rheology of freely slipping AFM media