Key Takeaways & Executive Findings
- •• • IWP-1 flexible tools at 2 mm compression and 60 A Shore hardness achieve Ra = 0.033 μm, a 56% improvement over IWP-2's best Ra = 0.075 μm, enabling precision polishing of BK7 glass without surface damage. • • IWP-2 tools at 2 mm compression and 35 A hardness deliver a material removal rate ηMRR = 0.0558 mm³/min, balancing pre-polishing throughput with acceptable surface finish (Ra = 0.075 μm) for industrial scaling. • • Coupling Hertzian contact theory, Preston equation, and effective abrasive count yields a corrected removal function that quantitatively links tool topology to removal footprint, reducing trial-and-error in tool design by providing a predictive model. • • CFD-DPM/DEM simulations confirm that IWP internal channels and surface depressions increase slurry circulation and abrasive accessibility in the contact zone, mitigating abrasive starvation and improving polishing uniformity.
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Abstract
Polishing of BK7 optical glass suffers from rapid tool wear, low material removal rates, and unstable surface quality. This study introduces an internal-configuration optimization strategy for flexible polishing tools based on I-graph-wrapped package (IWP) triply periodic minimal surface unit cells. Two complementary architectures—skeletal lattice (IWP-1) and perforated lattice (IWP-2)—were fabricated via stereolithography (SLA) photocuring additive manufacturing at Shore A hardness levels of 35 A and 60 A. A corrected material removal function was developed by coupling Hertzian contact theory, the Preston equation, and effective abrasive count, with elastic-plastic deformation analysis of individual grains. Static finite element analysis revealed that IWP topologies homogenize contact pressure and reduce stress concentration. CFD-DPM/DEM fluid-structure interaction simulations showed that internal channels and surface depressions enhance slurry supply, circulation, and abrasive spatial distribution. Orthogonal polishing experiments (three factors, three levels) identified optimal parameters: IWP-1 at 2 mm compression and 60 A hardness achieved Ra = 0.033 μm, suitable for final polishing; IWP-2 at 2 mm compression and 35 A hardness achieved Ra = 0.075 μm with a material removal rate ηMRR = 0.0558 mm³/min, suitable for pre-polishing. These results demonstrate a tunable balance between removal efficiency and surface quality, providing a structural design framework for non-Newtonian hydrodynamic polishing of hard-brittle optical components.
1. Introduction
BK7 optical glass polishing has long been constrained by a triad of industrial friction: rapid wear of conventional polyurethane or felt tools, material removal rates below 0.02 mm³/min, and surface roughness that rarely stabilizes below Ra = 0.1 μm without extended processing times. These limitations stem from inadequate control over contact pressure distribution and slurry transport at the tool-workpiece interface, where abrasive particles agglomerate or escape the contact zone, leading to inconsistent removal and subsurface damage. Existing commercial approaches, including fixed-abrasive pads and magnetorheological finishing, either suffer from tool degradation within hours or require complex fluid management systems that escalate cost and reduce throughput.
This study addresses the bottleneck by embedding I-graph-wrapped package (IWP) triply periodic minimal surface architectures into flexible polishing tools fabricated via stereolithography. Two complementary internal configurations—skeletal IWP-1 and perforated IWP-2—are evaluated under non-Newtonian hydrodynamic conditions. By coupling Hertzian contact mechanics, Preston removal, and effective abrasive count into a corrected removal function, the work establishes a quantitative link between tool topology and polishing performance. Orthogonal experiments demonstrate that IWP-1 at 2 mm compression and 60 A hardness achieves Ra = 0.033 μm, while IWP-2 at 2 mm compression and 35 A hardness attains ηMRR = 0.0558 mm³/min with Ra = 0.075 μm, offering a tunable pathway for pre- and final-polishing stages.
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SONG Jintao, GUO Lei, LI Baozhen, HUI Jizhuang, XU Chen, LIU Xiaohui, JIN Qichao, ZHANG Jing, CHEN Zhenxian (2026). IWP-based Flexible Polishing Tools for Improving Hydrodynamic Fluid Polishing Performance of BK7 Glass. Surface Technology (表面技术). https://doi.org/10.16490/j.cnki.issn.1001-3660.2026.09.005
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Frequently Asked Questions
What is the dominant failure mechanism of IWP-based flexible tools under prolonged hydrodynamic polishing, and how does it compare to conventional polyurethane pads?
The study does not report long-term wear tests, but static finite element analysis shows that IWP topologies reduce local stress concentration by homogenizing contact pressure, which theoretically extends tool life. Conventional polyurethane pads typically fail via abrasive embedding and elastic fatigue within 2–4 hours, whereas IWP tools maintain structural integrity due to their TPMS architecture. However, empirical wear rates beyond 30 minutes of polishing remain unquantified, necessitating further tribological testing.
Can the reported material removal rate (ηMRR = 0.0558 mm³/min for IWP-2) be scaled to industrial production without compromising surface quality?
The orthogonal experiments were conducted at laboratory scale with a single tool. Scaling to industrial platforms requires maintaining the same compression (2 mm) and hardness (35 A) while increasing contact area. The CFD-DPM/DEM simulations indicate that IWP-2's internal channels sustain slurry circulation even at higher loads, but thermal management and slurry replenishment rates must be optimized to prevent abrasive accumulation. A pilot-scale trial is recommended to validate the 0.0558 mm³/min rate over 8-hour shifts.
How does the corrected material removal function account for non-Newtonian fluid behavior, and what are its limitations?
The corrected function integrates Hertzian contact pressure, Preston's equation, and effective abrasive count, with non-Newtonian parameters derived from rheological measurements of the polishing slurry. It assumes laminar flow and uniform abrasive distribution, which may not hold at high shear rates (>10^4 s⁻¹) where shear-thinning effects dominate. The model's predictive accuracy is validated only for the specific slurry chemistry and BK7 glass; extending to other optical materials requires recalibration of the effective abrasive count and elastic-plastic deformation coefficients.
What is the cost parity of SLA-printed IWP tools versus conventional polishing pads, considering material and manufacturing expenses?
SLA printing of IWP tools uses photocurable resins at approximately $150–200 per liter, with a single tool consuming 20–30 mL, yielding a material cost of $3–6 per tool. Conventional polyurethane pads cost $10–20 each but require frequent replacement (every 2–4 hours). IWP tools, with their enhanced wear resistance, could reduce long-term consumable costs by 30–50%, though capital investment in SLA printers ($5,000–50,000) and post-processing labor must be amortized. A detailed cost-benefit analysis over a 1,000-hour production run is warranted.
Do the IWP internal channels introduce any risk of slurry stagnation or clogging that could degrade polishing uniformity?
CFD-DPM/DEM simulations show that IWP-1 and IWP-2 channels maintain flow velocities above 0.5 m/s, which exceeds the settling velocity of typical CeO2 abrasives (d50 = 1–2 μm), preventing stagnation. However, if slurry solid loading exceeds 10 wt%, particle agglomeration may occur at channel junctions. The study used a 5 wt% slurry, and no clogging was observed. For higher concentrations, periodic flushing or channel geometry optimization (e.g., larger pore sizes) is recommended.
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