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Abstract
High-quality part surfaces with high surface finish and form accuracy are increasingly in demand in the mold/die and optics industries. The computer-controlled polishing (CCP) is commonly used as the final procedure to improve the surface quality. This paper presents a theoretical and experimental study on the polished profile of CCP with sub-aperture pad. A material removal model is proposed based on the evaluation of the amount of material removed from the surface along a direction orthogonal to the tool path. The model assumes that the material removal rate follows the Peterson equation. The distribution of the sliding velocity at the contact region is presented. On the basis above, the approaches to calculate the polished profiles are developed for the sub-aperture pad polishing along a straight path and a curved path. The model is validated by a series of designed polishing experiments, which reveals that polishing normal force, angular spindle velocity, feed rate and polishing path all have effects on the polished profile. The result of experiments demonstrates the capability of the model-based simulation in predicting the polished profile.
NOMENCLATURE
| CCP | = | Computer-controlled polishing |
| MRIh/l | = | Material removal index |
| Fn | = | Polishing normal force |
| h | = | Depth of material removal |
| Hv | = | Hardness of the workpiece |
| k | = | Peterson coefficient |
| kn | = | Normal curvature of the tool path |
| kg | = | Geodesic curvature of the tool path |
| Pc | = | Contact pressure |
| Rp | = | The radius of contact circle |
| R | = | Geodesic curvature radius of the tool path |
| Sh | = | A theoretical parameter defined by Equation (30) |
| T | = | Dwelling time |
| vs | = | Relative sliding velocity |
| va | = | Feed rate |
| vm | = | Velocity due to the tool rotation |
| wp | = | Angular spindle velocity |
| wq | = | Feed angular velocity around the point O |
| y, z, c | = | Path tangent, surface normal and path curvature, respectively (Figure 2) |
| θ | = | As defined in Figure 3 |
| φ | = | As defined in Figure 4 |
| δ | = | Included angle between vm and va (Figure 3) |