Process modeling for robotic polishing
Abstract This paper presents the solutions adopted for a robotic polishing cell for mold manufacturing. Mold finishing is frequently carried out manually; these kinds of operations are iterative, time consuming and require experience. Automation can introduce cost reduction minimizing production times on such manual finishing operations. The research shown in this paper provides an overall solution without discarding aspects that could be relevant to the task considered in the mold making environment. Most of the mold makers usually employ CAD/CAM systems in order to design workpieces and to prepare the CNC programs to manufacture the parts, this CAD data can also be used to prepare programs for the actual robot finishing of these parts. In this work, an automatic planning and programming system based on data from a CAD system is described. The direct use of the paths implies difficulties of adaptation mostly when free-shaped surfaces are treated, so that the use of a constant contact force control has also been considered. To accomplish the automation of the process it is necessary to establish a behavior model of the system’s variables. This fact allows the definition of the task specifications of the tools and, as a result, both the planning system and the control strategy by stages of the polishing process.
Polishing process planning based on fuzzy theory and case-based reasoning
Process planning is a key step for obtaining high machine quality and efficiency in the polishing. By studying the polishing process planning idea of the skilled technician, a novel process planning method combining with artificial intelligence principle is proposed in this paper. Polishing planning model based on fuzzy theory and case-based reasoning (CBR) technology is investigated in detail, which consists of fuzzy comprehensive evaluation of material machinability, case retrieval, case inference, and case modification. Fuzzy comprehensive evaluation standard based on material physical mechanics performance index is used for determining material cutting performance level. Specific steps are as follows: establishing the factor set, establishing the weight set, establishing evaluation set, fuzzy evaluation of single factor, and fuzzy comprehensive evaluation. The primary cases are chosen according to the grade of material cutting performance. In case retrieval, all primary cases are retrieved in terms of the nearest neighbor principle and the similarity between two cases is calculated according to Euler distance. The retrieval features include the surface roughness before polishing, material characteristics, and the surface roughness requirements after polishing. In the case inference, the method of the cross-correlation coefficient is used for reasoning all cases retrieved in order to evaluate the impact of each process parameter on the surface quality and identify the relevance of each process parameters on the surface quality. In the case modification, the methods of linear extrapolation and parameter adjustment are used for adjusting and revising the process parameters of case retrieved according to the correlation coefficients. At last, example verification is finished and the experiment results are generally acceptable. It is concluded that it is feasible to solve the problem of polishing process parameters selection using this method.
Mucoadhesive Nanoparticles for Drug Delivery to the Anterior Eye
While the use of topical drops for the delivery of drugs to the anterior of the eye is well accepted, it is far from efficient with as little as 5% of the drug instilled on the eye actually reaching the target tissue. The ability to prolong the residence time on the eye is desirable. Based on the acceptability of 2-hydroxyethyl methacrylate based polymers in contact lens applications, the current work focuses on the development of a poly(2-hydroxyethyl methacrylate (HEMA)) nanoparticle system. The particles were modified to allow for degradation and to permit mucoadhesion. Size and morphological analysis of the final polymer products showed that nano-sized, spherical particles were produced. FTIR spectra demonstrated that the nanoparticles comprised poly(HEMA) and that 3-(acrylamido)phenylboronic acid (3AAPBA), as a mucoadhesive, was successfully incorporated. Degradation of nanoparticles containing N,N′-bis(acryloyl)cystamine (BAC) after incubation with DL-dithiothreitol (DTT) was confirmed by a decrease in turbidity and through transmission electron microscopy (TEM). Nanoparticle mucoadhesion was shown through an in-vitro zeta potential analysis.