Modeling of electric fields during electrostatic coating of metallic substrates in fluidized beds

Abstract

Electrostatic powder coating in fluidized beds is a technique that has been known for more than 30 years. The present paper attempts to model the changes in the electric fields produced by the progression of the powder coating layer on the surface of a metallic wire substrate immersed in a fluidized bed of charged powder. The intersections of wire geometries often present coating difficulties due to Faraday cage effects. The current modeling will show that as powder deposits on the substrate on areas where the electric field is strongest, the electric field is enhanced in the original weaker areas thus promoting powder deposition towards the intersections. Also, the effects of varying the size of the fluidized bed are investigated and show that as the bed size increases, while the substrate size remains constant, the electric fields in the bed increase significantly; however, the electric field enhancement at the intersections of the substrate decreases. Varying the charge density of the deposited paint layer on the metallic substrate shows that a minimum charge density of deposited powder is required for the electric field enhancement phenomena to occur. The current modeling employs commercially available Finite Element software.

Development of smooth finishes in electrostatic fluidized bed (EFB) coating process of high-performance thermoplastic powders (PPA 571 H)

“…Since the 1970s, powder coaters have paid particular attention towards fluidized bed coating processes, being considered low cost and environmental friendly alternatives to traditional coating and painting processes [1][2][3][4][5][6][7][8][9]. Early on, fluidized bed processes were mostly in use to coat small batches of large metallic parts, which were first preheated at high temperature (at least 300-350 • C) and, then, dipped in the bed of fluidized powders [3][4][5][6], generally a thermoplastic polymer.…”

“…Early on, fluidized bed processes were mostly in use to coat small batches of large metallic parts, which were first preheated at high temperature (at least 300-350 • C) and, then, dipped in the bed of fluidized powders [3][4][5][6], generally a thermoplastic polymer. Later, more sophisticated fluidized bed processes, based on electrostatic techniques, were adopted to coat also large volumes of small and complex shaped parts [7][8][9]. In that case, the coated parts had to be baked in order to melt the layers of electrostatically deposited powders and consolidate them in the form of a continuous film [8,9].…”

“…Later, more sophisticated fluidized bed processes, based on electrostatic techniques, were adopted to coat also large volumes of small and complex shaped parts [7][8][9]. In that case, the coated parts had to be baked in order to melt the layers of electrostatically deposited powders and consolidate them in the form of a continuous film [8,9]. In recent times, fluidized bed coating has been successfully * Corresponding author.…”

Fluidized bed coating of metal substrates by using high performance thermoplastic powders: Statistical approach and neural network modelling

“…In fact, just one analytical model is proposed in the literature and it is referred to thermoset coatings (Barletta and Tagliaferri, 2006b). Besides, the available finite elements models are mostly focused on the determination of electrical fields and they do not provide any coating thickness trends (Ali and Inculet, 2000a). Anyway, they can be assessed as first approximation models, plenty of limiting assumptions and lacking of accurate calibration procedures based upon reliable experimental data (Ali and Inculet, 2000a, b).…”

Development of matte finishes in electrostatic (EFB) and conventional hot dipping (CHDFB) fluidized bed coating process

“…In nineties, Leong et al developed experimental and numerical studies about correlation among film properties and substrate materials and geometries in CHDFB coating process [6]. Inculet and co-workers modelled the relationship between part shape and film uniformity in both electrostatic and tribo-charged fluidized bed [7,8]. More recently, Barletta et al built first approximation models describing the trend of average roughness of polymeric film deposited by EFB [9,10] and CHDFB [11,12] by varying the deposition conditions.…”