Issue link: https://www.e-digitaleditions.com/i/1040345
30 POWDER COATING, October 2018 Part rotation for custom coating Scott Rempala Mighty Hook Richard Dooley Mighty Hook Custom coating applications often run into limita- tions imposed by system design or by coverage com- plications due to a part's geometry. In these instances, part rotation becomes a necessary step of the process. This article examines part rotation devices and options that will help you meet your coating quality and production efficiency requirements. M ost coating operations benefit from hanging product within the horizontal and vertical plane of the conveyor, making coating as well as loading and unloading of parts relatively straight - forward. However, there are several instances where this is not practical or feasible. In many of them, some process of rotation or repositioning of the work product is required for either proper coating cover - age or to simplify the loading and unloading process. This article examines the different types and meth- ods of part rotation and how to determine which is best for your finishing line. Rotation applications There are several different applications that require part rotation or hanger repositioning. Here are a few examples: • Loading and unloading or transfer from single side of conveyor • Spraying both sides of a rack from a single side of the booth (180-degree rotation in booth) • Spraying geometrically challenging parts (90-degree rotation in booth) • Continuous rotation of radially symmetrical (cylindrical) parts in booth • Preventing rack-to-rack contact in accumula- tion zones of power-and-free systems • Close pack arrangement in ovens of power- and-free systems • Improved spray access to transverse mounted racks (45-degree rotation in booth) • Increased clearance of parts on inclines and declines The first four examples listed represent about 80 per- cent of the applications for custom coating and OEM requirements. The first two describe limitations imposed by system design and the latter two are lim- itations imposed by coverage complications due to the coated part's geometry. Since these make up the majority of rotational requirements, they will remain the focus of this article. Rotation devices Common terms which have been used to describe the devices that provide the required rotation are rota- tors or indexers. The term rotator usually connotes continuous or intermittent rotation in one direction, while indexer refers to a mechanism that moves back and forth from a detented position. A detent is a design feature creating a mated depression that requires additional force to move it to another posi - tion. Either type can be actuated manually or mechanically. The terms rotators or indexers are often used interchangeably. The simplest and most familiar device is a ball bear- ing or skate wheel rotator, as shown in Figure 1. This rotator turns freely in either direction and is usually manually actuated by hand, turning the rack, hanger, or hook to the desired position. Skate wheel rotators are sometimes fitted with a sprocket and can be friction actuated by a track (see Figure 2) or by a powered, variable speed track. The main ben - efit of this type of rotator is that it is usually the least expensive of the rotator options and typically in stock by most qualified vendors. Potentially obvi- ous limitations to this type of rotator are the limited weight load capacity and the fact that the rotator can freely rotate anywhere and everywhere in the coating system. Another standard option is a cast metal rotator, as shown in Figure 3. These utilize a small detent to pro- vide an indexing function at 90-degree increments. Again, limitations are weight load capacity and that the Technical Article Hanging and Racking