I don't really see where the huge time savings are going to take place on your substrate, truth be known. Electrostatic Application (e-stat) has it's time and place as well as fluidized bed coatings. I just happen to think you are going to be over engineering the wheel, if I may be so bold. As far as designing a rack.... the parts themselves can become thier own rack. Just for giggles.... let's set up an example with make believe "widgets", shall we?
Widgets are 1 3/4" X 8" long box tubing (look familiar?)
Now..... take and make a "hook" so that it looks like this "[". Make about 50 of them. Good.... now insert the top portion of the 90-degree angle into the open end of the widget. Do the same with the other side now. You now have a widget with two of these "[..........]" on either side.... With me so far? Good. Now....take another widget and hang on the free ends of those hooks. See how you just magically linked those together? One widget right on top of the other and now connected by a metal hook. Repeat this process linking widget to widget until you have maybe 8 or so of them together. Looks like a bunch of widgets chained together by hooks, right? You just made the widget the rack, my friend. Simple as that. Now you've just increased production time by 700%, therefore blowing the theory out of the water that fluidized beds would be faster in this example. ( I keep telling you people it's all in the prep! pay attention next time I speak,lol). To finish your "widget rack"...just take two more of those hooks and bend the top portion into something that resembles a coathanger type of curve (enough so that it will hang on a steel bar) for the top part. Now repeat the ENTIRE process as many times as need be to fill your oven chamber. This process will get you "volumetric efficiency". They will coat like a DREAM and depending on oven size.... you may be able to fit a few hundred widgets into the oven to be fired all at once. Coat them all, bake them all at once and you are now done. While your operator is waiting for the parts to bake and cure, he can be setting up for the next round or coating something else while the oven comes up to temperature. ( See how cost effective this is becoming now,hummmmm?). The whole process of an oven load of widgets in that manner should take you no longer than an hour or so. (the more you do things, the faster you will become at them). Again.... these widget numbers are just an example, as I do not know what oven size you have. Adjust accordingly.
The fact of all that is...... you just made "e-stat" tons faster and operator friendly ( e-stat is a set it and forget it type of thing.... fluid beds need your FULL attention while in process). I still say that your very own "widget" application is best suited for a powder gun and I stand by that fact. Again.... send a test piece out via U.S. Postal or UPS to anybody willing to help you out ( be fair and pay these guys a bit for what they do, please. Also guys.... be fair and help him out for he's in the same boat you are, basically!) to see what you should expect. It's a real world example, I say.
As far as coverages are concerned, yes. The powder will have a wrap around effect. This is where powder coatings excel. Electrostaic coatings (liquid AND powder) attract to any surface with a ground. It builds up in one area...then keeps wanting to find the path of least resistance. Therefore.... keeps moving to fresh metal.
Also... Yes, moisture and humidity WILL be a problem in fluidized bed applications. You are exposing the surface area of the polymer to ambient air multiplied by thousands..... no, millions of times what you would normally be doing in an e-stat application. As anybody can attaest.... moisture is the biggest killer to any powder. It gets wet...you throw it away. Period. Reclaim is not an option at that point without sufficiently drying it out (which I have yet to see happen without $$$$ machinery involved).
As for the questions and hammering me.... everybody can tell you from here, I love getting up on the soapbox for all to listen,lol. Keep em coming
Good luck and take the advice for what it's worth with somebody who's coated "widgets" like yours before in that manner..... it works and is THE way to go. Hope that helps you...... Russ