Issue link: https://www.e-digitaleditions.com/i/1051901
26 POWDER COATING, November 2018 Removing powder coating from silicone masking Q Who or what are the best resources for removing baked powder from silicone masking? C.A., Holland, Mich. A Well, you probably can't burn them off, but I don't know that for sure. Your masking supplier should tell you what temperatures are safe for the silicone masking material. Some type of blast- ing system or a tumbling method might do it, but I've never tried any of these. I suspect the downside to this type of mask is you have to dispose of them and buy more when they become loaded with baked-on powder. I've been asked this question previously, and I still don't have any answer. —G.T. Building a fluidized bed for powder coating Q We're very interested in building a fluidized bed for our product, which is non- ferrous. Sizes range from 6 to 24 inches in length. The maximum weight per piece is 10 pounds. Can you tell us where we can get used or new equip- ment and the expertise to build a bed from the ground up? This is an imme- diate need. We're serious about reach- ing this goal. We're also looking for a resident expert to assist in setup or in working with us. K.E., Monee, Ill. A One or two companies make fluid-bed units. Finding used equipment will be next to impossible, and you likely wouldn't want what is for sale. There can be other ways to do what you want by using something closer to standard equipment but set up in a modified configuration. I suspect that you'll want to consider some type of preheat to encourage attraction of the powder to the part. This could mean that you could use standard spray guns in a spe- cial booth. The problem with fluidized beds is that film build is usually incon- sistent with too much here and not enough there. Experts are available to design a system with you. Using an independent con- tractor will usually get you a better sys- tem. You can get equipment designed by an equipment company, but in to- day's business atmosphere it'll drive you insane before it's completed. See Powder Coating magazine's Online Reference & Buyer's Resource at www. pcoating.com to find help with your project from the start clear through production.—G.T. PC Editor's note For further reading on the problems discussed in this column, visit Powder Coating magazine's website at www. pcoating.com and search the Article Archive by subject category. All articles listed in the archive are available for free download to registered users. George R. Trigg is pres- ident of GRT Engineer- ing, Prospect, Ohio. He has been involved in the powder coating industry for more than 40 years. He holds a B S B A d e g r e e f r o m Muskingum College, New Concord, Ohio. Nick Liberto is presi- dent of Powder Coat- i n g C o n s u l t a n t s (PCC), a division of Ninan, Inc., 1529 Lau- rel Ave., Bridgeport, CT 06604. Established in 1988, PCC is an in- dependent engineering firm specializing in the use of powder coating technology. Nick has more than 3 decades of experi- ence in the powder coating industry and is a member of many industry associa- tions, including the Application Equip- ment Technical Committee of the Pow- der Coating Institute. A registered pro- fessional engineer in Connecticut, he holds a bachelor's of science degree in mechanical engineering with a minor in Muskingum College, New Concord, (PCC), a division of dependent engineering firm specializing the sources of these contaminants are. For instance, contaminants on the sur- face of the coating (not in or under the coating) come from sources after the coating operation (applying the pow- der). Conversely, contaminants in or under the coating can come from sources either before or during powder application. Contaminants on top of the coating are typically deposited in the cure oven and are airborne in nature. Contaminants in or under the coating can be mixed in with the reclaimed powder and applied before or during powder application. Visual inspection of parts before they enter the powder coating booth will tell you if there are contaminants on the parts before spray. Finally, spraying clean test panels with reclaimed pow- der will tell you if your reclaim is contaminated. Once you've identified where the contaminants are in your coating process, you can begin to eliminate them as coating defects. The best way to eliminate these contaminants is to trap and collect them at their source, which in your case is at the fabrica- tion stage. Air hoods and dust con- tainment systems will contain and collect contaminants as they are made by machining operations. If you can't eliminate the contaminants at their source, then isolate your pow- der coating process from your manu- facturing process. This is done by in- stalling an environmentally controlled room around the powder coating pro- cess. This room should be made of easy-to-clean materials and have posi- tive air pressure to the surrounding plant airspace to keep airborne con- taminants from entering the room. Finally, it's unlikely that these contam- inants are being deposited by your wash system. However, your wash sys- tem may not be removing them en- tirely from the part surface. Increasing dwell time and impingement pressure should fix this issue.—N.L.