Powder Material Utilization
Q. We are working on ways to reduce our waste powder. We do recover some powder, and other colors are low volume, so we do not bother to recover them for reuse. But we are still throwing away a lot of material every year. Any suggestions on how we can get more value out of our powder? A.F.
A. Overall material utilization is a function of initial first pass transfer efficiency (FPTE) and the reclaim system efficiency. FPTE can be improved by careful adjustment and control of the application process. There are many variables that come into play (flow rate, gun position, earth ground, etc.). Be sure you have good FPTE by testing the right settings, recording them and then putting a good process control plan in place. You can read a lot about this subject in various publications like Products Finishing, purchasing a good book on the subject or by attending one of many programs, such as those held by The Powder Coating Institute.
Reclaim efficiency starts with the type of system you use. A cyclone system is flexible for using many colors in a single system, but a percentage of the powder is moved to scrap with each cycle. Keep your system clean and maintain the filters. Keep your FPTE as high as possible. Use good racking arrangements that minimize overspray. Work on operator training and technique. This is true whether you chose to recover the powder for reuse or you decide not to reuse it.
The cartridge module system is less flexible for multiple reclaim colors, but it captures a higher percent of over-spray. Same rules apply: good racking, good technique, high FPTE. Note that the module may accumulate finer particles that can lead to a decline in FPTE. Keep the TE above 50 percent for best results and consume the over-spray as fast as you generate it. Check particle size periodically, and compare it with the fresh product to see if the fines are accumulating.
Work on being as precise as possible in your application setup for high FPTE and maintain your system for the best possible material utilization. You should also experiment with different powder materials. Some of the powder that cost less per pound may not have optimum application and recovery properties. Be sure to test the powder to determine the cost per applied square foot. In some cases, you can save money per applied square foot by using a better powder, even if it costs more per pound.
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