Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Page 166 of 331

Fig. 9. Cartridge booth system. The design of these units is the same as reciprocators with respect to the con- trol of speed and stroke adjustment; however, because the units must track parts moving along the conveyor, the addition of a programmable logic controller (PLC) is required. The PLC will accept inputs from encoders (that determine conveyor speed) and photo cells or limit switches (that determine part position). This information is used to determine at what speed the multi-axis machine must run to track the part and when the multi-axis motion program is to be executed. The purpose of this complex tracking and motion system is to provide gun dwell time and pow- der pattern direction. Robots Most robots provide six axes of gun motion by adding wrist movement. Robot- ic machines can be electrically or hydraulically driven. Because of their cost and complexity, these units are rarely used in powder coating systems. Another detri- ment to these units is that hydraulic fluid is not something you want to have around powder. Also, powder coating material is very abrasive and can play hav- oc with hydraulic seals and pistons. POWDER RECOVERY A powder booth/recovery system must accomplish two specific goals: contain the powder overspray within the booth and remove the powder from this contain- ment air so that it can be reused or disposed of properly. Powder booths are de- signed using several filtration techniques to separate the overspray powder from this containment air stream depending upon if the system will reclaim this pow- der or employ a spray-to-waste strategy, the number of reclaimed powders, and the time available to perform the color change. 165

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