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The last article in this series discussed the various types of automatic spraying machines used in the industrial wood finishing industry. Companies that install automatic spraying machines are frequently at the level of production that requires more finishing machinery than a single stand-alone automatic spraying machine.

Traditionally, the thought was that a company needing to make the transition from hand spraying to automation needed to install a very large and very expensive complete finishing production line with the idea that 100 percent of the finishing process would be completed on this line: Load white wood on one end and pack on the other.

As lean manufacturing methods have become adopted and resulting demand to finish “to order” has become the norm, the idea of finishing in large lots to be placed into inventory for later assembly has been replaced by small groups of finishing machines. Instead of one major finishing line, the trend is toward one or more small lines that will do special applications and/or afford a great deal of flexibility of color and process steps. The descriptive term “work cell” is currently used to differentiate this concept from a full process finishing line.

The simplest finishing work cell is a stand-alone automatic spray machine to replace hand spraying. Parts are manually loaded, passed through the spray machine, manually unloaded. The wet parts are then placed on racks or trolleys and allowed to air dry.

At some point, the manufacturer finds that he needs to use coatings that require more energy than air drying or the air drying process is too slow to keep production flowing smoothly through the plant (lean — just in time). The next logical addition to the stand-alone spray machine is the addition of an oven system that accelerates the drying process and/or allows the use of more high-performance coatings. There are many variations of ovens on the market. The simplest of these is an insulated and heated enclosure (room) where the drying racks are pushed into the heated room for a period of time.

The next stage up from the warm room is commonly called a “carousel” system where the drying racks are connected to an oval-shaped towing chain. The attached rack of parts is then towed through a hot air drying tunnel.

Note that both of these simple oven systems will achieve temperatures to about 125 degrees F and are quite satisfactory for drying stains, lacquers, acrylic, waterborne or other coatings that do not require high temperatures or high-energy lamps, such as UV or infrared radiation. These ovens are not physically attached to the spray machine, but they have the advantage of drying wet coated parts that may be coming from other sources such as hand spray booths.