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This is the last of five articles reviewing the different finishing application processes that are common when automation is being considered. This last article of the series is devoted to a process technology that is different and more specialized than previously discussed applications.

Finishing mouldings with automatic equipment designed specifically for this purpose is a unique process with its own features and benefits that are quite different from spraying and roll coating, as described in previous articles. Automatic spraying or roll coating is typically done using a “widebelt” conveyance that may be 4 or 5 ft. wide. By using a widebelt through the application machines, many parts can be placed side by side as long as they fit within the conveyor width. Moulding finishing equipment is designed to handle one long and narrow part at a time with line conveyance up to 12 in. wide with a standard belt width of only 8 in.

The difficulties of finishing mouldings manually or on a widebelt are:
• Parts are long and very narrow, making them difficult to sand and to handle
• Typically all three-sides are profiled (shaped in some way) and must be sanded and finished
• Occasionally four-sided sanding/finishing is required
• Finishing labor cost is the highest cost on mouldings
• Coatings transfer efficiency is the poorest on mouldings
• Finish sanding is difficult because of the shape and dimensions of the part

There is a full range of machines that are designed and manufactured to deal with all of these difficulties in an efficient manner. Because mouldings are profiled and finished one piece at a time, almost all applications require the coatings to be sprayed or vacuum coated. The remainder of this article recaps the primary process equipment available to automatically finish mouldings:

SANDERS

Typically moulding sanding machines are custom manufactured to meet the customer’s specific needs, which are frequently determined by the quality of the cutting tools used to manufacture the mouldings.
The abrasives found on a moulding sander may be sanding belts, resin impregnated abrasive wheels that are shaped to specific patterns and brushes with sandpaper strips. As a rule, it is best to sand with a belt on any part of the surface that is flat, while brushes are used for the portion of the moulding that has been shaped. Most sanding machines will have some combination of belts and wheels or brushes. A note of caution: It is tempting to use only wheels or brushes since the machine is significantly less expensive and much easier to set up and use. Note, however, that wheels or brushes will not remove chatter marks that may be apparent if the cutting tools used are not in excellent condition. Just remember that only sanding belts are aggressive enough to actually remove blemishes in the wood. Abrasive wheels and brushes are only suitable for “denibbing” of raised fiber.

SPRAYING MACHINES
There are several variations of spraying equipment for mouldings, but typically a spray machine for mouldings will house three or six automatic spray guns and have a least two fluid circuits. Most moulding profiles can be sprayed with two or three guns. Typically the spray machine will be dry filtered and capable of spraying any coating that is formulated to spray viscosities. The concern of potential line speed is always a factor considered for calculating production capacities. Spray lines for mouldings typically are operated at 80 to 120 fpm. The critical issue to consider is not the conveyor speed but the number of pieces per minute that can be logically loaded.