3. Machine Molding—Hand Molding—Extrusion
From here, the rather stiff wet mixture becomes bricks in one of two ways: It is either molded (by machine or by hand), or it is extruded. Molded bricks are made en masse when the batch feeder's auger forces the mix down into an open mold box that has slid beneath it to make 10 or more bricks at once. A robotic wheel then turns the lot of them onto pallets that are then carried away to the next stage, the chamber dryer, by automated “finger cars,” which have multiple prongs to hold racks of “green,” or unfinished, brick.
Alternatively, the wet mix is set aside for the hand-molding operation, where three craftsmen take hunks of wet brick to make “loaves” (see opening photo on page 116) they press into individual wood molds for custom shapes such as water tables, radials, sloped bricks, and bullnoses. As on the mass-molding line, the custom-brick makers line the molds with sand, which helps loosen the brick out of the mold and gives it color. They make between 400 and 500 bricks a day, compared with the 100,000 molded en masse. Once the bricks move to the finger cars, they are taken to the chamber dryers, ranged down a dim corridor like a series of crypts, where they warm at 300 F for about 24 hours. The empty finger cars return to the molding area for more wet brick.
Belden makes about 75 percent of its brick by extrusion, a process in which the wet mixture first is pressed through a vacuum chamber to compress it and then is pushed out like Play-Doh (a) through a die (b) that shapes a running strand of brick of a specific length and depth (with or without the “core bridge,” a set of horizontal metal rods that creates the holes in the beds of some bricks). The strand moves forward to be cut by a harplike contraption (c) strung with wires that cut the brick to a programmed height. Off to the side of this setup are a series of cast-iron dies the size of car wheels that create different shapes of brick. The design of new or custom dies is the job of the three-person Shapes Department.
Extruded brick, once it's cut and placed on a car, travels to what is called a tunnel dryer, which is heated to the same temperature as the chamber dryer. (However, extruded brick contains less water than molded brick, so it won't stick when pushed through the extrusion machine.) In either case, the bricks have been stacked exquisitely on their narrow edges in alternating directions to maximize air flow and enhance variation in their final color palette.