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This is a personal recollection on the Move fire on May 13, 1985
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A flask is a type of tooling used to contain a mold in metal casting. A flask has only sides, and no top or bottom, and forms a frame around the mold, which is typically made of molding sand. The shape of a flask may be square, rectangular, round or any convenient shape. A flask can have any size so long as it is larger than the pattern being used to make the sand mold. Flasks are commonly made of steel, aluminum or even wood. A simple flask has two parts: the cope and the drag. More elaborate flasks may have three or even four parts.
Flasks are often designed with bars that extend to span two opposite sides. The bars act as reinforcement to the molding sand, which is relatively weak in tensile strength. The bars help support the sand through the molding and pouring operation.
Flasks are designed with an alignment or registration feature, so that the two flasks can be aligned to one another to ensure a casting can be more dimensionally accurate and also in small flasks, so that they cannot be fitted together the wrong way.
Flasks usually have handles or trunnions designed into their construction, which assist in handling the flasks with cranes or other lifting machinery.
Some flasks are used to form a mold and are removed before pouring the casting, so another mold can be made. Other flasks are designed to contain the mold through the pouring operation, and then the casting is shaken out of the mold. The flasks are then used again and again.
Flasks are usually (though not always) the property of the foundry making the casting. The number of available flasks of a given size can be a limiting factor in the overall production rate.
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A flask is a type of tooling used to contain a mold in metal casting. A flask has only sides, and no top or bottom, and forms a frame around the mold, which is typically made of molding sand. The shape of a flask may be square, rectangular, round or any convenient shape. A flask can have any size so long as it is larger than the pattern being used to make the sand mold. Flasks are commonly made of steel, aluminum or even wood. A simple flask has two parts: the cope and the drag. More elaborate flasks may have three or even four parts.
Sand casting, also known as sand molded casting, is a metal casting process characterized by using sand—known as casting sand—as the mold material. The term "sand casting" can also refer to an object produced via the sand casting process. Sand castings are produced in specialized factories called foundries. In 2003, over 60% of all metal castings were produced via sand casting. Molds made of sand are relatively cheap, and sufficiently refractory even for steel foundry use. In addition to the sand, a suitable bonding agent (usually clay) is mixed or occurs with the sand. The mixture is moistened, typically with water, but sometimes with other substances, to develop the strength and plasticity of the clay and to make the aggregate suitable for molding. The sand is typically contained in a system of frames or mold boxes known as a flask. The mold cavities and gate system are created by compacting the sand around models called patterns, by carving directly into the sand, or via 3D printing.
In foundry work, the terms cope and drag refer respectively to the top and bottom parts of a two-part casting flask, used in sand casting. The flask is a wood or metal frame, which contains the molding sand, providing support to the sand as the metal is poured into the mold. In flaskless molding, the same terms are used, cope for the top or upper piece and drag for the bottom or lower piece. In the simplest sand-casting procedure, the drag is placed upside down on a board, around a pattern of the part to be cast. The pattern is a model of the desired casting. Talcum powder is often dusted over the pattern to aid in the removal of the pattern. Sand is sifted over the pattern until the model is covered by a few inches of sand. More sand is then dumped into the drag, and rammed with a wooden wedge, or mechanically vibrated to pack the sand down. The sand is then struck level with the top edge of the drag, using a wooden or metal strake. A board is then placed on top of the drag and the drag is flipped over. Then, the cope is placed on the drag, and dowels (or pins) are put in the sand to make holes for the sprue and one or more risers. Talcum powder and sand are again sifted over the pattern and rammed to fill the cope. The pins are then carefully pulled out of the sand. The critical part of the operation is to separate the cope and drag to remove the pattern. The pattern may be vibrated with a powered vibrator, or the pattern, and maybe the cope and drag flask, will be lightly tapped with a small hammer. The pattern is lifted from the sand, leaving a molding cavity. A passageway for metal to enter the mold, called a "gate", is then cut from the sprue hole to the void left by the pattern, and a runner is cut from the sand to allow metal to flow into the riser. The flask is then put back together, and metal can be poured into the mold. The metal will flow down the sprue, into the mold cavity, and back up the riser (of which there may be several). Once the metal has cooled enough to solidify, the flask can then be separated again, and the sand removed to reveal the rough casting. The rough casting is separated from the sprue and riser(s) either by sawing them off or just breaking the thin metal of the gates and runners. In some cases, the part design is more complicated, and intermediate flasks and mold sections are needed between the cope and drag. These sections are called cheeks.
Shell molding, also known as shell-mold casting, is an expendable mold casting process that uses resin covered sand to form the mold. As compared to sand casting, this process has better dimensional accuracy, a higher productivity rate, and lower labour requirements. It is used for small to medium parts that require high precision. Shell molding was developed as a manufacturing process during the mid-20th century in Germany. It was invented by German engineer Johannes Croning. Shell mold casting is a metal casting process similar to sand casting, in that molten metal is poured into an expendable mold. However, in shell mold casting, the mold is a thin-walled shell created from applying a sand-resin mixture around a pattern. The pattern, a metal piece in the shape of the desired part, is reused to form multiple shell molds. A reusable pattern allows for higher production rates, while the disposable molds enable complex geometries to be cast. Shell mold casting requires the use of a metal pattern, oven, sand-resin mixture, dump box, and molten metal. Shell mold casting allows the use of both ferrous and non-ferrous metals, most commonly using cast iron, carbon steel, alloy steel, stainless steel, aluminium alloys, and copper alloys. Typical parts are small-to-medium in size and require high accuracy, such as gear housings, cylinder heads, connecting rods, and lever arms. The shell mold casting process consists of the following steps: Pattern creation - A two-piece metal pattern is created in the shape of the desired part, typically from iron or steel. Other materials are sometimes used, such as aluminium for low volume production or graphite for casting reactive materials. Mold creation - First, each pattern half is heated to 175–370 °C (347–698 °F) and coated with a lubricant to facilitate removal. Next, the heated pattern is clamped to a dump box, which contains a mixture of sand and a resin binder. The dump box is inverted, allowing this sand-resin mixture to coat the pattern. The heated pattern partially cures the mixture, which now forms a shell around the pattern. Each pattern half and surrounding shell is cured to completion in an oven and then the shell is ejected from the pattern. mold assembly - The two shell halves are joined and securely clamped to form the complete shell mold. If any cores are required, they are inserted prior to closing the mold. The shell mold is then placed into a flask and supported by a backing material. Pouring - The mold is securely clamped together while the molten metal is poured from a ladle into the gating system and fills the mold cavity. Cooling - After the mold has been filled, the molten metal is allowed to cool and solidify into the shape of the final casting. Casting removal - After the molten metal has cooled, the mold can be broken and the casting removed. Trimming and cleaning processes are required to remove any excess metal from the feed system and any sand from the mold. Examples of shell molded items include gear housings, cylinder heads and connecting rods. It is also used to make high-precision molding cores.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
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