Making a Die-casting
In order to clearly understand the operation of the die-casting machine, let us follow the sequence of events that takes place in producing a casting. Two men are required to operate the machine. In [Fig. 27], the operators may be seen in their working positions. The first step is taken by the operator at the left who, with a hand-ladle, dips enough metal for one casting from the melting pot and pours it through nozzle G1 into the goose-neck. The second operator in the meantime is replacing the cores in the dies, adjusting the position of the sprue-cutter and closing the dies preparatory to making a casting. This being done, he elevates the dies and their operating mechanism, which are hinged and counterbalanced, as previously described, bringing them to an upright position. The die operator now mounts the box, raises the sprue-cutter to its open position to admit the metal; after which the machine operator turns the air valve with his left hand. The operation of this air valve admits the air behind the metal, forcing it into the die, and the same movement opens the exhaust valve slightly in advance. The exhaust valve is located upon the second length of piping just above the air valve, and as a link connects the two valves, the single motion exhausts the air from the die cavity and immediately afterward the air is admitted behind the metal, thereby “shooting” the metal into the die. This being done, the air is shut off and the die operator cuts the sprue by means of lever Q1, withdraws the cores in the die, throws the dies to the open position (which is indicated in [Fig. 27]), and operates the ejecting mechanism, thus removing the casting from the die. In the meantime, the machine operator is tending to his metal supply and getting a ladle full of metal ready for the next die-casting operation. By referring to the machines shown in [Fig. 17], it will be noticed that only a few are provided with exhaust piping for venting the dies. Another venting method will be described later.
Fig. 29. Trimming Die-castings on a Filing Machine
The number of die-castings which can be made on one machine per day of ten hours varies with the character of the pieces being die-cast, the number of pieces made at each operation of the machine and the ease with which the dies may be worked, which depends, of course, upon the number of cores and parts to be handled at each die-casting operation. The dies shown in the machine in [Fig. 26], produce four bearings at each operation.
Trimming Die-castings
At the end of each run the operators of the machines go over their work, breaking the castings from the sprues and throwing out all that are defective. No matter how carefully the die-casting molds have been made, there is always a certain amount of trimming to be done on the finished die-castings, on account of the crevices left in the die for air vents, or which exist from improper fitting of the parts of the dies. These “fins,” as they are called, are trimmed by hand operators in a special department. A general view of this trimming room is shown in [Fig. 28]. Usually it is sufficient to scrape these fins off with a scraping knife, but if the casting is especially difficult to produce, so that a large opening is required to admit the metal, it is sometimes necessary to trim unusually thick sprue sections by filing. [Fig. 29] illustrates the method of trimming such die-castings on a filing machine.
Fig. 30. General View of E. B. Van Wagner Co.’s Die making Department
