Die (manufacturing)
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See Die for other meanings of this word
A die is a tool used in the manufacture of parts by the molding process. They are typically manufactured by mold or tool makers
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Sheet forming
A die in manufacturing is a metal block that is used for forming materials like sheet plastic and sheet metal. For the vacuum forming of plastic sheet only a single form is used, typically to form transparent plastic containers (called blister packs) for merchandise. For the forming of sheet metal, such as automobile body parts, two parts may be used, one, called the tool, performs the stretching operations, while another part, called the fixture, contains the mating die and securely clamps the edges of the workpiece to prevent wrinkles. The workpiece may pass through several stages using different tools to obtain the final form. In the case of an automotive component there will usually be a shearing operation after the main forming is done and then additional crimping or rolling operations to ensure that all sharp edges are hidden and to add rigidity to the panel.
Molding
For the casting of plastic to make components (such as bottle caps or combs) or the forming of low melting point metals (such as zinc alloy pot metal, lead, aluminum, or magnesium), a multipart die is used in a process called injection moulding. For automotive parts such as the cases of automatic transmissions these dies may be quite complex, as they must be dissasembled in specific order to ensure that the workpiece is released freely from the casting die. Parts or products produced by this method are referred to as die cast. Compared to lost wax casting the marginal production can be quite cheap, once the substantial investment in tooling and materials handling equipment is made. Compared to sand casting the die casting method can reproduce fine details on complex parts and yield a smooth surface, greatly reducing machining and polishing requirements. As some small portion of metal may leak between the mating seams of the die this can result in a sharp edge of metal called flash, which must be removed by grinding and buffing. For small metal toys the term die cast is generally considered a mark of quality, especially when compared to the cheaper stamping of lithographed sheet metal, or bare stamped metal later painted.
Thread cutting
Another device also called a die is a nut-like thread cutting device for making screw threads on rod stock. This device may also be used to restore damaged threads - a method called chasing. (Other methods are generally used to produce machine screws and small bolts in quantity — they are formed by a process called rolling.)
Wire pulling
Wire-making dies have a hole through the middle of them. A wire or rod of Steel, copper, or other metals or alloy, enters into one side and is lubricated and reduced in size. The leading tip of the wire is usually pointed in the process. The tip of the wire is then guided into the die and rolled onto a block on the opposite side. The block provides the power to pull the wire through the die.
The die is logically divided into a few sections. First is an entrance angle that guides the wire into the die. Next is the approach angle which brings the wire to the nib which facilitates the reduction. Next is the bearing and the back relief. Lubrication is added at the entrance angle. The lube can be in powdered soap form. If the lubricant is soap, the friction of the drawing of wire heats the soap to liquid form and coats the wire. The wire should never actually come in contact with the die. A thin coat of lubricant should prevent the metal to metal contact.
For pulling a substantial rod down to a fine wire a series of several dies is used to obtain progressive reduction of diameter in stages.
Standard wire gauges used to refer to the number of dies through which the wire had been pulled. Thus, a higher-numbered wire guage meant a thinner wire. Typical telephone wires were 22-gauge, while main power cables might be 3- or 4-gauge.
Fiber optics
Methods similar to wire pulling are used to pull a glass rod down into a fiber for fiber optics use. In this case the initial rod will be composed of two or more layers of glass with differing refractive index so that the beam of photons remains in the center of the fiber, minimising losses due to optical leakage.
External links
- FAQ about Die Castings (http://www.diecasting.org/faq/)