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تاريخ : سه‌شنبه ٢۱ آذر ۱۳۸٥

die castin technical informatin

Die Casting, A Brief Description Die casting is a manufacturing process in which molten metal is injected, under pressure, into a hardened steel die or also called mold. Dies are often water-cooled. Dies are then opened, and the die castings are ejected (many times thousands of parts each day, sometimes only a few hundred). Once the tooling is paid for, die casting is a very inexpensive aluminum part manufacturing process. Metals: Aluminum die cast alloy A360. Aluminum die cast alloys A380 and A383. Aluminum die cast alloy A413. Size Range: Not normally over 2 feet square. Part Weights: .001 pounds to 10 pounds. Setup Cost: New tooling setup is free with free first article report. Tolerances: Aluminum die cast parts ± .002"/in. Add ± .001" to ±.015" across parting line depending on size. Surface Finish: 32-63RMS. Minimum Draft Requirements: Aluminum 1° to 3°. Normal Minimum Section Thickness: Aluminum die cast parts: 0.060" small parts, 0.090" medium parts. Ordering Quantities: Usually 1,000 and up but sometimes as few as a hundred. Normal Lead Time: Tooling: Sometimes as little as 4 weeks or as much as 12 weeks. Samples: Usually the week the die is available. Production: Starts usually within two weeks (sometimes less) after approval. What Die Casting Materials Do You Use? The following table will provide a general idea of the differences in Aluminum Die Cast alloys. ALLOY Aluminum alloys 360 380 383 413 Hardness 75 80 75 80 Shear Strength (ksi) 28 28 - 25 Tensile Yield Strength (ksi) 25 23 22 21 Ultimate Tensile Strength (ksi) 44 46 45 43 Thermal Conductivity 65 56 56 70 Electrical Conductivity (% copper) 30 27 23 31 Density (weight) Lbs./ in.3 .1 .1 .1 .1 (1= most desirable, 5= least desirable): Pressure Tightness 2 2 2 1 Die Filling Capacity 3 2 1 1 Anti-Soldering to Die 2 1 2 1 Corrosion Resistance 2 4 3 2 Machining ease & quality 3 3 2 4 Strength at high temperatures 1 3 2 3 Material cost 3 1 2 4 We will also machine the die cast parts we produce to our customer''s specifications. Cast-Parts We are a member of NADCA (North American Die Casters Association). NADCA helps manufacturers with information concerning die casting of all types. NADCA also publishes specifications for die cast parts. NADCA North American Diecasters Association Compare Die Casting to Other Manufacturing Processes Forgings Compared with forgings, die casting can be more complex in shape and have shapes not forgeable, can have thinner sections, be held to closer dimensions, and have coring not feasible in forging. Plastic Injection moldings Compared with plastic injection moldings, die casting are stronger, stiffer, more stable dimensionally, more heat resistant, and are far superior to plastics on a properties/coat basis. They help prevent radio frequency and electromagnetic emissions. For chrome plating, die castings are much superior to plastics. Die castings have a high degree permanence under load compared to plastics, are completely resistant to ultra-violet rays, weathering, and stress-cracking in the presence of various reagents. Manufacturing cycles for producing die castings are much faster than for injection moldings. Extrusions Compared to extrusions, die casting can be produced faster and more net shape. Features and depressions on the sides, tops and bottoms can be created in one operation. There is less waste using die casting than extrusion. Holes can be cast in place to save additional machining cost. Stampings Compared with stampings, one die casting can often replace several parts. Die casting frequently require fewer assembly operations, can be held within closer dimensional limits, can have almost any desired variation in section thickness, involve less waste in scrap, and are producible in more complex shapes. Die castings can be made in many shapes not producible in stamped form. Screw Machine Parts Compared with screw machine products, die castings are produced more rapidly, involve much less waste in scrap, can be made into shapes that are difficult or impossible to produce from bar or tubular stock, and may require fewer operations. Sand castings Compared with sand castings, die castings require much less machining, can be made with thinner walls, can have all or nearly all holes cored to size, can be held within much closer dimensional limits, and are produced more rapidly in dies which make thousands of die castings without replacement. Die castings do not require new cores for each casting, are easily provided with inserts die cast in place, have smoother surfaces and involve much less labor cost per casting. Permanent mold castings Compared with permanent mold castings, die castings can be made to closer dimensional limits and with thinner sections and holes can be cored to near net shape. Die castings are produced at higher rates with less manual labor, have smoother surfaces, and usually cost less per die casting. Glossary of Die Casting Terms Automation - Industry term commonly used to describe the mechanization of various aspects of die casting process. Biscuit - Excess of ladled metal remaining in the shot sleeve of a cold chamber die casting machine. It is part of a cast shot and is removed from the die with the casting. Blister - A surface bubble caused by gas expansion (usually from heating) which was trapped within the die casting or beneath the plating. Blow holes - Voids or pores which may occur due to entrapped gas or shrinkage during solidification, usually evident in heavy sections. (See porosity) Cavity - The recess or impressions in a die casting die in which the casting is formed. Cold chamber machine - A type of die casting machine in which the metal injection mechanism is not submerged in molten metal. Checking - Fine cracks on the surface a die which produce corresponding raised veins on die casting. Caused by repeated heating of the die surface by injected molten alloys. Also called heat checking. Die lubricant - Liquid formulations applied to the die to facilitate casting release and prevent soldering. Dimensional stability - Ability of a component to retain it''s shape and size over a long period of service. Draft - The taper given to walls, cores and other parts of the die cavity to permit easy ejection of the casting. Ejector marks - Marks left on castings by ejector pins. Ejector pins - A rod which forces the casting out of the die cavity and off cores. Ejector plate - A plate to which ejector pins are attached and which actuates them. Fillet - Curved junction of two surfaces, e.g., walls which would meet a sharp angle. Flash - A thin web or fin of metal on a casting which occurs on die partings, vents and around moveable cores. This excess metal is due to working and operating clearances in a die. Gate - Passage for molten metal which connects runner with die cavity. Also, the entire ejected content of a die, including castings, gates, runners sprue (or biscuit) and flash. Growth - Expansion of a casting as a result of aging or of intergranular corrosion, or both. Heat checking - (See checking) Hot chamber machine - Die casting machines which have the plunger, gooseneck (metal pressure chamber) immersed in molten metal in the holding furnace. Impact strength - Ability to resist shock, as measured by a suitable testing machine. Ingot - Metal or alloy cast in a convenient shape for storage shipping or remelting. Injection - The processes of forcing molten metal into a die. Insert - A piece of material, usually metal, which is placed in a die before each shot. When molten metal is cast around it, it becomes an integral part of the die casting. Loose piece, knockout - A type of core (which forms undercuts) which is positioned in, but not fastened to a die. It is so arranged as to be ejected with the casting and from which it is removed. It is repeated for the same purpose. Metal saver - Core used primarily to reduce amount of metal in a casting and to avoid sections of excessive thickness. Multiple cavity die - A die having more than one duplicate impression. Overflow - A recess in a die connected to die cavity by a gate to assist in proper venting. Parting line - A mark left on die casting where the die halves meet; also, the mating surface of the cover and ejector portions of the die. Plunger - Ram or piston which forces molten metal into a die. Porosity - Voids or pores resulting from trapped gas, or shrinkage during solidification. Process control - Where parameters of a process are studied and correctly applied in the manufacturing process to produce high quality parts. Runner - Die passage connecting sprue or plunger holes of a die to the gate where molten metal enters the cavity or cavities. Shot - The segment of the casting cycle in which molten metal is forced into the die. Shrinkage, solidification - Dimensional reduction that accompanies the freezing (solidification) of metal, passing from the molten to the solid state. Shrink mark - A surface depression which sometimes occurs next to a heavy section that cools more slowly than adjacent areas. Slide - The portion of a die cast die arranged to move parallel to die parting. The inner and end forms a part of the die cavity wall that involves one or more undercuts and sometimes includes a core or cores. Soldering - Adherence of molten metal to portion of the die. Trim die - A die for shearing or shaving flash from a die casting. Unit die - A die interchangeable with others in a common holder. Undercut - Recess in the side wall or cored hole of a casting disposed so that a slide or special form of core (such as a knockout) is required to permit ejection of the casting from the die. Vent - Narrow passage at the die parting which permits air to escape from the die cavity as it is filled with molten metal. Void - A large pore or hole within the wall of a casting usually caused by entrapped gas. A blow hole. Waterline - A tube or passage though which water is circulated to cool a casting die


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