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15 Plum Street
Verona, PA 15147
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Casting is not obsolete but it is an ancient process that has to compete with more modern manufacturing techniques. Some of these methods are forging, fabricating (cutting and welding), stamping, and sintering. At PicoPascal we want you to think about having your parts machined from solid blocks of material. Quicker Cheaper Stronger Reproducible Summary of Casting over other Manufacture Methods Casting requires a pattern or mold. If you do not have a serviceable pattern or mold then repairing or making one is very time consuming. Most castings require secondary machining. Since castings are usually irregularly shaped then in addition to the pattern or mold the machine shop has to make special jigs or fixtures to hold the casting during machining. The number of steps necessary to make a successful casting is neither quick nor easy. Presumably your part needs machined; it needs holes drilled, holes drilled and taped and surfaces flattened. Since the part needs machined anyway, simply have the whole part machined from a block of material. A variety of metals, plastics and other machineable materials are readily available.
Patterns and molds in addition to being time consuming are also expensive. Tooling (patterns, molds, & fixtures) costs can run into thousands of dollars before the first part is cast. If a later change is made then the tooling costs are repeated. Most production machining is now performed on modern CNC (computer numerical controlled) machining centers. Programming the machining of a part cut from a block of material will take a little longer than just programming the secondary machining of a casting but consider you have not invested in any tooling. Another big feature: it is much, much cheaper and quicker to make a design change. It may only take a minute or two to change a couple lines of code versus a month or more to change the tooling.
Wrought bar and plate from a mill usually has much better qualities for strength and toughness than a casting. Castings can be made strong with special alloys, techniques, and heat treatments but again this adds time and expense.
Castings, especially sand castings, vary from piece to piece. A foundryman is an artist, a craftsman, and a metallurgist with an incredible number of variables to deal with. He can make a crude casting quickly and easily and he can make an extremely sophisticated, accurate, and strong casting. However, he can not make a sophisticated, accurate and strong casting quickly, easily or cheaply. When we machine a piece from a solid block of material we shift the metallurgical issues from the foundryman to the mill that made the material. A mill that makes much the same thing every day; a mill that has great control over its processes and that can guarantee material to difficult specifications. Fixtures for the machining of castings will often cause distortion and inaccuracies. This is much less likely when machining from a solid block. Although burrs are often worse on wrought material the control of burrs is easier. Burrs can be removed as part of the machining process. On a casting the burrs must be removed as an additional process such as hand scraping or grinding.
You have a number of variables to consider. Deadlines, quantity, quality, and flexibility all have to be compared. At one extreme is the aerospace industry; they may make a block of material into 98% chips for the recycle bin and 2% into a useable part. Previously, they would have riveted many pieces of sheet metal together to make the same part. In this case a casting was not an option due to lack of consistency and strength. In the case of an existing part, if you use about a thousand pounds (500 Kg) or more of castings per year and quality is acceptable then casting is probably the way to go. Large and very small parts are best left as castings. The intermediate sized part is most favorable for change. Very favorable parts are the size of your fist or the shape of a book. A questionable part might be shaped like a picture frame. Every part will have to be evaluated individually to see if machining from a block makes sense. Due to ever increasing labor and environmental costs and improved productivity of modern CNC machinery the breakeven point between machining from a block and casting is shifting to machining from a block. A high speed, 5 axis machining center such as the one owned by PicoPascal Company allows one to machine features quickly that in the past were only realistically made by casting.
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