193:, of a casting is defined as the weight of the casting divided by the weight of the total amount of metal poured. Risers can add a lot to the total weight being poured, so it is important to optimize their size and shape. Risers exist only to ensure the integrity of the casting, they are removed after the part has cooled, and their metal is remelted to be used again; as a result, riser size, number, and placement should be carefully planned to reduce waste while filling all the shrinkage in the casting.
58:. Most metals are less dense as a liquid than as a solid so castings shrink upon cooling, which can leave a void at the last point to solidify. Risers prevent this by providing molten metal to the casting as it solidifies, so that the cavity forms in the riser and not the casting. Risers are not effective on materials that have a large freezing range, because directional solidification is not possible. They are also not needed for casting processes that utilized pressure to fill the mold cavity.
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Because all of the mold and material factors are the same for n. If a cylinder is chosen for the geometry of the riser and the height to diameter ratio is locked, then the equation can be solved for a diameter, which makes this method a simple way to calculate the minimum size for a riser. Note that
141:
The connection of the riser to the molding cavity can be an issue for side risers. On one hand the connection should be as small as possible to make separation as easy as possible, but, on the other, the connection must be big enough for it to not solidify before the riser. The connection is usually
77:
briefly states that the slowest cooling time is achieved with the greatest volume and the least surface area; geometrically speaking, this is a sphere. So, ideally, a riser should be a sphere, but this isn't a very practical shape to insert into a mold, so a cylinder is used instead. The height to
85:
The casting must be designed to produce directional solidification, which sweeps from the extremities of the mold cavity toward the riser(s). Thus, the riser can feed molten metal continuously to part of the casting that is solidifying. One method to achieve this is by placing the riser near the
170:
when casting ingots. It is essentially a live open riser, with a hot ceramic liner instead of just the mold materials. It is inserted into the top of the ingot mould near the end of the pour, and the rest of the metal is then poured. Its purpose is to maintain a reservoir of molten metal, which
333:
122:. An open riser is usually bigger than a blind because the open riser loses more heat to mold through the top of the riser. Finally, if the riser receives material from the gating system and fills before the mold cavity it is known as a
81:
The shrinkage must be calculated for the casting to confirm that there is enough material in the riser to compensate for the shrinkage. If it appears there is not enough material then the size of the riser must be increased.
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There are risering aids that can be implemented to slow the cooling of a riser or decrease its size. One is using an insulating sleeve and top around the riser. Another is placing a heater around only the riser.
86:
thickest and largest part of the casting, as that part of the casting will cool and solidify last. If this type of solidification is not possible, multiple risers that feed various sections of the casting or
244:
114:. Top risers are advantageous because they take up less space in the flask than a side riser, plus they have a shorter feeding distance. If the riser is open to the atmosphere it is known as an
106:
A riser is categorized based on three criteria: where it is located, whether it is open to the atmosphere, and how it is filled. If the riser is located on the casting then it is known as a
255:
200:
by setting the solidification time for the riser to be longer than that of the casting. Any time can be chosen but 25% longer is usually a safe choice, which is written as follows:
66:
Risers are only effective if three conditions are met: the riser cools after the casting, the riser has enough material to compensate for the casting shrinkage, and the casting
138:. Live risers are usually smaller than dead risers. Top risers are almost always dead risers and risers in the gating system are almost always live risers.
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if a top riser is used the surface area that is shared between the riser and the casting should be subtracted from the area on the casting and the riser.
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made short to take advantage of the heat of both the riser and the molding cavity, which will keep it hot throughout the process.
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328:{\displaystyle \left({\frac {V}{A}}\right)_{\text{riser}}^{n}=1.25\left({\frac {V}{A}}\right)_{\text{casting}}^{n}}
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diameter ratio of the cylinder varies depending on the material, location of the riser, size of the flask, etc.
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181:. With a hot top only 1 to 2% of the ingot goes to waste, prior to its use, up to 25% of the ingot was wasted.
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130:. If the riser fills with material that has already flowed through the mold cavity it is known as a
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For the riser to cool after the casting, the riser must cool more slowly than the casting.
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drains down to fill the pipe as the casting cools. The hot top was invented by
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One way to calculate the minimum size of a riser is to use
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Degarmo, E. Paul; Black, J. T.; Kohser, Ronald A. (2003).
16:"Underfeeder" redirects here. For the health problem, see
239:{\displaystyle t_{\text{riser}}=1.25t_{\text{casting}}}
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536:Metal Casting Computer-Aided Design And Analysis
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27:A bronze casting showing the sprue and risers
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527:Manufacturing Engineering and Technology
509:Materials and Processes in Manufacturing
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425:"Riser filled by electro-slag welding"
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525:Kalpakjian, Serope, et al. (2001).
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529:. Published by Pearson Education.
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491:Degarmo, Black & Kohser 2003
454:, Industrial Press, p. 129.
411:Degarmo, Black & Kohser 2003
390:Degarmo, Black & Kohser 2003
371:Degarmo, Black & Kohser 2003
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796:Semi-finished casting products
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102:Different types of risers
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468:American Iron, 1607-1900
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68:directionally solidifies
879:Casting (manufacturing)
511:(9th ed.). Wiley.
465:Gordon, Robert (1996),
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173:Robert Forester Mushet
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853:Tools and terminology
669:Investment (Lost wax)
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189:The efficiency, or
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45:metal casting
43:built into a
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679:Plaster mold
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18:Underfeeding
823:Fabrication
764:Terminology
637:Centrifugal
437:(136): 1383
162:feeder head
120:blind riser
50:to prevent
843:Metallurgy
713:Components
642:Continuous
343:References
136:cold riser
132:dead riser
124:live riser
116:open riser
112:side riser
838:Machining
833:Jewellery
662:Lost foam
657:Full mold
630:Processes
356:Ravi 2005
128:hot riser
108:top riser
56:shrinkage
41:reservoir
873:Category
848:Smithing
150:Hot tops
52:cavities
858:Welding
828:Forming
818:Casting
786:Foundry
745:Pattern
623:Casting
316:casting
232:casting
156:hot top
54:due to
39:, is a
543:
515:
475:
178:Dozzle
88:chills
62:Theory
37:feeder
791:Ingot
781:Dross
776:Draft
755:Sprue
750:Riser
735:Flask
720:Chill
280:riser
216:riser
191:yield
185:Yield
168:pipes
94:Types
33:riser
801:Slag
730:Core
704:Spin
684:Sand
541:ISBN
513:ISBN
473:ISBN
293:1.25
224:1.25
48:mold
647:Die
249:or
134:or
126:or
875::
433:,
427:,
397:^
378:^
363:^
154:A
31:A
615:e
608:t
601:v
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435:5
321:n
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306:A
303:V
298:(
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285:n
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270:A
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228:t
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212:t
20:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
