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Wheel Manufacturing Processes: Low-Pressure Cast vs Gravity Cast
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08-24-2009, 09:12 PM | #1 |
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Wheel Manufacturing Processes: Low-Pressure Cast vs Gravity Cast
The question regarding Low-pressure casting and Gravity casting has been asked a lot and it keeps getting ignored when asked so I`ll answer.
In a Wheel Manufacturing perspective: Gravity casting is a method of manufacturing a cast wheel of an specific metal alloy, typically aluminum, although Magnesium is also used, which involves supplying molten metal to a mould cavity via a feeder through a running system where the molten metal entry point is located above the top of the mould cavity. In this manufacturing process all the metal entering the mould is subject to turbulence. This turbulence can cause severe defects such as oxide inclusions and entrapped gas porosity and in some cases mould erosion and hotspots. Low-pressure casting in the other hand takes care of the disadvantages of Gravity casting by filling the mould through an in-gate just below the top of the mould cavity from a source under the mould through a method which allows complete filling of the mould. The force of gravity acts against the upward flow of the metal and eliminates the possible turbulence caused by the falling liquid metal. The molten metal is stored in a pressured container and by increasing the pressure metal is then forced into the mould. Low Pressure Casting Compared to Gravity Casting In low-pressure casting the method in which the metal is forced into the mould is the main difference/advantage over gravity casting and is absolutely controlled. As explained above it results in a low turbulence or turbulence-free mould filling with little to no corrosion. The molten metal in the furnace is in a closed container under protected atmosphere. Because of this the metal absorbs less hydrogen and any other impurities as well as the oxide formation being greatly reduced. As opposed to gravity casting, the metal surface is not interrupted constantly since it is been forced from under the metal surface. What you get is a very clean quality metal. Basically low-pressure casting uses positive pressure to move molten metal into the mold quickly thus resulting in a finished product with an Aluminum that is denser than Gravity cast. The cost involving the production of low-pressure cast are higher than gravity As per Tirerack.com: GRAVITY CASTING Gravity casting is the most basic process of pouring molten aluminum into a mold utilizing the earth's gravity to fill the mold. Gravity casting offers a very reasonable production cost and is a good method for casting designs that are more visually oriented or when reducing weight is not a primary concern. Since the process relies on gravity to fill the mold, the aluminum is not as densely packed in the mold as some other casting processes. Often gravity cast wheels will have a higher weight to achieve the required strength. LOW PRESSURE CASTING Low pressure casting uses positive pressure to move the molten aluminum into the mold quicker and achieve a finished product that has improved mechanical properties (more dense) over a gravity cast wheel. Low-pressure casting has a slightly higher production cost over gravity casting. Low pressure is the most common process approved for aluminum wheels sold to the O.E.M. market. Low-pressure cast wheels offer a good value for the aftermarket as well. Some companies offer wheels that are produced under a higher pressure in special casting equipment to create a wheel that is lighter and stronger than a wheel produced in low pressure. Once again in the quest for lighter weight, there is a higher cost associated with the process. In a Wheel Quality perspective The advantages of low pressure die casting process are several : - higher yield achievable - reduction of machining costs - excellent control of process parameters - good metallurgical quality - leads to an optimal use of the aluminum - excellent mechanical and technological properties of the castings. Disadvantages of gravity die-casting: - High porosity rate - High absorption of impurities - Less dense material which results in a heavier wheel to be able to achieve the required load rating - Very high process variations which leads to more defective units Gravity casting does get the job done but with a higher rate of defective units as opposed to a stronger and lighter wheel made by low-pressure casting. Feel free to post any questions you might have. |
08-25-2009, 11:56 AM | #6 | |
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I think I wrote something like this a while back.
But lets add to the Heirarchy of the production method. Gravity Cast Low Pressure Cast Double Chamber Pressure Cast Flow Form Cast (Spun Cast) Forged: Monoforged, 2PC Forged, 3 PC Forged Quote:
If I need to add explanation on Flow Form or forged methods I guess I could. (Someone can put this in alphabetical order make a master list, I grouped it by the casting method) Low Pressure Cast Miro - Low Pressure Cast, Taiwan (Except 935, made in Japan by NKB) VMR - Low Pressure Cast, Taiwan Alufulgen - Low Pressure Cast, Taiwan Linea Corse - Low Pressure Cast Axis Wheels - Low Pressure Cast, Taiwan Beyren/TSW - Low Pressure Cast, Taiwan (except Borque 3pc) Forgestar - Flow Form Cast, USA BBS - Flow Form Cast, Germany Advan - Flow Form Cast, Japan Enkie - Flow Form Cast, Japan Rays - Flow Form Cast, Japan HRE - Forged, USA iForged - Forged, USA Kinesis - Forged, USA Volk - Forged, Japan DPE - Forged, USA Neez- Forged, USA |
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08-25-2009, 03:06 PM | #7 |
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is NKB really made in Japan?
I thought it was just a Japanese based company that buys wheels from various factories around the world? I don't think they are actually made in Japan. |
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08-25-2009, 04:12 PM | #9 | |
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We could have a list but unless the information is confirmed it`ll be pure speculation. Here it is. Low Pressure Cast Miro - Unknown, Taiwan VMR - Gravity, Taiwan Alufelgen - Low Pressure Cast, Taiwan Linea Corse - Low Pressure Cast, Philippines? (Zoeb please confirm) Axis Wheels - Low Pressure Cast, Taiwan Beyren/TSW - Low Pressure Cast, Taiwan (except Borque 3pc) Forgestar - Flow Form Cast, Unknown BBS - Flow Form Cast & Forged, Germany/Japan Advan - Gravity & Flow Form Cast, Japan Enkie - Flow Form Cast, Japan Rays - Flow Form Cast & Forged, Japan HRE - Forged, USA iForged - Forged, USA Kinesis - Forged, USA Volk - Forged, Japan DPE - Forged, USA Neez- Forged, Japan |
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08-25-2009, 04:13 PM | #10 |
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yup, Philippines for Linea Corse
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08-25-2009, 04:18 PM | #12 | |
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Quote:
Updated: Low Pressure Cast Miro - Unknown, Taiwan VMR - Gravity, Taiwan Alufelgen - Low Pressure Cast, Taiwan Vortex Tuning - Low Pressure Cast, China Linea Corse - Low Pressure Cast, Philippines Axis Wheels - Low Pressure Cast, Taiwan Beyren/TSW - Low Pressure Cast, Taiwan (except Borque 3pc) Forgestar - Flow Form Cast, Unknown BBS - Flow Form Cast & Forged, Germany/Japan Advan - Gravity & Flow Form Cast, Japan Enkie - Flow Form Cast, Japan Rays - Flow Form Cast & Forged, Japan HRE - Forged, USA iForged - Forged, USA Kinesis - Forged, USA Volk - Forged, Japan DPE - Forged, USA Neez- Forged, Japan |
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08-25-2009, 04:22 PM | #13 | |
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08-25-2009, 04:27 PM | #14 | |
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Quote:
As to BBS - http://www.bbs-usa.com/public/tech_advantage2.cfm - Flow Forming, However yes they do Forged as well like you said. You are right I ment Japan on Neez a typo from me. Forgestar is only a few miles from us - been to their production here in the US. Miro have met with the owner multiple times - and been informed multiple times that the wheels are low pressure cast. Feel free to give them a call. As to Velocity being gravity - not to my knowledge. Where have you heard this? Velocity is on the board here they can confirm this. I noticed mention that Advan had a gravity cast wheel - what current wheel in their production is gravity casted? I wasn't aware of any. |
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08-25-2009, 04:50 PM | #15 | ||
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Advan, please see attached. VMR, please see below: From Peter himself. Source: http://www.e90post.com/forums/showthread.php?t=14304 Post: 12 I have also heard Peter himself state this personally. Quote:
Expect all these posts to be edited/deleted after I post them here so check them quick. |
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08-25-2009, 06:08 PM | #16 |
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I stand corrected Crimsone90 on the Velocity thing - pretty surprising actually cause I could have sworn they had told me it was low pressure cast.
Interesting that Advan is using a gravity cast - one thing is their method according to the picture is spun (like flow form) so I am guessing it's a hybrid method? I'll see if I can find out on the forgestar but the cutting production process is done all here, some huge machines. |
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08-25-2009, 06:37 PM | #17 | |
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Advan, since they are flow forming they save on tooling cost by using Gravity. Low pressure+Flow forming will make a stronger wheel but not by much. Remember, flow forming first cast a wheel blank and then "flow forms" the rim. |
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08-25-2009, 09:12 PM | #18 |
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This thread is definitely a good collection of information, for whose who seek it. But it seems that the thread is also directed toward us and so we will be glad to provide input.
VMR Wheels has been providing quality aftermarket wheels to various communities for more than five years. On the BMW side, our selection spans three generations of 3-Series vehicles from E36 to E92. Our factory posess approvals including the ISO-9001:2000 certification. On wheel specific regulations, theres JWL/VIA certifications, as well as meeting or exceeding criteria as published by SAE and TUV. Most individuals within the manufacturing community posess information about one another, with details including factory location, sales volume, country of origin, manufacturing specifics, choice of raw materials, where they come from, etc. In the sourcing process, I'm sure everyone has come across other brands being made, while walking thru the floors of various facilities. Every factory is put together differently, and without a complete analysis covering every field, the conclusions being made are subjective at best. Some might take a keen interest in seeing how the industry is connected with one another, but for others, their goal is to search out reliable vendors to purchase modifications for their vehicles. Before purchasing wheels or anything on this forum for that matter, I would recommend using the "search" button to research material that will make you comfortable with making such a large purchase. You can search for past information such as track record, customer testimonials, or even the approach one takes when certain issues such as warranty pop up. I do the same thing when modding my car . Any questions feel free to contact me directly. Last edited by Peter@VMRWheels; 08-25-2009 at 11:15 PM.. Reason: spell check |
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08-25-2009, 10:55 PM | #19 |
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benefits of different manufacturing processes
kinda of topic, but figured some of you might find this interesting.
difference in performance of different manufacturing processes: hint cast wins (they didnt test durability though) http://www.modified.com/tech/modp-09...ter/index.html |
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