Vertically-Speaking, Robinson Foundry Debuts Aluminum Green Sand Casting.
We are constantly looking for a better way," said Joe Robinson, Jr., chairman of Robinson Foundry, Inc., Alexander City, Alabama, when questioned about his foundry's push toward high-production, vertically-parted green sand casting of aluminum. "There is an untapped market we believe we hold the key to."
A profile of Robinson Foundry begins and ends with this statement by Joe Robinson. As a medium-sized, single-plant jobbing foundry, Robinson Foundry has learned the importance of reinventing itself in the eyes of its customers by entering new, uncharted markets. See for yourself:
* 1985--Became the first jobbing foundry to make a significant entry into lost foam when it started up its gray iron facility (see sidebar, "Robinson Opens the Door for Lost Foam").
* 1989--Followed its successful ferrous lost foam operation with the start-up of the Bodine-Robinson joint-venture aluminum lost foam operation.
* 1995--Became only the third independent foundry in North America to pour aluminum via vertically parted green sand casting, and achieved Tier I supplier status with General Motors for a water outlet in 1998.
* 2000--Installed North America's first low-pressure vertically parted green sand casting system for aluminum.
As a family-owned jobbing operation, taking the plunge into new processes and markets often is an act of faith because there is no precedent to follow. This examination of Robinson Foundry's entry into the new aluminum casting realm details the faith this firm had and the questions it had to answer to succeed in uncharted waters.
Aluminum Green Sand Casting?
In 1995, after the lost foam business was sold [gray iron to Citation Corp. (Citation Foam) in 1993 and aluminum to Intermet Corp. (Alexander City Foundry) in 1995], Robinson Foundry was casting gray and ductile iron on three vertically parted green sand lines.
"When we sold the lost foam casting facility, we knew we either could stay in the iron casting business and make a good living or we could find another way to grow the business," said Joe Robinson. "Our decision was to grow and this led us to aluminum green sand casting."
In listening to Joe Robinson and Robinson Foundry President Jerry Carter, the decision to diversify production sounded simple enough. Robinson Foundry had the production expertise in vertically parted green sand from its iron business and had the experience with melting and processing aluminum castings from lost foam. The trick was marrying the two areas of expertise together to make high-quality castings economically.
The impetus for this marriage was a customer, Ford Motor Co., which was looking for an aluminum EGR spacer component in lost foam. The problem was that the component didn't "fit" as a cost-effective choice for foam. Based on its experience in iron, however, Robinson Foundry knew that the aluminum design was a perfect fit for vertically parted green sand molding because of how it could be cored and oriented in the mold.
Although many of the same principles of shrink and fluid flow apply when converting a component from vertically parted green sand casting in iron to aluminum, both Carter and Robinson admit aluminum was a brand new ballgame.
"There were no books or documentation for us to follow," said Carter. "We were starting from scratch when it came to component design and gating."
For the spacer component, Robinson Foundry melted 319 aluminum in an R&D crucible furnace previously used for lost foam and cast it on one of its existing iron mold lines. With the first pour, the firm became the third independent foundry in the U.S. (Aluminum Casting & Engineering, Milwaukee, and Northern Aluminum Foundry, Fond du Lac, Wisconsin, are the other two) to production-cast aluminum on a vertically-parted sand line.
The success of the spacer component led Robinson Foundry to its "reputation making" job in aluminum green sand--an engine outlet component for General Motors (GM) (Fig. 1). Requiring volumes of 5000/day, GM also wanted the component machined and assembled. Robinson Foundry responded by developing a partnership With Latva Machine, Inc., Newport, New Hampshire, building a 10,000-sq-ft machining operation on the foundry grounds in 1998. The foundry now machines 15% of its total production in this facility). Cast in 319 aluminum, the engine outlet component paved the way for the foundry's certification by GM as a Tier 1 supplier for vertically parted aluminum green sand casting.
Although the foundry had built itself a niche with aluminum casting, it still was looking toward the future.
"Everything is about reducing weight in the automotive industry," said Mark Kress, sales manager. "Our future is providing an aluminum alternative that meets the necessary mechanical properties for the iron safety critical components. Aluminum has provided our automotive customers a 50% weight reduction."
Continued Joe Robinson: "We needed to find out what the acceptance in the marketplace would be for safety-critical aluminum castings produced using our green sand casting method. We went to 6 different brake suppliers. Visited engineering groups with the Big 3. The key was whether the necessary properties could be achieved and documented. Customers are hesitant to jump to a new technology. We have a lot to prove.
Robinson knew that it could achieve the necessary mechanical properties (tensile, elongation and fatigue life) in aluminum with its current green sand system, but the consistency from run to run wasn't evident. Product consistency is mandatory if customers are going to source the safety-critical parts such as control arms, knuckles and brake components, said Carter. Customers were not going to choose an unproven process for aluminum when permanent mold casting (due to its low turbulent mold fill and chilling characteristics of the mold) already was so well established.
In fact, the company considered joining the permanent mold realm, "but it didn't make sense to enter a market in which there were a lot of foundries with a lot of experience," said Joe Robinson.
This decision led the foundry back to its expertise in vertically parted green sand molding and the technological development of a low pressure vertically parted green sand casting system from Disa Industries, Oswego, Illinois.
"We went into the decision-making process with the question, 'If a component is currently being made in vertically parted sand molds as an iron casting, why can't it be made in aluminum?"' said Carter. "The key was to find a way to achieve the necessary properties."
In February 2000, Robinson Foundry became the first North American installation of this casting system (systems also are in operation in Austria, France and Germany).
At Robinson Foundry, the system (Fig. 2) consists of a 2.2-ton bottom pressure pour furnace that works in conjunction with the molding line. When a mold is ready to pour, the furnace's pour spout inserts itself into the sprue located on the lower side of the mold. A pneumatic system generates 1.5 psi of pressure within the melt to force the aluminum through the pouring spout and into the gating system.
This force provides the operator with direct control over the melt's flow rate and the start/stop of the pouring. The goal in the casting is a metal velocity of no higher than 0.5 in/sec throughout the fill. In addition, the metal flow rate, when it enters the runner system of the molds, must be increased to fill the casting cavities. If the metal flow is too rapid in the runner system, it will erode the mold walls and cause inclusions. If the mold cavity fills too slowly, it will result in improper casting solidification.
The metal fills the mold cavity from the bottom (reducing the size of gating system required for the casting, thus increasing yield by up to 15% over conventional pouring). Upon completion of filling, a sand core is pushed into the sprue to prevent the metal from running back into the furnace when the pressure is released (for more information, see "New Filling/Feeding Process Produces Vertically-Parted Aluminum Green Sand Castings," modern casting, April 2000, p. 54).
Robinson Foundry can cast 319 or A356 with this system. With up to 70% of the molds cored, the foundry can produce up to 300 molds/hr (10 sec cycle times/mold) with 8-12 Ib of aluminum castings/mold.
The pouring furnace arrangement on this molding line provides several advantages critical to handling molten aluminum:
* metal is drawn from the middle of the bath to ensure cleanliness and minimize the chance for oxide inclusions from the melt surface;
* degassing is performed within the chamber of the furnace while it is sealed, reducing melt exposure to the atmosphere and entrained oxides in the melt;
* new molten aluminum can be fed to the pouring furnace while in operation, increasing productivity;
"We could achieve the necessary mechanical properties in A356 by conventional pouring but it wasn't consistent enough for us" said Carter. "The bottom pouring ensures the consistency for the safety critical component market."
The combination of the melt handling and low-pressure bottom pouring allows Robinson to cast components with a tranquil fill. This eliminates mold wall erosion (sand inclusions) and reduces molten aluminum turbulence, which results from the metal folding over itself and the entrapment of oxides and gas (microporosity) in the casting as it solidifies. The result is components with typical tensile strengths of 40,000-45,000 psi and elongations of 5-7%.
The foundry currently casts three production jobs for the bottom pour system and four jobs on its conventional mold line. One of the bottom pour jobs is a 356 aluminum steering knuckle for an all-terrain application that the foundry is casting at a rate of 40,000 pieces/yr (with requirements of 80,000/yr expected in the near future).
"Similar to lost foam, the future for this production method rests on whether components are designed to take advantage of the process," said Joe Robinson. "That is what we are selling."
Robinson has set its future in aluminum. The foundry is in the initial stages of building its new 30,000-sq-ft facility for this innovative process, which is expected to be operational be next year. Melting will take place in a new 6-ton high-efficiency vertical shaft fumace, and a launder system will transport the melt to the pouring station. In addition, the foundry will be adding two coldbox core systems to supply the mold line.
"When we first started selling our new capabilities, we were selling a vision to determine the acceptance for the process," said Carter. "Although potential customers still are skeptical, the tensile properties and results go a long way toward their understanding."
Currently aluminum production is split 70% for gravity pour and 30% for bottom pour, but Carter expects these percentages to soon be reversed as the firm is an unchallenged leader in a new technology.
As Joe Robinson said, "We are constantly looking for a better way. There is an untapped market we believe we hold the key to."
Robinson Foundry, Inc.
Alexander City, Alabama
Metals Cast: 319, A356 and A357 aluminum alloys; ductile and gray iron.
Mold Capabilities: Vertically parted green sand.
Core Capabilities: Coldbox and shell.
Melt Capabilities: Careless induction and crucible.
Size: 120,000 sq ft.
Key Markets: Automotive, fittings, agriculture and heavy equipment.
Year Founded: 1946.
Plant Officials: Joseph H. Robinson, Jr., chairman; Jerry Carter, president; Mark A. Kress, sales manager; Ryan H. Robinson, manufacturing manager.
Robinson Opens the Door for Lost Foam
Lost foam casting has received a lot of acclaim recently for its ability to cast complex geometries that can eliminate down-the-road processing. The likes of General Motors and Saturn have invested their futures in this process.
Back in the early '80s, however, the future of lost foam didn't look so bright as many foundries had tried (some half-hearted) and failed with the process, giving the process a black eye among the design community. Then came along Robinson Foundry, Who embraced the process on both the gray iron and aluminum side and became the first North American jobbing foundry to make a significant entry into lost foam casting.
"We were facing a lot of offshore competition and had to find a better way," said Joe Robinson.
While Robinson first achieved prototype success with electric motor housings, the first commercial shipment was a gray iron exhaust elbow or Mercury Marine. "The only way to prove lost foam was to get tooling, but you couldn't get that without big money," said Rickey Robinson, talking about the early hurdles. "We took any foam we could get our hands on. There is so much known today about foam densities, glues, coatings and foam control--we were successful at a time when we didn't know whether or not we were doing things right. Anyone who tellsyou the process can't stand much variability didn't see our operation and the success we had."
Bruce McMellon, Vulcan Engineering, said that the Robinson brothers' entry was significant not only because it was the first iron jobbing foundry, but also because they did it without a customer or market in hand. "They created a whole new look to the process, creating an appeal beyond automotive."
Many also credit Robinson with furthering knowledge about the process among both foundries and end-users. "They knew they needed competitors to be successful and could grow lost foam if others got into it and established credibility," said McMellon. "That was as important as the actual work they did on castings."
Added Steel Founders' Society of America's Raymond Monroe, who was involved in the building of Saturn's lost foam casting facility and wrote the first comprehensive lost foam book: "The fact that these two boys from Alabama could sell the technology with commercial success--particularly with parts that couldn't be cast in any other way--opened a lot of eyes."
The lost foam family tree of two of the larger U.S. foundry groups' entry into larger-scale lost foam production also is traced to Robinson. Its iron business was eventually sold to Citation Foam; and its BodineRobinson joint-venture for aluminum was sold to Internet.
Michael J. Lessiter, editor/publisher.
A Foundation Built In Iron
Robinson Foundry opened its doors in 1946 as a gray iron supplier of ornamental castings and soil pipe fittings. Today, this business has grown into the Robinson Group that encompasses: the foundry; the Robinson-Latva machining facility; Robinson Iron, a specialist in restoring landmarks and ornamental castings; and Satterfield, Inc., a firm focused on industrial supplies, machined parts, electronics and specialty metal fabrication.
The growth of the foundry saw the addition of lost foam casting in the '80s (and subtraction in the early '90s), and then a transformation in the '90s into a high-production vertically parted green sand operation for iron and aluminum. In 1991, the foundry added the three high-production molding lines for iron (one of which is now used for aluminum).
For iron casting, the foundry melts in two 15-ton coreless induction furnaces and holds in two 40-ton vertical channel furnaces. Cores are produced in both coldbox and shell processes. Robinson uses stopper-rod pouring on both iron lines. The foundry's principal products in iron include motor mount and suspension brackets, axle tube housings, oil cooler housings and commercial fittings, and it casts more than 150 jobs/year for various customers.
Once the new facility for aluminum is complete, Robinson anticipates casting production will be split 40% for iron (80% ductile and 20% gray) and 60% aluminum.
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|Comment:||Vertically-Speaking, Robinson Foundry Debuts Aluminum Green Sand Casting.|
|Author:||Spada, Alfred T.|
|Date:||Sep 1, 2001|
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