Casting Moves from Ancient Art Technique into Computerized Modern Foundries
Foundries in California and New Jersey find market in precision casting for defense, aerospace, medicine, and other fields.
By Mark Langlois
Foundry casting may conjure images of ancient art, of tiny figures dug by archeologists brushing aside the dust of 5,000 years, but modern foundries cast parts for airliners, military helicopters and jet fighters. The old foundry with dirt floors gave way to green foundries with design rooms and CAD programs, shiny floors and computer-assisted furnaces.
When workers at Engineered Precision Casting Co. (EPCO), Middletown, New Jersey, prepare to pour molten stainless steel from the crucible into an investment casting ceramic mold, they use a computerized probe to confirm the temperature is about 1,450 degrees Fahrenheit. It was exactly that temperature when they poured the molten steel. The mold glows orange from the molten steel inside as they hang it on a rack to cool.
The molten steel sparks a bit and there is plenty of dust on the floor, but metal casting has come a long way since it was first used to make jewelry. Investment casting, one of many types of casting available at today's foundries, creates the tight tolerances and the fine finish required for aerospace and defense applications, among many other industrial uses.
"It's very accurate," said Bill Dubovick, president and CEO of EPCO, in an interview with Design-2-Part Magazine. An advantage of investment castings, Dubovick explained, is the finished cast is near the required tolerances. "This process reduces the extra steps. There is finer machining, but we get it down to the bare minimum." EPCO handles its finish machining in house.
EPCO (www.Epcast.com) casts roughly 100 alloys, said Dubovick, the son of company founder Walter Dubovick, who grew up in south Jersey with a friend named Nick Grant. When Walter Dubovick returned from building air strips in the Pacific Theater during World War II, he was unhappy at his job at LaGuardia Airport. He wanted to be his own boss so he went looking for a business.
Here, ceramic molds are cooling after being filled with molten stainless steel. Once the steel cools, workers remove the one-time ceramic mold. Photo by Mark Langlois.
By then, Grant had become a chief metallurgist at the Massachusetts Institute of Technology, and Grant had a new business idea for his old friend.
It isn't what you know, it's who
William Dubovick said the story goes like this, "Nick told him, 'We've been fooling around with this process at MIT– it's called investment casting. In fact, if you're interested, we have some equipment we can give you at a really good price.' My dad looked at the process, did a little market research on his own. He decided there was a market for investment casting.
In the late 1940s, people were hogging parts out of metal rods or blocks. It meant investment casting was competing against machining, and carving a part out of iron or steel takes a lot of time and wastes a lot of materials.
Casting is the word that describes a foundry process in which a molten liquid is poured into a mold that has a hollow cavity inside. The cavity is the exact replica shape of the desired part. During the casting process, the molten liquid fills the cavity and cools. As it cools, it hardens into the shape of the desired part. The part is removed by opening two halves of the mold in certain casting processes, including permanent mold casting, or by breaking apart the mold in the investment casting process. The part, which may require post production finishing, is also called a casting.
EPCO receives a CAD file or a blue print of a part from a customer, and EPCO workers create a tool from aluminum. That tool will create the wax pattern (an exact replica of the desired part.) Once the tool is complete, the wax pattern is filled repeatedly with wax in the part's shape. The wax pattern is glued to a short wax stand, one after another, so a number of parts can be cast at the same time. After the tree is completed, EPCO workers spend a week covering it with ceramics. They create a ceramic shell around it. They do this by repeatedly dipping it into a liquid ceramic slurry and then dipping it into a moist powdered ceramic to build up a ceramic shell.
Once the shell is about ?-inch thick, it is dried. It is heated in an autoclave to remove the wax. The shapes inside, replicas of the desired part, are now ready for casting. The mold is heated to molten metal temperatures, and molten metal is poured inside the ceramic mold. The mold is set on a rack to cool.
This curved part was cast at Engineered Precision Casting Co. for later use on an aircraft. Photo by Mark Langlois.
Once it is cooled, workers either vibrate or hammer away the ceramic mold, smashing it to pieces. They are left with numerous parts, side-by-side on the tree. They cut them off and then the part is finished.
In addition to casting, modern foundries use numerous finishing processes.
General Foundry Service (GFS), based in San Leandro, California, offers four different casting processes, plus CNC machining and pattern making, under one roof, an offering the company says matches a customer with the best manufacturing process for their part.
General Foundry Service (www.Genfoundry.com) has customers all over the world, but most of its customers are in the U.S. Western time zone, so when a customer has a question, GFS replies within hours. If the firm needs fast help from a supplier, the supplier is typically within roughly 40 miles.
"We're typically local. We're not in another time zone. But we do have customers on the East Coast, in Singapore, Ireland, and Israel as well. That's a smaller percentage," said Keith Krook, business development manager of GFS, in a telephone interview. "Because of shipping costs, our radius would typically go out to the Rocky Mountains, up to Washington and down to Southern California."
General Foundry Service employs 70 people in San Leandro, California, which is about a mile from where the company was founded 71 years ago. The foundry is ISO 2008 certified and it is working toward ISO 2015 certification.
A worker pours molten metal into a mold from a ladle. Photo courtesy of General Foundry Service.
For its defense and government work, GFS is ITAR compliant and has a unique Cage Code for federal work. Ed Ritelli, Sr., founded the company that his son, Ed Ritelli, Jr., now runs. John Ritelli, representing the third generation, has also joined the company and is working today as an outside salesman. General Foundry Service's most recent machine purchase was a new Zeiss coordinate measuring machine (CMM), an inspection machine that cost $150,000.
"We have five different foundry processes, a machine shop, and a pattern shop all under one roof. We have five options when other foundries, let's say domestically or off shore, they may have a sand foundry, or a plaster foundry or an investment casting foundry, but they don't provide everything under one roof. They don't have multiple solutions for the same problem, for the same opportunity, so to speak," Krook said. Options are good, but not the only benefit.
Customers consider many options
General Foundry Service offers precision sand casting, no-bake (air-set) sand casting, rubber plaster mold casting, and permanent mold casting. It also offers CNC machining and other finishing steps.
Permanent mold casting at GFS typically employs a two-part mold made of iron or Meehanite. Because the iron mold is more costly to make than a sand mold, for a permanent mold casting to be economical, it requires a parts run of 1,000 parts or more, depending on the complexity of the part. That number spreads the cost of the mold over the numerous parts, lowering the cost per part.
The water-cooled permanent metal mold is required for a complex part made in large quantities. The iron mold improves the surface quality. The process also controls shrinkage, according to process descriptions at genfoundry.com.
A worker at General Foundry Service closes a sand mold before the mold is filled. Photo courtesy of General Foundry Service.
Precision sand casting is a term used for GFS's "green-sand" molding process. In this process, according to GFS, the company's proprietary mixture of sand, clay, and water is packed around a pattern by hand, with power tools, or in a pneumatic machine that exerts a compressive force to pack the grains of sand and clay close together to form each mold half. The term "green-sand" implies that the sand binder is not cured by heating or chemical reactions, according to process descriptions at genfoundry.com.
The no-bake sand casting process, used to make larger castings, employs a proprietary mixture of sand and plastic binder, which is packed around a pattern to produce castings weighing 80 to 225 pounds, according to GFS. In the no-bake sand process, sand molds are created with wood, metal, or plastic patterns. A proprietary mixture of sand with a plastic binder is mixed and deposited into a box containing the pattern and all essential gating, risers, and chills for pouring. The sand mixture sets up hard in a few minutes, and the mold is removed from the process. Cores forming internal passages in the castings are made using the same process. Cores are placed in the molds, and the molds are closed and ready for pouring. This method is reported to create molds with excellent dimensional stability, and the casting surface is improved over other sand casting processes, according to process descriptions at genfoundry.com.
The rubber plaster molding process is said to be similar to the sand casting process, delivering a smoother surface with better dimensional accuracy. General Foundry Service says that metal shrinkage can be controlled better in plaster molds, leaving less warpage and distortion of castings than with the precision sand process. Because the rubber plaster molding process delivers parts consistently produced to close tolerances, it is said to greatly reduce and often eliminate costly machining and other finishing operations.
The rubber plaster molding castings are higher in unit costs than sand castings, but the process is used to create parts not obtainable with other casting methods. Parts made via the process are said to frequently have improved metal properties, including uniform hardness and machinability. The process is suitable for castings with extremely thin sections, according to process descriptions at genfoundry.com.
Krook says that GFS's lead times are reasonable, and that its pricing model is higher than even some other domestic suppliers because the company offers "all the value and all the services– some of the intangibles."
Here, a worker is removing the sand used in the casting of a metal part. The sand is recycled. Photo courtesy of General Foundry Service.
"We help customers design the part for a casting," he said. "The customer typically has a machined part or a sheet metal part, and they want to reduce the cost. I'm thinking, theoretically, a casting should be less expensive, so we help them design that part from whatever it started out as, into a cast geometry, and then into a machine casting geometry and, potentially, even an assembly and a powder coated or painted part.
"They're thinking in their minds that they just need a casting," he continued. "They're going to buy a casting from us and then go to a machine shop and have a machine shop machine it and then take it back and go to a powder shop and have them coat it. Then they go to an assembly house and have them assemble it," Krook said.
"What we say is, 'let us take the casting. We can machine it for you in our machine shop. We can send it out to our suppliers and eliminate all the headaches to go along with plating and painting.' We can do the light assembly in house when it comes back and have it inspected."
Put that weight on our shoulders
Krook said that GFS is able to provide a turnkey solution and take all of the headaches out of the customers' mind.
The General Foundry Service design process may include an important step that only a caster is trained to make. General Foundry Service may help the customer design a casting into a multi-component casting. That step may eliminate assembly by combining what used to be two or three parts into one casting.
That higher value casting reduces costs in the end, GFS argues, by turning three or four components into a single casting, thereby lowering the number of components, reducing warehousing costs, and reducing assembly costs.
"We'll save them money as far as part number, inventory, and assembly cost. We can make it all one casting. It's a little bit more tricky, but it's a higher value casting. We save them money down the road," Krook said.
Another benefit of the multiple processes is the rapid turnaround to help customers with early designing.
For Tesla, GFS produces prototypes– "very quick, very low volume, very fast prototypes"– as Tesla does its engineering. GFS knows that once all the prototypes are evaluated and modified and a final part is chosen, Tesla will mass produce it either domestically or overseas. Mass production for automotive isn't something that GFS gets involved in. "Quite frankly, we don't want to get into high volume production for automotive components. It's not a fit for us." Krook said.
"With semiconductor, it's the same way. They'll go to us for prototyping and they'll go offshore for production. In semiconductor, the final assembly of the machines is done off shore."
Quality seems to be more and more important in most industries, including military and aerospace, automotive, semiconductor, and medical, Krook said.
Foundry quality upgraded
General Foundry Service is ISO 9001: 2008 certified, and is working on earning 9001: 2015 certification next year. These days, Krook said, they're seeing a trend of more dimensional inspections, or building in more requirements, on components that used to be very straightforward parts. In the past, GFS might make a part, measure five dimensions on it, machine it, measure a few dimensions, and then paint it and ship it. Whereas now, he said, documentation requirements have increased to the point where they're likely to be required to measure every dimension on the drawing for the casting, measure every dimension on the drawing for the machining, and then measure the part after it's painted.
"We serialize and we document dimensions at the casting level, at the machining level, and at the assembly level for our customers," Krook said. "We can do about as much inspection as a customer wants, or as few dimensions as our customer wants. We'll do whatever the customer wants. We can help our customer with their downstream qualifications. We offer X-ray and die penetrant inspection, all kinds of testing at various levels of the production processes.
One of the benefits of the Silicon Valley supplier base is supply problems are solved quickly.
"We have a very strong labor pool. We have a strong supplier base. They're all Americans, and we're proud to make an American product," Krook said. "It's an American component that goes into an American product for our customers. Our supplier base is very close to us, within 20 to 40 miles of us, typically, for some of the smaller items."
Having a local supply base also eases the company's technology burden. General Foundry Service doesn't need to master 3D printing.
"We don't do it in house. We find our supplier base is phenomenal. The pricing is phenomenal, so we off-source those services. We tap into 3D printing of aluminum for sand molds and 3D printing of plastic patterns for the first stages of our tooling processes," Krook said.
A typical meeting between GSF and an OEM engineer might sound like this: "I've never made a casting. My boss said design this thing."
"No problem," Keith replied. "We'll design it to take care of your needs."
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