This technical information has been contributed by
Consolidated Casting Corp.
Investment Casting Company Adds Value with Full Range of In-House Manufacturing Capabilities
Quality, efficiency, and cost reductions are targeted in everything from design assistance to machining, welding, assembly, testing, and automated quality control.
By Mark Shortt
Editorial Director, Design-2-Part Magazine
Contract manufacturers in the U.S. today are going to great lengths to keep manufacturing work in the states. While many are adding manufacturing capabilities and value-added services whenever possible, others are integrating processes and procedures that can create efficiencies for their customers. One company, Consolidated Casting Company (now Signicast) of Hutchins, Texas, is doing all of the above as it aggressively strives to be the best preferred supplier to its customers. Over the last two-and-a-half years, CCC's owners have invested approximately $2.5 million into upgrading the company's facilities, equipment, and state-of-the-art technologies. As a result, the company offers a wide array of services for customers that want all of their work accomplished at one location.
"I think what makes us unique is that we have a multitude of value-added services that we can provide," says Jim Lukas, vice president of sales and marketing at Consolidated Casting Company. "I think what we offer is above and beyond what most companies in the industry offer. Many people in the industry farm out work that we do in-house, including layout and design assistance, tooling, machining, welding, and assembly, pressure testing, nondestructive testing, and material certifications."
One particular success story demonstrates how CCC was able to more efficiently manufacture a casting for a customer that was experiencing numerous problems with the previous suppliers. The casting was for a water-cooled manifold used in diesel engines for earthmovers and heavy-duty agricultural trucks.
Previously, the OEM had contracted with another investment caster for castings and design assistance. At that time, the part was designed as a two-piece investment casting that was welded together by an outside welding company, and then machined and pressure-tested by a third vendor. The OEM had major quality problems that developed into major finger pointing by the three vendors. The large customer was then forced to take over management of the supply chain.
"The customer decided to look for another vendor and found us because we could do the entire two-part, complete assembly in-house," says Lukas. "At the time, we had CNC machining, but we didn't have the types of pressure testing equipment that were needed, nor did we have a CNC robotic welder. So we decided to go out and purchase the equipment so we could produce the assembly completely in-house. In addition, our engineers were able to work out a more efficient design. What we did was engineer the component so that one of the parts would be a stamping instead of a casting. Our part ended up with a more stable base that would require less secondary straightening. And, when we engineered the cover that gets welded to the base, we engineered it as a stamping, which costs less than the casting, had less variation than the casting, and made the welding operation much simpler and less expensive."
After the cover is welded to the casting, a water pressure test is necessary at 80 to 90 psi to make sure the assembly isn't leaking. And after the casting is machined, an air pressure decay test is completed to make sure no leak paths have opened up during the machining operation. All of the testing was set up to handle this project. "So we ended up saving the customer over $300,000 per year on the overall program," says Lukas. "And we cut off 50% of the turnaround time because it wasn't going out to three different suppliers. The new design improved the quality of the parts and reduced the number of leakers at the final assembly stage. And a great deal of turnaround time was saved because the customer came to us for the entire assembly."
Although investment casting is its core business, CCC considers itself a full-service manufacturing company. The company has an extensive machining department with about 35 CNC machining centers of all kinds. It also handles automatic CNC robotic welding, subassembly and full assembly, warehousing, and distribution of finished parts. "Some investment casting companies do a little bit of machining, but very few have the extensive machining capabilities that we have here," Lukas explains. "We do in-house broaching, gun drilling, and milling and drilling. We also machine tube and bar stock for existing casting customers, and we do contract machining for customers and for other local casting companies."
The company's primary markets include oilfield services equipment, for which it manufactures mainly pumps and HV/AC parts; the power generation industry, for which it builds industrial gas turbines; and the valve industry, for which it produces valves of all kinds. The construction equipment industry has the company building diesel engine parts--like HVAC water coolers and manifolds--used in earthmovers and heavy duty trucks. Consolidated Casting also manufactures gear shift forks for tractors in the agricultural industry.
A Net-Shape Process for High-Temperature, High-Strength Materials
According to Lukas, investment casting yields the best-quality castings in ferrous materials--such as steels and stainless steels--with respect to surface finishes (usually around 125 RMS), dimensional control (typically +/- 0.005-inch), and metallurgical integrity, which he says is generally superior to other types of casting processes. If tolerances tighter than 0.005-inch are needed, they can be machined into the part. And if a surface finish needs to be better than an as-cast finish, the part can be machined. Extremely deep holes or threads also have to be machined.
Investment casting shouldn't be confused with die casting, because die casting is normally used for aluminum and magnesium alloys, Lukas says. The melting point of aluminum is only about 1220 degrees Fahrenheit, so the metal can be poured into a hardened steel die, or investment cast using lower-cost aluminum, wax injection pattern tooling and a ceramic mold. Since the pouring temperature of steels is about 3000 degrees Fahrenheit, a hardened steel mold would not withstand molten steel being poured into it at this high temperature.
"Most historians believe investment casting to be the original casting process used by Chinese and Egyptian artisans to make statues," Lukas explains. "They were first carved out of wax and then dipped into a type of ceramic mold material. After the ceramic sets up and cures, they would invert it and melt out the wax, giving them a hollow mold in which to pour the molten brass or bronze. After the metal cools, they would chip away the ceramic and the statue is left." He says the process began to industrialize during World War II because the machine tool industry couldn't keep up with the demands of the war. And with the aircraft and military industries needing higher-temperature, higher-strength materials that could not be readily machined, the investment casting process took off.
Investment casting is considered to be the most net-shape or near net-shape process available, says Lukas, because closer tolerances can be cast, and secondary machining is greatly reduced. It leaves very little material waste because machine operators don't throw away a lot chips, especially with costly materials like stainless steels. And with labor costs for machining skyrocketing, it makes parts more economical.
Solidification Modeling Software Optimizes Part Quality
SolidCast® and FlowCast®, designed by Finite Solutions, are two software programs that CCC uses for solidification modeling. "A lot of commercial foundries don't have this software, nor do they use it as extensively or effectively as we do," Lukas insists. "We can actually monitor the metal solidification process on a computer before we process the castings. The modeling gives us a lot of very useful information concerning the gating systems that are required to produce a high-quality casting. So it cuts down on many problems down the road. It allows us to optimize the gating systems, so that we're not over-gating the part needlessly and putting extra cost into the part. On the opposite side of that, we're not under-gating the part so it becomes full of porosity."
The casting company also uses Exact JobBOSS®, an enterprise-wide, integrated manufacturing software package that allows CCC to trace a product through the entire plant, from beginning to end. This includes production stages, inventory, planning, materials, management functions, deliveries, and cost tracking.
According to Consolidated Casting, it was the first investment casting company to achieve the QS9000 quality certification, which was originally developed and required by automotive companies because they felt the ISOs were not adequate to meet their needs. The company is also ISO 9001:2000 certified. "We handled a lot of automotive work a few years ago, but we've been phasing away from much of it because it's not as profitable as it once was," says Lukas.
Diverse Processes and Operations
In addition to casting and machining, the company provides CNC robotic welding and assembly using a completely automatic six-axis, two-station robotic welder. Consolidated Casting also uses a CNC welding lathe for OD welding. According to Lukas, the company has built much of its own specialized equipment for in-house use. This includes load testing equipment for applications up to 100,000 psi, as well as hydro and air pressure testing equipment that's needed for some components. The company also makes ceramic molds with automatic robotic arms that dip the parts into the ceramic solution.
Mal Engleby, one of CCC's owners and its president, is one of the company's primary design engineers. Consolidated Casting doesn't take design responsibility for its customers' products, but it does provide design assistance through its engineering staff. And unlike many companies, it also has a metallurgist on staff. "We work with all of the ferrous metals, a variety of steels, as well as stainless steel, nickel-based, and cobalt-based alloys," Lukas maintains. "We don't cast vacuum-cast materials, like titanium, which is very reactive and needs to be poured in a vacuum. Aluminum can also be investment-cast, but we chose not to do it. With aluminum, there are a lot of other options that the customer has."
Consolidated Casting has its own tooling department in-house, but still vends some of it out. The tooling is actually a cavity that's machined or burned into an aluminum mold base. It can be manual, semi-automatic, or fully-automatic, depending on the complexity of the part and the quantities involved. The company utilizes one wax pattern for each casting, made from the tooling. Then several patterns are assembled into a tree, or cluster, allowing multiple parts to be cast at one time. Larger parts are cast one at a time.
The cost of tooling, depending on the size of the part and its complexity, usually ranges from about $2,000 to $15,000, according to the company. The time to make the tooling ranges from two to five weeks. For tolerances, the industry standard is +/-0.005 inch per inch.
A Variety of In-House Testing
To expedite its customers' projects, Consolidated handles a variety of critical tests in-house. "We have many testing systems that not too many other casting companies are using, or that they have to go to outside vendors for," says Lukas. "These tests aren't done on all production parts, but we can qualify the quality of the casting in the initial sample development phases. And we also use them as a problem-solving tool if there is a problem with a casting. This testing might also be used where certain specifications require a higher grade of casting, including many of the aerospace, aircraft, and military applications."
Nondestructive testing (NDT), such as x-ray/radiographic inspection for internal defects, is performed for detection of internal flaws and surface defects that aren't visible to the naked eye. Magnetic particle inspection (MPI) is used to uncover surface flaws on magnetic materials, and fluorescent penetrant inspection (FPI) or liquid penetrant inspection (LPI) is used to uncover surface flaws on nonmagnetic materials. Consolidated also uses magnetic particle inspections for rescue tool parts that it manufactures for fire departments. Because these parts absorb high stresses, they need 100% NDT testing to confirm the integrity of the castings.
The company applies statistical process control (SPC) in the foundry and in the machine shop. In the machining process, for example, it's used to control the dimensions of the part. By running statistical control charts, CCC is able to track data and, based on the data, can see if any trends are developing that will result in defective parts if machine operators don't take action. The data gives managers a constant rundown on how the machines are performing, and allows them to make intelligent decisions as to when changes are necessary.
Automated Quality Control Equipment Boosts Accuracy
The casting company has also automated its quality control department. "We have automatic CMM machines, which is a good capability because a lot of other foundries don't have these automatic, programmable machines," Lukas maintains. "It allows us to program the machine so that the inspections are done automatically to inspect every feature on the parts. It's a lot more accurate and a lot faster than a person doing it. And we have optical comparators that reflect the image of the part on a screen. It's very useful when the part has a contoured surface that's difficult to check by other methods."
Another success story illustrates the company's capacity to redesign and engineer a more efficient part for a company that manufactures power generation equipment. The part was for a combustor assembly for a 75 kW portable power generator. "The parts started out with four investment castings, but after talking to their engineers, we were allowed to quote on the machining, too," Lukas recalls. "And then they showed interest in letting us do the subassembly work for them. We then started working with outside component suppliers that supply sheet metal parts, tubes, fittings, and other parts. Working with these suppliers, we re-engineered the fifth casting."
The fifth casting involved a fabricated piece of sheet metal, where the original manufacturer was welding tabs all around a sheet metal tube. But Consolidated believed there was a better way: The company cast the part as a ring, so that it could be welded in one place on the diameter instead of welding in each tab individually. The part was cast as two pieces in one, and, during the machining operation, CCC split the casting into two parts.
"We were able to engineer a more efficient design for them, and we could do the whole thing in-house, so we were able to make it more cost-effective for them," Lukas continued. "The change in design reduced the subassembly time by 26 minutes and achieved a greater than 50% per-part cost reduction."
According to Lukas, Consolidated Casting's capabilities are ideally suited to meeting new challenges. "We've gotten into computerized solidification modeling, fully integrated, lean flow manufacturing, and extensive value-added services because we have to compete against the low-cost operations overseas in China and India," he says. The company's robotic welding machine, for example, was something that it hadn't used before it started doing the earthmover and heavy-duty truck parts. Not only did CCC have to acquire the equipment for this work, but it came up with the knowledge and expertise to do the programming and process control. In addition, the nickel-based, stainless steel alloys, like those used for power generation equipment parts, have always been a more challenging material to cast. "This alloy is not typically cast overseas," says Lukas. "This is because the alloy is more prone to casting defects, like porosity, and it requires more gating systems and controls than standard steels."
For urgently needed parts, CCC has two rapid prototyping systems--stereolithography and machinable wax--in place. With stereolithography, the company can quickly generate 3D models of a part from a 3D computer model. Made out of a special material formulated for the investment casting process, the models can be generated in a couple of days. On the downside, the process is expensive because the material is very expensive. These methods are used for very complex parts, or parts that are needed very quickly. The plant can generate steel parts for the customer after the prototypes. The other prototype method, machinable wax, utilizes a special grade of wax that can be machined easily and quickly. Wax patterns are used to produce the cast samples. No tooling costs are necessary with either of these two processes.
"Performing for existing customers is the only way that a company can expect to grow its business with the existing customer base," says Lukas. "And good performance often translates into new business referrals. In addition to growing our business to the maximum extent possible with existing customers, our plan is to selectively add new customers that are a good fit for us strategically. We offer them design engineering services, quality, and fast delivery at good prices, so they'll never want to go anywhere else."
For more on Consolidated Casting (now Signicast), visit www.signicast.com.
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