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System Designers Shake Up the Cleaning Process

Oct. 10, 2007
Whether the chosen equipment is a design breakthrough or a thoroughly tested application of best-available technologies, decoring systems are getting the sort of careful attention that high-value castings deserve.
At Technocast, cylinder heads are cleaned of mold and core sand in an automated system of four fully enclosed cells, served by shuttle cars. The units close around the castings, and then administer high-frequency, low-amplitude vibration followed by air cleaning to remove sand from the complex structures.

Buyers want choices, which is what keeps product developers busy — even if their buyers are foundries and their products are the relatively un-noticed systems for removing sand cores. So much time and research is invested in developing core sand and coremaking technolgies, it should hardly be surprising that metalcasters also want new approaches to removing those cores from their finished castings.

Technocast, the new gray-iron foundry producing diesel engine blocks and cylinder heads in Saltillo, Mexico, is a ready example. The $160-million operation is a joint venture of Caterpillar Inc. and Grupo Industrial Saltilllo, producing the blocks and heads for Caterpillar products. It recently started operation after two years of development, and it’s expected to reach full capacity of more than 90,000 tons/year about two years from now.

The success of this project rests on maximizing the value of each casting produced. Foundry Solutions & Design recognized that fact in its approach to designing and implementing the decoring operation at Technocast. FS&D did the concept planning, engineering, and system integration for the automated handling, decoring, and finishing of Technocast’s various cylinder heads. The decoring cells were manufactured by the R. Scheuchl GmbH, and use high-frequency, low-amplitude transducers for decoring to break up hardened sand, followed by a rotating unit to remove sand from the cylinder heads’ internal passages.

FS&D’s president Ralph Perkul emphasizes that the installation involves the best available technology for the task: high-impact systems may damage the thin-walled castings, but the short-stroke, high-frequency method will not. FS&D has been designing similar systems for the past five years, always starting with computer modeling to anticipate any inherent problems, but choosing proven equipment to ensure the operations are effective and consistent.

Scheuchl’s decoring method is based on high-frequency, vertical oscillation of the casting, with amplitudes up to 36 mm. Inside the product, core fragments are broken up by concussive energy, and a subsequent sand-air mixture is removed by high-frequency rotation.

As detailed by Perkul the Technocast decoring station has four fully enclosed cells, and each set of two machines shares a shuttle car with two fixture plates. These fixture plates index to the appropriate position to receive the cylinder heads, then pass the product into the decoring unit. The unit closes around the castings, and a lifting device separates the castings from the loading device. The high-frequency, low-amplitude transducers move into working position, decoring starts. During this phase the cyclinder head is rotated to remove the sand out of the passages, and air is introduced to hasten the sand removal process.

Once the cycle is complete, the unit opens again and a gantry robot moves into position to remove the cleaned cylinder head. Waste sand is transported away by a conveyor running beneath the line.

Perkul says relying on available technology is important, because of the standards set by foundries for system reliability, in order to achieve their own customers’ quality and performance guarantees.

But, taking different approach, General Kinematics set out to develop a new design, based on customers’ requests for an alternative to the rotary cleaning systems widely available, including its own designs. The Ducta-Series was introduced earlier this year — a rotary sprue mill, a rotary shakeout, and a rotary media drum — all specifically developed for ductile iron castings, and designed with a single-layer wear plate shell to prolong service life. The patent-pending modular shell is designed to be replaced easily and affordably. Sand and media exiting the drum are collected with GK’s Syncro- Coil vibratory technology.

The first order has been received from a ductile-iron foundry in Michigan, where a Ducta-Sprue rotary sprue mill will be delivered by the end of 2007, to clean and break sprue and remove sand prior to remelting. GK’s product manager Tom Muschoot recalls that his firm had heard requests for an alternative rotary cleaning technology but always decided instead to promote its own vibratory systems. He continues that an ongoing trend toward more ductile castings caused them to revisit the idea because they “realized there were some advantages to rotary in ductile casting situations.”

“Ductile iron castings tend to require more force to aid in sprue removal,” Muschoot explains. Customers also appreciate the “tumbling and breaking energy generated in a rotary drum, to remove castings from gating.” GK continues to recommend and promote vibratory equipment for other types of castings, because the vibratory motion “produces significantly less scrap than rotary designs and cools and cleans gray iron, brass, and other castings, as well.”

The design process began in January 2007, he recalls, involving him and a GK regional sales manager, Richard Kempf. They developed a rough concept based on feedback other representatives and customers. From there, they worked with GK’s engineering department to design the final concept, using computer modeling to simulate the operation to ensure it met performance standards. “Overall,” he sums it up, “the entire product line went from inception to full production in under six months.”

For buyers, the Ducta-Series offers a lower cost of ownership over the life of the machine versus what is currently available in the market. Its initial cost is competitive with similar equipment, but Muschoot explains it is “significantly” less costly to own, operate, and maintain over the life of the machine.

These claims are based on the fact that the fabricated machine liners cost approximately 25% of the price of cast liners that are the current standard for rotary systems. Sand and media do not contact the drum’s primary surface, so the shell is not considered a consumable item. “Removing product from that surface allows the outer surface temperature of the drum to be cooler than other rotary designs. The fabricated liner is also significantly safer and easier to install than the cast grid systems found on the market today, and should last as long, if not longer, than those systems,” according to Muschoot.

He adds that liners in the drum and sand-collection conveyor are expected to last three years or more, depending on the product and application; the drum shell should not need replacement unless subjected to extreme heat. Chain and drive components are based on commercially available equipment, and should be replaced based upon normal wear. GK chose to use its own line of vibratory duty bearings, based on their performance and longevity versus standard bearings.

And, GK intends to keep improving and adapting the rotary technology. “As our product matures,” he explains,”we will take the feedback our customers give us and incorporate it into future designs and improvements.” Already, it has introduced a new vibratory media drum, Vibra-Clean, to perform similar functions as a rotary media drum but without the sort of tumbling that may damage fragile castings. Metalcasters then can “gently scrub their castings clean prior to sorting and shot blast, without the high percentage of scrap rotary technology generates when misapplied outside ductile casting.”

Foundries have been enthusiastic about the Ducta-Series, and GK has logged a “substantial” number of inquiries. Beyond the first Ducta-Sprue installation in December, subsequent orders will be fulfilled in the new year.

All in One: Shakeout, Cleaning, Sand Conditioning, and More

Pacific Alloy Castings, a gray- and ductile-iron foundry in South Gate, CA, updated its vibratory shakeout system earlier this year, and installed Didion Intl.’s ( Mark 5 Series rotary media drum.

The patented Mark 5 performs shakeout, sand conditioning, double sand screening, casting cleaning, and casting cooling, all in a single step. It separates the sand from the fragile castings; it conditions and “double screens” the sand; cleans the casting; and gates the runners and sprues, as well. The design is so efficient that it contains the sand within the system, so airborne dust is reduced — keeping the workplace cleaner and safer. Also, by combining the processes, Didion points out that foundries can save $40.00 to $80.00/ton in operating costs, which it claims is the industry’s lowest operating cost for a shakeout system. Other advantages include a low capital cost, minimal floor space, low energy costs, low maintenance requirements, low shot consumption, fewer replacement parts, cleaner working conditions, and cleaner returns to the remelt operation.

The return sand is blended and conditioned to be consistent in temperature and moisture content, all while keeping the sand in the system. Dust collection is efficient, because the drum has just a small open area, and counterflowing air minimizes airborne silica dust. Didion contends the Mark 5 demands 75% less dust collection than a vibrating shakeout rated at the same capacity.

Jim Leach, president (and owner) of Pacific Alloy Castings, emphasizes that he is not exaggerating when he calls the Mark 5 system “the best labor saving device I have installed since we stopped shoveling sand 30 years ago.”