Benton Achieves Quality, Quantity and Consistency in Coremaking.
When threatened with slower demand, you won't find many foundries that aggressively seek orders for hard-to-cast, complex parts. However, finding an overlooked, harder-to-service niche, like complex casting jobs, may lead to a fruitful future for those willing to take the risk.
This strategy has been key to growth at Benton Foundry, Inc., Benton, Pennsylvania. In the early 1980s, the ductile and gray iron jobbing shop was confronted with the same problem that faced many similar operations: customers were few and far-between. Benton opted for the more difficult (and potentially more rewarding) path: a production trend toward casting difficult or complex value-added components. By aiming for jobs that "no one else wants," the foundry has been able to boost per-part profit margins while tapping a market sector that often seems unapproachable.
The 140-year-old foundry specializes in complex custom parts for the mining, agricultural and electrical motor industries. Benton's coremaking operation is integral to its marketing approach. Without taking advantage of new technology and maintaining tight process control, the foundry could see high scrap rates and falling profit margins.
For its complex jobs, the foundry produces cores from the intricate to the simple for applications from jacketed manifolds, air starters and valve plates to circulator pumps and torque wrenches. Core assemblies can have as many as 10 pieces, and the quantity, complexity and variation of cores Benton is able to produce is no simple task. By looking at Benton's approach to coremaking, readers can gain insight into bettering their own processes and cultivating a rich future.
Seeking a Well-Defined Niche
The operation, which was launched as Harrington Foundry in 1862, was acquired by Hallstead Foundry and became Benton Foundry in 1958. In those days, the majority of the foundry's jobs were made via oil sand on 14 blow machines.
In 1975, when the current management took over the foundry, coremaking included both shell and oil, but this was soon to change, as Benton took on more complex jobs, spurring the move toward an all coldbox/shell operation.
In the last half of the '70s as many foundries were struggling, Benton decided to plow ahead in a different fashion than the norm. "Instead of approaching business from a desire to pour more tonnage, we wanted to make more profit and then pour more tonnage--it seems to go in better order that way," quipped Tim Brown, vice president-finance. "More coldbox jobs fit into this scheme very nicely."
Benton has tried to build on its expertise, taking on more complex jobs that further broadened its marketing focus and defined the foundry's niche. "In the early 80s, we were doing valve plates that were completely machined, and we thought those were difficult," Vice President Jeff Hall said. "Now we've taken our jobs up a few notches. We're getting into more and more assemblies, and now we're dealing with 3-4 cores per casting--and our customers are expecting the same type of quality."
"We want casting orders that are more intricate and require more machining," Brown said. "Casting price is an insignificant cost in the overall end product. Those types of castings require a well-trained, well-staffed coreroom that is up to the challenge and a production department that can coordinate these resources."
"We often pick up jobs that may be pushing the envelope of what we are able to do," Hall said, stressing that flexibility has been key to the foundry's success. "The end result is that we are able to do other jobs like it. We build on those experiences. It's enjoyable to look at a complex job and solve a problem."
Coldbox Takes Over
In 1979, the foundry began making coldbox cores, striving to improve its capacity for more intricate components, like water-jacketed manifolds. "We wanted to grow larger, and coldbox gave us an advantage in that area--not only with quantity, but with reliability and quality," said Brown.
In assessing the cost per ton of mixed sand, coldbox cores at Benton are cheaper than shell when approached on a total cost basis (material and equipment), according to Brown. However, some cores work better when they are hollow, he said, adding that it comes down to knowing process and product. "Thin rangy cores work better as shell. Larger jobs also may work better as shell cores due to weight."
Today, Benton's core mix is 85% coldbox and 15% shell. The foundry's sand usage has grown five-fold over the last 15 years--the coreroom uses 25 tons of silica sand/day just for its coldbox cores. The coremaking department produces 225,000 total cores/month (including 175,000 coldbox cores), yet the foundry maintains a core scrap rate of just 4%.
To keep up with the niche it had cultivated, Benton expanded its 175,000sq-ft facility by 25,000 sq ft beginning in 1991. The $8-million project included two electric furnaces and automatic molding lines for its iron casting operations. Today, molding operations include 14 x 19-in., 16 x 20-in, and 20 x 24-in, automatic molding machines. The foundry also manually molds small and specialty runs, operating 4 days/week, in two 10-hr shifts/day. Benton's business has grown 11-fold since 1975.
The switch to a primarily coldbox core-making system required some adjustment. "Switching to coldbox was a huge undertaking, considering the number of jobs we run," said Hall. "A high-volume operation may have 20 part numbers, whereas we have 8000. Here we can see coreboxes every other month or every 3 years, so, while we can 'tweak' the process to a degree, economically we can only go so far. In an automotive setting, core workers can spend hours on one job to refine processes, but here, we run over 20 jobs on each shift."
In addition to refining coldbox processes, Benton has purchased mixing and coremaking equipment over the last 22 years in an effort to capitalize on quality advantages of a more automated environment. Advancements such as volumetrically controlled pumps have increased consistency, and management is not afraid to try new approaches to coremaking and new equipment solutions. The foundry is expecting to double in size over the next 5 years, both through expansion and rearrangement of existing equipment.
The work flow through Benton's 50,000-sq-ft coremaking area (including storage, laboratory space and assembly) is linear and automated in an effort to minimize handling and breakage attributed to it, A bucket elevator receives new sand from an 80-ton sand silo and transfers it to a heater/cooler, From the heater/cooler, the sand is fed automatically to a mixer. After the coldbox resin passes through a heater, it also is added volumetrically to the mixer.
"In the old days, we had a 60F span in the temperature of our core sand and, just like motor oil, the hotter it becomes the more viscous it is," Brown said. "Now, sand is held at 65F constant. In the old days, resin was dumped in by hand, and resin levels could vary from 1.7-2.3% of the mix. Now, resin levels are cut from where they were 20 years ago because of automatic mixer control that can keep variation to a minimum, as close as 0.1% to what is programmed." Today, coldbox binder levels at Benton are 1.2%, 1.5% and 1.7% (which is used only for thin-section cores), and the foundry has added PLC controls for greater operational consistency at each machine.
Additives, including an iron oxide and a densifier, are added to the mixer, depending on the job. Castings that are highly cored and prone to pinholes require an iron oxide addition to the mix, while those with heavy, isolated sections prone to iron penetration use a densifier. The foundry has seven coldbox machines to run different jobs, depending on their cycle time and complexity, and all of the machines are fed by the same mixer.
The cycle time for a coldbox core varies from 8-30 sec. "We've gone from using one machine that was fed by hand to one machine that feeds seven stations and can make eight different mixes automatically," said Hall, stressing that this has increased efficiency, speed and reliability of the mix. After the cores are blown, an operator sets a hardened core on a belt where it is cleaned. Typically, each operator "runs" two machines.
The cores then move to assembly or storage. All in all, the operation keeps 10 days worth of cores on-hand. In the assembly area, there are books containing instructions for each job (Fig. 1), Workers gather all necessary cores, the proper glue and chaplets, and piece the cores together according to instructions. "We have a standard documented process on how to do things, not only as a department but also on a part-specific basis to maintain consistency," Hall said. "Every part number has a job card that includes pictures and instructions concerning the sand mix, percentage of resins, chaplets, the order of assembly, core-dipping procedures, and special handling considerations. Even if we haven't run a job in a year, there won't be any question as to what's required."
A job card is filled out for each step that the cores undergo, and those cards are sent to Benton's production office so managers know when to schedule the cores for use.
Casting scrap attributable to cores has been decreasing over the last 7 years, largely due to the foundry's documentation procedures, Hall said. "Even when we do something consistently wrong, we make mistakes that are easier to find and change. With the way technology has changed, including resins and equipment, the process refinement has continued for a long time and is on-going."
Coremaking for a new order involves reviewing experiences with similar jobs, tapping in-house knowledge and, sometimes, trial and error. When Benton first receives a job, the foundry drafts a complete workup on how to make the casting, documenting the entire process from coremaking through delivery. Instructions based on the initial design are used to cast an in-house sample.
All records are retained, even those records that show casting problems. With particularly complex jobs, Benton may review past records of castings that had similar design features. "We document what works and what doesn't, and we keep a 'change' log-when we have a problem, we know we don't want to go back there again," Hall said.
An example of Benton's core design process can be seen in a ductile iron 75-lb pneumatic wrench. The job was inherited from another foundry that refused to continue to make the complex casting, which required a 12-piece core assembly. The customer had trouble re-sourcing the part, but Benton agreed to take on the challenging component (with conditions concerning initial scrap during the foundry's learning curve" and arrangements to pay for tooling).
At first, the foundry had problems with gas and core breakage. As part of the foundry's trial-and-error approach, workers added stiffeners to the cores (rods wires and nails); strategically located chaplets to stabilize the cores; and added vents to the cope surface and through the parting line of the nobake mold to help gas problems. "The combination of the three ended up solving the majority of our ills with the part," Hall said, stressing that although the part was daunting at first, the foundry now has the expertise to take on similar value-added work.
Benton also has been environmentally conscious in its equipment and process choices. The foundry's coreroom utilizes a tower unit to scrub the air of spent acid and gas catalyst and remove residual odor. These emissions then are bulk-packaged and shipped to a service provider that recycles the amine gas While there is an initial cost for the recycling tanks ($150 each) and to send the amine and acid to a recycler, the overall cost is cheaper than disposing of the material as solid waste, Brown said. In addition, amine gas is reused, and considering that the gas can sell for well over $2/Ib, the practice is economically sound.
Gas catalyst usage is viewed in relation to batches of sand per barrel and as a function of resin percentage being co-reacted. By industry standards, Benton is within the top 10% in gas catalyst usage, according to Brown, who stressed that this is due to attention to detail by core-room supervisors, adherence to blueprints and consistent tooling and rigging procedures. A water-based graphite core wash is used on 5% of Benton's jobs--only those that require special attention.
Benton views itself as a "green" company, Brown said, stressing that the Clean Air Act and Title V both have impacted the way the foundry approaches the idea of a safe work environment.
Benton works with suppliers to provide in-house training seminars to help maintain a safe environment as well as optimizing binder and equipment performance. "Suppliers are an excellent source of information--they cover the use of products to environmental initiatives and tooling design," Brown said.
Maintenance Improves Quality
In addition to coremaking documentation, Benton keeps a close eye on preventive maintenance and tooling. Detailed maintenance records are important to maintaining consistency and quality (Table 1). In addition, tooling is inspected before placement for excessive wear or other problems. Machine uptime is good, with the average coldbox machine changeover taking 15 min. This compares with a 45 min-1 hr changeover with the foundry's shell core machine.
The foundry also is nearing the point in which tooling cycle counts are recorded by computer. "The idea is to be proactive with a customer and deal with problems in a timely fashion," Brown said.
In addition, Benton tracks the number of cores made per good casting for each order. The operation's goal is 95% on-time delivery, and even with increasingly shorter lead times, the foundry has still been able to accomplish this. "The hoops we have to jump through are getting higher and higher," Brown said. "In the 70s, our typical lead time was 8-12 weeks--now it's less than 4."
The foundry sees a 5-6% range of overall casting scrap, which, given the nature of the work, is excellent, Brown said. "Our ability to make things no one else seems to want to make and make them competitively--that's what makes us stand out. Even with the high number of orders coming through, westill achieve admirable scrap rates and on-time delivery."
"Not everything we have tried has worked," Brown said, "but, when you soar with eagles, every now and then you're going to clip a few trees."
Benton Foundry, Inc.
Year Established: 1958.
Metals: Gray iron (class 25, 30, 35 and 40) and ductile iron (Grades 65-45-12, 80-55-06, 60-40-18 and 100-70-03).
Molding: Automatic horizontal machines (five lines).
Coremaking: Shell (15%) and coldbox (85%).
Core Equipment: Four sideblow and three top blow machines; seven gassin gunits with purging heaters; packed tower amine scrubber; 250-lb batch mixer; volumetric resin addition system; sand heater/cooler.
Core Production: 225,000 total, including 175,000 coldbox/month.
Melting: Four electric furnaces (300 ton capacity/day).
Casting Size: 1-150 lb in quantities from prototype to several thousand pieces per order.
Employees: 250, including 40 in the coreroom (25 coldbox).
Key Management: Alfred "Fritz" Hall, president, Jeff Hall, vice president; Tim Brown, vice president-finance; Met Bartlow; coreroom supervisor; Brian Mohr, coreroom supervisor.
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|Comment:||Benton Achieves Quality, Quantity and Consistency in Coremaking.|
|Article Type:||Brief Article|
|Date:||Jun 1, 2000|
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