Harrison's super size nobake conversion: instead of gradually adding nobake molding lines and phasing out its existing green sand lines, Harrison Steel opted to install the second largest automated nobake molding line in North America and convert all molding over in 18 months.

The Harrison Steel Casting Co., Attica, Ind., had been contemplating switching its green sand metalcasting facility to a nobake operation for some time. The firm, which produces steel castings primarily for the construction/mining industry, wanted to make the conversion to improve quality and ease the pricing burden from its customers.

Harrison Steel looked several times at gradually adding nobake lines and eventually phasing out its six existing green sand molding lines. But economically, it didn't add up. In 2000, the firm decided to take a different look at what to do with its 623,000 sq. ft. facility. After crunching the numbers, the firm found an option that was economically feasible--wholesale conversion.

Harrison made the decision to purchase an automated molding Line (AML) from IMF, Luino, Italy, and decided that bigger was better. The firm selected an AML from a footprint of 52,000 sq. ft., making it the largest in the U.S. and the second largest in North America 

"We looked at nobake a few year earlier, but we looked at it as an addition to the g sand, and it didn't make sense economically," said Geoff Curtis, vice president/general manager. "Then we started looking at it a little fresher and asked, 'What's going to happen if we remove green sand from our operation?' We looked at the savings by people, process and quality. All of those things made sense."

After seven months of waiting for construction permits, the project was off and running--literally.

"We got our permits the clay before we made the purchase," said Jeff Franklin, senior engineer. "Six days later, we started construction. It was a very tight schedule all the way through."

The permits were approved on July 6, 2001. Harrison placed the purchase order for the AML on July 7, and on July 13 construction on the $12 million project began. By July 3, 2002, the first mold was produced.

Franklin said the conversion would have been nearly impossible to complete if it were not started during the plant's annual shutdown. In fact, the plan most likely would have been shelved for a year.

To add more pressure, a detailed analysis of the conversion utilizing Six Sigma philosophies concluded that the process could be completed in 18 months, providing significant cost savings right away. Harrison's future was cast, and there was no turning back.

Wholesale Conversion

By 2001, Harrison was convinced a wholesale conversion to nobake molding was its best option. Curtis said something had to be done if the company that was founded by his great grandfather, J.W. Harrison, nearly 100 years ago was going to remain competitive.

"I think there were several reasons we did it," Curtis said. "From our experience with nobake floor molding, we felt there were opportunities to improve our product with chemically bonded sand molding. And there also were cost pressures from our customers that drove us to pursue another way of producing molds."

Curtis said Harrison is now" at the stage where it is beginning to see economic benefits from the conversion. But the one area that paid off immediately was with employment. The firm was operating six green sand molding lines that required 12-14 people each. When business was good, there would be 100 or more working in the molding and sand preparation areas. Now, Harrison runs two shifts of 15-16 on the nobake line. Curtis estimated the firm cut its molding and sand preparation employment by 50%.

"In addition to quality issues and price pressures, the job market got so tight that it became very difficult to find enough people even when we were at lower production levels," Franklin said.

Coincidentally, the time frame proved to be almost ideal to stall the massive project. During peak production, Harrison was producing about 130 tons/day of ductile iron and carbon/low-alloy steel castings. When it started the installation, production was down 40% due to U.S. economic downturn from 2001-03.

"It turned out to he the best possible scanerio," Curtis said. "I would like to tell you that we planned it that way, but we got very lucky with busines being slow because the new pouring and cooling lines used up half of the existing floor space. I'm not sure we could have done this project if we were busy. It worked out in our favor that business slowed down."

Franklin acknowledged fine conversion was a risky move with production slowing, but said to do it at any other time would have been more chaotic.

"It was rather remarkable to take that sort of a leap when business is down," he said. "If we had waited any longer, we would have been in serious trouble. The market upturn came about the time we were getting the bugs out of the line. We would do one mold and they would say, 'Good, now you have to do more.'"

The Installation

The AML includes a pattern change area, pattern preheating, new sand and reclaimed sand heaters, a molding loop with a 3,600 lb./min, automatic mixer, automatic mold strikeoff and a mold preheat station. It also includes two mold wash systems, drying ovens, core setting, two automatic mold closing systems, a mold pouring and cooling system, two shakeouts and a 30 ton/hr. mechanical sand reclamation system coupled with a gas-fired. 3 ton/hr. thermal sand reclamation system.

The molding system has the ability to produce flaskless molds up to a maximum size of 63 x 96.5 x 36 in. over 36 in. at a rate of 10 molds/hr. The minimum mold size is 32 x 49 x15 in. over 15 in.

The entire system is computer controlled to preset and monitor all of the variable process requirements for each mold half. In addition to entering and removing patterns from the loop and recording production requirements for each pattern, the production management system controls mold fill time, sand type, compaction time and frequency, wash system requirements, auto closer processing information, pouring line assignment, and cooling line and cooling time assignment.

The journey through the AML begins when pattern boxes are mounted onto a molding plate and inserted into the line. Once there, a computerized library of all parts produced by Harrison is called tip to make sure the date is appropriate for the job. After it is verified, the pattern moves into a preheating oven to bring it kip to optimum operating temperature for the molding process.

The pattern is prepared, and the sand operator initiates it into the loop, send-inn it through the premolding stage where risers, sleeves, chills, etc. are placed. It is then presented to a double arm, articulated, zero retention, 3,600-lb./min, mixer. A computerized system checks the library to determine the necessary sand mixture. From there, an operator is needed to simply guide the mixer to distribute the sand evenly. The mixer automatically shuts off, and the 22,000-lb. capacity, variable frequency compaction table automatically compacts the mold.

The rest of the mold loop is entirely automated. Operators are needed only to oversee the production and check data. Sand is automatically struck off after mold filling and compaction. A powered bolster plate transfer car then moves the pattern in and out of the "fast loop." There are five positions from the strikeoff to the rollover that are in place for the curing process, which is timed, so that if a mold has timed out, it will enter the rollover draw, if it hasn't, it will wait.

A 43,000-lb. capacity automatic rollover strips cured mold halves from the pattern and places them on a flat belt conveyor that is equipped with weight sensors that determine the need to repeat the strip cycle in the event of non-stripping on the first draw cycle.

The 'mold cake" is then transferred to the preheating station, followed by two hydraulically operated wash stations that automatically align each mold half in the center of the station. Each mold half is then lifted and programmed by the management system to allow each section to rotate in an infinite number of pre-selected positions. Each mold entering the paint station is on its own cycle and is automatically returned to the conveyor belt.

After completing wash operations, molds are transferred to a 75-ft. drying tunnel. Core setting is then done in two areas. The first is positioned immediately after the drying oven on two 40-ft. conveyor belts. The second area is re served for molds requiring extensive coring, and is located near one of the two mold closing stations. The cores are put in place as the mold moves down the conveyor belt, moving every 6 min. At the end of the coring line, the mold is presented to one of two closing stations.

The operator then initiates the molds into one of the two fully automatic dosing systems. A first set of clamps centers the mold on a common X axis, and a second set of clamps centers it on the Y axis. The mold is then lifted and placed onto a cast iron pouring plate that has been previously loaded into the autocloser using a scissor lift system. When the drag is lowered onto the pouring plate, the autocloser repositions itself to accept the cope, which is mechanically positioned in the same way as the drag. Prior to final closing, the table supporting the drag lifts slightly, allowing it to "float" during the final mold closing operation.

After leaving the autocloser, the pouring basin is attached before the pouring plate and mold are transferred to one of two clamping stations. Molds are then automatically transferred to a pre-selected section of the pouring and cooling field as programmed by the management system.

Operators mark when the mold is filled, and computers track when it will be available for shakeout. Molds are transferred to shakeout by 1,500 ft. of roller conveyors. An automatic pushoff removes the mold from the plate, and the empty pouring plate returns to the closer while an overhead crane retrieves the casting. After shakeout, 85% of the sand goes through mechanical reclamation, and 15% goes through thermal reclamation.

The AML is capable of producing 10 molds/hr., and Franklin said the firm is currently turning out 9.5/hr.

Converting Production

As if ramping up the AML was not enough, Harrison also had to continue running its green sand molding lines to ensure casting delivery. During the ramp-up period, Harrison was running the two processes simultaneously.

"One of the hurdles we had to overcome was satisfying our customers because we didn't have the option of shutting a process down without converting," Franklin said. "We were sharing space and operating two systems side by side. Floor space was at a premium. You never knew from day-to-day what yell were going to face. We were definitely pressed for time. The sooner we could get on with it, the better off we would be. We really pushed through to get it done."

That push lasted about nine months. During that time, Franklin said planning was critical. The firm would occasionally start one crew early on the green sand lines to keep production going and then shut it clown for 2-3 hrs. to allow the operators on the nobake line a window of opportunity to work.

"It was extremely chaotic," Franklin said. "There were times when there were two or three of its spending our days just figuring out how we were going to keep firings running. Fortunately, it was a slow period: we were at 65-70% of normal capacity."

Some operators split their clays between the two different lines. In addition, green sand molds were placed on the new nobake pouring plates because it was the only space available and much of the equipment was shared.

"It was a juggling act," Franklin said. "A lot of tithes sonic operators hardly had time to take a break."

Franklin said Harrison was able to survive the chaotic scene because of sound planning that included everyone from the top-down.

"It took a great deal of cooperation on everybody's part," he said. "The bottom line was that everybody was in on it from the fork truck drivers up to senior management. There also was a tapering off of the green sand and ramping up of flaskless going on at the same time so we were able to put resources where they were needed."

The process was further complicated because employees were essentially learning the new nobake system on the fly. Because everything was sped up during the ramp-up period, operators had only 6-8 hrs. of classroom training on the new machines.

"We barely understood the equipment when we were expecting it to run at full speed," Franklin said. "There were a lot of growing pains. The soft ware and machinery would crash, and we were pushing the envelope on flaskless molding. There were physical limitations in equipment that we had to adjust for."

And of course, there were more surprises than the engineers anticipated.

"We learned an awful lot about how unforgiving the process is," Franklin said. "We had to learn the tricks. We spent a lot of time taking minute bits of backdraft out, and we had to learn how to have the come off the the pin correctly and keep the chills placed properly in the compaction process.

"Anything you could possibly do wrong, we found a way to do it wrong," he continued. "From a maintenance and engineering standpoint, it would have been nice to have more time to test and try equipment, but that wasn't an option. You do what you have to do."

Converting Tooling

while there was disorder on the shop floor, the patternshop had its hands full constructing 162 new nobake mold boxes. Some were for new jobs, but the majority were those converted from green sand. Tim Hays, senior casting design engineer, said the firm closely tracked 44 of those jobs. The patternshop spent an estimated 1 1/2 weeks on jobs that were not that complex (requiring a minimal amount of cores, no off-sets, build-ups, etc.). The more complex jobs took an average of 4 1/2 weeks to complete the conversion.

"The first operation was to strip the pattern off of the existing green sand mold boards and repair them to near-new condition," Hays said. "We had to test-fit a lot of the heavily cored jobs and make adjustments when needed."

The next step was to start constructing the mold boxes.

"We knew we were going to have to do some dimensional tweaking to the patterns," Hays said. "We had to figure out a way of removing the boxes and putting them back in tire right location. We asked ourselves, 'How can we put these boxes on and take them off while maintaining consistency with the parting line?' If we didn't do that, we would have cope and drag shift. We came up with a method of lining up the pattern and mold box with the center lines. We then added hardened pins to the bottom boards and cast the hardened steel bushings into the mold boxes to guarantee an exact match when a box needs to be removed for a pattern repair or emergency change."

Harrison employed the use of one outside patternshop to construct the mold boxes and used four additional outside shops, including its own in-house patternshop, to maintain construction of the 162 patterns and engineering changes to existing patterns.

"We decided on hardwood or plywood," Hayes said. "We knew of other metalcasting facilities using metal for the mold boxes, which are more rigid, but they are restricted to only three or four box sizes. We wanted a box unique to each pattern number while trying to maintain a 2.5:1 sand to metal ratio. That drove everything that we did."

Harrison selected plywood because its groins run in different directions, unlike hardwood, which is more likely to split or crack. But fine problem plywood poses is that the edges are not strong enough to resist the damage caused while striking off the top surface. The design Harrison chose was a plywood box with maple-lined leading and trailing edges.

The engineers also were charged with finding a more effective way of attaching risers to the patterns because it was becoming a burden to remove four or five risers from most boxes. The solution was to permanently attach the risers with a cap on top.

"There were a few things that came up that we did not consider," Hays said. "But we knew it was going to be a long process. There was a big push to get the conversion done in half the time because of savings."

The Benefits

Now that the conversion is complete, Curtis said Harrison is in the process of "backing up and picking our way back through all of this work we have changed." Because of that, he said it would be hard to measure the savings.

What Harrison does know is that it will benefit from more consistency in terms of tolerance and surface finish. And automating the process has eliminated human error and produced savings through reduced manpower.

Curtis is hoping all of that will help Harrison remain competitive in serving the construction/mining and power transmission industries and possibly expand its customer base, which is now largely dominated by construction/ mining customers.

Harrison has been through a lot during its conversion from green sand molding to nobake. The sprint to finish the project is evidence of that. But the bugs are being worked out, and quality is improving. Now, Harrison can focus on perfecting its new operation and increasing productivity.

"I think we are going to be pushing our production level," Curtis said. "It may even increase. We may be finding ourselves getting even more out."

The Harrison Steel Castings Co., Attica, Indiana

Metals Cast:       Ductile iron, carbon steels and low-alloy steels.
Molding Process:   Nobake.
Size:              623,000 sq.ft.
Market Served:     Construction, mining and power transmission.
Employees:         680.
2003 Production:   18,317 tons.

Kyle Bauer, Associate Editor