Nobake expansion without physical expansion.

In order to stay competitive in today's global marketplace, foundries must continually expand to ensure that they are not left behind by continuing technological advancements. But what happens when a foundry has nowhere to grow into?

Talladega Castings & Machine Co., Inc., a 50-employee 150-ton per month nobake foundry in Talladega, Alabama, had that exact problem when it decided to increase its production levels by installing a new nobake molding line. The foundry is located in the middle of a city (two blocks from downtown), and is bordered on all sides by businesses or city streets. With outside expansion being impossible, any increase in production needed to use its current space.

The firm, which casts carbon and low alloy stainless and heat resistant steel along with gray iron for the aluminum recycling and mining industries, has 44,000-sq-ft of manufacturing space. In order to fit a new loop molding line for flaskless cope and drag molds, the firm required creativity.

This article will show how Talladega Castings increased its production levels 25% through the installation of a loop molding line and an electromechanical rollover.

The Loop Molding Line

"We wanted to take some labor out of the job," said Terry Sides, acting plant manager at Talladega Castings. "We had previously been doing it all by hand. When we automated the line, we not only increased production, but we achieved better quality molds."

Since the installation, production has been increased from 30 molds per day to as many as 85. This also has helped to keep the overall scrap rate under 2.5%. The total cost for the loop molding line and rollover was under $120,000.

In 1998, a concept design was made for the loop molding line. The only space available was less than 800-sq-ft. The goals for the loop molding line were as follows:

* must double the production rate of molds;

* must accommodate a complete range of mold sizes from 22 x 22 in. to 46 x 60 in.;

* must allow any combination of mold sizes to be molded simultaneously with no set up changes;

* must include as many ergonomic features as possible;

* must be easy to operate.

With these goals in mind, a "P' shaped loop molding line (Fig. 1) was engineered. The roller conveyors for moving the patterns and molds were designed to take advantage of gravity with a 2.5-in, drop from start to finish. In order to meet the space constraints and also to elevate the mold from the molding station to the finish line, two chain transfer conveyors were incorporated.

These transfer conveyors use air bags to lift and transfer by chain the cope and drag molds. After the molds are stripped from the patterns, the patterns are transferred back to the molding line by the use of pop-up rollers and a gravity roller gate (Fig. 2). The spring assisted gravity roller gate allows easy access up and down the finish line. With this design, the molding personnel always are moving the cope and drag molds and patterns downhill.

After a period of study and consultation with the molding personnel, the height of the conveyors was set at 22-in., allowing the molds and patterns to be handled with minimal stopping or bending. Mold preparation, such as applying mold wash, venting, setting chaplets and cores, and actual closing of the mold are completed on the finish line with less effort.

Also included in the design was a new 300-500 lb continuous mixer set up to mix molding and core sand with new sand or reclaim sand options. "Since we were already installing new equipment, we felt that it was the perfect time to replace our existing mixer," Sides said. "We installed it right where the previous one had been located."

The loop molding line was installed in the summer of 1998. Within one week of the startup of the loop, Talladega's molder of 15 years, who had suffered from lower back pain, was pain free. There have been no back strains or injuries on the loop molding machine line since its start up.

Once this line was installed, production of flaskless molds was more than doubled, but it required 5 people to operate it. It became very obvious that a mold rollover device could improve efficiency as well as mold quality.

Installing the Rollover

The other major installation planned at Talladega was an electromechanical rollover (Fig. 3). There were several specifications that hindered the selection, installation and operation of a mold rollover. They were:

* space available for a rollover was limited;

* must mount flush to the floor with no requirement for a pit;

* must be capable of accommodating a large range of molds of any size at any time with no changes in set up;

* must eliminate the need for true position of the mold before entering the rollover;

* must not require any hydraulics;

* must be capable of drawing the pattern from the mold with no ratting of the mold cavity.

With this list of specifications in place, a search was begun for an off-the-shelf mold rollover. However, Talladega Castings quickly discovered that no rollover existed that could meet the listed specifications. All were hydraulic powered, required a 12-in, minimum pit, were limited as to mold size and required true positioning of the mold before entering the rollover. Most off-the-shelf rollovers also required the installation of some type of clamping device on each mold box for holding the pattern while it was drawn from the mold.

Since the type of rollover needed could not be found, the process was begun of designing a rollover that would meet the listed specifications. "We designed the concept ourselves and then contacted a supplier that had never built a rollover before," Sides said. "The reason we did that was because they were not handicapped in their thinking as to how designing a rollover should be done."

Using the concept drawing and specifications developed by Talladega Castings, engineering of the rollover began. This rollover would use a ball screw drive and linear bearings for clamping of the mold (Fig. 4) and a chain and sprocket drive system to roll the machine, thus eliminating the need for hydraulics. Instead of a clamping device for holding the pattern while it was drawn from the mold, the rollover would use electromagnets. This required the installation of a steel plate on the bottom of the pattern, eliminating the need for true positioning of the mold or a clamping system (Fig. 5).

"In the rollover, the electromagnets hold the box to the top while the mold is drawn out by the cylinder," Sides said. "The reason we went with magnets over a clamping system was because we need to produce castings that have a lot of different mold sizes. With such a variation in mold size, a clamping system just wasn't conducive."

The four electromagnets of 1300-lb capacity allow ample safety factor for a maximum mold weight of 2500 lb. The maximum pattern weight of 500 lb could easily be handled by two of the electromagnets once the pattern was drawn from the mold. By using electromagnets, the position of the mold in the rollover could vary greatly as long as at least two magnets could contact the steel plate.

Once the engineering drawings were completed, reviewed and approved, Talladega Castings' fabrication shop made all of the components for the rollover. After the rollover was then assembled, test run and delivered, the installation was completed over a three-day period. Within days of installation, the five-man crew was reduced to three with no loss in production.

"Not only have we decreased the physical labor involved, but we are now getting the most out of the people with have," Sides said. "Instead of having two men take the box off of the mold, we have one running the rollover while the other is coating. We no longer have people waiting around for someone else to finish."

The electromechanical rollover allows any combination of patterns in any order at any time to be run without any setup changes. The rollover can accommodate pattern sizes from 22-46 in. width, 22-60 in. length and 8-20 in. height.

Getting the Bugs Out

"The rollover has not worked completely trouble free, but it has delivered excellent mold quality and production has been maintained," Sides said. One problem plaguing the firm was a ballscrew would extert too much force, breaking the top of the rollover.

"We had to install limit and pressure switches so that if the machine exceeded a certain level of pressure or force, it would stop and go in reverse," Sides said. "When an operator was running the lift, he would only have a split second before it needed to stop before it broke at the top of the machine. By installing the limit and pressure switches, what we've tried to do is take the human error out of the process."

The gearbox drive systems with DC motors on both the ballscrew and chain drive incorporated variable torque clutches. These also were a major source of problem and required daily adjustment. Both of these clutches were removed and replaced with electronic shear pins. The electronic shear pin senses an increase in amperage of the drive motors and turns the motors off. The pressure needed for clamping the mold can be varied simply by adjusting the amperage setting of the electronic shear pin. This has proven to be a very reliable, trouble free device.

Finally, the firm experienced a problem involving the linear bearings and rails on the rollover. A sufficient torque setting was not incorporated when the rails were mounted, allowing the rails to work loose. This resulted in failure of the linear bearings and ultimately breakage of one of the rails. This problem was eliminated by installing new rails and bearings torqued per the manufacturers recommendation.

Eyes Toward the Future

While Talladega Castings continues to come up with unique and innovative solutions to maximize its production in its space, the firm has an eye on further expansion. "Eventually we're going to need a bigger facility so that we can continue to increase production and make bigger molds," Sides said.

The firm has been planning to move into a new foundry in recent years, but the downturn in the economy and the foundry industry as a whole has prevented them from making that jump. "When the industry experiences a turnaround, it'll be one of the first things we do," Sides said.

This article was adapted from a presentation at the 2001 Steel Founders Society T&O Conference.

For More Information

"Maximizing Productivity of Nobake Molding Operations," T.J. Gilbreath, MODERN CASTING, August 2000, p.39-42.

"Process Control for a Phenolic Urethane Nobake Foundry," J.A. Otte and W.D. Scott, AFS Transactions (97-151), p.153-160, 1997.