As agitator designs become more complex, building the molds becomes more challenging to both the moldmakers and to the equipment they use. Employing computer technology in both designing and building the molds, is the most practical method of improving productivity in these areas. It was interesting for us to learn how one company used the latest EDM Solutions to accomplish these difficult jobs.

A World Leader

We recently visited the Ostrom Tool Company, of Chicago, Illinois, and spoke with Leonard Ostrom, their president. We asked him how they became the world's leading producer of washing machine agitator molds. He explained that his father, Julius Ostrom, a Moldmaker since 1920, had decided to start his own business. Thus, in 1942, the Ostrom Tool Company was formed, and eventually, after completing his education, Leonard Ostrom joined the company.

Initially, most of their work was building thermoset molds for military use, but after the war they concentrated on components for household appliances -- principally washers, dryers and refrigerators. They started building molds for washing machine agitators, which at the time, were thermoset molds. However, in 1950, the washing machine industry switched over to thermoplastic materials.

Agitator molds were always a specialty, and Ostrom Tool concentrated on them, thus gaining a great deal of valuable experience, and also building an excellent reputation in the area. Today, it is estimated that the vast majority of all agitator molds ever built, were built by Ostrom Tool Co.

Very Early With EDM

Leonard Ostrom explained that although the early EDM Machines were quite primitive, they saw a lot of potential in their use. They were one of the early EDM pioneers in the Mold Building industry, and as the EDMs were upgraded, they always replaced their machines with newer models. EDM became vital to their operation, and as Leonard Ostrom explained it, "Our business was actually built around EDM machines."

Because of the contours and undercuts in the design of the agitators, the molds are segmented radially into a number of sections -- sometimes as many as nine. This is the only design that allows for pulling the undercut and releasing the finished parts. However, this type of construction requires that each section must be EDMed individually.

The early EDM Machines were quick to D.C. Arc if flushing was not perfect, and they required the constant attention of an operator. In order to help prevent arcing, brass electrodes were used instead of graphite. Due to the high rate of wear with brass, seven electrodes were required to produce a single mold. As the EDM Machines improved, arcing was controlled and they began to use graphite. This reduced the number of electrodes necessary to five. However, machining these complicated electrodes represents a sizeable portion of the expense of building an agitator mold.

Using The EDM Machines

Recently, because of a major project on a new agitator series, Ostrom Tool decided to look at the new breed of CNC Machines. They were interested in improving many areas of their EDM operations. Their goals were improved surface finishes, less electrode wear, and the ability to run unattended over nights and weekends. Time was not the most important factor, however faster cuts would help entice them to upgrade. A test cut was scheduled in order to see if their goals could be met. We spoke with Ken Byrge, Ostrom's Vice President, and Bob Dudek, Moldmaker/EDM Operator, to learn about the test results.

The configuration of the new agitator required an oblique downward movement of the electrode during the EDM cut. However, a series of orbiting steps were also required to attain the best possible surface finish, along with the minimum of electrode wear. Standard orbiting patterns would not suffice, since they would distort the agitator's shape. Custom software was written by Tom Powderly of SK Enterprises, in order to fulfill all the goals while producing the exact shape. The results exceeded all the requirements of Ostrom Tool, and a new CNC EDM was quickly installed.

The Results

Ken Byrge told us that the finishes are superior using the new EDM, and an entire mold can be produced with only two or three graphite electrodes. All the electrodes are machined to the same dimensions and are constructed from a medium density graphite. He also noted that the final electrode shows absolutely no sign of wear. Reducing the requirements from five to two or three electrodes represents a major cost savings.

In the past, the polishing department was required to correct the shape because of electrode wear, with the average mismatch being from .005" to .025". They also started polishing from a much rougher finish. Today, since the final electrode shows no signs of wear, benching time is reduced, and polishing the mold to a superior finish takes just a fraction of the previous polishing time. The parting lines are virtually invisible, and the precision and quality of the molded parts has never been better.

Bob Dudek explained that previously, they had always flushed through the electrode by drilling tiny holes in the tips of the vanes. They tried cutting with, and without flushing, and the results were satisfactory. The EDM cut was faster with flushing, and because of their experience in drilling the holes, and the fixtures they have devised, they will probably continue flushing the electrodes to maintain the extra speed.

EDMing Around-The-Clock

This has long been a goal of Ostrom Tool. However, it requires a steady, trouble free EDM cut every time. There always seemed to be a reason why it was not practical. With the new CNC EDM, it is finally possible! Now when the shop opens up in the morning, a finished mold segment is waiting to be unloaded.

After the initial roughing cut, the CNC EDM orbits through a series of steps reducing the power between each one, to attain a progressively finer finish. If a problem surfaces, the control will take action to correct it and continue the cut. If the problem cannot be corrected, the machine shuts off, rather than damage the part or the electrode. Since they started taking advantage of unattended EDMing during off hours, they can now EDM two agitator molds in the same time it previously took them to EDM one.

Ken Byrge commented that the new CNC EDM accomplished all their goals and more. He recalled, "In the 19 years that I have been at Ostrom, I have seen many changes in the EDM Machines. Most of the improvements have been in the electronic controls, and they continue to improve that technology with each new model. EDM is still basically the same process, but there is a world of difference between the EDM Machines that were here when I first started."

The Future For Ostrom Tool Co.

We asked Leonard Ostrom how he saw the future for Ostrom Tool Company. He commented that after 50 years, they are still building agitator molds and the market is still strong and growing. He talked about new markets for their products that are just opening up. He also told us, "New washing machine technology, which includes new agitator designs, is the reason that clothes are being washed much cleaner than just five years ago."

He credits their early use of EDM for much of Ostrom Tool's success, but more importantly, he credits the fact that they constantly upgraded to the latest models as new EDM technologies emerged. He also stated emphatically, that they will continue to do so.

The CNC EDM mentioned in this article was an EDM Solutions Polaris (Hi-Tech 5 Axis Series).