Almost every shop performs some sort of parts cleaning operation for its products. For some operations, the cleaning process may be as simple as toweling off the part before packaging. For others, the cleaning operation may be an essential prelude to a secondary operation or sensitive surface finishing. Shops typically determine the most suitable cleaning method over time, based on the jobs they run and the effectiveness of the given process. Such is the case for DuPage Machine Products Inc. (Bloomingdale, Illinois), which has tried several cleaning processes before discovering the effectiveness of its current hydrocarbon-based parts cleaning system.
The company sends every single part it produces through its current cleaning system—millions of parts per year primarily for the mobile hydraulics and automotive industries, produced from materials such as 303, 304 and 416 stainless and 12L14 and 1215 steel. The system’s speed and efficiency make the operation feasible, but it wasn’t always such a safe bet.
According to Dave Knuepfer, company president and CEO, DuPage has run the gamut of parts cleaning options through the years. He explains, “In the ’70s and ’80s, we had a vapor degreaser. In the early ’90s we had an aqueous system. In the late ’90s we switched back to vapor degreasing. Finally, towards the end of 2004, we bought our current system.” That current system—a Dürr Ecoclean Universal 81C—uses a non-chlorinated hydrocarbon cleaning process to deliver the reliability of solvent-based cleaning without the environmental complications of traditional chlorinated solvent washers.
The system rotates parts within the first and second cleaning steps, dislodging debris. It follows with a vapor degreasing step and ends with a drying stage. All steps are carried out under a vacuum for enhanced performance.
Baskets of parts can be fed into the front of the machine either manually or automatically. DuPage preloads baskets of parts onto pallets on a conveyor system that automatically feeds them into the cleaning cycle. The company uses six baskets at a time, approximately 9 inches wide by 18 inches deep by 5 inches high, stacked side by side and two-high to fill the chamber to its maximum capacity. The baskets allow a variety of part types to be processed without retooling.
As the baskets are loaded into the work chamber, the door automatically locks and the chamber is filled with cleaning fluid from the first flood tank, submerging the baskets and parts in a liquid bath. Once the parts are submerged, the cleaning media can envelop the parts completely to clean outer surfaces as well as holes and cavities. Because of the vacuum technology, even small blind holes can be cleaned effectively. Based on pre-programmed movement patterns selected by the operator through the control (a Siemens S7 PLC), the system agitates the parts baskets for more effective cleaning. Baskets can rotate within the cylindrical chamber from 10 to 360 degrees. The movement of parts within the cleaning solution, together with the recirculation of the fluid and/or ultrasonics, dislodges debris that may not have been removed by the hydrocarbon bath alone.
After the hydrocarbon bath, the cleaning fluid is drained. An optional second flood tank can provide an additional cleaning, or the hot vapor cleaning and vacuum drying process is initiated to thoroughly dry the parts, including blind holes and channels. After the drying process, the work chamber door automatically opens and the clean parts are removed, allowing the next batch to be loaded. The entire process takes from 6 to 12 minutes, depending on the part to be cleaned (blind holes, and so on) and the condition of the part (cleanliness) before cleaning. Parts are hot to the touch as they leave the system.
Worth The Investment
Mr. Knuepfer says the company has been quite pleased with the Dürr system. “Since buying the system at the end of 2004, we’ve had very few maintenance issues,” he explains. “We still have a vapor degreaser, using methylene chloride, at our other location. When we opened this facility, we started out bringing parts here for cleaning, but that wasn’t practical long-term. I was familiar with this system (Dürr), and it seemed like something that could work for us. It could have cost as much as $75,000 to move the old vapor degreaser here, so we made the decision to invest in the Dürr.”
The environmental considerations built into the system have also been popular at DuPage. Mr. Knuepfer says, “Our old vapor degreaser is a top-of-the-line model with all the bells and whistles—it is fully enclosed and complies with all EPA standards. But the solvent cost is high, and the record keeping alone, for environmental compliance, can create a substantial expense. With the Dürr, there is no requirement to register with the U.S. EPA, only the state of Illinois. We received a lifetime operating permit, versus an annual permit, because of the fact that the isopar hydrocarbon solvent is environmentally friendly. The operation of the Dürr is simple, requiring minimal training.”
Compared with the aqueous system the company tried before, the Dürr system has been particularly effective. “We scrapped way too many parts with the aqueous system,” Mr. Knuepfer elaborates. “Any time you introduce water to steel, you’re asking for problems. Although the cost of the Dürr can be expensive, we’ve found it well worth it. It’s easily the fastest, most efficient method we’ve tried. The parts come out bone dry. We’ve never had a cleanliness problem with any of our customers since making the change; we’ve not seen any rust issues in our plant, because the rust inhibitor is particularly effective.” With a fully air-conditioned facility, humidity is kept to a minimum, helping to maintain rust-free parts. But Mr. Knuepfer continues, “Once the parts reach the customer and sit on their shelves without air conditioning, you might expect different results, however, we have had very few issues with rust.”
This parts cleaning system has proven itself at DuPage as a highly effective cleaning method, using non-chlorinated hydrocarbons for safe and economical use of solvents to remove oils, greases, emulsions and swarf between and after manufacturing processes. Mr. Knuepfer feels it has been well worth the investment and is even considering adding a second unit down the road.