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Process Cleaning Magazine
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AMT-The Association For Manufacturing Technology
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When a part is placed in an ultrasonic cleaning system, air is often trapped within certain part features (1). That air needs to be removed to optimize the ultrasonic cleaning process, so pressure within the chamber is lowered to remove the air (2), and then more air is returned to the chamber (3) to bring it back to atmospheric pressure.
This recommended maintenance schedule demonstrates the limited requirements and expected durability of the dry scroll pumps.
Dry scroll vacuum pumps provide clean, oil-free air for a number of applications. Ultrasonic cleaning systems can benefit from their efficient operation.
Various part sizes and materials require different types of cleaning, but one thing is commonly clear and increasingly important: Every nook and cranny of each part must be entirely cleaned. In many applications, this thoroughness requires a cleaning system that is completely free of air pockets as well as clean, oil-free air to dry the part after cleaning.
Anest Iwata is the original developer of dry scroll pump technology—a reliable, clean, oil-free method with low maintenance costs. The company sees much of its business in food and beverage storage and packaging, plastic and injection molding, electronics, textiles, and laser cutting.
“Anything supplied by a food plant usually needs clean, dry air,” says Tom Fermann, sales manager for compressors. “These pumps supply absolutely oil-free air, which is the key to dry scroll technology. We use a special composite technology that keeps the heat down and allows the pumps to last just as long as oil-lubricated systems.”
Although dry scroll vacuum pumps can be used in a number of applications, they are a natural fit in ultrasonic cleaning.
Applying the Technology
As a part moves through an ultrasonic cleaning system, the contact time between the part and cleaning solution is very important. If the contact time is reduced, the cleaning agent becomes less efficient and the problems escalate. To make the system perform more efficiently, vacuum pumps are used for two separate functions — removal of air and drying.
During the cleaning application, the vacuum pump is used to remove any air in the cleaning solution so the system can effectively clean the entire part. The pressure in the chamber is lowered to evacuate the air and eliminate any air pockets that may have formed in the solution within the cleaning chamber. Air then is returned to the chamber to bring it back to atmospheric pressure. The cleaning solution then can completely encompass the part, enabling a thorough cleaning. When the part is removed from the chamber, the process repeats itself.
Depending on the part being cleaned, extreme cycle times can cause the pump to work quite hard as it cycles from atmospheric pressure to ultimate pressure, so the user must be aware of pump fatigue and the recommended maintenance schedule. Costs and the extent of the maintenance also should be taken into consideration.
The other key application of the dry scroll pump is vacuum drying of parts that have just been cleaned. The vacuum chamber is capable of drying the parts quickly to prevent any extraneous fibers or dirt from adhering to the parts. With no moisture on the parts, inspections can be performed quickly and easily. Effective cleaning and inspection can help to reduce the number of part rejects.
During and as a result of the drying process, a vacuum pump needs to expel water vapor (humid gas) that has accumulated inside of the pump so it does not cause the unit to fail. The Air Flush feature on the GVS-500 pump from Anest Iwata, located near the outlet port, allows the displacement of humid water vapor and particles. This process assists the pump in reaching ultimate pressure, allowing the system to work properly while also keeping maintenance costs to a minimum.
Maintenance Considerations
Pump fatigue is a concern with most ultrasonic cleaning systems, as the pump constantly cycles from atmospheric pressure to ultimate pressure. The dry scroll design uses low start-up torque and very little power variance, enabling these pumps to run for longer periods without fatigue issues.
The oil-free design also eliminates oil migration or oil misting in the various chambers and stations of the cleaning system. Unlike oil-lubricated vacuum pumps, which sometimes allow oil mist to escape from the outlet, many typical pump maintenance requirements are not necessary and typical maintenance costs, such as those related to filter replacement, are greatly reduced.
The oil-free scroll pump, by nature, provides customers with low vibration, low starting torque and quiet operation. While many vacuum pumps can exceed 90 db, most dry scroll pumps operate near the 60-db range, depending on the size.
A number of important factors should be considered when choosing a vacuum pump for any cleaning application. All operating parameters much be considered, along with part types and sizes and the washer system that is to be used. Understanding the cleaning system is a primary factor in helping to prevent maintenance and operational problems down the road.
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