Here's some advice from washer manufacturer Dürr Ecoclean.
Dürr Ecoclean provides the following tips to manufacturers in the USA seeking to enhance their existing parts cleaning process. Dürr supplies closed loop chamber washers and airless airtight degreasers for a wide range of parts, including CNC machined metal parts in baskets. In this article, the company explores how external factors, both upstream and downstream, can influence cleaning.
While parts cleaning equipment is paramount in determining cleanliness quality for a given manufacturing process, external factors also play a role. Some common sense actions and precautions can significantly improve cleaning results, as Dürr Ecoclean describes below.
Rule of thumb: Production-to-cleaning (avoid storage).
Move parts directly from the production line into the cleaning process. Avoid storing of parts, especially those parts having oil on them. The oil can congeal on the parts making them more difficult to clean, resulting in longer cycle times and increased manufacturing costs.
Deburr parts prior to cleaning.
Burrs left on parts can present cleaning complications. It is more difficult for cleaning solution to penetrate around the burr. Additionally, burrs can come off during the wash operation, which is harder on the cleaning and filtration systems. Remove burrs prior to cleaning whenever possible.
Reduce the quantity of parts in each batch.
If cleaning is unsatisfactory with a basket-style washer, try loading fewer parts into the basket. While this will decrease throughput slightly, it can improve cleanliness by allowing more cleaning media (solution) to access the parts. Higher throughputs or faster cycle times are of little value if the parts aren’t getting clean.
Use the correct type of baskets.
Dürr Ecoclean typically recommends baskets made of stainless steel round wire. Avoid baskets made of galvanized perforated sheet metal. The perforated metal basket has a reduced open area, and therefore allows less cleaning media to access the parts. Additionally, perforated baskets deflect ultrasound waves, which can render ultrasonic cleaning options ineffective.
Parts cleanliness testing and analysis.
In some cases, an improvement in cleaning is visible to the naked eye. Oftentimes, however, cleanliness testing is needed to assess whether a particular external change positively or negatively impacts the cleaning process. There are companies that offer cleanliness testing and analysis. Engaging this kind of service and detecting issues early can mean the difference between profitable manufacturing and reject batches.
Like cleans like.
The composition of contaminants on the parts can determine the cleaning process that is selected. If the contaminants are oil-based, such as coolant or oil-based cutting fluids, Dürr Ecoclean recommends a hydrocarbon cleaning process. If contaminants are water-based, such as cutting, grinding, or lapping compounds, aqueous parts cleaners can be considered. This general rule can influence cycle times, cleanliness levels, and repeatability.
Spotting indicates wet parts.
With hydrocarbon parts cleaning machines, parts should be water-free prior to cleaning. Prevent moisture from collecting on the parts, whether from the process or from the surrounding environment.
Pre-Dip wet parts (hydrocarbon cleaning machines).
If parts have water on them, as may occur after grinding operations, dip the basket of parts into a hydrocarbon bath prior to loading the basket into the cleaning machine. This can remove unwanted water.
Intermediate cleaning between manufacturing phases.
In multi-stage production processes, different media, cutting fluids, or coolants are sometimes used at different stages. The mixture of these media can have unpredictable effects on the cleaning process. If cleaning results are unsatisfactory, try cleaning the parts between these manufacturing phases, rather than just at the end of the line. This may improve the results. In any case, always make sure the contaminants being removed are chemically compatible with the selected parts cleaning machine.
Fine cleaning machines must be dedicated to fine cleaning.
Never use a fine cleaning machine for general purpose cleaning applications, even in a pinch. Fine cleaning may include the final wash stage or parts cleaners having tight specifications. If the fine cleaning machine is misused, dirt can accumulate inside and eventually make its way onto parts. This will degrade the fine cleaner’s effectiveness and affect contaminant loading in filtration systems. It can ultimately result in part rejects.
A dirty environment jeopardizes cleanliness.
It may be that when parts come out of the washer, they are clean. But after one hour in a plant with atmospheric particulates, they may get dirty again. There are times when a clean room is necessary. In such cases, parts may be transported via conveyor directly from the machine into a dedicated clean room.
Avoid human contact with clean parts.
Like debris and contaminants in the manufacturing environment, humans can unknowingly transfer contaminants onto the parts, such as oils from their hands, or strands of hair. Dürr Ecoclean recommends handlers wear lint-free gloves, hair nets, and work coats or body suits whenever possible.
Avoid dirty shipping packaging.
After all the preparations, the last phase (packing and shipping) must introduce no new contaminants. It is best to wrap the baskets in protective plastic. Make sure packaging crates or boxes are free of debris and particles that might spoil the cleaning unexpectedly.
Educate operators, handlers, and maintenance personnel.
Although cleaning is a necessary evil, basic training about cleaning principles and best practices can go a long way toward improved production overall. Obviously maintenance personnel should also be trained on how to get the most out of the cleaning machines they service.
It's true...maintenance counts.
Cleaning machines are particularly influenced by changes in external processes. Likewise, their performance can be adversely affected by poor or inconsistent maintenance. This is especially the case with aqueous parts washers. Unlike cutting equipment, where poor maintenance results in an eventual breakdown or gauged part failure, on a washer, poor maintenance can result in less visible issues that go undetected far downstream. Regularly scheduled maintenance based on the manufacturer's recommendations can reduce the likelihood of unseen issues and returned parts or batches.
Some cleaning chemicals are being phased out by the EPA making cleaning equipment that relies on those chemicals costlier to maintain. Washer manufacturers have been known to quote machines that rely on chemicals subject to pending or future environmental regulations. This may occur because a washer company’s equipment design is not compatible with newer cleaning agents or degreasers. When purchasing a parts washer, manufacturers should have a conversation with the potential supplier about the chemicals being used in the cleaning chamber. There are parts washers and solvent degreasers that meet EPA and OSHA standards and some are even BACT-approved (Best Available Control Technology) for use in California. It is recommended that manufacturers seek written assurances about known regulatory impacts for their regions.