Ultrasonic Cleaning of Complex Spare Part Designs

CLEANING ITEMS WITH COMPLEX DETAIL

Many of our customers ultrasonically clean parts with significant detail in the design, such as blind holes, threaded areas, metal folds, or other similar features. Although many of the contaminants being removed are loosely bonded to the surface, inconsistent results are found. Some of the parts are cleaned, while others are only partially cleaned. The following tips have been provided to maximize the performance of your ultrasonic cleaner to produce the most consistent results possible.

TIP #1: ATTEMPT TO RELEASE ENTRAPPED AIR

If your part design includes blind holes, it is very possible that an air pocket will be entrapped within the hole when the part is submerged into the ultrasonic cleaning tank, or rinsing tank. If air is entrapped, ultrasonic cleaning cannot take place at this location, and parts will not be cleaned successfully. Make every attempt to position the part so that the blind holes included in the design fill and drain when submerged or removed from the liquid baths. In most cases, the only way to accomplish this is the position the holes horizontally, or at a slight angle to allow the air pockets to be released.

If the design includes many blind holes in different orientations on the product, these parts may need to be rotated AFTER they are submerged to release any entrapped air.

If you are cleaning small parts which can be shaken once submerged, shake the basket after submersion, as this will tend to release many air pockets as the parts are moved in position.

TIP #2: DO NOT STACK PARTS ONE ABOVE ANOTHER

Ultrasonic cleaners work best when a single layer of parts is being cleaned. If parts are placed one atop another, the bottom part will receive significantly more ultrasonic cleaning power than the top part, a principle known as ultrasonic shadowing.

Each part submerged in an ultrasonic bath will absorb some or all of the ultrasonic energy being emitted by the ultrasonic transducers which are usually mounted on the bottom of the tank. The amount of energy absorbed will depend upon the material of construction, and the weight of the item. Heavy parts will absorb more ultrasonic power than lighter parts.

Since the part which is closest to the transducers absorbs some of the ultrasonic power, the part directly above it will receive the remaining power which was not absorbed by the lower-most part. For example, lets assume that you are cleaning 2 parts, one above the other, and the bottom-most part absorbs 75% of the emitted ultrasonic energy. This leaves only 25% power available to clean the top part, which may not provide enough power to remove the contaminant in question.

If parts are cleaned in bulk quantities, limit the thickness of the part batch, especially when removing contaminants which are highly bonded to the surface, such as burned carbons, coatings, or other similar contaminants.

TIP #3: OSCILLATE YOUR PRODUCT DURING ULTRASONIC CLEANING

If you have ever seen an ultrasonic cleaner in action, you will notice that contaminants are not blasted away from the surface of the parts, but are rather lifted gently from the surface. This is especially important to consider when cleaning parts with blind holes, details, or parts cleaned in bulk, since the very design of the material being cleaned can entrap these contaminants, thereby preventing it from being released into the cleaning fluid.

Parts with these characteristics should be oscillated upon removing the parts from the ultrasonic cleaning tank at the very least. Simply lift and lower the basket a few times before removal, making sure to lift the parts through the liquid surface. This allows cavities and blind holes to fill and drain repeatedly, which will flush out loosened contaminants.

Improvements will be evident when parts are also oscillated intermittently during the cleaning cycle. This will serve to flush out contaminants which have already been removed from the surface of the parts, thereby allowing the ultrasonic cleaning system to work on any remaining contaminants still attached. Many Zenith systems, such as the ultrasonic parts washer shown, include Intermittent Oscillation Systems that can perform this task automatically.