Getting the most from your Ultrasonic Cleaning System
“DO’s and DON’Ts”
by Arthur Liers, Vice-President, Sonicor Instrument Corporation
Purchasing the best ultrasonic cleaning equipment is certainly important, but using it most effectively is even more important. The following guidelines are intended to assist users by providing general information relating to the operation of ultrasonic cleaners.
1. Most ultrasonic systems show high bursts of surface energy on initial activation, especially in room temperature solvents.
2. Cold water will not normally cavitate well although there may be an initial burst of surface activity.
3. Do not introduce excessively hot water into a cold ultrasonic tank as it will cause undesirable start-up conditions and thermal shock.
4. Do not use water solutions above 180 degrees F at any time.
5. Do add chemicals to water prior to initial start-up and mix well, especially if powdered material, which should be pre-mixed before adding to ultrasonic tank.
6. Allow a sufficient degassing period after initial start-up, and prior to introducing work into cleaning tank. Degassing time will vary depending on several factors such as type of chemical liquid (i.e. solvent or aqueous), temperature, viscosity, etc.
Note: Normally solvents degas much slower than aqueous solutions. Degassing time can vary from a few minutes up to hours in large solvent cleaning tanks. For faster start-up, solvents should be heated to accellerate degassing.
7. Be aware that surface activity may disappear completely after work is introduced since the ultrasonic energy is now being utilized by and on the work.
8. Be aware that certain frequencies provide different surface activity. Generally, higher frequencies will show more violent activity than lower frequencies. Surface activity is not necessarily related to cleaning power. For instance, a low frequency system may show little surface activity and yet may clean a part just as quickly and as thoroughly as a higher frequency unit which produces violent surface activity, or vice versa.
9. Do not mechanically agitate parts, or introduce air or fast flowing liquid (i.e. recirculation filter system) into an ultrasonic cleaning tank.
Note: 1) Use recirculation-fliter systems preferably when ultrasonics are not being used, and make sure return line is beneath liquid surface. 2) Very slow controlled mechanical agitation may be utilized.
10. Position parts so that air is not trapped in blind holes and cavities, as no cleaning will occur in those areas. Liquid is required to carry the ultrasonic cavitation.
11. Do not use racks, trays, baskets etc., fabricated from heavy and dense material, since much of the ultrasonic energy will be absorbed by these devices and detract from cleaning.
12. Do not use racks, trays, baskets, etc., fabricated from or coated with soft material, namely, rubber, wood, soft thermoplastics, fabric etc.
13. Be aware that certain chemicals or excess amounts of certain chemical additives will not support ultrasonic cavitation. Check with your chemical or ultrasonic equipment supplier if in doubt.
14. Most ultrasonic units are “liquid level sensitive.” That is, at various liquid levels they display more surface activity than at other levels. This is a function of wave length and does not necessarily have any effect on the cleaning ability of the equipment.
15. Do not overload an ultrasonic cleaning tank with work. It is difficult to establish guidelines due to the wide variety of sizes, weights etc. of parts encountered. It is wiser to clean parts quickly and thoroughly. Start with a few parts, add additional items and check to insure same cleaning results.
16. Do not place anything on or against the radiating surfaces of ultrasonic tanks or immersibles as this may dampen ultrasonic activity, and can cause equipment damage.
17. Do not allow cleaning solutions to become excessively contaminated or sludge to build up on radiating surfaces, causing a loss of ultrasonic cleaning power and possible damage to ultrasonic equipment.