How Does Ultrasonic Cleaning Work?
Ultrasonic cleaning works through high-frequency sound waves transmitted through liquid to scrub clean the surface of immersed parts. The high-frequency sound waves, typically 40 kHz, agitate the liquid solution of water or solvent, and cause the cavitation of solution molecules.
What is Cavitation?
Think bubbles. Cavitation “bubbles” form when sonic energy creates a void (or cavity) which gets trapped as a bubble in a liquid solution of water or solvent. These microscopic bubbles implode with such force that contaminants adhering to surfaces are dislodged. An ultrasonic parts cleaner scrubs surfaces clean through implosions of tiny bubbles.
Industrial Ultrasonic Cleaning
Ultrasonic cleaners are suitable for cleaning a wide variety of materials, including metals, glass, rubber, ceramics and some hard plastics. Also known as an ultrasonic cleaning machine, an ultrasonic parts cleaner is especially useful for removing tightly-adhered contaminants from intricate items with blind holes, cracks and recesses. Examples of contaminants removed through ultrasonic cleaning include dust, dirt, oil, grease, pigments, flux agents, fingerprints and polishing compound.
The fluid used in an industrial ultrasonic cleaner can be either water-based (aqueous) or solvent-based. Both types of cleaning solutions contain wetting agents (surfactants) to reduce surface tension and increase cavitation. Aqueous cleaning solutions are generally more limited in cleaning effectiveness but better for the environment than solvent cleaning solutions.
In ultrasonic parts cleaning, the parts are typically placed in a basket or tray and then immersed in the ultrasonic cleaning tank. On occasion, parts may be racked and the rack is lowered into the tank. Items with blind holes may benefit from a rotating basket in an ultrasonic parts cleaner.
What is an Ultrasonic Bath?
An ultrasonic bath is another name for an ultrasonic cleaner. The “bath” part of ultrasonic bath refers to the liquid or solvent solution in a tank, while “ultrasonic” refers to the method of cleaning using high-frequency sound waves.
How to Use an Ultrasonic Cleaner
Ultrasonic cleaning machines are widely used in many industries, including medical device, automotive, aerospace, dental, electronics, jewelry and weapons. Ideal items for ultrasonic parts cleaning include medical and surgical instruments, carburetors, firearms, window blinds, industrial machine parts and electronic equipment.
The time required for ultrasonic cleaning depends on the material and soils, but typical cleaning times range from 3 to 6 minutes. Some delicate items such as electronics may require a longer cleaning time. Higher heat helps loosen dirt and chemical bonds faster, so most industrial parts cleaners apply heat in the range of 135 – 150 °F.
It should be noted that cleaning in an ultrasonic bath cleaner does not sterilize items. In medical applications, sterilization typically follows ultrasonic cleaning as another process step.
How Does an Ultrasonic Cleaning Machine Work?
An ultrasonic cleaning machine, sometimes called an ultrasonic bath machine or ultrasonic washer, includes the following basic components: ultrasonic cleaning tank, ultrasonic generator, and ultrasonic transducer.
- Ultrasonic Cleaning Tank – The ultrasonic cleaning tank holds the fluid of the ultrasonic bath and the items to be cleaned.
- Ultrasonic Generator – The ultrasonic generator transforms AC electrical energy to an ultrasonic frequency.
- Ultrasonic Transducer – The transducer converts the ultrasonic electrical signal to mechanical energy.
What is an Ultrasonic Transducer?
The ultrasonic transducer is the key component in an ultrasonic cleaning machine. The ultrasonic transducer is a device that generates sound above the range of human hearing, typically starting at 20 kHz, also known as ultrasonic vibrations.
An ultrasonic transducer consists of an active element, a backing and a radiating plate. Most ultrasonic cleaners use piezoelectric crystals as the active element. The piezoelectric crystal converts electrical energy to ultrasonic energy through the piezoelectric effect, in which the crystals change size and shape when they receive electrical energy.
The backing of an ultrasonic transducer is a thick material that absorbs the energy that radiates from the back of the piezoelectric crystal.
The radiating plate in an ultrasonic transducer works as a diaphragm that converts the ultrasonic energy to mechanical (pressure) waves in the fluid. Thus when the piezoelectric crystal receives pulses of electrical energy, the radiating plate responds with ultrasonic vibrations in the cleaning solution.
What is an Ultrasonic Generator?
The electronic ultrasonic generator is a power supply. It transforms AC electrical energy from a power source such as a wall outlet, to electrical energy appropriate for energizing a transducer at an ultrasonic frequency. In other words, the ultrasonic generator sends high-voltage electrical pulses to the transducer.
The ultrasonic generator working principle is to send electrical energy pulses to the transducer, which transforms energy into mechanical (pressure) waves in the cleaning fluid for vibratory ultrasonic washing action.