Ultrasonic Cleaning Systems for Precision Optics

An automated multi-tank cleaning and drying system for precision optics

An automated multi-tank cleaning and drying system for precision optics

Specifying ultrasonic cleaning systems for precision optics requires close collaboration between optics manufacturers establishing optical cleaning requirements and engineers at firms supplying the equipment and chemicals to fulfill those requirements.  It is not the intent of this post to specify cleaning equipment and procedures.  Instead it’s our objective to provide an overview of Elmasonic equipment for cleaning ophthalmic optics.

And a wide range of equipment it is – ranging from individual cleaning tanks to fully automated multi-stage wash-rinse-dry cleaning lines in a clean room.   We’ll briefly describe cleaning chemicals formulated for specific functions from mold manufacturing to cleaning for inspection and cleaning for coating.

Other equipment supporting cleaning optics includes water treatment plants, filtration systems, solvent treatment plants and laminar air flow modules to support clean rooms.

Our role, other than to provide these introductions to equipment and chemicals, is to put you in touch with equipment specialists for cleaning ophthalmic optics, and to follow through as needed to assure your specifications are being met.

A Brief Introduction to Cleaning Precision Optics

Basic Cleaning and Rinsing System

The Elmasonic X-tra Flex Line, is available as a single washing unit Flex 1 and with an accompanying rinsing unit as a Flex 2 system both sharing a support frame.  The system is designed for use with water-based cleaning solutions. The cleaning and rinsing tanks are equipped to provide a ± 2cm vertical oscillation, a technique proven to greatly enhance cleaning action.   These units can be purchased in dual-frequency modes, either 25/45 kHz or 35/130 kHz.  Cleaning and rinsing baskets can be positioned above the tanks on special supports allowing efficient drip-off of the liquid.  Up to 5 user-defined cleaning programs can be accommodated.

Among other features the X-tra Flex Line is equipped with heaters and timers, a degas mode to remove entrained air from fresh cleaning solutions and a sweep mode for uniform distribution of cleaning energy in the bath.   Optional pump filter units are available to help prolong cleaning bath life.  Rinse tanks can be equipped with a shower rinse station using city or DI water. The line is available in 5 tank capacities ranging from 8.5 to 44 gallons.

Manual and Automated Precision Optical Cleaning Lines

The X-tra Flex Line described above can be extended by incorporating one or more cleaning and rinsing stations, followed by a drying station in the Elma X-tra Pro configuration.  These units can be combined at the outset or added when the need arises.   They can be furnished to support manual transport of product between cleaning, rinsing and drying stations or for automated cleaning, rinsing and drying managed by a touch screen to control and monitor processing and transport.

Cleaning Optical Products with Solvents

Specially designed ultrasonic cleaners are required when using flammable solvents to remove protective lacquers.   The Elmasonic X-tra LSM is designed for solvents with flash points at or above 55˚C exemplified by NEP (N-ethyl-2-pyrrolidone) or NMP (N -Methyl-2-pyrrolidone). They have built-in protection against the formation of explosive atmospheres and are available with an optional solvent cooling system to retard the generation of vapors.  Dual frequency (25 or 45 kHz) X-tra LSM units should be operated in areas with adequate ventilation, ideally equipped with exhaust systems and fire suppression systems.

Accessory Equipment

  • Solvent recovery systems, as noted above, are available to prolong solvent life by separating out soluble contaminants
  • Water treatment plants with capacities from 100 to 2500 liters per hour
  • Pump and filter units for removing particulates from cleaning solutions and rinsing water
  • Laminar flow modules to generate clean room conditions
  • Dryers can be specified as filtered circulating warm air or infrared

Cleaning Solution Chemistries for Precision Optics

In addition to solvents mentioned above there are biodegradable water-based cleaning solutions to support every stage of precision optics manufacturing – both the optics and the molds used to form the optics.   They range from neutral to mildly and strongly alkaline.   While specific cleaning procedures will be developed for a particular process here are a few examples of aqueous cleaners:

  • Neutral cleaning concentrate elma clean 320 is designed for precision optical glasses to remove dust, fingerprints and other slight organic and inorganic contaminants using demineralized water.
  • Neutral foam-inhibiting elma clean 260 dip&splash removes oils, fingerprints and dust from glass surfaces, either in an ultrasonic cleaner or as a spray.
  • Mildly alkaline elma clean 310 is used to clean before coating organic and inorganic high-precision optical glasses to remove dust, fingerprints, light oils and greases and resin residues.
  • Mildly alkaline elma tec clean A1 is used for fine cleaning glass substrates, glasses and optical assemblies.
  • Alkaline elma clean 300 is designed to clean before coating organic and alkali-proof inorganic glasses and for final mold cleaning. It removes dust, fingerprints, oil and grease traces.

Contact the Experts for Advice

The ultrasonic cleaning specialists at Tovatech are your first stop in the process of specifying a system designed to meet your precision optics cleaning requirements.  We’ll prepare you to take equipment and chemistry selections to the next step and put you in touch with specialists in assembling, delivering installing and servicing units from single tank cleaners to multi-unit cleaning, rinsing and drying systems.  Contact us when you’re ready to start the discussions.

About Rachel Kohn

So how did an MIT Ph.D. end up selling refrigerators? When I figured out that a lot more scientists buy lab refrigerators than innovative leading-edge instruments. I hope that my many years of lab experience will help you find the right equipment for your work. Before co-founding Tovatech I worked in business development and project management at Smiths Detection, Photon-X, Cardinal Health, and Hoechst Celanese. And before that I spent 12 years as an R&D chemist at Hoechst Celanese and Aventis working on advanced drug delivery systems, polymer films and membranes, optical disks, and polysaccharides. Some day, eventually, I’ll make enough money to develop an innovative technology that will change the world. Read More