Ultrasonic Cleaning Best Practices & Choosing Your Metal Baskets

Ultrasonic cleaning for parts plays an important role for many of today’s manufacturers. It saves them time and money, and compared to manual cleaning, is especially adept at removing dirt and debris from the surface of a manufactured part. However, to get the best results from ultrasonic parts cleaning processes, manufacturers need to have a well-designed ultrasonic parts cleaning basket.

• What is Ultrasonic Cleaning?
• Why Use Ultrasonic Cleaning?
• Ultrasonic Cleaning Basics
• Ultrasonic Cleaning in Manufacturing
• Ultrasonic Cleaning Metal Baskets
• 4 Things to Look for When Choosing a Basket
• Wire Basket Considerations for Ultrasonic Cleaning
• Choosing Marlin Steel for Your Basket Needs

What is Ultrasonic Cleaning?

Ultrasonic cleaning is basically “cleaning with sound.” The technology blasts high-frequency, high-intensity sound waves that humans cannot hear (generally 20–40 kHz but sometimes as high as 1 MHz) into a liquid to clean products placed in the liquid. The vibrations caused by the sonic waves help dislodge contaminants from the submerged object.

The technology is unique in its ability to remove contaminants that other methods of cleaning, such as spray washing, turbulation, agitation, and brushing, cannot. For example, ultrasonic cleaning can reach blind holes, thread roots, parts with complex geometry, minute surface contours, and a number of areas of a product that would otherwise be nearly impossible.

Why Use Ultrasonic Cleaning?

Along with its superior cleaning capabilities, there are three other big benefits of using ultrasonic cleaning technology.

Saving Time and Money

Employee Health Benefits

Manual cleaning can expose employees to harsh solvents and highly caustic chlorinated and fluoridated agents and hydrocarbons. On the other hand, ultrasonic cleaning systems with their non-toxic, water-based detergents are safe for users.

Environmental Benefits

Manual cleaning can release hazardous waste into the air, and other forms of immersion cleaning use far more energy than ultrasonic cleaning, increasing your company’s carbon footprint. Ultrasonic cleaning happens in an enclosed environment, so there’s less pollution. Plus, most ultrasonic cleaning detergents have EPA approval.

Ultrasonic Cleaning Basics

There are a number of ultrasonic cleaning systems on the market, and the unit you choose will likely depend on a number of factors, such as:

• What types of contaminants need to be removed? Light oils, or excessive heavy dirts and sludges?
• What are the ultrasonic power requirements? 
• What frequency (kHz) is needed? 
• What is the required cleaning process (proper cleaning time and temperature, etc.)

From there, you’ll want to determine which cleaning solution is needed. Generally, one single detergent will not remove every type of contaminant. Some of your options include:

• General-use soap solutions that can remove oil, grease, and carbon deposits.
• Descalers, which are more acidic and can remove corrosion, rust, hard mineral deposits, and heat scale.
• Enzyme detergents, which remove oils from stainless steel, aluminum, brass, and titanium parts, and also eliminate biological contaminants from medical and dental tools.
• Low pH cleaners, acid solutions that clean and shine metals but may damage aluminum, copper, and brass items.
• Specialty detergents used to clean specific contaminants such as ink, resins, or epoxies.

When choosing your solution, always keep in mind the type of part you’re cleaning and what it’s made of. You’ll also need to consider waste disposal; while most solutions are EPA approved, depending on the contaminants removed a specific type of waste disposal may be required.

Ultrasonic Cleaning in Manufacturing

Ultrasonic cleaning is used in many industries and has become very popular within the manufacturing sector. Today, industrial ultrasonic cleaners are used in the automotive, aerospace, medical, pharmaceutical, engineering industries, and more. Manufacturers have embraced the technology because it’s less time-consuming, more cost-effective, and more precise than manual cleaning.

Ultrasonic Cleaning Baskets

When cleaning parts in an ultrasonic cleaner, they’ll need to be placed in a container. However, this parts cleaning process can be tough on the containers that hold parts through it. This is because the process of ultrasonic cavitation involves the use of very strong vibrations and potentially caustic liquids to shake dirt and debris loose and strip it from the surface of an object. Ultrasonic cleaning baskets are repeatedly exposed to these stresses as they carry new loads of parts through the process.

Additionally, if an ultrasonic cleaning basket isn’t properly designed, it can end up damaging the parts it holds. Unfortunately, not all ultrasonic cleaning baskets are well-designed. In fact, there are far too many manufacturers who end up buying a parts cleaning basket on the cheap, only to find out that the basket has fatal flaws that interfere with their ultrasonic cleaning processes.

4 Things to Look For When Choosing an Ultrasonic Cleaning Basket

To help you avoid buying bad baskets that impede productivity, here’s a list of things to look for when choosing your ultrasonic parts cleaning basket.

1. Open Space

For an ultrasonic parts cleaning process to be effective, the ultrasonic waves generated in the cleaning tank need to be able to reach the parts being cleaned. This is one reason why the vast majority of ultrasonic cleaning baskets are made from stainless steel wire mesh instead of sheet metal.

The open space between the wires of an ultrasonic parts cleaning basket allows the ultrasonic waves from the cleaning machine’s ultrasound generator to reach the interior of the basket—and thus the parts inside. Solid basket walls would block the ultrasonic waves—reducing the effectiveness of the cleaning process to a simple soak in mild chemicals instead of blasting debris from parts.

Another problem caused by a lack of open space is that it prevents the runoff from the ultrasonic cleaning process from leaving the basket easily. This poses a risk of contaminants landing back on parts—negating the effectiveness of the parts cleaning process.

2. Protection for Held Parts

Depending on how delicate the parts being washed are, there may be a need to prevent part-to-part contact so they don’t get scratched or dented. In some cases, it may be necessary to prevent any part-to-metal contact as well (this is when soft polymer coatings may be necessary).

This is because, during the ultrasonic cavitation process, parts are being shaken incredibly fast. Repeated impacts with a material with the same hardness, even when each individual impact has little to no pressure behind it, can cause damage to a part. So, when dealing with ultrasonic cleaning baskets, it’s important for the design to minimize the risk of direct part-to-part contact. This is usually done by adding dividers to the basket.

3. Corrosion Resistance

Ultrasonic parts cleaning typically involves totally submerging a parts cleaning basket in a fluid bath. While the specific chemicals found in the bath will vary from one ultrasonic parts cleaning process to the next, even the mildest solutions can be potentially damaging to parts cleaning baskets.

This is why ultrasonic cleaning baskets should almost never be made from plain steel or iron that is susceptible to corrosion from contact with water. Any ultrasonic cleaning basket intended for long-term commercial use needs to be made from materials that will resist corrosion when immersed in the ultrasonic cleaning fluid your process uses. Or, that basket should have a protective coating that resists the chemical and prevents it from attacking the metal being coated.

This will help to prevent rust from forming and destroying the basket (and from being transferred to your parts by a rusted basket).

4. Strong Welds and Wires

The basket needs to be solid enough that exposure to high-intensity vibrations from the cleaning process won’t shake it apart. This often means using thicker steel wires with lots of welds.  However, in trying to maximize open space between wires in an ultrasonic cleaning basket, some manufacturers use extremely thin wires that are spaced wide apart. While not always a bad idea, if the welds holding these wires in place are too weak, they could break under the strain of the ultrasonic cavitation process. This can, in turn, cause the basket to fail spectacularly during the wash process.

So, when checking ultrasonic parts cleaning basket designs, it’s important to check that the basket’s wires are sufficiently thick and are welded securely enough to withstand repeated prolonged exposure to ultrasonic vibrations.

Marlin Steel does this by using virtual physics simulation software to test how well the basket’s design will hold up to a client’s parts cleaning process. In seconds, the software can simulate weeks, months, or years of use in minutes and show Marlin’s engineers what would happen to the basket. If the basket would change shape by so much as a hair’s width, it fails the test and the design team modifies it before testing again.

When checking a custom (or stock) ultrasonic cleaning basket design, be sure to ask what welding processes and tools the manufacturer uses to ensure consistent and strong welds.

Wire Basket Considerations for Ultrasonic Cleaning

In ultrasonic cleaning applications, choosing the optimal cleaning basket is a must. To make sure you get the product that’s right for you, there are nine things that the engineer designing your ultrasonic cleaning baskets has to know first. If that sounds daunting, don't worry – the experienced team at Marlin Steel can help you with get the answers!

Dimensions of Your Ultrasonic Cleaning Machine's Wash Tank

To ensure that the basket will actually fit in the washing equipment being used, the manufacturer needs to know the dimensions of that equipment first. Additionally, if the basket is to be used with other processes, the manufacturer will need to know the dimensions of that equipment as well (plus how you plan to move the basket from Process A to Process B).

Chemicals Used in Your Ultrasonic Cleaning Process

To optimize a custom wire basket design to better resist corrosion and rusting, the manufacturer needs to know what chemicals will be used in the wash tank. Knowing the chemicals used in your cleaning process helps the manufacturer choose the best basket materials and coatings to prevent corrosion and premature basket failure.

Whether Lateral or Rotation Motion Will Occur

Some ultrasonic cleaning processes involve moving the basket up-and-down, side-to-side, or even flipping the basket upside down mid-cleaning. To account for this, the custom basket maker needs to know whether such motion will occur. If so, they may need to add lids or other securing mechanisms to hold parts in place.

Whether the Basket Will Be Used for Other Processes

If the parts going through the ultrasonic wash process will be subjected to other processes (before or after the wash), it may be possible to design the basket to work with those other processes as well. Doing so helps to minimize the need to manually handle the parts, since they won’t have to be moved from one container to another for each process. This, in turn, helps reduce the risk of damage from mishandling parts.

Strength of the Ultrasonic Generator(s)

Different ultrasonic cleaning machines will have different levels of intensity for their ultrasound generators. The stronger the generator (or generators), the sturdier the basket will need to be. This plays a role in how thick the wires of the basket are and how thoroughly they’re welded together.

Weight and Shape of Held Parts

How much a part weighs, and its shape, can influence the way they apply stress to the basket. For example, a basket meant to hold a heavy, sharp-edged object through a parts washing process may need thicker wires—particularly near where the part has hard edges.

Thickness of Wire Mesh

Some metals have higher or lower tensile strengths than other metals do. Metal wires with a very high tensile strength won’t need to be as thick to carry a load as ones made from a softer alloy. For example, grade 304 stainless steel has an ultimate tensile strength of roughly 90 ksi (621 MPa), and an aluminum alloy might have an ultimate tensile strength of 26.1 ksi (180 MPa)—depending on alloy materials. To hold the same amount of weight without losing shape, wire mesh made from aluminum would have to be much thicker than mesh made with grade 304 stainless steel.

However, whichever alloy you use for the wire mesh, it must be able to withstand repeated exposure to the chemicals used in your ultrasonic cleaning process. Because of this, it may be better to use a slightly thicker wire mesh made from a resistant alloy than a thinner one made from a less resistant material. 

So, establishing exactly what size of wire mesh is the best for your particular ultrasonic cleaning application is impossible without some detailed information. However, the average thickness of a steel wire mesh for an ultrasonic cleaning basket typically ranges between 0.121” thick and 0.25” thick. For most smaller parts, this is thick enough to support the weight of the held parts without significantly reducing wash performance.

Also, as wires get thicker, the spacing between them is usually increased to avoid reducing ultrasonic wash performance.

Woven or Welded Steel Wires

The wire mesh of custom baskets can be woven together or welded together. Which is best for your manufacturing business will depend on a few factors, such as the weight of the held parts, the thickness of the wires in the mesh, and the intensity of the ultrasonic vibrations. 

Welding wire mesh creates a more rigid and sturdy wire basket, and is optimal for holding heavier parts, distributing the weight of held parts along connected wires more evenly. Weaving wire mesh is less expensive, and is usually preferred for lighter baskets that hold smaller parts, since they don’t have to deal with as much physical stress.

Basket Coatings

Adding a protective coating to an ultrasonic cleaning basket can be a good option for protecting ultra-delicate parts that have a “no scratch” surface requirement. However, adding a coating isn’t always necessary and, in some situations, it can interfere with the cleaning process.

For example, adding a soft, thick coating of PVC or similar materials can cushion the impact when parts hit the inside of the basket (preventing scratches). But, thicker coatings of material can adversely impact the open space between wires, which may block ultrasonic vibrations from reaching the parts the basket holds (impairing the cleaning process). Additionally, a soft and porous coating may retain contaminants that can be transferred onto held parts, which may reduce the effectiveness of the cleaning process.

Choosing Marlin Steel for Your Cleaning Basket Needs

The team at Marlin Steel is dedicated to “quality engineered quick.” No matter your part cleaning basket needs, we can create it quickly and cost-effectively. We’re ISO 9001:2015 certified and 25% of our team are mechanical engineers who go through a detailed QA checklist to ensure you always receive the highest quality product. Ready to build the best basket for your ultrasonic cleaning process? Reach out to the Marlin team to get started!