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Choosing the Right Cup for Your DAC Mixer

Dual asymmetric centrifugal (DAC) mixers have become a staple in R&D laboratories around the world since Hauschild Engineering revolutionized the industry with the introduction of the legendary Hauschild SpeedMixer® almost 50 years ago. 

The basic principle behind DAC mixing consists of spinning a container, or cup, attached to a high-speed mixing arm in one direction, while the cup also rotates in the opposite direction on a different axis. The combination of forces generated by these opposing rotations allows for quick, efficient and homogeneous materials mixing.

Today, the vast majority of DAC mixers use disposable cups, syringes and cartridges. Not only does this eliminate the need to clean the equipment, it also eliminates any concern about contamination in color master batches, pharmaceutical products, or other sensitive materials. Finally, disposable containers offer a convenient way to store the material after it has been mixed.

With all the benefits of using single-use containers, it’s important to understand that not all mixing cups are created equal when it comes to size, shape and quality. That’s why it’s essential to choose the right cup for the mass and volume of materials being mixed, according to Ian LaRose, VP of Technology at Hauschild Engineering.

“The first thing to look at is the mass and volume of the materials,” says Ian. “Mass defines the size of the mixer, whereas volume defines the size of the cup.”

A good rule of thumb when considering cup size is to choose a cup that will be only 1/3 to 1/2 full when all materials being mixed are combined. For example, 50ml of mixing material requires a 100 to 150ml cup.

“It’s important to leave space for the material to move during the mixing process,” says Ian. “Filling the cup too high could result in the vortex not reaching far enough into the cup, leaving unmixed material.”

Just like filling a cup too full can result in a mix that’s less than ideal, using a cup that is too big can be equally troublesome. Going back to our rule of thumb again, filling a cup less than 1/3 full can result in the vortex not covering the bottom of the cup and creating a dry spot.

Shape is also an important factor to consider in cup selection. Some cups are just fundamentally different in the way materials flow through the container. “If you’re using a cup with somewhat squared off corners, it can be hard to get the material fully mixed in those corners,” says Ian. “The cups Hauschild supplies have rounded corners, which is more conducive to the best mixing.” 

Not only do rounded cups allow for mixing of thicker materials, they allow for mixing of regular viscosity materials at a slower speed. This reduces the temperature and typically increases viable working time, especially with reactive materials like an epoxy or urethane. 

“Ultimately, if you mix at a lower speed, you get less temp generation, which keeps the reaction slowed down,” adds Ian.

Cup material is another important factor to consider in cup selection. As mentioned above, 90% of all laboratory mixing applications are performed with disposable polypropylene cups. However, there are a few exceptions to using the standard food grade polypropylene mixing solution:

TIN CANS – Standard paint cans are an inexpensive option for materials that are incompatible with the standard polypropylene cups or require high temperature processing.

ALUMINUM – Aluminum cups allow for processing higher temperature materials better than standard cups. They are lightweight and allow for higher sample loading than comparable tin or PTFE options. 

GLASA – Glass containers are resistant to some chemistries that polypropylene cups are not suited for. They can also be autoclaved, which makes them ideal for biological applications. Fun fact: glass containers are often a favorite for preparation of nano-scale liposomes for specialty drug delivery applications. 

PTFE – This cup material is resistant to many extremely corrosive/aggressive chemistries that would not be stable in a standard polypropylene jar. They are also suitable for higher temperatures and can be autoclaved for cleanliness. The downsides are that they are heavy, quite a bit more expensive than standard polypropylene cups, and the polymer is softer compared to many other cup materials. 

POLYURETHANE – Polyurethane cups are extremely durable and more resistant to higher temperatures than standard polypropylene cups. This makes them ideal for applications such as grinding/milling, or processing materials that require higher processing temperatures. They are, however, more costly than standard cups, so they are typically cleaned and reused. 

“The beauty of using Hauschild SpeedMixer® is that they are capable of mixing almost any type of container,“ says Ian. “If you’re unsure about what type, or you need a custom solution, talk to us about building a holder that can work with your specific cup or need.”

He stresses that when starting a new mixing application, it’s always best to talk to an expert who can help you set up the ideal solution for your application.

“One thing that really sets Hauschild apart is that we take ownership of the whole process,” says Ian. “Even if you’re not using a Hauschild SpeedMixer®, we can help you put a system in place that either accommodates what you’re using or delivers an optimal solution to your mixing needs.”

We’re happy to help you determine the right disposable or specialty cups, cartridges or syringes for your specific needs. Contact the Hauschild team today.