The Slot Die Coater Questions You Need Answered: Read Now

So you need a slot die coater—or do you? Conversion Technologies International has the information you’re looking for as you start planning future projects. Read below to get in the know!

How does a die coater work?               

A slot die coater positions a die over a substrate—you can consider the die the mechanism and the substrate the surface. Each die has a small, narrow opening. That opening, or slot, is responsible for dispersing the solution in question. What’s interesting about slot die coating is that this mechanism allows us to control the thickness of the coating. That’s accomplished through the positioning of the slot die head—the distance controls the thickness. Generally speaking, the more precision in manufacturing, the better. Slot die coating gives us that extra dimension of precision.

Another great aspect of slot die coating is its continuous nature. You don’t have to worry about starts, stops, and resets. The slot die coating process allows us to continuously deposit solution at a steady rate. This avoids unevenness, ensuring its overall aesthetic consistency. It’s important to remember that when you’re manufacturing on a large scale, inconsistencies equal materials wasted and money lost.

With that in mind, while it might be tempting to seek out a slot die coating machine for sale, buying your own machine isn’t always the answer. It’s not always necessary, for one thing. Unless you’re operating on a very large scale, investing in equipment could be less cost-effective than it seems. When you invest in a coating machine, you’re also operating in operations and facilities. Rather than doing that, you could outsource to a third party manufacturer like CTI. You won’t have to worry about trial and error or silly mistakes—you’ll be working with the experts!

How thick is slot die coating?

There isn’t a single level thickness for slot die coating. Rather, the thickness of the coating can vary depending on your project. What you should think about is less the “average” thickness of slot die coating, and more the machine’s capabilities. With the right calibrations, we can achieve coatings with the thicknesses ranging from tens of nanometers to hundreds of microns.

However, we do use slot die coating machines more often for thin—sometimes even extremely thin—layers. Most slot die coaters specialize in coatings under two microns. Keep in mind, the positioning of the slot die coater isn’t the only thing contributing to the layer’s thickness. You should also consider the slot die’s formation, the substrate surface, and the solution’s viscosity. A thicker solution is slower to disperse, which means it stays thicker longer. You would need to dilute it further, while at the same time changing the rate of the deposition, in order to thin out the solution.

Fortunately, you can! The slot die coater’s flexibility is one of many reasons why we like this machine.

What’s the difference between slot die coating and curtain coating?

When utilizing curtain coating, we position the slot die further away from the substrate than we would with standard slot die coating. This forces the process to rely on the falling “curtain” of liquid. The proximity between the slot die and the substrate with standard coating ensures we maintain a greater degree of control than we would with curtain coating. However, the curtain coating process maintains a certain type of appeal for specific products.

A limitation with standard slot die coating is that substrates with larger variation can struggle with the lack of space. Curtain coating offers a certain flexibility they need. Additionally, it requires a minimum speed. That minimum speed can ensure a faster completion rate than the typical project.

Of course, curtain coating isn’t the only alternative to standard slot die coating…

What’s the difference between slot die coating and blade coating?

One of the main things you should know off the bat is that we typically recommend slot die coating for projects requiring thinner coatings. If you need a thick layer, the blade coating may be a better match.

Essentially, blade coating uses a blade to spread the solution across the substrate. While this ensures the “smoothing” of thicker solutions, it can lead to more variations and inconsistencies. For projects wherein that consistency isn’t as much of a concern, no worries! But if you require greater precision, slot die coating could be what you’re looking for.

Blade coating does tend to be more versatile, with an easy set up you can apply to a wide variety of materials. It’s also more affordable than slot die coating. But remember—if you need that uniformity, blade coating may not save as much money as you think. If you have to repeat the process multiple times in order to achieve your desired results, you’re wasting money.

How do I know which process is right for me?

If you’re uncertain about which process or machine is right for your needs, we recommend consulting with the experts. Third party manufacturers like CTI can not only provide you with the products you need—we can also handle future tasks. Need a slot die cutting machine? We may be able to help you as your business’s needs evolve. Looking for a super thin coating? We’ve already done that for clients in the wind and energy industry—check it out!

Get started by calling us at 419-924-5566 or contacting us here. Now’s the time to act!