Coating Tech Slot Dies – where precision, manufacturing, education meet expertise

Rich Palzewic

Staff

February 17, 2025

EAU CLAIRE – After outgrowing its former space, Co-Founder Mark Miller said it was time for Coating Tech Slot Dies in Eau Claire to move into a new location.

That growth, Miller said, led to a new 25,000-square-foot facility in the Gateway Industrial Park on the city’s northwest side.

“The new space gives us much more room,” he said. “We broke ground in spring 2023 and completed the project in April 2024. It took time to slowly move everything over from the old location to the new one. Right now, the facility (2218 County Line Road) is surrounded by a cornfield, but there will be more buildings coming to that area (soon).”

Miller said the new building was built with future expansion in mind.

“We definitely have space for more equipment,” he said. “The site sits on five acres of land and allows us to add another 75,000 square feet in the future (if needed).”

Because much of the work Coating Tech Slot Dies does is high-precision, Miller said the new building had to be built with precision in mind.

“The problem with high-precision work is you also need precision temperature and humidity control,” he said. “Our temperature control is within one degree, and humidity must stay within about 15%. We also couldn’t have floor vibration from outside sources like trains going by, etc., so getting an existing building up to snuff would have been difficult – that’s another big reason we built new.”

Miller said the investment Coating Tech Slot Dies has in its HVAC system “is intense” because it has to maintain that temperature and humidity control.

Continued growth

Because of his experience in consulting, Miller said Coating Tech Slot Dies had a customer on day 1 of operations – which started in 2012 in the Chippewa Valley Technical College’s (CVTC) former incubator space.

“CVTC had this incubator, and we started in a space of about 4,000 square feet with one precision grinder,” he said. “That worked for a few years as we were growing, but eventually we needed to buy more equipment. As we grew… and had multiple pieces of equipment stuffed into the space, we kind of took over the area.”

Around the same time, Miller said CVTC “let us know their incubator program was ending, and we had to find a new space.”

“We had plenty of warning – they were very nice to us,” he said. “We had about a year and a half to find a new space, either an existing building or a new one.”

General Manager Michelle Lien said the company also invested in a significant amount of new equipment for the new building.

“Part of the move was to improve our capabilities and make more of those capabilities internal,” she said. “The move went well, and we really didn’t miss a beat. We did it in phases.”

The growth, Miller said, continued with Coating Tech Slot Dies doubling in size in 2022 – prompting the hire of Lien.

“We had 11 employees in 2022,” he said. “We now have 24.”

What are slot dies?

Miller, who co-founded the company with Tim Marion, said “slot dies are not something most people know much about.”

Slot dies, he said, are a behind-the-scenes, business-to-business type of thing.

“If you think about how 3M makes a lot of its products, the easiest one to picture is a piece of Scotch tape,” he said. “A piece of Scotch tape has a piece of plastic and glue on top. The plastic is extruded through an extrusion die and the glue is placed onto the plastic as a liquid and then dried into place. When it’s placed on the plastic as a liquid, it’s placed on there by one of about 20 different ways to coat – using a slot die is one of those methods.”

In simpler terms, Miller said to think of using a roller or spray gun to paint a wall.

“A slot die is the most precise way you can paint something,” he said. “It’s very similar to a spray gun – it’s a pressurized system that applies coating. When you look at the different coating techniques, slot dies have enough precision where you can do optical films, which are very difficult to make.”

Precision is “absolutely needed,” Miller said, with slot die coating.

“You need to have the precision to lay that liquid down in one-micron thickness,” he said. “One micron is one-ninth the thickness of a human hair. For that fluid to lay down with that precision, you need to be able to machine the metal that controls the flow of that fluid to the same precision. We’re able to manufacture metal down to one-micron flatness across the size of a tabletop that could be 80 inches wide. We hand work that – you can’t do that with a machine. It takes many weeks to go from a raw piece of metal to a precision instrument that you can use for coating material.”

According to the company’s website (slotdies.com), slot die coating was developed because a better and more efficient coating method was required.

This process, it states, has been successful in replacing other coating methods in applying many types of solutions.

A slot die is capable of holding a fluid’s temperature, distributing a fluid uniformly and defining a coating width.

The die, the website states, is comprised of steel body sections that house the fluid flow chamber.

Modest beginnings

Miller said though he and Marion started the company in 2012, the journey to get to that point started before that.

“I’m a chemical engineer who graduated from the University of Wisconsin-Madison,” he said. “After graduation, I was hired by 3M and went to work in the Twin Cities. That’s where I got exposed to this technology, (which) I knew nothing about – a slot die.”

Miller said he learned how to use slot dies at 3M.

“I always joke that I spent the first 10 years of my career breaking the equipment, and then I spent the next 10 years learning how it was made,” he laughed. “Once I learned how it was made, that made for a powerful combination. A lot of people in metalworking don’t know how their metal is utilized. If you know how it’s utilized, it helps make a better product.”

Miller said he was eventually hired by a company that manufactured extrusion dies but didn’t know how to use slot dies.

“We built a team, and one of the team members was Tim Marion,” he said. “We helped that business grow. Eventually, I left and did some consulting. Tim eventually left the company as well, and we partnered to begin Coating Tech Slot Dies. Initially, the focus was to manufacture the equipment places like 3M would need, but also be a process development partner to make the best tape, optical film, etc. We’ve had great growth since 2012.”

Confident in their work

Miller said sometimes, the Chippewa Valley is referred to as “Die Valley.”

He said there used to be only a single slot die company in the area, but that eventually grew to eight in a two-mile radius in the Chippewa Falls/Eau Claire region.

“There’s probably just a handful of them left,” he said. “When you look at our competitors, we feel very comfortable telling prospective clients to go and look at the other places. What’s interesting about ‘Die Valley’ is that these people are providing slot dies to the world. We’re exporting to China, Korea, Germany, Brazil, etc. We have sales agents all over the world.”