This email address is being protected from spambots. You need JavaScript enabled to view it. is a fluid coating expert with experience and knowledge in the converting industry accumulated since 1996....more

Slot Die DOs and DON'Ts

If you'd like to hear from Mark Miller's own lips rather than read his Coating Matters blog post titled, "Slot Die DOs and DON'Ts," click on his podcast below:

We have seen it numerous times–equipment is mishandled and damaged unnecessarily. While these nicks and dings can add up to expensive maintenance costs, they are avoidable. So what should a maintenance manager do?

Taking a slot die as an example, I would like to walk through the ideal scenario to reduce maintenance costs to a roll-to-roll manufacturing plant.


Whether it is proper coating technique, handling, disassembly, or cleaning, maintenance crews and operators can learn a lot in a little time. Developing a protocol sheet for each area of operation and maintenance with a process owner and a control plan will help keep equipment in proper working conditions, even with changeover in the plant. With a slot die in particular, a day of training will identify and embed in the operating personnel the five variable components (lip offset, lip geometry, attack angle, die to substrate gap, and lip gap); the critical flow surfaces (both inside and outside the slot die); and the connections between the components and surfaces.

Preventive Maintenance

With a regular training plan comes a regular maintenance schedule. While training can occur on an annual basis, a PM schedule for equipment should be more regular. For a slot die, this would include inspect and replacing seals, shims and bolts that have become worn or damaged. To reduce downtime, it may be helpful to have an identical piece of equipment as a replacement while this PM is occurring.


Operators and maintenance personnel are not the only ones who need training. A coating operator who is following the coating and keeping a daily journal of what effects the product, should be presenting some best practices once a week during a production meeting. Engineers and managers would gain a lot from compiling and disseminating this information throughout crews and shifts. Identifying equipment and process headaches will shorten development efforts also. Coating operators are on the front lines and see obstacles before the next product is developed.

Boundary Conditions

When setting up a PM and training schedule for a specific piece of equipment, realize that one component in a roll-to-roll process is part of an overall system. A slot die needs to interact with web guiding and tensioning systems, backing rolls, fluid delivery pumps, and curing stations to provide the end product. If only one of these items is understood and maintained, the whole system is at risk. You are only as good as your weakest part.


A coating line and a slot die are designed to cover a range of applications. Knowing what these limits are and what products can operate within these limits is important. I would prefer to see the pump operating in the mid-range of output instead of on the edge. This will lead to a catastrophic failure at the most inopportune time. If the equipment is not tuned properly for the product line, invest in the upgrade.

Overall, if your coating facility invests in training and preventive maintenance, while understanding boundary conditions and equipment expectations, you can expect to be successful as long as the lines of communication are open.

If you are interested in discussing this concept further, contact Mark D. Miller, Founder and CEO of Coating Tech Service, LLC at This email address is being protected from spambots. You need JavaScript enabled to view it. or 612-605-6019.

Mark's Coating Matters | Process

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