Add PCM to Reduce Setups, Quality Checks in Coil Coating

    Posted by Mike Bonner

    Jul 17, 2015 11:00:00 AM

    coil coating technology system 

    Setups are the bane of every coil coater. They are required for every color and/or product change. In addition to “setups," some folks call them “color changes," others call them “clean-ups," but whatever you call them, they add cost to running your line and, in a time when job sizes are shrinking and color changes are becoming more prevalent, these are increasing the operating costs of all coating systems.

    By adding Saint Clair Systems' Profile Correction Module (PCM) to your coil coating technology arsenal, you will be able to drive down the number of setups and quality checks you need to do.

    What’s in a Setup?

    No matter what you call them, setups require you to determine:

    • The proper line speed
    • The proper roll speeds
    • The proper nip pressure
    • The proper kiss pressure
    • The best coating viscosity

    And these are only the coater variables. They don’t even include the oven zone temperatures, which impact the outcome, but are difficult to change. This is why that most coaters set their oven profiles and vary their coater setups to work with their oven setup.

    And this makes sense.

    It provides at least one stable set of conditions to work around and reduces the number of variables to get to the goal.

    Why are Setups Important?

    That goal is to meet all of the customer required coating parameters in a minimal run time. The critical parameters include:

    • Color match
    • Finish quality
    • Dry film build
    • Adhesion
    • Impact resistance

    And which of those parameters are important may differ from customer to customer – even for the same color. This means you may have multiple setups for the same white, one for a customer who is focused on adhesion and impact resistance, and a slightly different one to optimize color match and surface finish for another.

    Regardless, the key of any setup is to change each variable as necessary to meet those key parameters – often called “spec."

    Why Do I Need a Pre-Run Quality Check?

    Pre-Run quality checks are often called test strips or test shots. They are a short length of strip, coated then cured and then tested for each of the required parameters. If any of the parameters are “out of spec”, the process must be repeated; changing the variables until the setup produces acceptable results in each of the key areas.

    So why are they necessary?

    If the coater setup doesn’t produce coil that meets spec, it is expensive - period. One solution is to recoat the strip – that means double the time to produce the product – not good. Or the customer may not allow recoating, then you’ve spent your time making scrap – even worse. Or the customer may accept it, but as “degraded product” at a lower price – if you’re lucky, you might break even.

    The real problem is that there are so many variables working against one another:

    • Viscosity varies with temperature which changes the nip pressure to get the same wet film.
    • Trying to change viscosity by adding solvent changes the volume solids in the paint, which changes the wet film required to get the same dry film.
    • Most coatings are “thixotropic” meaning that they change viscosity when placed under shear. Variations in the pan in temperature, viscosity, and flow rate change the way the paint behaves.

    How Can the PCM Possibly Help?

    With so many variables interacting, how can the PCM possibly help?
    To begin with, the PCM provides a consistent, repeatable film to the pickup roller. It is always of consistent viscosity from edge-to-edge, and it is “pre-sheared” as it is supplied to the applicator nip thus eliminating any pan based variation.
    Just eliminating this variation shortens the setup time and reduces the number of variables that need to be adjusted. For instance, without pan-based edge-to-edge variations, nip pressures can be equalized between the operator and drive sides eliminating film highs & lows on each side of the strip. The pre-shearing also provides some leeway in the roll speeds and kiss pressures by making the paint more predictable. 

    Adding Stability Shortens Setups

    The improved control provided by the PCM produces acceptable run parameters quicker and reduces the number of trials necessary for first-time colors. 

    But it goes beyond that.

    On repetitive colors, this reduced variation can make a setup more predictable, resulting in a known “recipe” that will produce a known outcome. In these instances, test strips can be eliminated altogether. This shortens your overall setup time and improves your production efficiency.

    Download the free Dimension Request Memo to learn how we can customize solutions for your line.
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    Topics: Coating Technology, PCM

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