Powder Coating Q&A: Adding More Cure Capacity
Q. We have an old cure oven that we use for a liquid paint that gives us about eight minutes of metal temperatures between 365°F and 400°F on our heaviest part. We have trouble with consistent color and gloss with some of our colors, and we think it is related to the cure oven. We recently took on some work from another manufacturer, and we cannot get a full cure on the powders that are approved for its products. The powder film looks good when it comes out of the oven, but it is not scratch resistant, and a cleaner that we use before packaging takes off some of the coating. Our oven is too short, and we are not sure of the best way to add more capacity. Can the powder material supplier change the new powders so they will work in our oven? Should we consider adding an infrared section or adding more convection time to the oven?
A. First, you could slow the line down, which will give you more exposure time. Second, the supplier may be able to give you a lower cure temperature/faster cure powder that will help. That may add a little cost, and the powder is less stable in a hot atmosphere, but it is a viable way to help with a short oven.
If you exhaust these options and think an oven addition is the only way to get the needed capacity, then you will need to evaluate several issues. More convection will probably work well if you have enough space in the line to install it. Convection curing is reliable across a variety of parts, and the cost operation is modest. If you do not have the space, consider an infrared (IR) booster oven, which can be an excellent way to get more cure power in less space. Keep in mind that IR curing is less flexible across a variety of part shapes and masses, so you will want to test it before you commit. With IR, you can get more cure impact in a smaller space. The challenge is to make sure the part geometry has enough surface, low enough mass and hidden surfaces to take full advantage of the radiant energy from the IR emitter. Compare the size, cost and benefit carefully to determine what type of oven will work best for your application.
Originally published in the April 2016 issue.
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