RDS is happy to provide you with complete information on our coating rods and accessories, as well as processes and technology. A review of the most frequently asked questions, however, may give you more insight to common industry concerns.
| Q. How often does a coating rod need to be replaced?
| A. The life of a coating rod depends on the type of rod, how it's used, how abrasive the coating or substrate is, what the rod is made of, and how well it is maintained. Either the wires will wear down from abrasion or the valleys will fill in with coating. Before using a rod, substrate and coating together, it's almost impossible to predict how long a rod will last.
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| Q. What is the best method for keeping coating rods clean?
| A. Production and laboratory rods should be washed and rinsed as soon as possible after use. You should soak the rod in a solvent that is appropriate to your coating, rinse and wipe clean. RDS Coating Rod Rinse and Clean Tanks are the ideal way to maintain your laboratory rods.
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| Q. After metering a coating across the substrate, a dark streak of heavier coating appears. Why is that?
| A. This is most likely caused by a gap between the windings allowing an extra amount of coating to squeeze through. Dirt between the wires can also cause the same anomaly, but will more often repel the coating.
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| Q. I am using a wire wound rod to apply a film coating to a plastic substrate, and have found repeated light streaks with heavier coating on either side. What causes this to happen?
| A. This type of pattern is caused by a piece of foreign material or a hardened agglomeration of the coating under the rod, or a bump in the wire winding.
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| Q. What is the difference between a wire wound rod, a gapped wire rod, and a formed rod?
| A. A wire wound rod is tightly wrapped with stainless steel wire and is used to apply an even wet film coating on various surfaces. The gapped wire rod is used with heavier coatings or with applications where rod marks are a problem. Formed rods are actually solid steel rods that are machined to match the pitch and radius of a wire wound rod. However, the groove design permits better flow-through for highly precise metered coatings, as well as easier cleanup. Formed rods can be designed to achieve positive results for many non-standard applications.
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| Q. What should I do about lines from the rod when they appear in the coating?
| A. This is usually due to "film split"... a result of high surface tension in the coating. If coating is thixotropic (thins out when stirred or mixed), change the rod speed or else add a surfactant to the coating.
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| Q. How do I correct uneven variations in the weight of the coating? I've checked the rod and other variables and all seems right, yet the coating is thicker in some parts.
| A. The substrate could be the culprit; it may be thinner and stretch more on one side than the other. Even tension is very important. Variations in tension will cause variations in coat weight and thickness. A method for accommodating "baggy edges" is necessary if the substrate used is not uniform.
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| Q. Do coating rods need to be plated?
| A. Plating is not necessary for corrosion resistance and durability as the bare rod and wire are corrosion resistant stainless steel. Chrome plating is well worth the investment to protect against abrasive coatings and/or to enhance lubricity.
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