A Guide to the Cost of Failed Masking in Finishing

Penny Wise but Pound Foolish…A Guide to the Cost of Failed Masking in Finishing Processes

Part 1

A rack of discards sits in the middle of the room. Shelves of streaked parts, awaiting their disposal. “What happened”, we ask? “Oh, the plugs must have leaked as they were coated”, was the reply. We discuss whether rework is an option, but in the end, it is cheaper to just scrap them rather than strip and start over. At $50 per part.

Masking can fail causing the need for rework for several reasons:

1)      The mask has reached its end of life

2)      The mask is not sized or applied properly

3)      The mask is not correct for the process being used

For this article we will focus on the first mode of failure – the plug or cap has outlived its usefulness.

Used Masking PlugsWalking through manufacturing plants and coating operations, we often see the same sight. Buckets, bins and shelves with full of used silicone and EPDM caps and plugs covered in coating, torn and deformed from overuse. While it is true that these plugs and caps are designed for reusability, they do have an end-of-life. When they are used past this point, issues can quickly mount.

Although most coatings don’t adhere to silicone, over time repeated bake cycles will cause both silicone rubber and EPDM rubber to dry out. As this happens, caps and plugs become less pliable, crack, craze and build up coating with each new use. Once this happens, plugs will not seal properly, and caps will begin to tear and leak.

Some coatings, such as plating, involve the use of chemicals. Some of these chemicals can be caustic and will greatly reduce the life span of any rubber materials used for masking. In some case the caps or plugs may become very soft, deform and tear. Depending on the chemicals and processes, this could take many cycles before it becomes a problem – or it could be just one. This is why it is so important to test and establish life cycles for all silicone and EPDM masking caps and plugs.

When these products reach their end of life, they need to be replaced. For high volume processes which require multiple plugs per piece or large custom masks, those in charge of the purse strings may want to push the limit for this lifespan. However, using the example at the beginning of this article – how many tapered plugs can a company purchase for one $50 lost part? How many pull plugs add up to the cost of chasing powder coating out of threaded holes?

Our team at CFS will gladly work with your process engineers and finishing departments to determine the best timeframe for the replacement of your masking parts. It can be as easy as putting a procedure in place to replace masking on a set schedule – say the first production day of the month.  In other cases, we can make recommendation on the number of cycles that a custom mask can endure and suggest testing criterion.

At CFS our goal is to partner with you to ensure that rework and scrap due to masking failures are kept to a minimum. Contact us today to speak with one of our team members and learn how we can help you minimize your losses!