FOD Definition: FOD stands for “foreign object debris” and is all widely used term, especially in manufacturing, aviation and aerospace. FOD can mean foreign objects, particles or pieces in components, fixtures or assemblies in the manufacturing industry. These unwanted pieces or particles can affect the finish, texture and sometimes even fit of components and parts. Avoiding FOD through inspections and quality control is vital for a quality thin-film ceramic finish.
Consistency of Finish is dependent on several factors, and minimizing chances of FOD is one major factor.
In this tech report, we're going to focus on what FOD means in the coating processes relevant to thin-film ceramic coatings in manufacturing and aerospace. In higher end manufacturing applications, coatings are typically one of the last steps in the manufacturing process, whether it be a functional part, or a technical part going inside of a very critical assembly.
FOD can be detrimental, or have detrimental effects down the road depending on where that particular part may end up.
Take for example, a part is specified as a "Class A" finish with zero allowable flaws. The customer is looking for a smooth consistent finish, and upon removing a masking plug, residual blast media that was trapped inside of the hole spills out, once the part has been packaged. This blast media is now on a finished part as a contaminate and is an example of FOD.
Example of FOD in thin-film ceramic applications: Failure to strain your paint prior to loading it into your application equipment. In some cases, the paint has particulate left over from the grinding process of making the paint, which can transfer through the paint gun, and onto the part. It ends up leaving a spotty, rough texture on the part, where it should be totally smooth and consistent.
FOD can also be dust particles, bugs, and anything that may be a foreign object, that lands or ends up being part of the finish, or on the surface of a finished part.
FOD also can occur on complicated masked parts.
Masking materials such as vinyl tape or silicone pugs can be a major contributor to FOD during coating, and masking removal. These masking materials are flexible, and once coatings have been applied, paint flakes can often fall off of the masking materials when removing them from a part. If proper care isn't used to remove this residual debris, it could easily be classified as FOD.
Whether it's plugs (shown above) or masking tape, the best masking is done with new, clean masking materials.
With thin-film ceramic paints, FOD can be very noticeable, even with minute contaminants because of the thin-film and precise surfaces that are finished. Small bits of blast media, or flaked-off dry paint from masking fixtures all can be considered as FOD, and result in a subpar product if delivered to the customer.
Dust and particles collect in coating shops, so every part of the process should involve protections and inspection to ensure residual particles aren't left on finished parts.
Parts inspected at the end of the process commonly are blown off with clean air after being coated to make sure that residual pieces of FOD are blown off the part. Clean application equipment will help ensure that FOD won't be present.
These steps, as well as ensuring application equipment, airlines, and masking fixtures are totally clean prior to doing your application, will definitely reduce the risk of FOD.
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Surface Prep Best Practices for Applying Thin-Film Coatings