Troubleshooting Multi-step Processes
Surface preparation processes are varied and can often include multiple steps. For a successful bond, all steps must be consistent and effective. When the desired result is not produced, every surface preparation step must be reexamined. A couple of the 5 Primary Uses of the Surface Analyst include developing appropriate surface preparation processes and then troubleshooting these process. When surface requirements are not met, the Surface Analyst™ will develop new processes, reexamine existing processes, and troubleshoot unknown issues.
An engineer from a top aircraft manufacturer specializing in major defense applications was teaching mechanics how to use the Surface Analyst to verify clean surfaces during their assembly process. Their surface preparation process included three steps: solvent wipe, hand abrasion, and a different solvent wipe. After these steps, the engineer measured the composite panel surface using the Surface Analyst. The contact angle was embarrassingly high, at 70°. In a typical preparation process situation, the higher the contact angle, the less reactive, or “dirty” the surface is. The lower the contact angle, the more reactive, or “clean” the surface is. These measurements indicate a surface’s preparedness to bond.
Needless to say, this measurement tilted a few heads. Their surface showed more contamination after the specified preparation process than before! When and where in the process was this happening?
Revealing the Truth Beneath the Surface
This is where the Surface Analyst came in to break the process down. The original contact angle taken prior to any surface treatment read 70°. After the first solvent wipe, the contact angle read 50°. After the hand abrasion, 30°. So far, so good. But, after the final step of the solvent wipe, the contact angle hit the roof, reading higher than the original angle of 70°.
This led them to investigate the solvent itself, which was stored in an opaque container. The team poured the solvent into a clear beaker. Surprisingly, the cleaner was a dark charcoal color, rather than clear. That’s when the team explained to the engineer that they first used the solvent to soak other parts and then poured it into a container for reused in the surface bonding preparation process.
The Surface Analyst revealed that the manufacturer was using an extremely contaminated solvent to “clean” their surfaces. While the coloring of this solvent is obvious contamination, a solvent can quickly obtain contamination and may lose its integrity well before showing physical proof. But, with in-place verification procedures with the Surface Analyst, the quality of a solvent would never be ambiguous.
Based on these results, the company refined their surface preparation process and use of solvent protocol. This was made possible due to the Surface Analyst. The instrument detected and identified the Achilles heel of the surface preparation process. As a result, the company’s process became stronger, more efficient, and track-able. For technicians, mechanics, engineers, and anyone involved within the manufacturing process, the Surface Analyst verifies surface’s proper preparation within every step of the process, and can troubleshoot reliably when issues arise. These uses and several others, demonstrate how the Surface Analyst can improve and monitor the surface preparation process for reliable bonds.