Cleaning Dry Film Lubricants
Question: I have a 0.009-inch inner diameter tube that is six feet long.
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Question:
I have a 0.009-inch inner diameter tube that is six feet long. We draw this tube using a soft-core process. However, it is difficult to remove the graphite/MoS2/KSi/NaSi dry film lubricant from the inside the tube.
The manufacturer of the lube suggests a hot alkaline wash followed by a cold water quench and then a nitric acid solution rinse. However, I have been getting some good results using a hot ultrasonic cleaning process. Good, but not 100% clean.
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I am trying to hit a home run by removing all of the tenacious soil, but my cycle times are now too long–I am using a mid/high pH (8-11) surfactant and sonicating while flushing the ID.
If I were to use an acid instead of the base, would I fare better? I also have developed a wet abrasive blast process, but my results are poor. What are some good rules of thumb to follow with respect to abrasive size and liquid media? Thanks! J.K.
Answer:
First lets focus on the positive. It sounds like you are doing a lot of things right, given the very difficult cleaning job due to the small inner diameter of these parts. Considering the soil and the size of the tubing, I think the choice of ultrasonics is a good one. Is the tube immersed while you are running the ultrasonics and flushing? In addition to removing soils from the outside of the tubing, it would assist in carrying the ultrasonic waveform to the inside. I do not think the ultrasonics would be very effective if you were flushing alone, however.
Additionally, the pH you quoted is rather wide (8-11). I believe a cleaner in the higher part of that range (11) would be more effective than one with a lower pH for the removal of this tenacious soil. I do not believe that an acid cleaner would necessarily do significantly better in this process than the current cleaner.
Two other possible factors to work on would be temperature and ultrasonic frequency. The higher the temperature, the shorter the cleaning time should be and the more effective the cleaning process. You could also look at the ultrasonic frequency. You did not indicate the frequency you are currently using, although the lower you can go in the frequency, the stronger the energy of the implosion and the better chance you have for soil removal. However, that may not speed up your cleaning process, since at lower frequencies you are also generating fewer implosion sites. Another caution is to be cautious as you lower the frequency. Too low a frequency could damage delicate parts.
