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Stripping plastisol from plating racks
Q. What are advantages and dis-advantages of the different methods for removing the plastisol coating from plating racks?
Which is the best method?
shop owner - Ontario, California, USA
2006
A. Hi, Francisco. Please start us off by telling us what you presently do and what issues you have with that method? We usually find that when people take the time to present their own situation and findings they get a good response; whereas the question usually remains of little interest and unanswered if presented in the abstract. Thanks!
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006
Q. I currently use a burn-off oven to remove the plastisol. Years ago, I used the Methylene Chloride process, but it was too "messy" and since it was harmful to the operators, it was decided to use the burn-off method. The issue that I have is that some of my customers are concerned about the potential degradation of the copper material because of the exposure to high temperatures. After burn-off the racks do not present any visible damage and the copper does not appear to get annealed. We are currently having an independent lab test the behavior of copper under different temperatures and timing to prove the capability of the process. Prior to the testing being complete I wanted to get some feedback from people that have had experience with plastisol removal.
Francisco Cervantes [returning]- Ontario, California, USA
2006
A. Nothing you have said so far would give your customers a cause for concern, unless it is their racks.
Copper is the opposite of steel for annealing or hardening. If you take copper to a high enough temp and cool it very fast, it will go dead soft. If you bring down the temp moderately slowly, copper will harden. So, if you do your burn off in the afternoon, you can turn off the heat and let the furnace coast down and, depending on the temperature reached, it will actually harden.
- Navarre, Florida
2006
A. Jim:
I'm not so sure about your explanation of copper annealing.
I have annealed lots of copper by heating to moderate temperatures, say 450 °F, followed by slow cooling.
Jeffrey Holmes, CEF
Spartanburg, South Carolina
2006
I do not have heat treat books anymore, so do not know the temperatures involved. I was referring to taking it to dead soft, which took quite a bit higher temperature. How much hardness change did you get with a 450 °F anneal cycle?
I thought that most burn off ovens went to above 600 °F, but have zero direct knowledge.
- Navarre, Florida
2006
Q. I set the oven temperature to 490 °F so that it will not exceed 500 °F. The process takes approx. 4 - 5 Hrs.
I do not see any physical changes to the material and it does not appear to be "soft". But I have one customer in particular that claims that copper looses some of its current carrying capabilities and hardness after being heated to ? degrees.
- Ontario, California, USA
2006
A. While there will be some change in the electrical properties of copper after heat exposure, it will be so small for your application as to be irrelevant. Most plating racks are designed to carry more current than they will be used for to prevent any unnecessary temperature rise and thus increasing resistance.
Think about it -- The bulk of the rack is in the process tank, so it cannot rise in temperature but slightly above the tank temp (vs. current carrying capacity in air). Exception is the hook and a small part of the vertical spline(s). A very minor increase in the size of that part of the fixture will more than compensate for any change in the copper.
The customer has far more to worry about the cleanliness of the buss bar and the rack contact points than they would ever find in soft vs. hard copper.
If the plated part meets spec, what is their problem?
- Navarre, Florida
2006
Q. I am interested in finding out which is the best way to take plastisol off plating racks. I heard people using nitrogen and some burning it off.
If burning it is easier, what is the temperature? Thanks; whatever info you can send would be appreciated.
Roger
- Waterbury, connecticut, USA
April 6, 2014
A. Hi Roger. I haven't heard of using liquid nitrogen but it sounds feasible. Have you tried any approach yourself?
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 6, 2014
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