Trigger 37 said:
Grandad35,... I would appreciate your thoughts on what dralsop has done and the aggressive process he has used to clean a very difficult printhead.
I have to make a confession. In my first post in this thread, I mentioned that I got a replacement print head under warranty after the heat sink came loose. I didnt know it at the time, but I caused the heat sink to loosen by an attempt at a boiling water cleaning. The boiling water didnt clear the clog in that instance (disassembling the print head did the trick). I tried boiling water again at a later date (on the same replacement print head) and the heat sink came loose on that print head also. In this case, it only took two mistakes to see that the heat sink was fastened to the print head with an adhesive that didnt like heat. Once this was found, the heat sinks were re-glued on both heads (the print heads had to be removed to do this) to restore both to full functionality. One of the repaired heads has been running without problems for about 2.5 years (the other is a spare, as are 2 new heads that are packed away with a spare i9900).
A defective head from another printer that was previously dissected (
http://www.nifty-stuff.com/forum/viewtopic.php?pid=13256#p13256) was put it into boiling water for 10 minutes with one of the rubber grommets left in place. The boiled rubber grommet was not distorted and had the same feel as the non-boiled grommets. This isnt exactly surprising, since most common rubbers used for these types of applications have a continuous use temperature of at least 212 deg F. Even neoprene (with the lowest temperature rating) is rated at 180 deg F continuous use, so a short exposure to 212 deg F shouldnt be a major problem. I dont have the multi-holed rubber piece that seals the print head to the carriage, but it should be similarly rated.
I dont know what the black plastic carrier is made from, but it is obviously a high temperature polymer. By feel, the stiffness of this part was unchanged between room temperature and 212 deg F, so it should also be OK in boiling water.
The actual print head is made from a ceramic like those typically used in mil spec components.
*Mil spec electronics (
http://www.national.com/news/1996/9610/ds90c.html) must operate from -55 to +125 deg C.
*The print head runs through a soldering operation, and most solders dont melt until about 200 deg C.
*The print head locally runs up to about 300 deg C to generate the bubbles that fire the ink droplets.
Similar numbers apply to the flex cable and circuit board, so 100 deg C on these parts should be OK.
in summary, a print head MAY tolerate boiling water, but if there are glued components involved (e.g. a heat sink), it may be damaged by the elevated temperatures. As was stated with the disassembly technique, I wouldnt do it unless the next step is to replace the print head and there is nothing to lose. It would not be my first procedure to use on a normal clog.
Based on what we know about the possibility of impurities in the water depositing conductive salts on sensitive electronic circuits, only use distilled water for this procedure. Because the lack of impurities in distilled water can greatly increase the tendency of water to super heat above the boiling point and suddenly erupt (
http://www.phys.unsw.edu.au/~jw/superheating.html), be sure to follow the safety precautions given in the link.