If you have a head strike the most important thing to do is act quickly.
What does a head strike look like?
If the film is moved or buckles up during printing the tell tail signs are smudges in the printed ink. If this happens you have a small window of opportunity to avoid permanent damage to your print head.
What happens to the print head if it touches the film while printing.
The exit holes in the nozzle plate are microscopic and very sharp, this is the shiny surface you can see on the underside of the print head that is cleaned at the end of the day. As the nozzle plate comes into contact with the film it acts like a cheese grater. The nozzle exit holes scrape the coating and ink from the surface and this in turn blocks those nozzles.
But its still printing ok?
There many nozzles in a print head and a few missing will very often not show up. This does not mean you can carry on printing as the clock is ticking from the second the print head scrapes the film, wet or dry. So here is what to do if you have a head strike, this is a massive inconvenience but it is the only option to avoid permanent damage to your print head.
Stop printing, cancel the job, do not pause as this is going to take some time.
Clean the surface of both print heads manually like you do at the end of each day.
Fill both capping stations with the cleaning/capping solution.
Press the x home button on the printer control software to park the print heads.
Wait one hour, you can choose to leave the printer on soak until the following morning if its getting late.
The next procedure must be done in this order.
Perform an ink fill for 30 seconds, first on head one, then on head two.
Now perform two strong cleans on head 1 (not both) and then two strong head cleans on head two.
Wait a couple of minutes for the ink pressure to stabilise and print a head status nozzle test.
If you have missing nozzles, you must perform the above again but leave the printer on soak over night or over the weekend. Most head strikes are recoverable if dealt with quickly, certain film coatings can be worse than others.
Single sided gloss backed film (standard Resolute Premium DTF film) is the most forgiving. The coating is very thin and does not gel the ink. Ink gelling is the same as in the DTG process, put a drop of white ink onto pre-treatment and it gels and gets a skin on very quickly. The images below show a lab drop test, this is a specific amount of ink not just a regular drop.
A drop of ink onto standard Resolute Premium film after 2 mins, surface is liquid but the edges are drying.
A drop of ink onto Anti Static film, the ink has gelled in just 2 mins meaning the nozzles could be unrecoverable.
These images show the importance of acting quickly should you have a head strike, and the differences in the coatings used to give films different properties. Head strikes are rare if you have loaded your film correctly and do not try and move or reposition it while printing. The most important thing to remember is, dont panic, stop the printer and perform the necessary steps to recover the head and avoid irreparable damage to the print head.