horizontal black "stitch" marks on printed ceramic tiles

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Hi, looking for some help. So I printed 15 tiles, 5 of which have these horizontal black marks on them that almost looks like stitches. They are in roughly the same position on each tile. I am not totally sure if it was 5 in a row that came out like this or not, I do know that the first and last tile I did came out looking fine though. I've never had a problem like this before and didn't do anything different as far as I know. :confused:

Many thanks,
Owen

That has come from printhead strike.

Basically the print head brushed against the paper you are printing on. This can happen occassionally due to the paper not being perfectly flat.

Not much can be done except keep a very close eye on your next few prints as you will be able to see it on your print out.

Thank you very much. Now you mention it the paper did look more wavy than normal after coming out of the printer. I've gone through a fair number of tiles getting things coming out how I like so you've saved me going through any more!

Thanks again,
Owen