Head Strike

While working on a small print job I found I didn't have enough EEF in letter size, which is what the job required. I have plenty of EEF in 17 x 22 inch (U.S. C) sheets, however. Just cut one into four 8.5 x 11 inch sheets. Easy.

I did that, and noticed immediately upon making the cuts the edges of the pieces curled slightly. I didn't think much of it, and set to making the four prints as usual. To accommodate the print size without clipping (that is, without the 7900 cutting off part of the image) I had to feed the sheets sideways, that is, insert the wide edge into the printer. I've done this before; I have a custom paper size set up for that: 11 inches x 8.5 inches with 0 inch margins. It's a little tricky to drop the sheet into the printer and make certain it's straight, but as I said, I've done this before with these small sheets, so I had no trouble.

The first three of four prints were fine. The last one, however, emerged from the printer with a smear of ink on the trailing edge. The print itself was perfect. The ink smear was just inside the edge of the sheet. When I laid the sheet flat on a table, it was clear the offending edge had curled more than the previous three sheets. The smear was the result of the print head striking the paper; I heard it happen, a faint swish that wasn't part of the normal sounds of printing, on the last pass of the print head before the sheet was ejected.

Looking at all four prints, I could see the first three had caught up in the time that had elapsed since they were printed. The long cut edge of each had curled about the same as the fourth sheet.

Per my wife, who has some expertise in the paper production industry, it seems the newly exposed edges of the sheets I cut from the larger sheets picked up enough moisture to cause the curl. After the cuts, each sheet had one new long edge, and one new short edge. Only the long edge curled upward, toward (or into) the coated side; perhaps the direction of the paper fiber was a factor. Room humidity was in the high 40% range.

Head strike ink smear near the sheet's edge. Ouch!

I had two sheets left from a box of letter size sheets. These are perfectly flat. I reprinted the last photo on one of those. More of this paper is due to arrive today, along with the roll of Epson Hot Press Natural I mentioned in the previous posting.

The head strike happened two days ago. The print has not flattened on its own; it still has the curled edge. Why did the first three sheets print without incident and the four suffered the head strike? Time was certainly a factor. I started printing immediately after cutting the sheets, and the curl worsened in the 15 or so minutes between printing the first sheet and the last. In addition, I suspect I fed the first three sheets with the cut (curled) edge first. The leading edge would have been held flat enough against the platen by the rollers just above the print head. The last print was fed with the curled edge trailing. EEF is stiff enough that the curl would have "popped up" when the trailing edge exited the rollers above the print head. Another lesson learned.

  --Jay