It is unusual for a printer to print only one copy of your brochure, poster, custom pocket folder, or print book signatures on a press sheet when he produces your job via sheetfed offset lithography. This would not be efficient. Nor would it be economical.
Instead, he usually lays out a number of pages (on a computer in the digital prepress component of custom printing) in a certain order on the press sheet so they will fall in the right position when the large press sheet has been folded and trimmed.
What exactly does this look like? What do you see on a printed but untrimmed press sheet?
Sheetwise vs. Work and Turn vs. Work and Tumble
Let’s say you’re printing a 9” x 12” custom pocket folder with a 4” pocket. Prior to converting, this job is a four-page, 18” x 16” product (plus any build for the spine, plus any glue flaps and/or bleeds). The 18” dimension would include two 9” pages, and the 16” dimension would include the 12” side plus the open (unfolded) 4” pocket.
Your custom printing supplier can get two of these on a 25” x 38” press sheet. If your press run is 5,000 copies, this would only require him to print and convert 2,500 sheets. This will save him time and money. To do this he has a number of options.
Sheetwise
Your printer can lay out these two pocket folders side by side on a 38” wide by 25” high press sheet. (Picture two completely unfolded pocket folders, one on the left and one on the right, standing on their 16” sides). The printer can first print one side (the exterior front and back, for instance). After these 2,500 printed sheets have dried, he can turn them over and print the other side: the interior pockets. However, he must first clean the press and hang new plates. (This is called a wash-up. It takes time and costs money.)
Work and Turn and Work and Tumble
If your printer flips over one of the pocket folders on the press sheet, so the front of the sheet includes one custom pocket folder’s front and back covers and one pocket folder’s interior two pockets, he can print one side of the sheet, wait for it to dry, and then print the other side of the press sheet without washing up and rehanging new plates. (That is, the same plates are used for both sides of the press sheet.) Depending on how he turns the press sheet, this approach is called either work and turn or work and tumble.
Specifically, work and turn involves keeping the gripper edge of the press sheet (the leading edge) the same when the printer turns over the sheet (from side to side). In contrast, work and tumble involves turning the press sheet in a tumbling (end over end, rather than side over side) manner. The gripper edge changes from the front of the sheet to the back of the sheet and the side guide stays the same.
Of course, all this happens after the sheet has dried. If the ink is wet, it will offset onto other pages.
When to Use Sheetwise vs. Work and Turn/Work and Tumble
Let’s say your pocket folder has heavy ink coverage on the exterior covers (front and back), but nothing inside. Once the open pockets have been folded up and the glue tabs have been folded over and attached, the interior of the pocket folder would appear to have some interior color. It will just have been printed on one side of the press sheet prior to folding. (That is, the interior pockets would have initially been printed as part of the exterior of the folder.)
In this case it would be prudent to print the job sheetwise, since only one side would need to be printed. Flipping one of the pocket folders over on the press sheet prior to printing would gain nothing and necessitate two print runs, one for either side of the press sheet. In this case, having both images side by side in this “two-up” sheetwise imposition would be ideal.
Or, if the printer needed to print heavy ink coverage on the exterior covers of the pocket folder and light ink coverage on the interior, he might also choose a sheetwise imposition to avoid overinking the interior pages.
In other cases, he would probably choose work and turn or work and tumble imposition, depending on how he wanted the images to fall on the final press sheet (again, this might have a lot to do with the amount of ink coverage). Once he has imposed the images (in this case, the custom pocket folders) on the press sheet, he can choose whether to turn the sheet from side to side or end over end, after the ink has dried.
Remember, the same holds true whether your printer is producing two pocket folders on a sheet, four brochures on a sheet, or a sixteen-page print book signature (eight pages on each side of the press sheet). The printer must determine the most efficient and economical way to position the pages on the final press sheet to avoid overinking the printed product and make sure the folded piece allows each page to fall in the proper position.
This entry was posted
on Sunday, July 20th, 2014 at 9:06 pm and is filed under Pocket Folder Printing.
You can follow any responses to this entry through the RSS 2.0 feed.
Both comments and pings are currently closed.