Uneven Print length on JV33

Here's the deal. Customer supplied artwork for a pop-up trade show display.

Printing the graphics on Intellicoat's PosPro300 polycarb media and the print lengths are coming out different by at least 3/8ths of an inch between panels. Since the graphics contain both horizontal headers and footers that need to line up as well as text that runs across multiple panels this difference is unacceptable.

I set the artwork up with an outline around the entire print area so that the media would always only move the amount necessary for the next print head pass. ie: There are no blank areas that would see the media advance to the next area that has something to print.

The media has a matte finish coated print surface, but a glossy polycarbonate back to it. All panels were printed at the same time and used the take up reel. No adjustments were made to the media feed compensation other than the initial check prior to printing the first panel.

Printing was done @ 720x1080 bi-directional 12 pass using wasatch rip.

Has anybody had this issue before? Did you manage to solve it?

 

Yes, all the files were created from the same multi-layer photoshop document. Identical file resolutions, sizes, etc. The files all line up perfectly on-screen. I saw no indication of banding anywhere on the prints that would indicate slippage and as mentioned in the original post the media compensation was adjusted just prior to the start of printing, but not during. Both panels were printed as a single ripped file. I double checked the layout file and no scaling was inadvertently applied in the rip.

The strange thing is of the two panels I've printed, the first panel which didn't use the take up reel until it had printed far enough to reach the take-up reel, is the longer of the two. I would have expected the exact opposite with the tension applied from the take-up system creating longer prints and not shorter.

The 6 - 8 foot tall vinyl banners printed on smooth finish 13oz double sided show a maximum of 3/32" difference, but they were not all created from the same master file. Most are within 1/16th - 1/32nd of an inch of each other across 8 feet. This certainly hints that the PosPro media could be the culprit and are within a range that would workable on this project if I could get the same results from the PosPro.

My service manual lists nothing in the way of print length or media feed calibration. Is there any way to calibrate this to make sure you're getting the right length prints? I know it was possible on my older epsons.

 

Update, taking the take-up reel out of the equation brought everything within tolerances and all the panels now line up within 1/32nd of an inch to each other over the 8' height.

I moved a work table over to front of the machine and had the prints roll out onto a bunch of old 3" tubes to further reduce friction and prevent the pieces from bunching up on the floor and gathering dirt. Think assembly line or shipping rollers to get an idea of the quick and dirty set-up I came up with using old media rolls.

The poly media was definitely part of the problem. I think the smooth finish back prevents the friction feed rollers from gripping properly. I did another job that had 8 - 8' vinyl banners. Just for shits and giggles I did two without the takeup reel and then 6 with and they were all the same length.

This worked much better than my local Mimaki tech's suggestion which was (of course) "buy a flatbed printer".