Thank you, Paul. I'm glad someone shares the same experience. I have this banding rather randomly at different areas -- not the whole print. And this happens on 44" roll, not on 13" roll (haven't tried other sizes). I guess tension is not uniform for larger rolls. I will try printing at 2880 dpi and reducing the paper feed parameter (doing this kind of experiment is expensive ). Also let me measure my print dimension and report back.
The canvas I use is Epson Matte canvas. It's manual recommends +50 for 78xx/98xx series but doesn't say for 7900/9900 (printer is still too new or paper is the old stock). I thought these two generations of printers should be similar so I set at +50. Apparently that's not the optimized setting for 7900/9900.
LeiMeng--OK that's what I wanted to hear--errrr sort of. Just to make sure that your banding situation is the same as mine. And it is. It's random and at different areas around the canvas. What I think is going on is that since canvas is a stretchy type media--more so than paper--when the back tensioner pulls back constantly you have these areas where the canvas can slip under the rollers. It may be due in part to slight variations in the canvas or it may in part be due to the rollers being of different adjustment or maybe a little glazing on their surfaces. Whatever the cause, I think the canvas does not advance as much as it should in an area and because canvas does stretch, this is allowed to happen a small ammount here and there, and the print head then prints a partial overlap pass where it just printed one on the previous shuttle. Perhaps this happens on a couple of head passes, but eventually the canvas releases, and catches up to the rest of the sheet in it's feed to where it should be. Consequently, there is a "jump" where the print head skips a row or two as far as a complete inking pass, which then creates the sporadic white banding we are both seeing. Your like the only other person so far that I have heard reporting this except for myself.
I didn't even realize what was going on till one day I was printing profile targets off my canvas rolls. They consistantly showed passes of ink laid down between the rows of color swatches where there should have been pure white. At first I thought I was seeing color bleed or something. Now since I was doing profiling for all kinds of media for the new printer, I had also other targets of papers from sheets laid down next to ones of canvas made off the rolls. Quite by accident when two targets were next to each other and lined up I first noticed that the canvas one seemed shorter than the paper one. When I measured, sure enough almost 1/4 inch too short from the ten inches it should have been. That's when I figured things out. Up to that point I tried every adjustment I could think of including back tensioning adjustments in maintenace mode II. Nothing helped except printing at 2880 and printing at -70 paper feed. In this case the paper feed and closer passes at 2880, allowed me to slow the advacing canvas down--thus lessening the shorting and banding--but I knew this was no solution. On a print of 6 foot I was looseing a inch by the way. This is why it's important for you to measure your prints and post the results, so that this problem can be nailed down from consistant reporting results from different machines LeiMeng.
Next I tried printing the canvas targets with sheets cut from the rolls. Voila! No more short prints! No head pass overlaps leaving color between the rows of target color. It also occurred to me that this was the problem with the banding I was seeing.
Planten has nothing to do with it neither does suction, or any other of the adjustments. It's the back tensioner. If it's possible, we need a way to turn it off for certain media. Maybe an increase or adjustment of feed roller pressure but you would tend to think that might cause other problems such as roller tracks and pinching
I never had anything of a problem like this using my 9600 for six to seven years with the same media's.
Hey Paul--
The info I got on the slight loss of canvas length and the reason for the cause differs from what you posted above. It's not the printer but the inherrent nature of canvas to shrink a bit when the wet ink hits it and dries. I have been told this is normal and has always been the case with canvas. Most folks expand their image a certain percentage to compensate in the long direction if this would be a problem for them. It's not a large ammount--maybe 1/4 inch on a six foot piece.
Like I said before in other posts I will be fabricating a free wheeling spindle using my old 9600 spindle and a propriety home made bracket above my 9900, and use this for canvas. The regular in machine media holder will be used for paper.
This problem is not gonna be unique and there needs to be a gathering of us who are afflicted with it so that we can get epson's attention and action. I'm hoping a firmware update with an option to turn off the back tensioner and let it free wheel would be possible--but for some reason I tend to think that since it is all geared together probably with the motor that this might not be entirely possible.
I would wish that anyone using the 7900 or 9900 with canvas start measuring their output and if seeing shortages report it here on this thread. We can then direct Epson to it so they can fully embrace the reality that they need to do something about it.
I burned up two and a half 44" full rolls of canvas and ink trying to figure this problem out.
Paul Leverington---Epson 9900 owner
