I'm assuming you are talking about the random dark horizontal lines. If not, you need to be clearer about the problem, preferably by marking up the pic. And lighten it up a bit please, it's dark and hard to see.
This is likely because of the weight of the roll of banner. The SP-540 can sometimes have difficulty pulling heavy rolls of material, like banner, and you will get random media feed slippage, causing slight overprinting in the area of slippage. In addition to the weight, banner has a tendency to stick to itself on a new roll, and this "static stickiness" requires additional effort from the feed motor to overcome, adding more load in addition to the weight of the media. There are 3 solutions.
1. Use all the middle pinch rollers. This has its own issue, as banner is thicker and softer than vinyl when heated, leading to roller pressure marks, which show up when printing, due to the tiny head to media distance difference in the area of the pressure marks, which results in a tiny bi-directional misalignment, showing as a grainy vertical stripe where the middle pinch rollers are.
2. Unroll the banner material in the back to reduce the pulling force needed to pull the banner, as you have effectively eliminated the weight and stickiness of the banner roll as an issue. However, it is a PITA, as you have to babysit the printer on longer banners.
3. This solution eliminates the issues in #1 & 2. First, you only use the outer pinch rollers for this approach. There is a media brake for one of the media roller shafts in the back. Remove the other roller shaft and set aside. Take the remaining one and run it through the core of the heavy material, like a paper towel holder. Now engage the media brake on this roller and push the media roller shaft donuts tight against the sides of the roll to keep it from free rolling. I estimate it reduces the feed motor pulling force needed by around 80%. Disclosure - no scientific measurements done (LOL), just a guess when pulling the banner through the machine by hand when loading it. No need for the middle rollers and no need to babysit unrolling the media. This technique has been 100% effective for every one of my customers who have had the problem I see in your pic.
PS - for future issues, I would suggest you post in the Roland equipment forum, as you will likely get more responses that way. But please continue this thread here, as starting a second thread on this in another location just confuses things.
