Hey.
What did you do with pating line issues on Roland 50? I am experiencing same issue right now and I have tried a lot of things already..
About Roland 52, I am having once again some issues with it. I love the mill once it is works but otherwise it is a lot of headache, and since it is newer mill, CAP (our supporter) doesn't know much about fixing it yet....
CAP used to know a great deal about the Rolands since, before they were bought out by Zahn, were the distributors and knew how to repair them. Perhaps the older CAP people who knew a lot were replaced by new tech support people who know very little.
Parting line issues can be caused by numerous things, unfortunately. I would first make sure the collet has been tightened per Roland's specifications (there's a Youtube video on it). If that has been done, then I would check to see how many hours are on the spindle. If its at or near or beyond 2000 hours, then a new spindle may be in order (those are around $1500 btw). If thats not it, the z, y, and/or x axis may be out of alignment. A repair tech should be able to evaluate it for that. To fix an axis issue could be as simple as replacing some tension wires, some pulleys, gears, or other simple components; or it could be as pricey and complex as replacing the spindle sled (sled, housing, holder, whatever its called). Thats all for the 50. The 51 doesn't have all those components and I have not experienced repairs for that yet; I think the 52 has the same build on the inside.