R2 Bed Leveling Issue or Print Warping?

I've finally been able to set aside some time to get my Kickstarter R2 printer setup, and I've had great success with a few smaller prints that probably use only about the center 3-4 inch portion of the bed.

I've moved on to print some other larger objects, and despite spending 90+ minutes a few different times running through the initial z-offset, fine-tune z-offset, and running through the bed leveling (guided mode) - my prints start to peel up at the edges, even though at first glance the first layers appear just fine. Running the various "lines" tests I felt I got the bed relatively level, with lines appearing fairly even on both sides. I have also noticed that most of the spiral level bed test have blended together into one line, with the exception of the little tiny zigzag pattern on the outermost ring/edge at the 3 o'clock position.

I'm using Cura for Robo 2.5, and included a screenshot of my printer settings in the gallery as well. The prints didn't exhibit the "curling" at the edges until at least a couple of hours into the print job. The first print of the bottom half of the case utilized a 6-line thick brim, while I used no brim/skirt/raft on the top portion of the case. Current z-offset is -7.15. My Robo R2 did not come with their little leveling gauge/tool, so I've been using either a half sheet of either plan white printing paper or a half sheet of thin/light card stock to help set my z-offset.

I'm using eSun PLA Pro+ filament - extruder temp of 210, heated bed at 60. Even with a brand new roll of filament, the issues occur.

I would greatly appreciate any advice you can provide me. While I fully admit I'm a 3D printing novice, I haven't encountered these issues with my Robo C2 once I successfully calibrated my z-offset.

 

I'm unsure why the forum felt my content links were inappropriate, but the project I'm currently working on is a 3d Mini-NES case. Enough people have printed this that I'm fairly certain it's not a 3D model issue.

This Google Photos gallery helps illustrate my issues, please feel free to leave comments/suggestions:
(I left small comments/notes on each image to help describe what is going)

 

I +1 the Glue stick on the R2 original bed.

I would also back off on the hot end temp. Try a closer to 200c. I can print most PLA's at @198c on both of my printers.

 

@Geof and @jscottb Duly noted - I'll adjust the heated bed profile to 50c, the hot end temp to 200c, cover the original R2 bed with glue stick and will report back. And silly question, but what's the best "solution" to clean the bed off with between prints if I've used glue stick?

Any ideas as to what might cause the little zigzag pattern on the outer ring around 2:30-3 o'clock on the spiral level picture? I used to get that for outer 4-5 rings on the right edge of the bed only around the 3 o'clock position, and presumed it was a leveling issue. The spiral level test in the gallery is the best I've managed to achieve - although some of the lines/rings don't blend together as well into one line as they do on my C2.

Thank you both for your prompt help/suggestions.

 

@Geof understood - I'll lower temps first, and update the gallery with pictures. Should I lower both bed to 50c and hot end to 200c (as suggested by @jscottb) , or just bed first, followed by glue stick (if warping occurs), and then all of the above?

Purple elmer's glue stick is exactly what I have - you can always see where it is

 

One step at a time it is

And not sure if this helps, but I uploaded and placed a new image of my initial R2 circle level before the refined R2 circle level. If you look closely/zoom in on the right half, start at the outer edge and move towards center, you can see the zigzag/zipper like pattern extends almost all of the way into center. That was before my 2 different bed-leveling/z-offset sessions

 

I'm going to try the other suggestions first (one at a time like we discussed), but I agree I probably need a bit more tweaking to get that last portion "leveled out". Right now, I'll focus on the presumed warping issue we have at hand. I've also included my last attempt at showing the zigzag/zippered pattern with my original Circle level on the left and the updated Circle level on the right after the two different 90 minutes fine tuning sessions

Edit: I forgot to ask, since neither of my C2/R2 units including the z-offset leveling tool/paper, is the single sheet of white paper, or the thin white card stock, a good way to help define the initial z-offset? That's all I've been using, but the fine-tune z-offset takes a long time to go though as I print a line or three, switch sides, and repeat the process until I'm fairly happy. I thought using a small level might help the process go quicker/smoother, but I don't think it had any effect on expediting the process.

What do some of you utilize as a z-offset helper?

 

@Geof I've added 2 new photos to the end of the gallery. First one is my updated Spiral Bed Level from this morning - I raised the front right side of the bed (probably about a half turn), and set the bed to 50c as you suggested - and the zigzag is all but gone now! I'm noticing some lines between (but not gaps) on some of the right arcs, but that's hands down the best spiral left I've had. The left edges might flattened a bit more compared to the right edges - maybe the left side is a slight bit higher?

2nd picture is a quick shot for the in-progress webcam from the R2 from about 5 minutes ago - it's not looking promising for that one skinny piece on the right front edge, but that piece is also designed to break away after the job completes - it serves as a support for another portion of the case. I'll take some pictures of the finished results, but thus far, trial one of 50c bed, 210c hot end, and no glue stick looks like it will need more tweaking

 

Just to be sure, you believe the bed should be raised a bit closer to the hot end - so my current z-offset is -7.15 - which would mean I could try going to something like -7.12, or -7.10?

I'm a little concerned that closer might cause wagon wheel tracks on the left side, but it can't hurt to try. I can access the R2 remotely to cancel the job, but might let it ride out since no one is at home to manually remove the print job (1st world problems), and it would be nice to see how the back left corner turns out since the webcam doesn't show that side

 

I've read many threads on the auto-leveling method(s) the C2/R2 utilize and I finally have begun to understand the complaints. I must admit that I'm forced to chuckle that the closest I've come to a level bed has been my own manual tweaks with that spiral level test, a standard household level, and some guidance from forum members such as yourself @Geof. I realize it will be along time before an auto-level can probably best the manual tweaks and human judgement calls, but I would hope the auto level could come close to "good enough."

I think I mentioned it earlier, but what do others use to calculate their z-offsets with? Since I never received that tool with my C2/R2, i normally use either a plain white half-sheet of printer paper, or a half-sheet of thin card-stock.

 

I have no doubt my troubles with the C2/R2 pale in comparison to what those with the R1 went through

I'll adjust my z-offset a bit more (raise the bed closer to extruder) but is it reasonably safe to say that while lowering the bed temp to 50c helped, I should probably head for step 2: purple glue stick + heated bed at 50c

If that fails, we'll lower the extruder temp to about 200c as @jscottb suggested