Frame warp
I just got, and have started assembling, my MK3, my first 3D printer.
So far, so good, but there is one thing that concerns me. After using two levels to verify I was working on a truly flat and level surface, I have observed a 1.5mm corner-to-corner warp in the frame plate. I realise the pictures are a little obscured; I put down a very thin trash bag to protect my table, it's maybe a few microns thick.
I don't think this warp is going to be enough to affect print quality, but I'm curious what the rest of you think.
I also had another thought: in the online manual, on the step for aligning the aluminum extrusions, there is a long list of comments by people who found the same issue I did at that step--a front left to back right wobble. I was able to correct this with a second set of hands and slow, careful retightening and torquing of all the bolts, but one person there mentioned their warped frame, which made me wonder.
So, if you have a front left to back right wobble, check your frame. You may find the same warp.
Re: Frame warp
I'm surely not the only owner who was entirely unable to find a level surface to even verify my build, let alone install the printer on for use. I simply assume that my frame is not true and have installed wave washers to manually flatten the bed, and I would judge the results as acceptable, including the ability to get decent adhesion of a circle that covers much of the bed.
I see people installing the somewhat weighty MK3 into an Ikea Lack setup which appears to be made of criminally flimsy material (although I expect the design adds strength), and can't imagine how that could ever remain flat after a few humidity cycles.
I would say (as a novice) that as long as your X-axis bearings don't grind at extremities, you're probably just fine.