Hey all,

I’m a noob to desktop FDM, and I recently came to own a CoLiDo DIY.

My latest frustration with the machine is my inability to level the printbed. From the factory, this printer has no provision for leveling. I have added a typical heated aluminum bed, attached with M3 hardware and springs, to corner mounts of my own design. I’ve seen numerous examples of this mod by other owners of this machine. So I don’t think that I’m attempting anything terribly ambitious.

The issue is, using common leveling procedure, I can’t get the bed level. The more I try, the worse it gets. Here’s the procedure that I’m using.

1) Adjust the height of the corner nearest the x-y home position of the printhead, to the middle of its adjustment range.

2) Using the metal card supplied with the printer, set the z-stop such that the extruder nozzle causes some drag against the metal card, but no slop or binding.

3) Starting from the top, left corner (home position), move to the next corner, clockwise. Repeat the height adjustment with the metal card.

4) Continue clockwise to adjust the last two corners.

Now I understand that this can be an iterative process, but when I go back to the first corner, it’s now 3mm off (nozzle too high). So I repeat the process, tightening the corners where the bed is too high, and loosening where they are too low. Same result. After three repetitions, I’m no closer to having a level printbed, but I’m at the limit of travel on all four corners. Two are as tight as they can go. Two have the thumbscrews nearly falling off.

Am I just missing something? I have a pretty solid understanding of physics and mechanical systems, but it’s also my m.o. to miss the obvious. So don’t worry about offending me if you have a really basic suggestion.

Some other related info:

The machine is fixed to a pretty flat and level surface.

I have verified that the aluminum plate and glass plate both are flat, on and off of the printer.

The 8mm linear rails appear to be straight. Though I haven’t actually removed them from the machine to verify against a precision reference.

The LM8UU bearings are a waste of matter, and I plan to replace them, but they don’t seem to be allowing a lot of radial play.

I don’t have my DIY bed heater power supply hooked up yet. So I don’t know how much the glass changes shape when heated.

I have tried the leveling procedure in different orders, like opposites corners, and starting with different corners.

I have tried different hardware. Always the same result.

I would be really grateful for any help with this issue. I understand that this machine is pretty crude and limited in precision, but some of the basic issues I’m having are starting to get my down.