So I’m setting up my Geeetech A10 printer I got for X-mas and everything went together pretty smoothly. I leveled the 4 corners of the bed using the “leveling paper” provided (0.2mm) and when I went to check the middle of the bed I couldn’t fit the paper under the nozzle without pressing down on the bed. Checked the corners again and still the same result when checking the middle. Even heated the bed up to 100C for about 30 minutes and then rechecked and still the same.
Cooled the bed and leveled the corners using a 0.20mm feeler gauge. Checked the middle with feeler gauges and found the bed - nozzle gap was around 0.04mm. So is a difference of ~0.16mm acceptable or should I probably should ask for a new bed?
The bed is also higher at the mid points of the sides but not as much as the middle so seems to be an even bow to the middle. Also this is the bed with the provided surface build sticker. No bubbles in the surface sticker.
This is the state of low-price consumer 3D printing, and is why measuring flatness of the bed with a sensor like a bltouch and then compensating for its lack of flatness is so common. What you got might actually be better than average for low-end equipment. Also, the rolled aluminum used for heat beds has internal stresses that cause it to warp when heated. This means that what you measure cold will not be the same when it heats up. That’s why we heat up the bed before measuring how flat it is.
You can choose to put up with a slightly unflat bed one way or another, or spend significantly more to get a flatter bed. You won’t get a flatter bed without going to cast aluminum, generally speaking.
Options, listed in order from least to most expensive:
If you printer didn’t include any form of height probe, you can, by rebuilding your firmware to use G29 Mesh Bed Leveling [sic], also probe manually and store a height map in a grid across your bed and use that to compensate. How fine a grid depends on how accurate you want; you can do up to 9 X and 9 Y stations, if you really want to do 81 measurements at least once.
You can augment your bed with a cast aluminum “bunk bed.” An intermediate step I took before I started over was to buy a piece of 1/4" cast aluminum which I clipped directly to the wrought aluminum hot bed of my first printer, and turned down acceleration in Y a lot; I traded off some speed for a flatter bed.
You can replace your bed entirely with the same cast aluminum, in which case you also need a heater. You can use either DC or AC heaters. These are usually heater wire embedded in silicone. It is best to protect both, but especially AC, with a TCO (thermal cut-off fuse) thermally bonded to the silicone that will permanently open if the temperature gets too hot. Note that TCOs by their nature should have their terminals crimped, not soldered, to the wire… I eventually went this route on both of my printers. But it took a few years.
On both of my printers, I have only done the manual level and have not gone as far as getting a more expensive bed and heater. My prints have been more than acceptable but I have not printed anything that needed high precision. I usually try and get the best “average” on all measured areas which seems to be “good enough” for what I use it for. If you are having issues, then it might be useful to use a leveling probe.