Bed height changes. Glass bottom isn't flat

I've been trying to figure out why my printer can print small things, but not bigger ones and found that it changes its height and the magnets that are supposed to keep it in place, aren't even connected on one side while there aren't enough of them on the other. On one side, the middle magnet set is missing. On the other side, 1 middle magnet is missing and the others are not connected. It came like this and I didn't know that was wrong. The glass bed also bows down in the middle about 1 or 2 mm. Is that something that can be fixed in the software or do I email robo about it or is there a fix I can do myself for it?

 

the magnets you can just glue back on, mine came loose a month or so after I got the printer. I also printed up some PLA gap fillers to fill in the holes where the magnets aren't so as to alleviate any bowing of the bed. It didn't really help any, but it made me feel better. The bowing in the middle of the Bed, I made a few rounded spacers that attach to the center two Y axis bearing holders that ride just under the bed surface. They are a bit to thin and need to be shimmed a bit to get closer to the bed, but they helped somewhat (as far as i can tell).

The bigger problem I've noticed, is my glass bed is bowed, so the center of the bed is rougly .1mm lower than either end. I'm tempted to purchase a piece of 3/8" thick glass for a new print bed, but at $200 im fine with the slightly bowed bed for now

 

fascinating that it's not just me. Thank you! What did you do to change your print settings in mattercontrol to get good prints every time with a slightly bowed bed. I made a mistake when I originally posted. It should say 0.1 and 0.2 mm, not 1 or 2. It's just enough to make the settings take a while to adjust for each object instead of just being design and print.

 

Ive has to play around with the first layer heights. It was at .5 or so, but i changed it to 50-60% depending on the size of the part. When doing small parts that are centered in the bed, the bow isnt as big of a deal, but the parts i have that cover the entire bed end up with a perfect first layer in the center and the edges being a bit to thin. After 3 or 4 layers imyou cant even tell the bow is there, so i have just been dealing with it.

Im more surprised the autolevel compensation isnt able to compensate (enough) for the bow than i am about the glass being bowed, its almost worthless having the autolevel. I say this because 1 out of 10 times my robo wont do the autolevel sequence and just locks the Z axis rods steady until it does a layer change. I notice better first layers when it doesnt auto compensate on larger parts than when it does.

 

If any viewer reading this has information on the autolevel process, I'd be happy to hear it. I've heard it uses up to 9 points of reference in the auto-level? Was I misreading that or is that real? If that's real, is there a way to take a measurement at both sides of the ends, then in the center of the bed and a bit farther out from the center in both directions on Y? If it's true that the auto-level can take and compensate for many more points than the 3 it uses by default, how would I set that up to the be the gcode default setup going in so I don't have to retype it every time I start up the program?

Thank you, Invertmast! It helps so much to know someone else has these problems and how you've dealt with them. My filament stops coming out as when I set a z offset, the object bows upward and stops the filament from coming out. Do you know how to fix that? The weird thing is, sometimes it's perfect, other times it stops and I have to open the screws (why isn't that feeder a latch or something that can be easily replaced by a printed part when it wears out?) and fish the chewed up filament out. I don't understand that.

 

You can adjust your Z offset to increase the distance a bit between the extruder and the build plate, then you can adjust the first layer height setting to get it where it needs to be.