Printbed Height difference????

I tried searching for this, but i'm not finding this exact problem.

I have the folger tech prusa i3 (bought dec 2014 ) still runs great except this issue now

So i started printing again. I had to re-level my printbed as my cats like to walk across it. I have an aluminum bed w\aluminum bearing brackets, rubber hose spacers between bed and Anodized Aluminum Heated Bed Build Plate. I leveled all four corners to exactly 0.05mm ( smallest feeler gauge i have ) but the CENTER of the bed is .35mm taller. I tightened the screws on the printhead bearing holder on the x axis rods...in case they sagged over the years. Hoping the low point would rotate upward and bring the head up in the center. Nothing. PUt a new sheet of glass on it..nothing. measure distance between z axis brackets and base, equal distance.

I'm at a loss. Can't figure out why the head dips the closer it gets to the center of the bed.

Any ideas?

here is my setup

Maybe the bed itself has warped over time? Leveling the bed with four corners attached to the base plate usually makes things worse.

Common problem with prusa's really, the weight of the extruder is bending/rotating the X axis rods because the extruder's mass is not centered. I also had this problem with my prusa.
Remove the extruder and the problem disappears.

Edited 1 time(s). Last edit at 02/20/2017 11:11PM by PvtPrivate.

I'm beginning to see that is the problem.

Remove the extruder and the problem disappears....so does my extruder lol.

Any other advise? Better design? Something I can print to change the way it hangs or something?

Your extruder looks like it would put a fair amount of torque on the rods at the center point. Perhaps one with the motor's mass over the rods rather than to the side torquing them would prove better.

What about the spaces between the screws. That is, these points:


screw..........X..........screw


X................................X


screw.........X..........screw

Perhaps if you measure the distance there it'll tell the tale of what is happening.

Edited 1 time(s). Last edit at 02/21/2017 02:49AM by anvoice.

Quote
anvoice
Your extruder looks like it would put a fair amount of torque on the rods at the center point. Perhaps one with the motor's mass over the rods rather than to the side torquing them would prove better.

Sounds good, but all designs i see on thingiverse and myminifactory hang like this...plus have more to them like fan shrouds and larger gears and ect...more weight. Except Bowden designs that don't even have the motor on the x carriage, but i'm not really printing a whole lot of stuff to warrant that big of a change.

Hmmm.

Edited 1 time(s). Last edit at 02/21/2017 03:44AM by Badkitty.

Unbolt the extruder motor from the x carriage and turn your entire extruder motor, extruder, heatsink and fan through 90 degrees and re-bolt it to your x carriage to reduce the torque you are applying to your x carriage bearings. Make a 3 point mount for your printbed instead of the 4 point one you have at present to allow proper levelling without applying twisting forces to the print bed.

Thats what I would do......errr..did.