Is the glass not flat? Levelling problem...

Hi,

I'm facing a bit of a conundrum. I've used the day seperating my ormerod and collecting it again. But avast - the problem I was trying to solve persists.

I couldn't figure out why I wasn't able to levell by bed. It is a 3 spring connection with an replacement out of alu - when I have tightened the and gotten the two screws closest to the z-axis level (like level as level can be ). I move onto levelleing the third screw. When the bed is level at this point being something like X180 Y100 . I move to either side and at X180 Y20 its -0.5 and almost exact opposite x180 Y180 something like +0.5.

What can cause this? Im blaming the glass. But is it fair? Have anyone tried something similar?

Edited 1 time(s). Last edit at 11/27/2014 08:48AM by Aagaard.

Most likely your Y smooth rods under the bed are not parallel, so the bed is rising and falling as it moves back and forth. Levelling this is usually a case of twisting the y-axis ends on way (or the other...), and tightening them in place once straight.

Ian
RepRapPro tech support

Y axis smooth rods not parallel, adjust the acrylic endparts

Quote
ormerod168
Run the nozzle out to the outer corners of the bed, any difference in these corners (while moving the nozzle in the plus minus y-direction) is caused by the outer y-rod, this misalignment if any, is mirrored in the outer bed corners

[forums.reprap.org]

Erik

I suspect that the two ground rods that the bed moves on are not 100% parallel in the vertical plane. Non-parallel rods result in the front of the bed rising or falling relative to the back of the bed as you slide the bed from side to side, giving exactly the symptom you describe. There is no adjustment as such because the position relies on the self-centering action of the countersunk bolts, but you can slacken the end-plate mounting slightly and then carefully twist the acrylic plates, then re-tighten. On your machine the left end of the front rod (furthest from the Z support) appears to be higher than its right end relative to the rear rod. It may be easiest to slacken the right-hand printed part (that holds the Y idler pulley) and adjust only that side (in your case twist it up by about 1.5mm) because those bolts are accessible without needing to remove anything. In an extreme case you'll need to fettle the countersunk mounting holes in the printed part to allow it to be adjusted (or print a new part).

Note the exact distance between the front and back rods is relatively unimportant, as that can be adjusted by the bed levelling screws, the only critical thing is that the rods are parallel - and exactly at right angles to the Z ground rod in both YZ and XZ planes if you want to achieve zero compensation. While the instructions tell you to set the extruded aluminium sections to be at right angles, it is really the ground rods that set the relative orientation of the axis - which may not be exactly parallel to the extrusions (but they should be close enough).

It is less important to ensure the rods are parallel in the horizontal plane because the bed just rests on the front bearing and so a slight movement of the bearing in the X direction will not affect anything, it is only movement in the Z direction that will affect the height of the front of the bed.

Dave

HI Guys,

Just thought I would let you know. I followed your advice - tried turning the rods ad all other kinds of stuff without great succes. Then went an printed a new Y-idler-bracket. AND it solved it! I've now succesfully printed [www.thingiverse.com] without bed compensation! Thanks again!

Aagaard