Dip in Bed Height in the Middle of the Y Axis
Posted: Wed Jun 24, 2020 6:48 am
Are there any tricks to getting the bed of the A20M to roll absolutely flat along the Y axis, rather than dipping down while it is near the middle?
The "front" and "back" extremes of the Y axis appear to keep the bed at the same height when the bed is totally cold and perfectly flat. Also, the Y axis rail appears perfectly straight (on the top at least) and level according to a good-quality level and a straightedge.
Yet as I roll the bed towards the middle of the Y axis, the spacing between the hotend and the bed varies tremendously, with a large dip as the bed gets towards the middle (e.g. when the hotend is above the center of the bed). Again, at either extreme of the Y axis, the spacing between the bed and the hotend appears consistent -- and, of course, I can adjust the thumbwheels to change it, as needed (no problem there).
I can't explain why the bed "dips" as it moves from the edge to the center of the Y axis, and then returns back to approximately the original height at the other end of the Y axis -- when the bed is cold, and has been verified to be perfectly flat when cold. (Again, heating has absolutely nothing to do with it, as I have the printer turned off during all of these tests and measurements.)
I am suspecting some sort of problem either within the Y-axis rail itself (i.e. within the gap that the rollers ride on) or in the roller/roller-assembly itself.
Anyone else find tightening or loosening things up making a difference?
Even with a BL Touch auto leveling sensor I can not use my printer, because this difference in bed height along the Y axis (dip in the middle) is so dramatic.
Thanks!
The "front" and "back" extremes of the Y axis appear to keep the bed at the same height when the bed is totally cold and perfectly flat. Also, the Y axis rail appears perfectly straight (on the top at least) and level according to a good-quality level and a straightedge.
Yet as I roll the bed towards the middle of the Y axis, the spacing between the hotend and the bed varies tremendously, with a large dip as the bed gets towards the middle (e.g. when the hotend is above the center of the bed). Again, at either extreme of the Y axis, the spacing between the bed and the hotend appears consistent -- and, of course, I can adjust the thumbwheels to change it, as needed (no problem there).
I can't explain why the bed "dips" as it moves from the edge to the center of the Y axis, and then returns back to approximately the original height at the other end of the Y axis -- when the bed is cold, and has been verified to be perfectly flat when cold. (Again, heating has absolutely nothing to do with it, as I have the printer turned off during all of these tests and measurements.)
I am suspecting some sort of problem either within the Y-axis rail itself (i.e. within the gap that the rollers ride on) or in the roller/roller-assembly itself.
Anyone else find tightening or loosening things up making a difference?
Even with a BL Touch auto leveling sensor I can not use my printer, because this difference in bed height along the Y axis (dip in the middle) is so dramatic.
Thanks!