Delta Tilt Exposed

[STEAM]

I recently completed upgrade of a Rostock Max V2 with the Duet 2 WiFi and incorporated a BLTouch for a Z probe. When running the bed mapping routine, I get strong evidence of effector tilt. I am using the standard Rostock arms with ball cups.
I do not have a screen shot of the resulting bed map, so I will describe it.

The routine begins closer to the Y tower, then decrements X toward the X tower. After completing this line, then Z is incremented toward the Z tower followed by incrementing X toward the Y tower. It zigzags in this fashion until completion. The resulting map shows ridges and valleys. A valley results when X is decremented toward the X tower, and a ridge when X is incremented toward the Y tower. These ridges and valleys decrease near the Y tower to nearly a flat surface. The Z delta between the ridge and valley is largest near the X tower.

I conclude that:

• the effector is tilting

• the effector is rotating about the Z arms.

• tilt appears to be on the order of 0.2°.

By using my cellphone with clinometer app, the bed and towers are within 0.1° of square. The towers are parallel both by clinometer and visual comparison of one tower to another.

Possible causes of tilting include, Z arms are forcing the rotation of the effector along with the cheapskate not being parallel to the bed; there is slop (backlash, loose pulley, belt tension difference, or?) between the X and Y towers.

The Z tower has some influence over the tilting, since when Z is incremented near the X tower, the Z height is higher. The valleys and ridges are smooth. One explanation is that nearer the X tower the Z increment places the effector in a bind, which is relieved by a tilt in the XY tower.

[STEAM]

A little more detail: Relative to the nozzle (upgraded to E3D V6), the BLTouch is mounted toward the X tower and toward Z tower. Also, the difference between the ridge and valley on the X tower end is about 0.4 mm. That's not much in absolute size, but more than a usual layer thickness.

So when Z is incremented on the X tower end of the zigzag, the effector on the Z tower side is pulled up. That pull-up fades, so to speak, as the effector moves toward the Y tower.

There are many variables involved. If I follow Occam's razor, then there appears to be a bind between the X and Z tower and/or arms. It looks like the X and Z towers are not parallel or are closer together than X to Y and Y to Z. Furthermore, it could very well be a temperature sensitive issue and inconsistent temperature expansion and contraction of the Rostock melamine plates and/or melamine expansion and contraction with changing humidity. To say nothing of the Rostock frame rigidity.

The brute force solution is either the Duet smart effector or the 713maker.com FSR approach.

[Veti]

try a Film Pressure Probe first. they can be bought for 2 euros. i use them on my delta.