Build plate, high spot in the center...

[Matt_Sharkey]

Ed is totally right with the adhesion bit. I calibrate my printer to be dead on with the center since most of my prints are single objects with a large central footprint.

But I have tried to make batch prints that use the whole plate and the pieces on the edge just fall off on their own accord. Its all about knowing the practical limits of your machine, and in general "just because you can, doesn't mean you should"

[Tim]

We're talking fractions of a millimeter here. The x gantry probably bows a total of 0.10mm from center to edge. Y axis is also subject to this, but less, more like 0.03mm

Remind me to post the matrix of values I get from the Z-grid correction using the inductive proximity sensor and the Smoothieware firmware. It clearly shows the bowing in both directions, more in the X direction than in the Y direction, but clearly present in both directions, just as you state. The Z-grid correction is just wonderful. . . I don't have to shim anything, I just run the Z-probe routine and the firmware forever after corrects for all the bowing, in both directions, automatically.

[Matt_Sharkey]

I just run the Z-probe routine and the firmware forever after corrects for all the bowing, in both directions, automatically.

I need dis.

[Tim]

I need dis.

Yeah. Unfortunately I don't know how this works in Marlin; there appears to be support for "mesh bed leveling", pretty recent. Firmware code comments date to this past September. Firmware code comments are at https://github.com/MarlinFirmware/Marli ... d-Leveling and one user's experience getting it working is at https://plus.google.com/113825989556871 ... vXpQNAqd6f.

Assuming it works like the version in Smoothieware, I can't recommend it enough!

[Tim]

Remind me to post the matrix of values I get from the Z-grid correction using the inductive proximity sensor and the Smoothieware firmware. It clearly shows the bowing in both directions, more in the X direction than in the Y direction, but clearly present in both directions, just as you state.

Here's a quick plot I made:

Plate surface profile, as measured by the Z-probe

All I did was to use the (Smoothieware) g-code command to save the probe grid data to the SD card, then read that into octave and plot it.

The Z-probe only works on a metal surface, so I have the Zebra plate under it, and the Zebra plate is pretty flexible and can easily get bent out of shape. This is a solution that causes the problem that it's meant to solve. Anyway, it's probably not very representative of a glass plate, but I wouldn't be able to get this plot for a glass plate using the Z-probe.

The bowing here has a maximum deviation of about a quarter millimeter on the X axis. This is probably because at the time I had a screw in the frame putting additional tension on the belt. I have since realized the problem with doing that, and removed the screw. The bowing in the Y direction is visible but slight, and the Y direction is dominated by a tilt that I did not bother to correct manually. In fact, I haven't touched the bed screws for a long time.

[dklassen]

Found the issue. Don't know why I didn't sport it earlier. Its the aluminum heating plate not the x rail.

[Slipshine]

Tim when you print does it use this pattern of offset for the entire build or just the first layer.