Folger Tech Kossel Auto Bed Level Issue...

Hey guys,

I have an issue with the Auto bed leveling routine. It only probes the front half of the bed. After the routine it starts to print... but in some places it is hitting the bed, and others its at the right height for printing. Yes I know you can't print straight onto the alu bed... this is just for testing.

Video demonstrating this issue below:
[www.youtube.com]

This is a FolgerTech kossel. Gcode below:

G28 ; home all axes
G1 Z30 F1000 ; lift nozzle
M280 P0 S15 ; deploy probe
G4 P2000 ; pause 2 sec for probe deployment
G29 ; auto level
M280 P0 S160 ; retract probe
G4 P2000 ; pause 2 sec for probe retraction
M117 Printing...

Firmware below...
[dl.dropboxusercontent.com]

Any ideas?

Thanks in advance
-Adrian

I just noticed that the printer sees the bed as a concave surface.... I remember seeing a guide about concavity calibration somewhere, but I can't seem to find it.... any suggestions?

It seems to me that every firmware seems to implement auto-level differently. For instance, I was thinking G29 only probed 3 points, so it is possible that your points are only on one side of the bed.

Presently, I am using RichCattell's Marlin-Master branch and I am auto-calibrating the bed with a G30 A (for auto) command. At a 0.05mm precision, it takes around 35-40 iterations to calibrate my bed, probing auto-generated 7 points.

Ok, so I followed this article

[builda3dprinter.eu]

Seems to have gotten me within 0.3mm accuracy between highest point of the bed and lowest. This is using the manual calibration method.

But I seem to be getting strange printing issues... The print tends to start off fine but then as it prints the head is slowly rising higher and higher... even though it is still on the same layer. What the? Has anyone seen this before?

Quote
bobhaha
The print tends to start off fine but then as it prints the head is slowly rising higher and higher... even though it is still on the same layer. What the? Has anyone seen this before?

What was the cause of this behavior? I'm seeing the same thing myself, and assuming since it's been a couple years you just may have some insight for me. I've done a good bit of searching, but you're the only one I've found mentioning this.