False "Object does not fit into print volume" warning from OctoPrint

Question

Octoprint warns me that the objects do not fit into the print volume. I noticed that this happens after a power-off cycle. Since I was overly anxious until today, I always uploaded the GCode file again and it didn't complain any more.

Of course, always uploading the files again is also error prone. So today I gave it a try and simply started to print the object. As far as I can tell, it prints nicely.

Image: Octoprint saying something like "Object does not fit into print volume" in German

Is this a known bug in OctoPrint? Are my files really damaged after a power off cycle?

The values (0.00, -3.00, 0.00) seem to be constant in this error message, no matter what object I want to print.

I'm using OctoPrint in the PrusaPrint flavor and I'm running version 1.3.10 (hopefully a recent version, since I usually update). I generate the G-Code with Slic3r.

Answer 1

That's the purging that Slic3r PE adds, the broad line of filament at the edge of the sheet. That is outside the official print volume, which triggers this error.

The G-Code generated by Slic3r PE at the start of the file contains the following lines:

G1 Y-3.0 F1000.0 ; go outside print area
G92 E0.0
G1 X60.0 E9.0  F1000.0 ; intro line
M73 Q0 S174
M73 P0 R173
G1 X100.0 E12.5  F1000.0 ; intro line
G92 E0.0

You can see that it explicitly goes to -3 on the Y axis, and then extrudes two times on a line along the X axis.

The model size detection is labeled as beta in the settings dialog. It's not very reliable at detecting stuff like this purging line outside the boundaries.

Answer 2

This answer is correct, it's normal for Prusa printers to purge at -3 mm on the Y axis.

This answer is an addition that describes how to get rid of the error.

1. Open Octoprint web UI
2. Go to Settings -> Printer Profiles
3. Find active profile, click on the pen icon next to it (Edit Profile)
4. Go to Print bed and build volume
5. Tick Custom bounding box
6. Enter -3 to Y Coordinates Min input box
7. Hit Confirm

Answer 3

As the other answer have mentioned, this is normal and done in order to purge material remaining in the nozzle before printing.

This OctoPrint tutorial by Prusa now documents the installation and defines the custom bounding box as follows:

Under "Print bed & Build volume", change the values in the table below. All other values can be left to default. This will only affect Octoprint's control over your printer, and will not affect sliced G-codes.

	Form Factor	Origin	Heated Bed	Width	Depth	Height	Custom Bounding Box
MK3S	Rectangular	Lower left	Yes	250 mm	210 mm	210 mm	X: 0/250, Y: -4/210, Z: 0/210
MINI	Rectangular	Lower left	Yes	180 mm	180 mm	180 mm	X: 0/180, Y: -3/180, Z: 0/180

_{(emphasis mine)}

This tells Octoprint that -4 is a reachable position, so it will not complain about commands moving there.