fine print until halfway: sudden offset jump and spaghetti

[tibi3000]

Hi,


two weeks ago I assembled a Rostock Max v2 and in the meantime, I made some nice prints. Great 3D printer btw and excellent assembly manual!

So I'm relatively new to 3d printing, but I made more than 10 objects without major problems up until now. Today I decided to make something 'slightly' more complex, namely the cellular lamp from nervoussystem at thingiverse (http://www.thingiverse.com/thing:19104). After some initial tweeking, I started the print at 80% speed and with 85% extrusion factor. It printed fine until about halfway, when all of a sudden the printer starts 'printing in the air'. This resulted in a beautiful blob of spiderweb filament on top of my print.

After this event, it seems that it is still printing layers of the lamp based on the movements of the extruder, but the offset (Z offset, but also X and Y) seems to be wrong.

For not having to throw away my print, I removed the spiderweb blob, looked which layers were already printed, removed these from the gcode, and restarted the print. To my own surprise this worked quite well and the printer resumed more or less where it had left off. After 3 layers, I experienced exactly the same problem (only three layers higher).

I again repeated the process of removing the gcode lines that were printed and restarted the print. I wasn't sure if the problem was related to the Mach board having to process too many instructions, so just to make sure, I set the speed to 50%. Print worked again pretty well for about an additional 1 cm of Z height (=50 layers) and again the same problem occured.

Any thoughts on what the cause of this strange behaviour could be? This seems to be either Mach related or a hardware-related problem (e.g. due to my soldering skills ). Any thoughts on where to start looking?

I attached two images, one with the current unfinished print and one with the spider web blob (note that I cheated a little with the spiderweb blob as I removed it first and then placed it back for the picture).


Thanks in advance!

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[Eaglezsoar]

One possibility is that the drivers on the Rambo board are overheating. Open the LCD door and place some kind of fan in the opening and again try to print the lamp.
If this succeeds then you would need to increase cooling on the Rambo board by making sure the fan behind it is spinning as it should, get the adhesive heat sinks
and place them on the back of the Rambo where the driver chips are located. Please let us know the results.

[tibi3000]

Will give that a try, thanks!

[tibi3000]

I found the problem! Posting this so you don't have to go through the same hassle as I did.

The problem was that the filament guider got stuck behind the X-axis cheapskate carriage (see photo). This pulled the X axis carriage and consequently gave it an offset, which translated in an X, Y and Z offset in cartesian coordinates and resulted in the "spaghetti" print of previous post.

This only occurred starting from a certain print height as the filament guider needed to be sufficiently bent before it could get stuck. That was also the reason that my first prints didn't have this problem (these prints were all smaller prints).

My low-tech solution: I attached an elastic to the filament guider that pulls very very very gently on the guider, keeping it away from the carriages (see photo as well).


Hope this saves someone else from 'debugging' their prints!

[geneb]

Great catch!

g.

[Eaglezsoar]

Thanks for letting us know what the problem was and how you fixed it.
Great job in finding the problem!

[McSlappy]

Great catch!

I see what you did there!

[Eaglezsoar]

Great catch!

I see what you did there!

What is the secret?

[geneb]

He was commenting on a pun I didn't actually intend to make.

g.