Head moved down and dipped into object

Good Evening,
i have printed today an object that was roundabout 16cm hight.
At almost 10cm my printhead moved down after a layer and dipped into my print.
i printed from sd card, after i recognized it o have homed all axes and stopped printing.
On my PC i had a lot of unreadable stuff in my print console.
Any idea what can cause this habit?
BR
Lars

Edited 1 time(s). Last edit at 03/05/2015 03:07AM by Psike2k12.

I have never heard of anything like that before. What slicer and host are you using?

Check that file on the SD card is not corrupted as the only way I can imaging the nozzle going downwards is if it was told to do so. Not sure how that would put rubbish on the screen though.

Another possibility is the board received rubbish through the serial port and that happened to contain G1Z. Marlin will still accept serial commands while running from SD. I don't know how serial comms would get corrupted when it goes via USB. Normally it just disconnects if there is noise. Check that the power and ground connections on the Melzi are tight.

Edited 1 time(s). Last edit at 03/05/2015 05:23AM by nophead.

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[www.hydraraptor.blogspot.com]

I have used Cura to slice and had never any kind of issues,
I`m printing now almost 2 yeas with the same setting and never faced any issue.
It was my first STL that came from Mashmixer and checked it with Netfabb, maybe its the Object that causes the error.
Then i went to Cura and sliced it there as usual and saved on SD CARD
I will give it a second try maybe it was a ontime thing.
What will happen if i start a Print from SD card can and broken USB signal can cause issue, like woke-up signal or something else?

BR
Lars

Try saving the file on your PC and comparing it with the file on the SD card in case the SD card is corrupt. They do wear out eventually but I would be surprised of 3D printing caused enough writes for that.

If the auto reset jumper is off you can disconnect and reconnect the USB while printing from SD. If something sends data down it though it could disrupt the print.

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[www.hydraraptor.blogspot.com]

You might also look at the GCode around the layer height that the problem occurred and see if the Z value keeps incrementing upwards before and after the failure. The problem with post-processing of STLs is that errors can be introduced but the evidence should be there if this has happened.

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I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.

I had the same issue 2x now: somewhere in the middle of the print it move to position [0,0,0] whacking through your builded parts. Then it asks on the screen an user conformation.
I tracked this down to the used SD card. It only happens on a very old SD card of 128mbyte. My guess is that these cards are so slow, that it cannot keep up with the dataflow needed, or that it halts the cpu in a wrong way. Anyhow not using that particulair card solved the issue for me.