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Fan control and printer halts

Posted by bobtidey 
Fan control and printer halts
November 29, 2014 01:08PM
I had my first mid-print freeze in over 10 months of use, It was actually a simple shape basically a 4mm high cylinder but occupying most of the bed. All was fine until 3.6mm then it just stopped mid layer.Temps still on, but no control until I paused and reset.

I decided to try to recover by editing the g-code at the stop point and printing the remaining codes. First attempt was unsuccessful, but then I noticed a whole bunch of M106 and M107 commands interleaved with the normal G codes at the start of the remaining code. I edited those out and managed to complete the print with just a small glitch near the stop point caused by a bit of ooze.

On digging deeper, the M106 and M107 are commands for controlling the fan (which I don't use). I use slic3r and I think these commands are being inserted because I had default auto-cooling ticked. I have now disabled this.

On checking back through previous G-code files I find that some also have M106, M017 commands in them. Typically they seem to occur just once in the file after a few mm of printing, but they hadn't caused a problem till now.

This raises a couple of questions.

What is slic3R's algorithm here? There is a general explanation of auto-cooling but I don't understand why it would burst them together like this. I was using 1.2.1 for the latest print but have used earlier versions which also put these commands in.

What is causing the firmware a problem here? In principle they should be benign commands but maybe if they are bunched then something is going haywire. I was using zombiepants 0.98e at the time. I don't know whether the issue is specific to that.

I started a new thread for this, but it is possible that some of the freezes mentioned in other threads have similar causes.

I have attached a section of the original gcode for the layer that froze and would not restart. Near the end there is a whole bunch of the M commands, but nowhere else in the file even though other layers are similar.
open | download - freeze.g (29.6 KB)
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