Large Print Separation @ Layer

So... I've been using the following on my ABS printer.

• Boro glass (3/16 10x10 from McMaster)
• L'Oreal Elnett Satin hairspray
• Extruder Temp: 220 (colorfab XT) / 180 (PLA)
• Bed Temp: 70
• 2 Perimiters to make sure the plastic is flowing before the model starts
• All other feeds/speeds as specified in Getting Started (I think)

For single/solid objects (hip-hop-hippo), it's worked very well.
For large objects where there are big moves without extrusion (first on a case for my LCD XXL display, now on the Lotus Nightligh [which I never got to stick before], I'm starting to see breaks and Y axis shifts in the layers (X&Z are fine).

The boro is held to the bed with 3 binder clips -- it can't move; at least it can't move by 1.5" (the width of the Lotus nightlight in the pic)... anyone have ideas on what needs to be changed?

I think I should turn down the non-extrusion speed, but I'm not sure exactly which variable that should be...

 

How tight is your y belt?

 

Wow, looking at that print I would have aborted a lot earlier.


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I'll check the belt tension -- what should I look for (inches of deflection, snug, or tight?)
It said it was going to take 4 hours to print, so I went to bed after the first 10 layers and found this in the morning... it seems to do better if you're watching it!

I'm pretty amazed that "the rest" actually got made -- since there was no support, I figured it would've globbed and made just a ball of stuff...

 

I'm not sure it's tight enough; I can depress the belt around 1/2".
Then again, I can touch the X belt to itself (though that is a lot longer).

I took 11 teeth out of it (just enough so it required a little tension to line up both holes on the endstop...

 

What belts, bed or extruder ?
What tension should it be ?
My model is only 3 inches tall, it started to separate at 1/3rd of an inch.

 

I've had 2 bouts of separation-

1. Because the tension wasn't there -- I tensioned them so they would both twang a little (I suppose I should get a tuner or something to make a consistent tension). I think I was OK earlier because I didn't have the large mass of a borosilicate plate on the platform. But my print quality has improved a lot as well.
2. After 60% of my PLA spool was used up, the Robo had a hard time unwinding the filament (so on Rapid X away from the spool, it would make a horrible noise and would then be off. I'm relocating my spool topside because of this.

Note that tensioning your belts changes your Z calibration, so reset/re-level after doing it.

I'm thinking I need to set up a webcam and record during each print -- that way I have a better idea of why a print failed... then again, I wouldn't have been able to see the "can't unwind spool" from a pic of the bed....