Slicer error or Calibration problem?

[cpunches]

I did several prints over the weekend since I finally seem to have my hotend working (yay!). Most of the prints came out great. There are two that I ran into a problem with however. The first was this guy: http://www.thingiverse.com/thing:27408 He was printing great until about halfway through. It appears that the nozzle tugged just enough on him that he was spun and then of course the print was ruined. I initially put this down to the base coming unstuck for some reason. I wasn't in the room at the time so I can't be for sure exactly what happened. I do have a great looking half of a gnome is someone needs one..

the second print I started was this one: http://www.thingiverse.com/thing:89654 This one was going to be a 7 1/2 hour print. I went ahead and started the job as I figured this would be a good test of a long running print (the longest I've done so far took 3.5 hours and came out great). At 7 hours of the 7.5 I heard a tearing sound and saw the print get pulled up a little from the bed. The layers got shifted at that point and the remainder of the print was going to be ruined so I killed the job. (I have an idol that looks like she's had brain surgery. I may turn it into a planter..) Now if the point where the job got messed up was at the same height I'd say it was definitely a calibration issue of some sort, but the idol was at a point nearly 4 inches higher than wear the gnome got ruined.

So, could it maybe be a slicer issue that would cause the nozzle to "dip" during a travel and catch the print, or might it still be a mechanical calibration issue of some sort, like a belt slipping or something?

Any thoughts are appreciated.

[Jimustanguitar]

On tall prints with small bases, the nozzle dragging over the print will have a lot of leverage will easily knock a part off of its base. Why this happens is the harder part to figure out. The part could be warping as it cools. This tends to magnify on each layer and will cause problems the taller a part gets. The other thing that may be causing behavior like this is when your extruder steps per mm or slicer extrusion multiplier is off. If you're overfilling the part, it will eventually become convex and hit your nozzle.

[cpunches]

Thanks Jim.

[Batteau62]

I have had prints where a small loop or bump of abs, that gets raised, catches the hot end. This has caused my glass to shift. Make sure you have plenty of clips holding it. I also have z lift set to lift the hot end over/ crossing perimeters and on retracts. My last print of the Voronoi lady was pretty tall, and was set to use a raft, which I think printed as just an extra base layer. Consequently I sweated every little raised loop and bump!

[cpunches]

What did you set your z-lift to? I set mine to 1mm. I was surprised how much of a (better) difference that made on some of the prints I was doing. Does the z-lift setting apply to both retracts and perimeter crossing, or are there 2 settings?

[JohnStack]

High verticals sound like candidates for mouse ears. 4 inches high is all I've done though.

Gnomes make better statues than fertility dolls, IMO.

I am using the same z-lift. Not sure if there are two settings but interested in finding out. If there was ever a class on this stuff, it would be more than a week...

[Eaglezsoar]

Cpunches, which slicer are you using?

[cpunches]

I'm using slic3r, the version installed with Repetier Host.

[Batteau62]

I have my z-lift at 1mm too. I also have the "Avoid crossing perimeters" box checked in Print settings tab:Advanced. Thinking that any tool path that doesn't risk hitting the print is a good thing.

[geneb]

1mm z-lift is WAY too high. Try .2, that's what I'm using.

g.

[Eaglezsoar]

Does kisslicer have the z-lifts that you guys are discussing?

[cpunches]

1mm z-lift is WAY too high. Try .2, that's what I'm using.

g.

I'll take your word for it gene, but could you tell me why it's too high?

This is one of the many settings that can be tweaked that I really don't have an idea of what they do, nor the effect.

thanks.

[geneb]

That's what I got told on #reprap.

g.

[cpunches]

That's what I got told on #reprap.

g.

Good enough for me

Here's the two candidates for the island of Misfit Toys that I got ruined.

[Polygonhell]

The reason that people recommend Z lift in line with the layer height in that Z motion on conventional printers can be extremely slow, and large lifts as a result lead to blobs because they take too long. On a rostock it's largely irrelevant how much lift as long as the Z speed is set to match the travel speed.