Z height drop during print

[WayneMcCleve]

I have Rostock V1 with out any mods. I have been try to solve multiple issues pertaining to Z height and discovered that one of the issues was already being discussed in the forums - although not completely solved yet. It is discussed in this thread (http://forum.seemecnc.com/viewtopic.php?f=37&t=4868) "Unsolved Mystery. Weird Z0 behavior around build perimeter".

The other issue, that I initial assumed was related to the a fore mentioned "Weird Z0 behavior..." is that while printing the z height will drop slightly and catch on my build with the result being that the XY indexing is thrown off and the build will continue to print albeit off by a few millimeters to as much as centimeter. This happened twice during a long failed print I did last night. I had really good adhesion so this was not due to the part rising off the platform. I have also seen it when completing a layer and the extruder tip drags across the build back to start the next layer (quite common).

What I have done to try to fix:

1) re-calibrated z=0 (many times due to the other issue)
2) checked cheapskates for correct operation tension, etc.
3) checked belts for tension and signs of where or missing teeth
4) ensured tightness of all allen pins securing belt/cog to stepper motor
5) took apart arms, pins, swivels, etc. to ensure there is no "delta arm blues" lubricated and re-assembled per spec

Any help would be much appreciated. I assume something is just loose enough to cause this intermittently but don't know what to try next.

[techstorage]

Hi, did you see the special news about this on the main page, outside of the forum?

http://seemecnc.com/blogs/news/14684425 ... -perimeter

They state... We discovered an error in the firmware pertaining to the Carriage Horizontal Offset value. The value that was in place was 35 while the value should be 37.5. We believe that this difference in offset values for the carriage is and has been enough to cause many of the printing height issues near the edge of the bed between the towers.

[WayneMcCleve]

Hi, did you see the special news about this on the main page, outside of the forum?

http://seemecnc.com/blogs/news/14684425 ... -perimeter

They state... We discovered an error in the firmware pertaining to the Carriage Horizontal Offset value. The value that was in place was 35 while the value should be 37.5. We believe that this difference in offset values for the carriage is and has been enough to cause many of the printing height issues near the edge of the bed between the towers.

Yes, unfortunately the stated solution ISN'T a solution (look at the comments form several on that thread) yet the thread has the "*Solved*" prefix and the associated youtube video on the SeeMeCNC channel is still offering the Carriage Horizontal Offset value change.... frustrating.

Anyway, this thread is for a problem that I don't believe to be related where somewhere in the middle of a print I lose Z-height usually resulting in a failed print. Intermittent problem and hard solve... for me anyway

[geneb]

The issue is solved for the guy that started the thread. There's absolutely no reason for Jim to not stick *Solved* on his post.

g.

[nU.metA]

We are having the same issue here. Haven't been able to find much on it at all. It seems like we have to recalibrate ours after ever print or so. At this point i'm wondering if it's our surface. What do you have yours mounted on?

[jeffhuber]

nU.metA, more information would be helpful. for example - my hot end was smashing into the heated bed at random times and the reason turned out to be the gear pulleys that go over the stepper motor shank had becomes loose. I now check this by running script 1,2,3 and then watching to see if when i click home - if the hot end moves to either direction - there is an issue. You can visually line up the tower between the arms to make this really easy to see. it will move *away* from the culprit gear pulley.