Tall print - Z axis stops prior to completion  

RE: Tall print - Z axis stops prior to completion

I have also checked the Z axis "manually", by running the assembly up to the max extent.

In my mind, this confirms that there is no physical obstruction preventing the upward travel of the assembly.

The printer seems to think that the printhead is still moving up (X and Y axis still moving as expected, and filament is still being extruded as expected), when in fact it is not.

RE: Tall print - Z axis stops prior to completion

Also, I am printing with PLA (near the end of the roll - the filament has been behaving well for other prints).

The shape of the print is a simple rectangle with a honeycomb pattern infill.

The print is adhering well to the plate and not coming loose during the print.

I have seen some discussion about the print head "bumping" the print and breaking it loose.  That is not the symptom that I am seeing.  In my case, the filament continues to be extruded at the same elevation as the prior pass.

RE: Tall print - Z axis stops prior to completion

Attached picture of the top of the print - after the printhead made several passes at the same elevation, and was simply smearing more filament around.

RE: Tall print - Z axis stops prior to completion

OK, an interesting development:

Because the print that failed twice was a large thing, it was taking a lot of time and filament to get to the failure point.  So I wanted to make a test piece that I could use to help diagnose the issue.  I took the original 4" x 4" x 6" rectangle and scaled the x and y axis only so that the shape was 0.5" x 0.5" x 6".

Started the print running, and sure enough, it made it past the height that the original shape was failing at (4" tall).  SO, I can confirm that there is no physical obstruction that is preventing vertical movement.

In fact, it almost made it to the full 6" height - but not quite.  At about 5.75", the print nozzle was not lifting clear of the previous depositions and knocked the print loose of the print bed.

I am not sure where to look next...  My best guess is still the gcode is corrupted somehow, or the printer is misreading something in the file.

Is there a way of attaching a gcode file to this post?

RE: Tall print - Z axis stops prior to completion

Yes it is possible to add Gcod, STL and .3MF Files to the forum, 

simply add them to a ZIP file, and attach the ZIP File

If I understand correctly, you are printing a 13mm x 13mm x 150mm model to investigate a printing issue at 100mm height, 

this would be a rather tall slender model, 
you may be better stabilising it with outriggers to reduce the chances of wobble, causing a failure. that may not be part of your investigation. 

something like this, perhaps?

Regards Joan

RE: Tall print - Z axis stops prior to completion

If it's likely the gcode, can you re-slice the object and try a fresh file?

RE: Tall print - Z axis stops prior to completion

I understand your point regarding tall and narrow objects. 

The problem first showed up on a very stable object, and did not become dislodged from the bed.  I only started the narrow print as a test because it printed faster.  That tall and narrow object was very stable, and did not break loose from the bed until the nozzle started bashing into it.

RE: Tall print - Z axis stops prior to completion

I did re-slice the object when I attempted to print the narrow version of it.

The same kind of problem occured, only at a different elevation (the narrow version printed over an inch taller).

RE: Tall print - Z axis stops prior to completion

Hmmm.  Not sure if the file is actually attached to my previous post.

Here is a zip containing the larger block as well as the narrow version.

RE: Tall print - Z axis stops prior to completion

the file was attached on your second try. 

you have very little surface contact on the build plate. especially on the tall thin print. 
I think that will promote failure of tall thin prints.

I would use 70C for the bed temperature. and would put a brim on the model to promote adhesion. 

regards Joan

RE: Tall print - Z axis stops prior to completion

Joan,

I hear what you are saying with regard to tall prints that have very little surface area.

However, the first time this failure mode manifested was on a tall print that had a significant amount of surface area (4" x 4", and with infill).  The filament nozzle was digging into the print to the point that the entire machine was flexing and making odd noises - yet it still did not break free from the print bed.

Yes, the narrow version breaks free sooner than the larger version, but the print only breaks free from the bed AFTER the nozzle stops moving up (and begins gouging the top of the print).

RE: Tall print - Z axis stops prior to completion

I was able to catch the point of failure on video today. 

IMG_4560

RE: Tall print - Z axis stops prior to completion

I see the print get a little wobbly but I don't see a failure... 
at about 29 seconds there appears to be an overlap of the filament on the right side of the print... 

what to you see?

Joan

RE: Tall print - Z axis stops prior to completion

It does seem to stop lifting on the last couple of layers in that video., it starts squishing at the same height. I've only seen that kind of thing with my printer when a large part starts warping, but this is a narrow part, so that can't be it. I see Z hop which still seems to be working. Why it starts jumping between the same two Z heights I have no idea. Maybe time to contact support?

RE: Tall print - Z axis stops prior to completion

At about 11 seconds, the last successful preimeter layer is completed.  Then it appears that the print head drops down to start the infill.

The failure point is when the Z axis stops moving up the appropriate amount - about the middle of this clip.

After this point, all the subsequent layers are deposited at the wrong height.  You can see the new layers are no longer smooth lines, but rough and distorted.  The nozzle is being pushed THROUGH previously deposited material - and the print is getting pushed around, then eventually it breaks free of the plate (the moment it breaks free of the plate is a few seconds after the end of this video clip).