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Siggi

Cura 3.3.1 insert pause at height hitts the object

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I insert a pause at height 17 (want the printer to make a break for a moment at this layer)

reaching this layer the printhead hardly hits in the object and then pauses. It destroys the print by hitting it. i have to reset the printer. what am i doing wrong?

see attached screenshot the cura settings for pause.

Edited by Siggi

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Hi berndjm,

sorry, i don't want to try this a third time, because it diggs very hardly, and the forces are high (dont want to destroy my nozzle)
When i analyse the code i can see following:

in lines above it is at position Z3.3

then the pause script starts and moves the head down to 1mm ---->>> G1 F300 Z1

then the scriptz elevates it to  15mm --->>>   G1 F300 Z15

thereafter back to 3,5   G0 X144.47 Y126.99 Z3.5 (what would be alright.

 

The code to move the head down to position 1mm is definitely wrong --- buggy script

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All of the above problems happen on my UM3 Ext also when I use the pause at the layer number so I have gone to pause at height using mm.  It does not crash the part this way, but I am not getting good results by just taking my layer height of .27 mm and multiplying by the layer number of 33.  So I just finished a print using 33 * .27 = 8.91  It came out too low so I am trying a print at 10 mm right now.  Maybe there is a scale factor on the .27 mm to help get a more accurate height.  Right now the process is to print one and then make another guess for the next one.  Got to be a better way....

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I had the same problem. Pause using height in mm works, but when using height in layer height, the nozzle smashes down into the object before heading to the pause position. I watched it happen before my eyes - very shocking to say the least. Fortunately it was a small part, but still wasted filament and 35 minutes of my time.

 

It seems like it would be simpler to pause on a particular layer, because the slicer knows exactly where each layer is. Why should I have to calculate what CURA already does? Doesn't make sense to me why it would be harder for CURA to stop at a particular layer and lay down the proper code to pause the print head.

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I can't solve the problem, and I can't quite isolate what causes it, but what I can figure out may be helpful. And it would be helpful for someone to post some of the .gcode files with the offending crashing movement.

 

Here's a simplified version what the script is trying to do:

* Look at all of the lines in the gcode, letting most of them through passively. For each line:

* * If the line has a " Z" coordinate, then make a note of it; this is the current Z.

* * If we're pausing at, say, layer 10, and this line is anything other than ";LAYER:10", then just go on to the next line in the gcode..

* * If we're pausing at, say, 10mm, and this line doesn't have a Z coordinate that's greater than 10 millimeters, then just go on to the next line in the gcode.

* * If we reach the end of the file, we're done.

* Okay, if we made it here, it must be time to pause. Add the following commands (and a few others) to the gcode:

* * Move to the current Z position that we made a note of earlier, plus 1mm. (On the Ultimaker, this is intended to be "Lower the build plate a tad.")

* * Move the head to the X/Y park position.

* * If the current Z position is less than 15 millimeters, then move Z to 15 millimeters.

* * Pause.

* * Move the head and the built plate back to their original locations.

* Now just don't change any of the rest of the gcode; we're done.

 

The problem with this is that there are some Cura-generated gcode files where the first few layers don't contain Z coordinates, at least not in the format that the script is expecting. As a result, the script's "current Z" stays at zero while it's reading those layers.

 

If you're pausing at a layer, and the target layer is in the early part of the file that doesn't contain the expected Z coordinates, this results in the failure you're seeing. The script tries to lower the build plate by 1mm; but since it still thinks that the current Z coordinate is zero, it winds up lifting the build plate until it's 1mm below the print head, smashing the print head into the object.

 

If you're pausing at a height, and the target height is in the early part of the file that doesn't contain the expected Z coordinates, then the script still fails, but in a more subtle way; it won't generate the pause until the first layer that does have a Z coordinate in the expected format. So the print head and build plate don't do anything wacky, but the pause is too high.

 

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I loaded the latest version of Cura (3.4.0). "Pause at layer height" works wonderfully well now, but the "pause at mm height" doesn't work at all - it doesn't insert any code into the g-code file. Actually, I prefer "pause at layer height", otherwise you have to calculate what height you want the machine to pause at. I would also suggest that, after the resume code and reheating of the nozzle, the machine would ask you if you wanted to purge the filament. I know there is a purge option in the post-processing dialogue, but that option does not allow time to remove the excess filament prior to repositioning the nozzle for continued printing, which can carry blobs of material over to your print and mess it up. 

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