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I am having a strange intermittent printing error specific to one particular object I'm trying to print.

A picture of my print error

My printer is a BCN3D Sigma R17. I am printing a thin wall (0.6mm) cup object. I'm using:

  • Simplify3D with Sigma Progen profiles
  • 0.6mm brass nozzle (w/thermal paste)
  • 0.1mm layer height
  • Spiral (vase mode)
  • Filaform PLA.

As you can see in the images, the first few layers print ok, but then the nozzle seems to collide/penetrate the previous layer and grinds against it as it moves around in a circle. The result is a combination of rough textured surface and good quality surface. One half of the print also seems to be thicker, presumably from the increased extrusion width caused by squashing layers in the z-axis. I’ve tried

  • changing model's wall thickness,
  • disabling spiral mode
  • increasing layer height
  • changing filament
  • upgrading printer (latest stepper drivers)
  • changing extrusion width
  • performing full calibration

All without success. You can view the gcode and S3D fff profile here: https://drive.google.com/drive/folders/0B6SnaYyiYI7vcGU1U3Uxb0RrX3M?usp=sharing

The image shows some filament left hanging from a stopped print. It seemed to be squeezed out from excess pressure, as if it was being blocked during the print due to being pushed against the layers.

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  • $\begingroup$ Perhaps your Z moves are too fast, and some of them stall. Have you noticed anything like this? If you move the bed down 100mm with small moves, and then up 100mm with one large move, does t return to the same location? $\endgroup$ – Davo Aug 31 '17 at 11:47
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Well, for a 0.6 wall thickness using a 0.6 nozzle you should have one line for the whole wall. But I´m seeing in your prints walls of 0.1 and 0.4 as infill, Why? I´m using simplify3D and I can see the results about walls and infill prior to send to the printer. On this kind of parts avoid infill and give priority to walls.

So the main problem with your gcode is that wall thickness, is too much difference between the filament extrusion 0.6 vs 0.1 this is 16.6% of the printing flow, so you need to set print flow to 16.6% or 20%, not 80%. You must need to use retraction to avoid blobs and set a lower temperature.

I saw this video to control Coast issues, but is explained how to set settings on Simplify3D; I hope you can visualize your issues before printing. https://www.youtube.com/watch?v=WWpdGY0V-gM

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Although this reply is pretty late, there are some issues I would like to point out:

  1. In the cup.gcode file there seems to be an issue with the layer height. The height for the second layer is larger than the third layer!
  2. If you see that the cup prints good on one side (also thicker on one side), this is a good indication of a bed leveling issue. Although you indicate you did a full calibration, I would still re-check the bed leveling. The extruder head movement in the X-Y should be as closely parallel to the bed as possible.
  3. The cooling settings in your Simplify3D profile are low. I would bump up the fan speed to ensure that the strand being laid down is sufficiently cooled to prevent overheating from subsequent loops.
  4. Try slowing down the Z-axis speed. Stepping too quickly can cause skipped steps depending on the acceleration settings and mass/inertia of the head.
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I'd suggest you change the Flow (%).

It is usually at 100%, but can be adjusted. I'd suggest printing at 80%, and adjusting from there.

Layer height, printing speed or other configurations always change the Extrusion Rate with it, because for example higher layers always require more material extruded at the same printing speed.

How it is done with your specific software, I cannot tell.

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  • $\begingroup$ you shouldn't need to change the flow rate for layer height, the slicer calculate that for you. only if the filament diameter isn't 100%, which you can also input the diameter and it will try and calculate it. $\endgroup$ – Eric Kelly Oct 3 '17 at 13:29
  • $\begingroup$ @EricKelly That is true, but obviously the calculation is incorrect, way to much material is being extruded. Adjusting the flow rate is crucial to optimal prints. $\endgroup$ – Markus Appel Oct 4 '17 at 9:52
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if something strange appears after few layers/some time it's usually the issue of overheating steppers

if this is the case i suggest to

  • tune up Z stepper current
  • add cooling fan which blows on your steppers

see also: this and this

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