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Psyonic

Nozzle clips part at start of layer

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Hi All,

When a layer finishes the nozzle moves to the start point of the next layer, but the Z axis only moves AFTER the nozzle has moved to it's start point. When the nozzle gets to the start of the next layer it clips the already printed piece and on delicate parts can break them off! This is particularly bad when printing parts with multiple, spindly rising pieces (see pic). (has happened to me a number of times!)

I have "Z Hop When Retracted" turned on but it NEVER Z Hops. This is mostly unnecessary anyway except for that final move back to the layer start point.

I can't find a setting to change this behavior, does anyone know if I can force Cura to move the Z axis at the end of a layer but BEFORE the nozzle moves to the start point of the next???
Or could someone please explain to me why the Cura team feels this behaviour is best??

iPhone_590da_IMG_4302.thumb.JPG.e66faed1740ed519f023750249b0cfb7.JPG
Related setting I have turned on:

Layer Height : 0.2
Combing : All
Retract Before Outer Wall : ON
Avoid Printed Parts When Travelling : ON (excellent setting!)
Avoid Supports When Travelling : ON
Travel Avoid Distance : 0.625 (default)
Z Hop Only Over Printed Parts : ON
Z Hop Height : 2mm (excessive I know, just for testing)

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You can also retract on layer change.  Not sure if that will help.

 

You can also turn combing off.  When combing is on it tries to stay within one of your "spindly pieces" (let's call them islands) whenever possible and will not retract if it can stay within the island.  But with combing off it will retract a lot more.

 

I'm a bit confused about this whole issue - I have printed things thinner than this and not had this issue before.  Although I had more cross connections - maybe it's more about the wobbling.  Maybe lowering the acceleration will help?  (less vibrations?)

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I have retraction on and it does retract at the last "island" before it moves to the beginning of the next layer, that not an issue. It's not "filament retraction" that is the problem, it's the fact that the print head moves to a place with already printed material before the Z axis moves down to print the next layer.

When the nozzle passes over an island that has not already been printed it's fine, there's no material to hit, the problem is when it goes back to the first island it printed to start the next layer, when it gets there it hits the already printed material and only then moves the Z axis down.

 

Do you know if it can be set to move the Z axis at the last island, before moving to the start of the next layer??

 

As you can see in the snippet below, it finishes a layer with "G0 X177.816 Y153.585" then starts the next layer with "G0 X177.816 Y153.585 Z4.6"

From what I can tell, the last line of the previous layer "G0 X177.816 Y153.585" should not be there! Perhaps this is a bug??

 

G0 X180.98 Y152.661
G0 X177.816 Y153.585
;TIME_ELAPSED:600.611000
;LAYER:22
G0 X177.816 Y153.585 Z4.6
;TYPE:WALL-INNER
G1 F1500 E788.87369
G1 F3600 X177.511 Y153.598 E788.88384

Edited by Psyonic

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