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Scars on Top and Bottom layers

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How to remove scars from top and bottom of my print. I have try to reduce Extruder steps also change retraction distance to a higher value but no success. 
Here is my print

Material BLack Pla

Layer Height--0.15
Initial layer height --0.15
Wall line Width 0.4

Wall Thickness - 1
Wall Line Count - 2
Top Bottom Thickness - 0.8
Top Layers 6
Bottom Layers 6

Infill - 10%
Inital temp 215
Temp 207

Retraction Distance - 9mm
Retraction Speed - 60mm/s

Print Speed - 40
Infill Speed - 100
Travel Speed - 100
Initial Layer Speed - 20.0

 

20181025_201025.jpg

20181025_201043.jpg

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If you mean the single diagonal lines, these are not scars but sort of "travel lines" (I don't know the official name), where the nozzle travels from one point to another without stopping extrusion. I guess the idea behind this is that this causes the least amount of pressure- and flow change in the nozzle, and thus the most stable temperature and extrusion? But I don't know if there is a setting where you could turn this on or off. I just consider it part of this specific production method. Like seam lines and ejection marks are part of the injection moulding process.

 

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Your Retraction Distance looks awfully long at 9mm. I say that because mine is 0.9mm and I do not suffer from travel lines. My retraction settings are 

image.png.c942e4d2cf8f7ab4ae6d5d8345c3c640.png

 

With PLA I found 5.5mm for retraction distance to be fine but I changed it to 6.5mm for nGen material.

 

I always print with Combing Off

 

 

 

 

 

image.png

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On 10/26/2018 at 1:26 PM, geert_2 said:

If you mean the single diagonal lines, these are not scars but sort of "travel lines" (I don't know the official name), where the nozzle travels from one point to another without stopping extrusion. I guess the idea behind this is that this causes the least amount of pressure- and flow change in the nozzle, and thus the most stable temperature and extrusion? But I don't know if there is a setting where you could turn this on or off. I just consider it part of this specific production method. Like seam lines and ejection marks are part of the injection moulding process.

 

 

I switch from direct extrude to Bowden setup and then the travel line show up. I also cut the teflon tube to minimize  the distance from motor to hot end but same result. Sometimes i hear click on extruder motor. My step/mm are at 100. And the calibration show that i am extruding the exactly 100mm. 

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6 hours ago, yellowshark said:

Your Retraction Distance looks awfully long at 9mm. I say that because mine is 0.9mm and I do not suffer from travel lines. My retraction settings are 

image.png.c942e4d2cf8f7ab4ae6d5d8345c3c640.png

 

With PLA I found 5.5mm for retraction distance to be fine but I changed it to 6.5mm for nGen material.

 

I always print with Combing Off

 

 

 

 

 

image.png

 

With direct extrude i did not suffer from travel line, but when i switch to bowden extrude then the travel line shows up. 

I set the retraction value to 9 because when i do those retraction test which can be found on Thinginverse none of other numbers make a difference. 

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