Translation between Tuning setting and PrusaSlicer?  

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delirium8413
(@delirium8413)
New Member

I have been working with PETG  lately (Specifically the Prusa Face Shield - US version) and found it to be a bit fiddly with some print settings. During the print I have had to increase the "Flow" and decrease the "Speed" as soon as the print starts to get a good first layer.

On the printer I have been setting the Speed to 93 and the flow up to 103.

I am making a guess that for the Speed I would multiple all the values in the "Speed Print Moves" setting by 0.93 and input that new value?

For Flow woud I just change the Extrusion Multiplier from 1 to 1.08? This is assuming speed 95=1 and the increase to 103 would be ~8% (or 0.08) increase, if I did my math correctly.

Posted : 09/04/2020 12:15 am
JoanTabb
(@joantabb)
Moderator

Hi Delrium, 
Is your printer standard, with the 0.4mm nozzle?  Are you using 7x7 Mesh Bed Levelling? it tests 49 points instead of the standard 9 points and generally gives a better first layer. 

Are you ensuring the build plate is clean? is it the textured build plate? 

I wash my build plates with fairy liquid and water, then dry them and for textured build plates I do not use any other surface preparation.  

Are you increasing Flow, because you are not getting enough squish on the first layer? 

if so, did you do your Live Z adjustment with PLA, or PETG? 

if you adjusted your live Z with PLA, then it may be incorrect for PETG...  

have you tried the 'Life Adjust Z My Way' process for adjusting  Live Z?

https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/life-adjust-z-my-way/

there is a zipfile at the bottom of the first page that contains three files, one for PLA, one for PETG, and one for ABS

use the appropriate one to adjust your live Z and this may help 

Generally speaking, the prusa slicer default for flow it 95% if you are running 103% for the the first layer I would expect you to suffer over extrusion on higher layers... 
On My two Mk3's I see slight over extrusion with the default 95% flow. so I usually reduce my extrusion multiplier to 0.95... to compensate. 

I appreciate that you have been testing to get prints, and found something which works. to a degree... 
but you may be using the wrong process... 

My suggestion to move forward is... 
1, Take your build plate to the sink and wash it well

2, slice your Gcode with 0.95 extrusion multiplier

3, set your Live Z with the PETG file for 'Life Adjust Z My Way'

4, clear the test patch off the build plate without touching the surface of the build plate

5, Print your headshield file, without adjusting flow. and see what happens

Flow and Print speed are separate items, if you want you can reduce the first layer print speed in prusa slicer, or you can dial back the feed rate on the LCD...  but you shouldn't need to do this... 
Good luck,  Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 09/04/2020 2:12 am
delirium8413
(@delirium8413)
New Member

Thank you for the information, it is a lot to process and work through at the moment.

Short Version: I did try some more adjustment of the first layer with the default settings and I think that seemed to get things sorted out. I suspect that the stickiness of the PETG is what has thrown me off the entire time. This morning going from 0.815 to 0.910 made the difference in using the default settings.

Longer version: While doing my initial first layer the line was looking like there were sections missing. If I would try to go lower it seemed to just start making a glob on the print until it go to a point when it was obviously to close to low. Then with fiddling with the extrusion while it was going I managed to get good lines and square at the end. Now I suspect it was just the PETG sticking to itself more than the sheet until it had a bit of a build up to lay out part of a line that was throwing me off. Overall though with the prints that have completed with the extra excursionist they all came out looking pretty good over all. I'll need to compare them to the one in process now.

As for my PLA prints I have a smooth sheet for those because I found the textured sheet, what I am using for the PETG, more challenging to get good adhesion to.

Thank you again. With the frustration I was having with this learning these intricacy you helped everything click into place and make it a great learning experience. Also sorry if this is a bit scattered and rambly; it is early, pre-coffee, and I am excited to have learned new things.

Posted : 09/04/2020 12:35 pm
JoanTabb
(@joantabb)
Moderator

Early days, 
it is easy to go down the wrong rabbit hole... and get lost in the warren... Lol... 

Lots of things interact on a 3D printer, 
In general the Prusa printers are pretty well configured in the firmware, but there are loads of things we users can screw up, and reduce the print quality... 

The textured heatbed is a bit of a 'Binary experience'   you either Love it, or Hate it, there doesn't seem to be a lot of middle ground

I find the textured heatbed works best if it's really clean, and I find that Dish Soap and water are excellent at cleaning grease and other soluble contaminants off the surface...    I take my build plate to the Kitchen sink and give it a damned good scrub with hot water and soap...

then rinse well and dry immediately... 


I generally use the 'Generic PETG' settings and just reduce the default retraction to 0.4mm and generally that will work with most PETG's  after that you can often twiddle a few settings to improve results. but for a starting point with an unknown PETG,  the generic settings are a good starting point.. 
Hope this helps, 
regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 09/04/2020 2:32 pm
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